commercial poultry nutritio

COMMERCIAL POULTRY NUTRITIONTHIRD EDITION

by

STEVEN LEESON, Ph.D.Professor of Animal Nutrition

and

JOHN D. SUMMERS, Ph.D.Professor Emeritus

Department of Animal and Poultry ScienceUniversity of Guelph

Guelph, Ontario, Canada

PUBLISHED BYUNIVERSITY BOOKS

P. O. Box 1326Guelph, Ontario, Canada

N1H 6N8

Nottingham University PressManor Farm, Church Lane,Thrumpton, Nottingham,

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Commercial Poultry Nutrition, Third EditionUniversity BooksP.O. Box 1326Guelph, Ontario

©2005 University Books

All rights reserved. No part of this publication may be reproducd, stored in a retrieval system,or transmitted in any form by electronic, mechanical, photocopying or photographing or otherwise, without the prior written permission of the publisher.Canadian cataloguing in publication data

1. Poultry - Feeding and Nutrition 2. Birds 3. NutritionI Leeson, Steven, 1948, II Summers, John D. 1929.

ISBN 0-9695600-5-2

Digitally reprinted in 2008 from:

All rights reserved. No part of this publicationmay be reproduced in any material form(including photocopying or storing in anymedium by electronic means and whether or nottransiently or incidentally to some other use ofthis publication) without the written permissionof the copyright holder except in accordance withthe provisions of the Copyright, Designs andPatents Act 1988. Applications for the copyrightholder’s written permission to reproduce any partof this publication should be addressed to the publishers.

British Library Cataloguing in Publication DataCommercial Poultry Nutrition, Third EditionI. Leeson, S., Summers, J.D.ISBN 978-1-904761-78-5

Disclaimer

Every reasonable effort has been made to ensure that the material in this book is true, correct, complete and appropriate at the time of writing. Nevertheless, the publishers and authors do not accept responsibility for any omission or error, or for any injury, damage, loss or financial consequences arising from the use of the book.

PREFACE

The first edition of this book was published in 1991, while the second edition followed in1997. It has been an interesting exercise to follow the development of poultry production overthis time, and to encapsulate ideas of associated changes in nutrition and feeding management.For example, in 1991, the emphasis in broiler nutrition was on maximizing growth rate,together with the new approach of considering breast meat yield. In 1997, the concept of compensatory growth was emphasized, as a necessary management tool to control metabolicdisorders. In the intervening eight years, poultry geneticists have obviously reduced the incidence of these disorders, and so we are once again considering rapid growth throughoutthe entire grow-out period. It is such evolving circumstances within the industry that dictatethe need for periodic reappraisal of our feeding programs.

We have changed the layout of the book to accommodate a two-column presentation of material. In response to reader requests, we have also included commercial data on the nutrientrequirements of layers, broilers and turkeys. This data is taken from Management Guidesavailable in early 2004. We realize that such information changes as bird genetics change. The reader should always source the latest information available on a specific breed, from thebreeding company, and use this information, rather than that presented in this book as themost accurate assessment of nutrients for a specific strain.

Many of the ideas in this book are based on work carried out in the Department of Animaland Poultry Science at the University of Guelph. In this regard, we are indebted to the manysponsors of our research program, and in particular, the on-going support of the OntarioMinistry of Agriculture and Food, Guelph, Ontario.

Once again, we are indebted to the corporate sponsors of this book. Their names appear inthe front covers, while their company logos are displayed on the back cover. Their generoussupport allows us to subsidize the cost of this book, and in so doing, hopefully allows us toreach a wider audience.

Special thanks to Laurie Parr for her conscientious effort in typing the original version of thebook, and to Ford Papple of Papple Graphics for his assistance and ideas with the layout anddesign. Thanks to Linda Caston for again proof reading numerous versions of the book, andher attention to detail is much appreciated. Also thanks to Greg Hargreave, Baiada Poultryfor agreeing to proof read the final version. Greg’s constant reminder of the importance ofbrown-egg layers is much appreciated.

Steven Leeson and John SummersGuelph, 2005

PREFACE

The first edition of this book was published in 1991, while the second edition followed in1997. It has been an interesting exercise to follow the development of poultry production overthis time, and to encapsulate ideas of associated changes in nutrition and feeding management.For example, in 1991, the emphasis in broiler nutrition was on maximizing growth rate,together with the new approach of considering breast meat yield. In 1997, the concept of compensatory growth was emphasized, as a necessary management tool to control metabolicdisorders. In the intervening eight years, poultry geneticists have obviously reduced the incidence of these disorders, and so we are once again considering rapid growth throughoutthe entire grow-out period. It is such evolving circumstances within the industry that dictatethe need for periodic reappraisal of our feeding programs.

We have changed the layout of the book to accommodate a two-column presentation of material. In response to reader requests, we have also included commercial data on the nutrientrequirements of layers, broilers and turkeys. This data is taken from Management Guidesavailable in early 2004. We realize that such information changes as bird genetics change. The reader should always source the latest information available on a specific breed, from thebreeding company, and use this information, rather than that presented in this book as themost accurate assessment of nutrients for a specific strain.

Many of the ideas in this book are based on work carried out in the Department of Animaland Poultry Science at the University of Guelph. In this regard, we are indebted to the manysponsors of our research program, and in particular, the on-going support of the OntarioMinistry of Agriculture and Food, Guelph, Ontario.

Once again, we are indebted to the corporate sponsors of this book. Their names appear inthe front covers, while their company logos are displayed on the back cover. Their generoussupport allows us to subsidize the cost of this book, and in so doing, hopefully allows us toreach a wider audience.

Special thanks to Laurie Parr for her conscientious effort in typing the original version of thebook, and to Ford Papple of Papple Graphics for his assistance and ideas with the layout anddesign. Thanks to Linda Caston for again proof reading numerous versions of the book, andher attention to detail is much appreciated. Also thanks to Greg Hargreave, Baiada Poultryfor agreeing to proof read the final version. Greg’s constant reminder of the importance ofbrown-egg layers is much appreciated.

Steven Leeson and John SummersGuelph, 2005

SPONSORS

We are indebted to the following companies for their financial support which allowed us to subsidizethe cost of this publication.

ADM Animal Health Nutrition4666 Faries Pkwy.DecaturIL 62526U.S.A.

Alltech Inc.3031 Catnip Hill PikeNicholasville, KY40356 U.S.A.

Danisco Animal Nutrition411 E. GanoSt. LouisMO 63147U.S.A.

DSM Nutrition Products Inc.45 Waterview BlvdPursippanyNJ 07054-1298U.S.A.

Hyline InternationalP.O. Box 65190West Des Moines, IA 50265U.S.A.

Novus International Inc.530 Maryville Centre Dr.St. Louis, MO63141 U.S.A.

Provimi Holding B.V.Veerlaan 17-23NL-3072 AN RotterdamTHE NETHERLANDS

Vetech Laboratories Inc.131 Malcolm RoadGuelph, OntarioN1K 1A8 CANADA

The publishers of the original version of this book are indebted to the following companies for their financial support which allowed them to subsidize the cost of the original publication.

TABLE OF CONTENTS

CHAPTER 1 GLOBAL POULTRY PRODUCTION

CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION

CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS

CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS

CHAPTER 5 FEEDING PROGRAMS FOR BROILER CHICKENS

CHAPTER 6 FEEDING PROGRAMS FOR BROILER BREEDERS

CHAPTER 7 FEEDING PROGRAMS FOR TURKEYS

CHAPTER 8 FEEDING PROGRAMS FOR DUCKS AND GEESE

CHAPTER 9 FEEDING PROGRAMS FOR GAME BIRDS, RATITES AND PET BIRDS

APPENDIX - INGREDIENT COMPOSITION DATA

INDEX

1

SECTION 1.1World Animal Production

GLOBAL POULTRYPRODUCTION 11.1 World animal production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Poultry meat production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Egg production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.4 Future considerations for poultry production . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.5 Global feed production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

P roduction of most farm animal specieshas increased over the last 10 years,and predictions are for this trend to

continue in the near future. Poultry hasseen the greatest increase in productionand again, this trend will likely continue. Bothpoultry meat and eggs are well positioned tomeet demands for increased supply fromour growing world population. Predictionof world populations is always subject to adjustment, but it seems as though we willhave around 7 billion people to feed by2008. However, an obvious trend occurringis that this population is quickly aging andalso living in urban settings of ever increasingsize. Today almost 2% of the world’s pop-ulation live in the 10 largest cities in the world,and by 2008, we will likely have 20 cities withpopulations in excess of 10 million people.These large urban populations obviouslyrely almost 100% on food supply from ruralareas. Traditionally such rural food supplyhas been grown adjacent to the urban pop-ulations, but this situation is becomingincreasingly more difficult as these urban populations reach 10-15 million. National

and international movement of feed andfood will become critical to feeding these largeexpanding populations. The population inthe developed world is predicted to changelittle in the next 10 years, and so virtually allgrowth will be in developing countries, andespecially in Africa and Asia. With its unpre-dictable weather patterns, Africa has alwayshad difficulty feeding its growing population,and with increased urbanization, this situa-tion will only deteriorate.

In all countries, there is an aging of thepopulation, and it is predicted that the proportion of people � 60 years of age, willdouble in the next 30 years. The purchasingpower of many such individuals may not beadequate to sustain their usual diet supply.Up to now, and in the near future, we havebeen able to meet increased demands for foodthrough a combination of increased supplycoupled with improved production effi-ciency. Such improvements in efficiency ofproduction will allow us to gradually upgradethe general nutritional status of the world population as a whole and it is evident that

Page

CHAPTER

1.1 World Animal Production

2 CHAPTER 1GLOBAL POULTRY PRODUCTION

SECTION 1.1World Animal Production

the poultry industry is playing a major role in thisimportant development. In the past, we have hadto face criticism of the energy used in animal production and especially from the point of viewof the inefficiency of consuming animal vs. veg-etable protein. Of the total energy used by mostdeveloped countries, less than 4% is used for foodproduction. During this food production, by farthe greatest quantities of energy are used duringprocessing and household preparation to meet thestringent demands of the consumer. Consequently,of the 4% of energy used by the agrifood business,only 18% (or 0.7% of total energy needs) is actu-ally used in primary animal production. Increasedhuman consumption of vegetable proteins as analternative to meat and eggs has failed to mate-rialize, essentially due to excessive energy use nec-essary during manufacture, which is the same crit-icism originally aimed at animal production.The production of synthetic meat analogues is thusvery energy intensive, and their limited impact overthe last decade attests to problems with economic viability and/or consumer acceptance.With the economy of many third world countriesimproving, there appears to be increased demandfor animal products and especially poultry meatand eggs.

In developed countries, the current concernsregarding meat and eggs are not lack of supply,but rather wholesomeness and food safety. Theconcern about genetic modification of plants andanimals quickly evolved in Europe, such that currently their use is not allowed in food production. Many plant species such as corn andsoybean meal are now routinely geneticallymodified and used as ingredients in diets for poultry and other animals in many countries.

Concern about using animal proteins in dietsfor farm animals also arose in Europe following

the outbreak of BSE in the mid 1990’s. Europeansare still uncertain about the health status of theirruminant animals, and the ban on using productssuch as meat meal continues. While it is possible to formulate diets without meat meals,it is more expensive, and does add a major financial burden on most animal industries sincethey have to find alternative means of disposal ofwaste by-products.

It is impossible to produce meat or eggsthat are guaranteed to be free of pathogens. Anon-tolerance scenario for organisms such as salmonella is untenable, and any such regulationsare unrealistic. Certainly there will be increasedemphasis on pathogen reduction, and both thepoultry meat and egg industries have made significant progress with programs such asHACCP at processing plants, feed mills andpoultry farms. Feed is one potential route of entryfor pathogens into meat and eggs, and so for-mulation will have to be modified, or alternateadditives used, to try to reduce pathogen loadof feed to acceptable levels of tolerance. Feedprocessing is now viewed with an aim topathogen control, in addition to concerns aboutfeed intake and bird growth. There will undoubt-edly be reduced emphasis on antibiotic growthpromoters as are now commonly used in broilerand turkey production and this situation adds evenmore demand on feed pathogen control programs.

On a more positive note, the production ofso-called designer foods continues to increase;with the best example being omega-3 enrichedeggs. It is simple to modify the fat-solublenutrient profile of meat and eggs, and so therewill be an increased demand, within nichemarkets, for food products modified in relationto improved human nutrition.

3CHAPTER 1GLOBAL POULTRY PRODUCTION

SECTION 1.2Poultry meat production

T he broiler chicken industry has shownunparalleled growth over the last 30years, although there are now signs of a

maturing market in many countries. The industry is relatively easy to establish and whilethere are regional differences, production systemsin most countries are modeled in a similar manner. Because of the increased growth poten-tial in modern strains of broiler, it is now realizedthat some degree of environmental control is essential. Such systems can be full environ-mental control through to curtain sided housesin tropical countries. Even with the latter, cheapertype housing, it seems essential to ensure adequateair movement and so tunnel ventilation hasbecome popular over the last 10 years. Optimumgrowth rate cannot be achieved much beyond therange of 15-30ºC and so the ventilation systemsare designed to hopefully maintain the birds’ environment within this temperature range.

Chicken is usually the least expensive meatin most countries and consequently it is first orsecond for per capita consumption. This com-petitive situation has occurred due to continuedimprovements in efficiency of production that oftennecessitate acceptance of new ideas and inno-vations by poultry producers and agribusiness.On the other hand, production systems for com-peting meat products have shown little changeover the last two decades. Interestingly, theswine industry is now starting to use ‘poultry’ models in production systems.

Much of the success of the chicken meat industry relates to development of new consumerproducts, largely because of continued advancesin further processing. The most successful singleproduct is undoubtedly the ‘chicken nugget’, nowfeatured by most fast food and retail outlets. Overthe last 10 years, some 30,000 non-chickenfast-food outlets in North America have added

chicken products to their menu, and duringspecial advertising campaigns, chicken productscan be the leading sales item over such conventional products as hamburgers. So-called ‘fast-food’ stores are increasing in numberin Europe, in Asia and in South America, and this will likely lead to increased demand for chicken. In addition to developing new uses forconventional parts of the chicken and turkey carcass, the industry has also been successful indeveloping technology to use its own ‘by-products’ and then finding markets for these(or vice versa). The demand for chicken wingsand chicken feet together with mechanicallydeboned meat exemplify these types of products.In addition to increasing overall poultry meat consumption, these products also lead toimproved overall efficiency of production andhelp maintain the economic advantage seenwith poultry meat.

Poultry meat is also ideally suited in terms ofmeeting demands for leaner meat by healthconscious consumers. There has been consid-erable publicity over the last few years con-cerning the relative fat content of various meats,yet the fact remains that when comparisons areconducted on comparable products, poultrymeat is the leanest product. Comparison of a highly trimmed steak or pork chop vs. a wholebroiler carcass certainly reduces the advantageusually seen with poultry. However, the valid comparison is trimmed steak vs. poultry breastfillet, in which case the poultry product is by farthe leanest. Broiler chicken and especiallyturkey are therefore ideal products for segmentsof the food industry wishing to provide low-fatmeals. Poultry meat also has the almost uniqueadvantage of not being discriminated against dueto religious or cultural beliefs, making poultry prod-ucts popular with airlines, hotels, institutions, etc.

1.2 Poultry Meat Production


SECTION 1.3Egg production

The poultry meat industry has come underrecent scrutiny regarding the use of growth promoters in the feed. When these are removedfrom diets, broilers most frequently developnecrotic enteritis and coccidiosis, and so theirmain mode of action seems to be control overclostridial infection. When growth promoters arenot used in the feed, then alternate strategies suchas competitive exclusion, water acidification, man-

Table 1.1 Poultry meat production(million tonnes)

1993 2005World 48 80North America 15 25S. America 6 12Europe 10 13Asia 14 22

Table 1.2 Broiler meat production(million tonnes)

1993 2005World 41 68North America 13 21S. America 5.5 11.5Europe 9 10.5Asia 12 20

Table 1.3 Turkey meat production(million tonnes)

1993 2005World 4 5.5North America 2 3S. America 0.1 0.3Europe 1.5 1.8Asia 0.1 0.2

Table 1.4 Egg production (million tonnes)

1993 2005World 38 57North America 6 8S. America 2.5 3.4Europe 10 10Asia 18 32

1.3 Egg Production

T he egg industry is enjoying increasedproduction as consumers become moreeducated about the nutritive value of

eggs and as more eggs are processed. The mis-information from the 1980’s regarding the relationship between cholesterol intake andblood cholesterol levels has been superceded bypertinent information detailing the relevant contribution of various dietary nutrients to serum

nan-oligossaccharides and pro- and prebioticsare often considered. Ironically, while growthpromoters are often banned as feed additives, analternative strategy is to use them as water medication. Table 1.1 shows total poultry meatproduction worldwide, and in major producingareas, while Tables 1.2 and 1.3 show the break-down for broiler and turkey meat production.

cholesterol in humans. Eggs are relatively inex-pensive per unit of protein and energy contained in yolk and albumen, and so egg consumption continues to increase in developingcountries.

The egg industry produces either brown- orwhite-shelled eggs. While white eggs predom-inate in North America, consumers in many


SECTION 1.4Future considerations for poultry production

5

countries demand a brown egg. Unfortunately,such demand is based on the naive view thatbrown-shelled eggs are more nutritious or whole-some. In developing countries, this myth iscompounded with the demand for a highly pigmented yolk, and both of those factors addto the cost of production. North America has alsoseen great success in production of designer eggs,since some 5% of shell eggs are now enrichedwith nutrients such as omega-3 fatty acids andvitamin E. This profitable segment of the egg industry has not merely displaced demand fornormal eggs, but rather has created a genuineincreased demand for eggs and egg products.

In North America, the most dynamic segmentof the egg industry relates to processing and further processing of eggs, paralleling the success seen in the poultry meat industry. By 2008,it is estimated that at least 50% of eggs in North

America will be processed in some way orexpressed in an alternate way, only 50% ofeggs will be marketed in the shell. Expansion ofegg processing is raising new challenges to pro-duction, where for instance egg mass is much moreimportant than egg size per se, and where shellquality is of lesser importance. It is likely thatthe white-egg strains will be developed for theprocessing industry, while brown-shelled strainswill be selected for characteristics importantfor the shell egg market. Disposal of the end-of-lay bird is becoming more difficult in manyregions and so it seems important to develop newfood products from this potentially valuableresource. Converting spent fowl into animal feedingredients and especially for layer feed seemsa very shortsighted approach in terms of consumerperception. Table 1.4 shows global and region-al egg production.

1.4 Future Considerations for Poultry Nutrition

Over the last 20 years, developments inpoultry nutrition have paralleled, ormade possible, increased productivity

of the various poultry industries. As productionconditions and goals have changed, we have beenable to revise our estimates of nutrient require-ments. Greater variation in production goals hasimposed some degree of complication to feeding programs, because ‘global’ recom-mendations are now often not applicable. Thefuture emphasis in poultry nutrition must bethe development of life-cycle feeding programsfor various classes of birds, rather than consid-eration of individual diets in isolation.Unfortunately, there is still a dearth of researchinformation that views recommendations within the context of an overall program. Withthe sophistication we have today in our production

systems, birds seldom fully recover from inappropriate nutrient intake at any time intheir production cycle.

Because feed still represents 60 – 70% of thecost of production of most poultry products,there is a continual need to evaluate new or different sources of ingredients and to continu-ally re-examine the more common ingredients.A yearly review of the published research dataindicates that ingredient evaluation occupies themajor portion of practical poultry nutritionresearch, and feed manufacturers should beaware of the potential of such new ingredients.Often, so-called new ingredients are not new inthe sense of being novel to poultry feeding perse, rather they have not been as seriously con-sidered in a particular geographical location. A


SECTION 1.4Future considerations for poultry production

Table 1.5 Bird numbers (millions)

1993 2006BROILERSWorld 30,700 46,000North America 8,500 13,000South America 3,700 7,500Europe 6,600 6,600Asia 9,700 18,000

TURKEYSWorld 580 700North America 300 320South America 20 40Europe 230 280Asia 25 30

LAYERSWorld 3,800 5,500North America 480 600South America 300 350Europe 770 750Asia 1,850 3,500

good example is the consideration of wheat asan ingredient in many areas of North America,whereas wheat has been a standard in other countries for 20-30 years. Under such conditions,feed manufacturers are encouraged to take a moreglobal perspective on ingredient evaluation,because, for example, if wheat can be usedsuccessfully in Europe with strain A of broiler, inall likelihood it will be appropriate in another country assuming comparable conditions.Nutritionists must now have first-hand knowledgeof production techniques to ensure that all conditions are comparable, as failure to do sois undoubtedly the reason for problems thatperiodically occur with such ‘new’ ingredients.In this context, justification of ingredient max/minconstraints used during formulation is becomingmore critical. As previously mentioned, thegoals in many production situations vary commensurate with consumer demand for endproducts and/or manipulation of bird manage-ment. As such, nutritionists are now faced withan array of alternate programs dependent uponsuch specific, and often specialized, needs.The best example of this trend is nutritional mod-ification aimed at manipulating meat or egg composition. Changing the proportion of energy:protein or amino acids or limiting feed intakeduring specific grow-out periods is known to influence fat deposition in the carcass. Likewise,choice of ingredients may well influence egg com-position in relation to needs to improve humanhealth. It is likely that nutritionists will be facedwith increasing pressure from their customers,in terms of diets and programs aimed at meet-ing such market niches. In these situations, knowledge of ingredient profile and compatibility

within a diet and feeding program become evenmore critical. A more holistic approach in the devel-opment of feeding programs will allow the poul-try industry to pursue its goals of increased pro-duction, improved efficiency and increasedspecialization. It is hoped that the material provided in the following chapters willgive the reader a background in developingsuch programs. Table 1.5 shows the expected num-ber of birds that we will likely have to feed by 2006.


SECTION 1.5Global feed production

7

T he poultry industry accounts for 20–40%of animal feed use in most countries,and this proportion is invariably increas-

ing over time. Table 1.6 shows estimates offeed production for broilers, turkeys, layers andassociated breeders.

As a generalization, the numbers shown in Table1.6 can be multiplied by 0.6 for an estimate of cereal needs and by 0.3 for needs of ingredients

such as soybean meal. The feed industry willundoubtedly become more regulated and becomepart of any tracking initiatives introduced foreggs or meat. Regulation concerning the use andreconciliation for most drugs is now mandatoryin many countries, through such programs asHACCP. Undoubtedly the cost of such extraregulation and control will be passed on to the poultry industry and eventually to the consumer.

1.5 Global Feed Production

Table 1.6 2006 Feed production (million tonnes)

Broiler Turkey Total Broiler Turkey Pullet Layer

Breeder Breeder Poultry

World 184 15 28 2.8 30 192 452

North America 52 4.2 7.9 0.8 8.4 54 127

South America 30 2.4 4.6 0.5 4.9 31 73

Europe 26 2.1 4.0 0.4 4.3 28 65

Asia 72 5.9 11.0 1.0 11.7 75 177

8

9

INGREDIENT EVALUATION AND DIET FORMULATION

22.1 Description of Ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1. Corn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112. Wheat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153. Milo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194. Barley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215. Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236. Wheat by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257. Bakery meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288. Rice by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299. Soybean meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3110. Soybeans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3511. Canola meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3712. Corn gluten meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4013. Cottonseed meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4214. Flaxseed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4415. Meat meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4716. Poultry by-product meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5017. Feather meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5218. Fish meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5419. Fats and oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57OTHER INGREDIENTS20. Oats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6521. Rye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6522. Triticale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6623. Molasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6624. Dehydrated alfalfa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6725. Full-fat canola seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6726. Groundnut (peanut) meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6727. Peas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6828. Safflower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6829. Sesame meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6830. Lupins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6831. Blood meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6832. Sources of calcium, phosphorus and sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6933. Trace minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7134. Synthetic amino acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

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CHAPTER

10 CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION

2.2 Ingredient testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77a. Bulk density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77b. Proximate analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 c. Amino acid analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79d. Metabolizable energy (AME or TME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80e. Near infra-red analysis (NIRA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80f. Urease testing of soybeans and soybean meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82g. Protein solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82h. Protein and amino acid dye-binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83i. Fish meal gizzard erosion factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83j. Sorghum tannins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84k. Gossypol in eggs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84l. Fat assays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84m. Hulls in rice by-products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85n. Mineral solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

2.3 Feed additives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86a. Pellet binders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86b. Anticoccidials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86c. Antibiotics, growth promoters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88d. Antifungal agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90e. Probiotics and prebiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91f. Yeast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92g. Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92h. Pigments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96i. Flavoring agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96j. Worming compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97k. Odor control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

2.4 Feed toxins and contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98a. Mycotoxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98b. Plant toxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99c. Autointoxication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106d. Bacterial toxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106e. Chemotherapeutic drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107f. Toxic seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

11CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION

SECTION 2.1Description of ingredients


2.5 Feed manufacture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110a. Vitamin-mineral premixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110b. Vitamin stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112c. Pelleting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112d. Expanding, extrusion and thermal cooking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

2.6 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115a. Water intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115b. Water output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117c. Water balance and dehydration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117d. Drinking water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118e. Water restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118f. Water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119g. General management considerations with water . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

C orn has become the standard againstwhich other cereals, cereal by-prod-ucts and other energy-yielding ingre-

dients are compared. In most poultry diets,corn will be the major contributor of metab-olizable energy. World production is around600 m tonnes of which 240 m tonnes are pro-duced by the U.S.A. Although China is theworld’s second largest producer at around 100m tonnes, Brazil at 40 m tonnes, is the sec-ond largest world exporter. The feed indus-try usually uses the equivalent of U.S.A.grade #2. As grade number increases, bulkdensity declines and there are greater per-missible levels of damaged kernels and for-eign matter allowed in the sample. Corn grade#2 should contain no more than 5% damagedkernels and 3% foreign material. Whiledamaged kernels are unlikely to affect its ener-gy value, foreign material is likely to reduceits energy value and hence monetary value.

Broken kernels are also potential sites for moldinfestation.

The energy value of corn is contributedby the starchy endosperm, which is composedmainly of amylopectin, and the germ, which contains most of the oil. Most corn samples contain 3 – 4% oil, although newer varietiesare now available which contain up to 6 –8% oil, and so contribute proportionallymore energy. These high-oil corn varietiesalso contain 2 – 3% more protein, and pro-portionally more essential amino acids. Theprotein in corn is mainly as prolamin (zein)and as such, its amino acid profile is not idealfor poultry. This balance of amino acids, andtheir availability, must be seriously consid-ered when low protein diets are formulated,because under these conditions the cornprolamin can contribute up to 50 – 60% ofthe diet protein. Corn is also quite high in

2.1 Description of Ingredients1. CornOther Names: Maize

Nutritional Characteristics:



the yellow/orange pigments, usually containingaround 5 ppm xanthophylls and 0.5 ppmcarotenes. These pigments ensure that corn-fedbirds will have a high degree of pigments in theirbody fat and in egg yolks.

While #2 grade is the standard for animal feeds,lower grades are often available due to adverse

growing, harvesting or storage conditions.Dependent upon the reason for lower grade, thefeeding value of corn usually declines withincrease in grade number. Table 2.1 shows themetabolizable energy value of corn necessarilyharvested at various stages of maturity due toadverse late-season growing conditions.

Corn Moisture at 100 kernel wt at AMEn (kcal/kg) atdescription harvest (%) 10% moisture (g) 85% dry matter

Very immature 53 17 3014Immature 45 22 3102Immature 39 24 3155Mature 31 26 3313

The energy value of corn declines by 10 – 15kcal/kg for each 1 lb reduction in bushel weightbelow the standard of 56 lb/bushel. However, theselower bushel weight samples show no consistentpattern with protein or levels of most aminoacids, although there is an indication of loss ofmethionine content with the immature samples.

Another potential problem with handlingimmature, high-moisture corn is that the dryingconditions must necessarily be harsher, or moreprolonged in order to reduce moisture level to anacceptable 15%. Excessive or prolonged heatingcauses caramelization of corn which then has acharacteristic smell and appearance, and there isconcern that lysine will be less available becauseof Maillard Reaction with available carbohydrates.

As detailed in subsequent ingredients thereis processing of corn that yields products suchas gluten meal and corn oil. However, in NorthAmerica well over 95% of corn is used for animal feeds.

There is some debate regarding the ideal sizeof ground corn particles for various classes of poultry. Within reason, the finer the grind, thebetter the pellet quality, while in mash diets, toofine a grind can lead to partial feed refusal.Table 2.2 indicates guidelines for expected distribution of particle sizes of corn ground to be‘fine’ vs. ‘coarse’. There seems to be somebenefits in terms of AMEn of using a finer grindfor birds up to 3 weeks of age, while a coarsegrind is better for birds >21 d of age.

Depending upon the growing season and storage conditions, molds and associated myco-toxins can be a problem. Aflatoxin contaminationis common with insect damaged corn grown inhot humid areas, and there is little that can bedone to rectify the horrendous consequences ofhigh levels of this mycotoxin. There is an indicationof aluminosilicates partially alleviating theeffects of more moderate levels of aflatoxin. Ifaflatoxin is even suspected as being a prob-lem, corn samples should be screened prior to

Table 2.1 Corn maturity and energy value



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blending and mixing. Zearalenone is anothermycotoxin that periodically occurs in corn.Because the toxin ties up vitamin D3, skeletal andeggshell problems can occur. With moderate levels of contamination, water-soluble D3 via thedrinking water has proven beneficial.

Mold growth can be a serious problem in cornthat is transported for any length of time.

Damaged kernels and foreign material aregoing to reduce the economic value of corn.However, Dale and co-workers at Georgia suggestthe energy value of these contaminants is littledifferent from whole corn. Broken kernels werejust 200 kcal/kg lower than the AMEn of corn,while foreign material tested 600 kcal/kg lowerthan corn. Therefore having #4 grade corn with10% damaged kernels and 5% foreign materi-al vs 5% and 3% respectively for #2 grade,relates to a reduction of just 25 kcal/kg for this#4 vs #2 grade corn.

If corn is to be fed in mash diets, then thereseems to be an advantage to grind to as uniforma particle size as possible, (0.7 – 0.9 mm). Thissize is often referred to as ‘medium’ grind. Birdsfed fine or coarse-ground corn seem to exhibitlower digestibility values. Corn presents someproblems to the manufacture of pelleted diets,and often good pellet durability in diets containing� 30% corn can only be obtained by inclusionof pellet-binders.

With corn shipped at �16% moisture and sub-jected to � 25ºC during shipping, mold growthoften occurs. One solution to the problem is toadd organic acids to the corn during loading forshipments. However, it must be remembered thatwhile organic acids will kill molds, and prevent re-infestation, they have no effect on anymycotoxins already produced.

Particle size Grind(microns) Fine Coarse

<150 5 <1300 11 2450 16 3600 17 3850 22 41000 16 41500 10 52000 1 102500 <1 24

>3000 <1 44

Table 2.2 Particle size distribution of corn (%)



Dry Matter 85.0 Methionine 0.20Crude Protein 8.5 Methionine + Cystine 0.31Metabolizable Energy: Lysine 0.20

(kcal/kg) 3330 Tryptophan 0.10(MJ/kg) 13.80 Threonine 0.41

Calcium 0.01 Arginine 0.39Av. Phosphorus 0.13Sodium 0.05 Dig Methionine 0.18Chloride 0.05 Dig Meth + Cys 0.27Potassium 0.38 Dig Lysine 0.16Selenium (ppm) 0.04 Dig Tryptophan 0.07Fat 3.8 Dig Threonine 0.33Linoleic acid 1.9 Dig Arginine 0.35Crude Fiber 2.5

Nutrient Profile: (%)

Bulk Density:

Formulation Constraints:

kg/m3 lb/ft3 lb/bushelWhole kernels #2 696 42.2 54

#4 632 38.3 49Ground corn 642 40.0 51Corn screenings 475 30.1 39

Bird age Min. Max. Comments0-4 wk - 60% Usually no problems with upper limits. From 0-7d, birds

may not digest as well as adult birds.4-18 wk - 70%

Adult layer - 70% Higher levels cause more problems with pellet durability.

Moisture CP Fat Ca/P AA’s Other

All deliveries Wkly 6 mos 12 mos 12 mos Molds – mycotoxins, AME,12 mos1

1 Assay to be conducted within 30 d of yearly harvest.

QA Schedule:



2. WheatNutritional Characteristics:

Wheat is commonly used in many coun-tries as the major energy source in poultry diets.There is often confusion regarding the exacttype of wheat being used, because wheats aredescribed in a number of different ways.Traditionally wheats were described as being win-ter or spring varieties and these were usually grownin different regions because of prevailing cli-mate and soil conditions. Wheats are sometimesalso referred to as white or red, depending uponseed coat color, and finally there is the classifi-cation of hard vs soft. In the past, most winterwheats were white and soft, while spring wheatswere hard and red. In terms of feeding value, themain criterion is whether wheat is soft or hard,because this will have an effect on composition,and especially on protein. Because of developmentsin plant breeding, the seed color and time of plant-ing can now be more variable. Hard wheats havea greater proportion of protein associated with thestarch and so contain more protein that is also high-er in lysine. The proteins in hard wheat areuseful in bread making, while the soft wheats aremore useful in manufacture of cookies andcakes. Durum wheat used in manufacture of pastais a very hard wheat. The physical hardness ofthese wheats is due to the strong binding betweenstarch and the more abundant protein.

Varietal differences based on ‘hard’ vs ‘soft’varieties seem to have inconsistent effects on AMEand amino acid digestibility. A more consistentvarietal effect is seen when genes from rye aretranslocated into wheat ostensibly to improve baking characteristics. These translocated wheatvarieties (often termed 1B → 1R) have 10%lower amino acid digestibility and in the case oflysine, the differences may be as much as 18%in favor of the non-translocated varieties.

As with corn, the grading system for wheatrelates to bulk density and the proportion of broken grains and foreign material. For #2grade there is a maximum allowable inclusionof 5% foreign material and broken kernels.Feed grade wheat can have over 20% broken ker-nels and foreign material.

The composition of wheat is usually more variable than that of other cereals. Even withinthe hard wheats, protein level can vary from 10to 18%, and this may relate to varietal differencesand variance in growing conditions. Most hardwheats will not have to be dried after harvest,although drying conditions and moisture content of wheat at harvest appear to have little effect on feeding value. Environmental temperature during growing seems to have a majoreffect on wheat nitrogen content, and althoughhigh temperature can result in 100% increase innitrogen level, the relative proportion of both lysineand starch tend to be decreased.

Depending upon the growing region, frost damaged or sprouted wheat is sometimes avail-able to the feed industry. Frost damage effectivelystops starch synthesis, and so kernels are small andshrunken. While 100 kernel weight should bearound 27 g, with severe frost damage, this canbe reduced to 14 – 16 g. As expected, themetabolizable energy level of this damagedwheat is reduced and under these conditions, thereis a very good correlation between bulk densityand metabolizable energy. For non-frosted wheat,however, there does not seem to be the same rela-tionship between energy level and density.

Wheat will sometimes sprout in the field.Sprouted wheat would probably be rejected



16

simply based on appearance, although researchdata suggests that metabolizable energy level isonly reduced by 3 - 5%. There are no problemsin feeding sprouted wheat, as long as it has beendried to � 14% moisture, and can be economical if discounted accordingly. Wheat con-taminated with ‘rust’ however seems to moreseriously affect feeding value, and metabolizableenergy value can be reduced by up to 25%.

While wheats are much higher in protein content compared to corn, and provide only slightly less energy, there are some potential problems from feeding much more than 30% ina diet, especially for young birds. Wheat contains about 5 – 8% of pentosans, whichcan cause problems with digesta viscosity, leading to reduced overall diet digestibility andalso wet manure. The major pentosan components are arabinoxylans, which are linkedto other cell wall constituents, and these are ableto adsorb up to 10 times their weight in water.Unfortunately, birds do not produce adequatequantities of xylanase enzymes, and so these polymers increase the viscosity of the digesta. The10 - 15% reduction in ME of wheats seen withmost young birds (<10 d age) likely relates to theirinability to handle these pentosans. Variabilityin pentosan content of wheats per se likelyaccounts for most of the variability of results seenin wheat feeding studies, together with ourinability to predict feeding value based on simple proximate analyses. These adverse effectson digesta viscosity seem to decrease withincreased storage time for wheats. Problems withdigesta viscosity can be controlled to someextent by limiting the quantity of wheat used, especially for young birds, and/or by usingexogenous xylanase enzymes (see Section 2.3 g).

Wheats also contain -amylase inhibitors.Although these inhibitors have not been fully

identified, they are thought to be albumin proteins found predominantly in the endosperm.These inhibitors can apparently be destroyed bythe relatively mild temperatures employed during pelleting. Compared to corn, wheat is alsovery low in levels of available biotin. Whereasit is sometimes difficult to induce signs of biotindeficiency in birds fed corn diets devoid of synthetic biotin, problems soon develop if wheatis the major cereal. While newly hatched chickshave liver biotin levels of around 3,000 ng/g, thisnumber declines to 600 ng/g within 14 d in thewheat fed bird. Adding just 50 µg biotin/kg dietalmost doubles the liver biotin reserve, while adding300 µg/kg brings levels back to that seen in theday-old chick. There is also concern that wheatcauses a higher incidence of necrotic enteritisin broiler chicks. It seems as though wheatprovides a more suitable medium for the pro-liferation of certain pathogenic bacteria. The problem is most severe when wheat is finelyground, and incidence of necrotic enteritis canbe tempered by grinding wheat through a rollermill rather than a hammer mill. Fine grindingof wheat can also cause beak impaction inyoung birds. The proteins in wheat tend to be‘sticky’, and so adhere to the beak and mouth lining of the bird. Severe beak impaction tendsto reduce feeding activity, increase feed deposited in open bell drinkers, and provides a medium in the mouth region that is ideal for bacterial and fungal growth. These problems canbe resolved by coarse grinding of wheat.

Using wheat in diets for meat birds does however improve pellet durability. The same proteins that enhance the baking characteristicsof hard wheats, also help to bind ingredients during pelleting. Adding � 25% wheat to adiet has the same effect as including a pellet binderin diets that are difficult to pellet.



17INGREDIENT EVALUATION AND DIET FORMULATION

One advantage of wheat, is that it can be fed aswhole grain to birds after 10 – 14 d of age.Offering whole wheat and a balancer feed withadequate minerals and vitamins provides a veryeconomical way for farmers to utilize home-grownwheat. In recent studies we offered broilers a conventional three diet program, or after 7 d ofage, a choice between whole wheat and crumbled broiler starter through to 49 d. From7 – 21 d, male broilers voluntarily consumed about15% of their ration as wheat, while from 21 – 35d and 35 – 49 d this increased to 34% and41% respectively. Table 2.3 shows performancedata of these birds. Body weight was onlyslightly depressed, although carcass weight wassignificantly reduced and breast yield wasreduced by about 10%. The free-choice wheatsystem did however show a saving of 10% in feedcost per kg liveweight gain although feed costper kg of breast meat was not different. Anotheradvantage claimed for feeding whole wheat to

broilers is greater control over coccidiosis.Whole wheat feeding stimulates gizzard and gastric motility and the enhanced activity within this acidic environment is thought toreduce oocyte viability.

Potential Problems:

Wheats contain variable quantities of xylan,which is poorly digested and results in wet viscous excreta together with poor digestibility.As detailed in section 2.3g, this problem can beovercome by using synthetic xylanase enzymes.Feeding much more than 30% wheat can leadto beak/mouth impaction that can reduce feed-ing activity. Such material building-up in the mouthcan be a site for mold and mycotoxin develop-ment. This problem can be resolved by grindingwheat more coarsely. With wheat as the majorcereal, there is need for greater levels of sup-plemental biotin, since biotin availability inwheat has been reported to be as low as 0 – 15%.

Diet Body Wt Feed:Gain Protein Energy Carcass Wt49d (g) Intake Intake (g)

(g/kg Bwt) (kcal/kg Bwt)Control 3030 1.93 370 6044 2230b

Free-choice wheat 2920 1.99 364 6106 2135a

Table 2.3 Broiler performance with free-choice wheat

Adapted from Leeson and Caston, 1993



Dry Matter 87.0 Methionine 0.20Crude Protein 12 - 15 Methionine + Cystine 0.41Metabolizable Energy: Lysine 0.49




kg/m3 lb/ft3 lb/bushelWhole kernels #2 738 46 57

Feed grade 645 41 50

Ground wheat 530 33 42

Bulk Density:

Bird age Min. Max. Comments0-4 wk 15% 20 (40)1% Minimum constraint used if improved pellet

quality desired.4-18 wk 15% 25 (50)%

Adult layer 15% 25 (60)% Maximum value in parenthesis if a synthetic xylanase used.


1 Higher inclusion level with enzymes.


All deliveries Wkly 6 mos 12 mos 12 mos Xylan, AME each 12 mos1

QA Schedule:

1 Assay to be conducted within 30 d of yearly harvest.



3. MiloOther Names: sorghum, kaffir corn

Nutritional Characteristics:In many characteristics, milo is almost com-

parable to corn in feeding value. There seem tobe more varietal differences with sorghum,although on average, its energy value will be slight-ly less than that of corn. For those not wantingany marked degree of pigmentation of eggs orskin, milo offers the best high energy alternativeto corn.

The feeding value of milo is essentially 95 – 96%that of corn, although in many markets it ispriced at less than this. The starch in milo is intimately associated with the protein, and thisleads to slightly reduced digestibility, especiallyin the absence of any heat processing. Themajor concern with milo, is the content of tannins, which are a group of polyphenols having the property of combining with variousproteins. Birds fed tannins therefore exhibitreduced growth rate and in some instancesincreased incidence and severity of skeletaldisorders. Hydrolyzable tannins are charac-terized by having a gallic acid unit combined byester linkages to a central glucose moiety.Condensed tannins on the other hand are basedon flavan-3-ols (catechin). Because tannins inmilo are essentially condensed tannins, studiesinvolving tannic acid (hydrolyzable) as a sourceof tannin may be of questionable value. The tan-nins are located in the outer seed coat and theunderlying testa layer. Generally, the darker theseed coat, the higher the tannin content, althoughthe tannins in the testa layer may be more indica-tive of general tannin content in the milo.

So-called bird resistant milos are usuallyvery high in tannin, and are characterized by adarker seed coat color. These higher levels of tannin can result in up to 10% reduction ofdry matter and amino acid digestibility. Thereis a good correlation between tannin content andAMEn, and as a generalization the following formula can be used:

AMEn = 3900 – 500 (% tannin), kcal/kg.

Tannins are most detrimental when fed toyoung birds, and especially when protein content of the diet is marginal. For example, it isusually recommended that milo with more than1% tannin not be used for turkeys under 8 weeksof age. The relationship between tannins and dietprotein or amino acids is not clear. Certainly feed-ing more protein or higher levels of certain aminoacids seems to temper any growth retardation. Thefact that methionine supplementation can over-come detrimental effects of tannins on growth rate,without alleviating problems with digestibility, sug-gests that birds can compensate for inferiordigestibility by increasing their feed intake.Tannins also seem to increase the incidence of legproblems, especially in broiler chickens. The exactmechanism is unknown, although because bone mineral content is little affected, it is assumed torelate to derangement in the development of theorganic matrix, especially in the region of the growthplate. There seems no advantage to increasing sup-plemental levels of any minerals or vitaminswhen high-tannin milos are necessarily used.



Various mechanisms have been tried toreduce the level or effect of tannins in milo.Unfortunately, most of these processes involvewet chemical treatment, which although quitesimple, are expensive when re-drying of themilo is considered. Water treatment (25% withpropionic acid for 10 d) has been shown toimprove protein and energy availability by up to10%. Alkali treatment seems the most effectivemeans of reducing tannin levels, and productssuch as potassium and sodium hydroxide haveboth been used. Adding non-ionic polymers, such

as polyethylene glycol also seems to be beneficial,while the problem of impaired bone developmentcan be partially corrected by adding up to 0.8%available phosphorus to the diet of young birds.

Potential Problems:

The major potential problem is tannin con-tent and so this antinutrient should be assayedroutinely. As described in section 2.2 j, seed coatcolor of milo can be used to give an indicationof tannin content.





kg/m3 lb/ft3 lb/bushelWhole seed 560 35.0 44.8

Ground seed 545 34.0 43.5

Bulk Density:



4. BarleyNutritional Characteristics:

Barley is a cereal with medium content of bothenergy and protein, and while it can be used inpoultry feeds, most is used in swine diets. Youngbirds are less able to digest barley, althoughthis may be a consequence of ß-glucan content,and so this effect may relate to variety andgrowing conditions. The protein content ofbarley is usually around 11 – 12%, although muchhigher levels to 14 – 16% are sometimes encoun-tered. These high-protein varieties are oftenlittle changed in content of essential aminoacids. The lysine content of barley, within therange of 10 – 14% CP, is described by the equa-tion 0.13 +0.024 x %CP. The metabolizable ener-gy level of barley is correlated with bulk densi-ty, and there is a strong negative correlationwith fiber.

Barley contains moderate levels of trypsininhibitor, whose mode of action relates to seques-tering of arginine, although by far the majorproblem with barley is content of ß-glucan.

Most varieties of barley will contain 4 – 7% ß-glucan, although with dry growing conditions that involve rapid maturation and earlyharvest, the content can increase to 12 – 15%.As previously described for wheat, the mainproblem of these ß-glucans is the bird’s inabilityto digest the structure, resulting in the formationof a more viscous digesta. This increased viscosityslows the rate of mixing with digestive enzymesand also adversely affects the transport of digest-ed nutrients to the absorptive mucosal surface.The rate of diffusion to the intestinal microvilliis a function of the thickness of the unstirred bound-ary layer, and this increases with increaseddigesta viscosity. Motility of the digesta will alsoindirectly affect the thickness of the unstirredboundary layer, which will also affect rate of absorp-tion of all nutrients. The adverse effect of ß-glucanis most pronounced with nutrients such as fatsand fat-soluble compounds. Adding syntheticß-glucanase enzymes to diets containing morethan 15 – 20% barley seems to resolve many of

Bird age Min. Max. Comments0-4 wk - 40% Maximum inclusion level necessarily reduced with 4-18 wk - 50% high tannin samples, especially for young birds (20% max).Adult layer - 40%



Tannin, AME – each 12 mos or more All deliveries Wkly 6 mos 12 mos 12 mos often if seed color variable.

AME after harvest.

QA Schedule:



these problems, the usual outward sign of whichis wet litter. Unfortunately, the description of exogenous enzymes is not standardized, as neither is the standard for units of efficacy, andso it is often difficult to compare products on thebasis of the concentration of specific enzymes.Early studies show that any product should provide at least 120 units ß-glucanase/kg diet.

Enzymes seem to be less efficacious as thebirds get older. Our studies show slight improve-ment in energy value of high ß-glucan barley whenenzymes are used in diets for adult birds, and thatsome enzymes actually cause reduction in energyvalue when used with low ß-glucan barley.With this low ß-glucan barley, the addition of ß-glucanase enzymes actually caused birds tobe in severe negative nitrogen balance for the 3d duration of the balance study. For younger birdshowever, the efficacy of ß-glucanase enzymesis well established and many nutritionists consider barley plus enzymes as being equiva-lent in feeding value to wheat. These values canbe used as a basis for economic evaluation of

enzymes. While ß-glucans are most oftenregarded as being problematic to birds, there seemsto be one advantage to their inclusion in the diet.Feeding ß-glucans reduces blood cholesterol inbirds, and this likely positive effect is reversed byuse of synthetic ß-glucanases. The mode ofaction of ß-glucans may well be simply viasequestering of fats and bile acids in the digesta.

Barley can be used in choice-feeding studies, as previously described for wheat. Dueto the physical structure of the kernel however,with its sharp spinets, birds are often reluctantto consume whole barley grain. Turkeys atleast seem to readily eat whole barley in achoice-feeding situation after 50 d of age.

Potential Problems:

The moderate level of energy usually limitsthe inclusion of barley in most poultry diets.Additionally, the level of ß-glucan can be problematic in terms of poor performance andwet litter/manure. Synthetic enzymes can be usedto overcome most of the problems.

Dry Matter 85.0 Methionine 0.21

Crude Protein 11.5 Methionine + Cystine 0.42

Metabolizable Energy: Lysine 0.39

(kcal/kg) 2780 Tryptophan 0.19

(MJ/kg) 11.63 Threonine 0.40

Calcium 0.10 Arginine 0.51

Av. Phosphorus 0.20 Dig Methionine 0.16

Sodium 0.08 Dig Meth + Cys 0.32

Chloride 0.18 Dig Lysine 0.31

Potassium 0.48 Dig Tryptophan 0.15

Selenium (ppm) 0.30 Dig Threonine 0.29

Fat 2.10 Dig Arginine 0.41

Linoleic acid 0.80

Crude Fiber 7.50




5. RiceNutritional Characteristics:

Almost without exception, rice is grown forhuman consumption, although periodically inrice growing areas, samples unfit for humanconsumption, or damaged samples are availablefor animal feeding. Rice is a relatively poor qual-ity ingredient for poultry, containing only 7 – 8% CP and providing just 2600 – 2700 kcalME/kg. Rice does contain high levels of trypsininhibitor that will be destroyed at normal pelletingtemperatures. As detailed in the next section on

cereal by-products, rice bran and rice polishingsare more commonly used in poultry feeds thanis rice grain itself.

Potential Problems:

Because most feed sources will have been graded as unfit for human consumption, then thereason for rejection should be ascertained.Mold growth and mycotoxin (aflatoxin) contamination are often the basis for such grading.

kg/m3 lb/ft3 lb/bushelWhole barley 674 42 53.8

Ground barley 417 26 33.3

Bird age Min. Max. Comments0-4 wk - 10 (30)%1 ß-glucan content usually 4-18 wk - 15 (40)% dictates maximum inclusion level Adult layer - 15 (30)%

Bulk Density:


1 with ß-glucanase enzyme


All deliveries Wkly 6 mos 12 mos 12 mos AMEn1 12 mos; ß-glucan, bulkdensity-monthly since correlateswith AME

QA Schedule:

1 within 30 d of yearly harvest.







kg/m3 lb/ft3 lb/bushelWhole kernels 722 45 57.6

Ground rice 626 39 49.9

Bulk Density:


QA Schedule:

Bird age Min. Max. Comments0-4 wk - 15% Maximum constraints due to low energy.4-18 wk - 25%Adult layer - 20%

Moisture CP Fat Ca/P AA’s OtherAll deliveries 1 mos 1 mos 12 mos 12 mos AME1

1 within 30 d of yearly harvest.



During the processes of cleaning wheat andsubsequent manufacture of flour, up to 40%by weight is classified as by-product material. Thereis considerable variation in the classificationand description of these by-products, and greatcare must be taken when formulating withwheat by-products in different countries.Traditionally there were three major by-products,namely wheat bran, wheat shorts and wheat mid-dlings. Bran is the outer husk, and so is very highin fiber and rarely used in poultry diets.Unfortunately, in many countries the term wheatbran is used to describe wheat middlings. A checkon crude fiber level of wheat by-products isnecessary to ensure correct terminology. The finermaterial removed during bran extraction, was tra-ditionally termed wheat shorts. As wheat isground through a series of grinders of decreas-ing size, middlings are produced, most of whichis extracted as flour. Wheat middlings are the majorby-product from the final extraction of flour.

In the U.S.A., the term red-dog was sometimesused to describe the very fine material extract-ed from ‘red’ wheats, and was similar to shorts.Today most by-products are combined at the flourmills, and commonly called wheat shorts. Theonly other by-product produced in reasonablequantity is wheat screenings, which as its nameimplies, is material removed during initial clean-ing and separation. If screenings are composedmainly of broken wheat kernels, then their nutri-tive value is little different to wheat.

Wheat by-products such as shorts can containvery high levels of ‘natural’ phytase enzyme. Whenmore than 15% shorts are used in a diet thisendogenous enzyme can be greater than levelsof commercial phytase added to the diet, and soinfluence assay results. While endogenous phytase levels are high, it is questionable if thisenzyme is beneficial to the bird at the pH of theproventriculus or small intestine.

Wheat shorts: Shorts are the major by-prod-uct of flour manufacture and since they are usu-ally a composite of various fractions, nutrient pro-file can be variable. The major difference willbe in the quantity of bran included in the mate-rial, and so this directly influences its energy value.If wheat shorts contain much more than 5% crudefiber, it is an indication of a greater proportionof bran-type residues. Dale (1996) suggeststhat the metabolizable energy value of wheat by-product is directly proportional to its fiber content, and that ME can be described as:

3182 – 161 x % crude fiber (kcal/kg)

With an average fiber value of 5%, ME isaround 2370 kcal/kg. However, it is commonto see a range of 3 to 10% CF depending uponflour manufacturing procedures, which equatesto a range of ME values of from 1570 to 2700kcal/kg. Measuring crude fiber level of wheatby-products is obviously important in quality assurance programs. As described previously withwheat, most by-products will contain xylan,

6. Wheat by-productsOther Names: wheat shorts, wheat middlings, wheat bran, wheat millrun,wheat screenings




and so xylanase enzyme is advisable if inclusionlevels are >15% for young birds or > 30% for birdsafter 4 weeks of age.

Wheat bran:The main characteristics are highfiber, low bulk density and low metabolizableenergy. Bran is however, quite high in protein,and amino acid profile is comparable to that seenin whole wheat. Bran has been claimed to havea growth promoting effect for birds which is notdirectly related to any contribution of fiber to thediet. Such growth promotion is possibly derivedfrom modification of the gut microflora. The energy value of bran may be improved by up to10% by simple steam pelleting, while the avail-ability of phosphorus is increased by up to 20%under similar conditions. Bran would only beconsidered where limits to growth rate arerequired, and where physical feed intake is nota problem. High bran diets promote excessivemanure wetness, and transportation costs ofbran diets are increased in proportion to thereduced bulk density of the diet.

Wheat screenings: Wheat screenings are aby-product of the cleaning and grading of wheatthat itself is usually destined for human consumption. The product is therefore availablein most countries that have significant wheat production. In addition to broken and cracked

wheat kernels, screenings will also contain wildoats and buckwheat as well as weed seeds andother contaminants. The higher grades (#1 or #2)contain significant proportions of wheat, and sotheir nutrient profile is very similar to that of wheat.The weed seeds, depending upon variety, maybe of some nutritional value. Since certainweed seeds produce a feed-refusal type reactionin layers, only the highest grades should beconsidered for high producing stock. The weedseeds can pose problems to arable farms that usemanure from birds fed coarsely ground diets containing screenings, since some of the weedseeds can pass undamaged through the digestive tract. The level of screenings used infinisher diets of meat birds should also be severely limited, since breakage of the gut dur-ing processing leads to fine particles of black weedseeds adhering to the fat pads of the bird – such birds are easily recognized and often condemned due to fecal contamination. Number1 and 2 grade screenings can be used up to 40%of the diet for broilers and layers.

Potential Problems:

The fiber content will directly influenceenergy value. With wheat screenings there willlikely be some weed seeds present, and these maycause feed refusal.



Shorts Screening Bran Shorts Screenings BranDry Matter 90 90 90 Methionine 0.21 0.21 0.10Crude Protein 15 15 16 Meth + Cyst 0.40 0.42 0.20Metabolizable Energy: Lysine 0.61 0.53 0.60

(kcal/kg) 2200 3000 1580 Tryptophan 0.21 0.20 0.31(MJ/kg) 9.20 12.55 6.61 Threonine 0.50 0.42 0.34

Calcium 0.07 0.05 0.10 Arginine 0.80 0.60 0.85Av. Phosphorus 0.30 0.20 0.65Sodium 0.07 0.08 0.06 Dig Methionine 0.16 0.15 0.08Chloride 0.10 0.05 0.20 Dig Meth + Cys 0.30 0.32 0.15Potassium 0.84 0.55 1.20 Dig Lysine 0.48 0.39 0.42Selenium (ppm) 0.80 0.57 0.92 Dig Tryptophan 0.15 0.15 0.24Fat 4.0 4.1 4.5 Dig Threonine 0.41 0.31 0.28Linoleic acid 1.6 0.7 1.7 Dig Arginine 0.71 0.52 0.79Crude Fiber 5.0 3.0 12.0

kg/m3 lb/ft3 lb/bushelWheat bran 193 12 15.4Wheat shorts 480 30 38.4Wheat screenings 740 46 58.9

Bird age Min. Max. CommentsShorts, and 0-4 wk 10% 20%Minimum if pellet durability an issueScreenings 4-18 wk 30%

Adult layer 30%Bran 4 wk+ 10% Energy will be the limiting factor


All deliveries Wkly 6 mos 12 mos 12 mos Crude fiber on all deliveries. AMEn yearly


Bulk Density:


QA Schedule:



Bakery meal is a by-product from a range offood processing industries. In order to ensure con-sistent composition, individual products must beblended or the supplier large enough to provideadequate quantities from a single manufactur-ing process. The most common by-products comefrom bread and pasta manufacture, as well as cook-ies and snack foods. By-products from snack foodscan be quite high in salt and fat. Bakery mealis often derived from pre-cooked products andso digestibility is often higher than for the orig-inal starch components.

Fillers are sometimes used to improve flowcharacteristics of high-fat bakery meals. The most-common fillers are soybean hulls and limestonewhich influence nutritive value accordingly.The metabolizable energy value of bakery mealcan be described as:

4000–(100x% fiber + 25 x % ash) kcal/kg with4% fiber and 3% ash, ME becomes 3525 kcal/kg

Potential Problems:

Quality control programs must ensure consistent levels of sodium, fiber and ash.





Bulk Density:

kg/m3 lb/ft3 lb/bushel353 22.0 28.0

7. Bakery mealOther Names: Cookie meal, bread meal Nutritional Characteristics:



Rice by-products are the result of dehullingand cleaning of brown rice, necessary for the pro-duction of white rice as a human food. Rice by-products are one of the most common cereal by-products available to the feed industry, withworld production estimated at around 45 mtonnes. The by-product of preparing white rice,yields a product called rice bran, which itself iscomposed of about 30% by weight of rice pol-ishings and 70% true bran. In some regions, thetwo products are separated, being termed pol-ishings and bran. Alternatively, the mixture is some-times called rice bran, whereas in other areas themixture may be called rice pollards. The polishingsare very high in fat content and low in fiber whilethe true bran is low in fat and high in fiber. Theproportions of polishings and true bran in amixed product will therefore have a major effecton its nutritive value. In the following discussion,rice bran refers to the mixture of polishings andbran. The composition of any sample of mixedrice bran can be calculated based on levels offat vs fiber.

Because of a high oil content (6 – 10%)rice bran is very susceptible to oxidative rancidity.Raw bran held at moderate temperatures for10 – 12 weeks can be expected to contain 75 – 80%of its fat as free fatty acids, which are themselvesmore prone to rancidity. Rice bran should be stabilized with products such as ethoxyquin.Higher levels of ethoxyquin give greater protectionagainst rancidity although economical levelsappear to be around 250 ppm. Rice bran canalso be stabilized by heat treatment. Extrusionat 130ºC greatly reduces chances of rancidity, andof the development of free fatty acids.

When high levels of raw rice bran are used(�40%) there is often growth depression and reduc-tion in feed efficiency, likely associated with thepresence of trypsin inhibitor and high levels ofphytic acid. The trypsin inhibitor, which seemsto be a relatively low molecular weight structure,is destroyed by moist heat, although phytic acidis immune to this process. The phosphoruscontent of rice bran is assumed to be only 10%

Bird age Min. Max. Comments0-4 wk 10% Concern over sodium content4-18 wk 15%Adult layer 15%


All deliveries 1 mos 1 mos 6 mos 12 mos Na content of all samples if snack foods part of bakery meal


QA Schedule:

8. Rice by-productsOther Names: Rice bran, rice polishings, rice pollards Nutritional Characteristics:



available for very young birds. However, phos-phorus availability may increase with age, andif this happens, it could create an imbalance ofcalcium:phosphorus. This latter effect is suggestedas the reason for improved growth response inolder birds fed rice bran when extra calcium isadded to the diet. Phytase enzyme can be usedto advantage in diets containing > 15% ricebran. Because of the potential for high fiber con

tent, use of rice bran may be improved withaddition of exogenous arabinoxylanase enzymes.

Potential Problems:

Rice bran should be stabilized with anantioxidant if storage at the mill is to be longerthan a few weeks. Heating is advisable if youngbirds (< 3 weeks) are fed > 10% rice bran, to limitadverse effects of trypsin inhibitor.

Bran Polishing Bran PolishingDry Matter 90.0 90.0 Methionine 0.29 0.21Crude Protein 13.0 11.0 Methionine + Cystine 0.30 0.52Metabolizable Energy: Lysine 0.51 0.50

(kcal/kg) 1900 2750 Tryptophan 0.18 0.12(MJ/kg) 7.95 11.52 Threonine 0.38 0.32

Calcium 0.06 0.06 Arginine 0.52 0.61Av. Phosphorus 0.80 0.18Sodium 0.10 0.10 Dig Methionine 0.15 0.16Chloride 0.17 0.17 Dig Meth + Cys 0.22 0.24Potassium 1.30 1.17 Dig Lysine 0.39 0.41Selenium (ppm) 0.19 0.17 Dig Tryptophan 0.13 0.08Fat 5.0 15.0 Dig Threonine 0.28 0.25Linoleic acid 3.4 6.2 Dig Arginine 0.40 0.48Crude Fiber 12.0 2.5

kg/m3 lb/ft3 lb/bushelRice bran 417 26 33Rice polishings 480 30 38

Bird age Min. Max. Comments0-4 wk 10% Fat rancidity the major concern4-8 wk 20% High phytate contentAdult 25%


Bulk Density:




Soybean meal has become the worldwide standard against which other protein sources arecompared. Its amino acid profile is excellent formost types of poultry, and when combined withcorn or sorghum, methionine is usually theonly limiting amino acid.

The protein level in soybean meal can be variable, and this may be a reflection of seed variety and/or processing conditions involved infat extraction. Traditionally the higher proteinmeals are produced from de-hulled beans,whereas the lower protein (44% CP) mealsinvariably contain the seed hulls, and are high-er in fiber and lower in metabolizable energy.There is some variation in seed type used and thiscan affect protein and fat content, which are negatively correlated. Whereas fat content of theseed is dictated early in seed development,protein is deposited through to the end of maturity, and therefore growing and harvestingconditions tend to have more of an effect on protein content of the seed. For soybean processors, about 65% of the value of soybeansis attributed to their protein content, and 35%to the oil. In recent years, there have been a number of ‘new’ varieties introduced, and someof these are produced by genetic engineering.At this time (2004) there are no new GMO

products modified in terms of enhanced nutrient profile or reduced anti-nutritional content. Current GMO soybeans are modifiedfor agronomic reasons, and there is no indicationthat they have different feeding value. In the future,there seems great potential for reduction in con-tent of anti-nutrients within GMO soybeans.

Soybeans have to be heat-treated in order toinactivate various anti-nutrients. During processing,soybeans are dehulled (about 4% by weight) andthen cracked prior to conditioning at 70ºC. Thehot cracked beans are then flaked to about 0.25mm thickness to enhance oil extraction by a sol-vent, which is usually hexane. Hexane must beremoved from the meal because it is a highlycombustible material and a potent carcinogen.Problems occurring during processing that resultin residual hexane in the meal are usuallynoticed by severe and sudden liver failure in birds.Soybean meals tend to be very dusty, and in mashdiets, soy is responsible for some of the dust foundin controlled environment poultry houses.Soybean meal is also notorious for its poor flowcharacteristics and for bridging in storage bins.Addition of products such as bentonite clays, evenat levels as low as 2.5 kg/tonne, can greatly improvethe flow characteristics of soybean meal.


All deliveries monthly All deliveries 6 mos 12 mos Fiber for all deliveries

QA Schedule:

9. Soybean mealOther Names: High protein SBM Nutritional Characteristics:



Soybeans contain a number of natural toxinsfor poultry, the most problematic being trypsininhibitor. As with most types of beans, thetrypsin inhibitors will disrupt protein digestion,and their presence is characterized by compensatory hypertrophy of the pancreas.Apart from reduced growth rate and egg production, presence of inhibitors is therefore diagnosed by a 50-100% increase in size of thepancreas. Fortunately, the heat treatmentemployed during processing is usually adequate to destroy trypsin inhibitors and otherless important toxins such as hemaglutinins(lectins). In developing countries, trypsininhibitor levels are sometimes controlled by fermentation or germinating beans, where after48 hrs of treatment, protein digestibility is almostequivalent to that seen in conventionally heatedbeans. Trypsin inhibitor levels are usually‘assayed’ indirectly by measuring urease activityin processed soybean meal. Urease is of littleconsequence to the bird, although the heat-sensitivity characteristics of urease are similar tothose of trypsin inhibitors, and urease levelsare much easier to measure. Residual urease insoybean meal has therefore become the standardin quality control programs. Urease is assessedin terms of change in pH during the assay,where acceptance values range between 0.05 and0.15. Higher values mean there is still residualurease (trypsin inhibitor) and so the test is useful to indicate undercooked meal. However,while low values mean that the proteases havebeen destroyed, there is no indication of potential overcooking, which can destroy lysineand reduce ME value. For this reason other testsare sometimes used. A fairly easy test to accom-plish is protein solubility in potassium hydroxide.Dale and co-workers at the University of Georgiahave shown a good correlation between theamount of protein soluble in 2% KOH, and

chick growth, determined in a bioassay. Heatingtends to make the protein less soluble, and so highvalues suggest undercooking, while low values meanovercooking. Values of �85% solubility indicateunder-processing and � 70% mean the samplehas been over-processed. The assay is influencedby particle size of soybean meal and time of reaction, and so these must be standardizedwithin a laboratory. As soybean meal is heated,its color changes and again this can be used inquality control programs. Simply measuring colorin a Hunterlab Color Spectrophotometer can indicate degree of cooking. Degrees of ‘lightness’,‘redness’ and ‘yellowness’ can be measuredsince these change with cooking temperature andtime. Again it is important to control particle sizeduring this assay.

Discussion about soybean meal qualityinvariably involves the significance of trypsininhibitor relative to other antinutrients. It isoften claimed that only about 50% of the growthdepression resulting from consumption of under-heated soybean meal is due to active trypsininhibitor. The other antinutrients of importanceare isoflavones, lectins and oligosaccharides.Lectins are antinutritional glycoproteins thatbind to the intestinal epithelium resulting inimpaired brush border function. Such ‘thickening’of the epithelium results in reduced efficiencyof absorption. There are strains of soybeansthat contain no lectins, and so studying their feed-ing value provides some information on impor-tance or not of lectins. Feeding uncookedlectin-free soybean meal produces greater broiler growth than does feeding regular uncookedsoybean. However, the growth is still less thanusing trypsin inhibitor-free soybeans. Thesedata support the concept that lectins are muchless important than are trypsin inhibitors inassessing nutritive value of soybean meal.



While undercooking of soybean meal is themost common result of incorrect processing, over-heating sometimes occurs. It seems as thoughlysine availability is most affected by over-cooking of soybeans, since addition of other aminoacids rarely corrects growth depression seenin birds fed such meals. When soybeans are over-cooked, KOH protein solubility declines. Usingdata from Dale and co-workers, it seems asthough problems of using overheated soybeanmeal can be resolved by adding 0.5 kg L-LysineHCl/tonne feed for each 10% reduction in protein solubility below a value of 70%.

Over the last few years there has been growing concern about some of the less digestiblecarbohydrates in soybean meal. The -galacto-side family of oligosaccharides cause a reduc-tion in metabolizable energy with reduced fiber digestion and quicker digesta transit time. Birdsdo not have an -1:6 galactosidase enzyme in theintestinal mucosa. Apart from reduced digestibil-ity, there is concern about the consistency of excreta and its involvement in foot-pad lesions in both young turkeys and broilerbreeders. Soybean meal usually contains about6% sucrose, 1% raffinose and 5% stachyose, allof which are poorly digested by the bird. Adding

raffinose and stachyose to isolated soybean protein to mimic levels seen in soybean meal,causes a significant reduction in metabolizableenergy. These problems limit the diet inclusionlevel of soybean meal, especially in turkeyprestarters. The solution to the problem relatesto change in soybean processing conditions oruse of exogenous feed enzymes. Extractingsoybeans with ethanol, rather than hexane,removes most of the oligosaccharides. Themetabolizable energy value of soybean mealextracted from low oligosaccharide varieties ofsoybeans is increased by about 200 kcal/kg.There are now some galactosidase enzyme products available which are designed specifically to aid digestion of vegetable proteinsand presumably these help in digestion of products such as raffinose and stachyose.

Potential Problems:

In most feeding situations, the main concernis usually processing conditions and knowl-edge of urease index or protein solubility.Soybean meal is also very high in potassium. Inregions where animal proteins are not used,then necessarily high levels of soybean meal canlead to enteritis, wet litter, and food pad lesions.






kg/m3 lb/ft3 lb/bushel640 40 51.5

Bulk Density:



QA Schedule:

Bird age Min. Max. Comments0-4 wk 30% Higher levels may lead to wet litter due to high K intake4-8 wk 30%Adult 30%


All deliveries All deliveries 6 mos 12 mos 12 mos Urease or KOH solubility each 6 mos, AMEn each 12 mos



10. SoybeansOther Names: Full-fat soybeans

Nutritional Characteristics:Soybeans provide an excellent source of

both energy and protein for poultry. As with anyingredient, their usage rate depends upon economics, although in the case of soybeans sucheconomics relate to the relative price of soybean meal and of supplemental fats. Soybeanscontain about 38% crude protein, and around20% oil.

Comparable to the manufacture of soybeanmeal, soybeans must be heat processed in someway to destroy the trypsin inhibitors and toimprove overall protein digestibility. Feeding rawsoybeans or improperly processed soybeanswill cause poor growth rate or reduced eggproduction and egg size. If processing conditionsare suspect, the birds’ pancreas should be examined, because if trypsin inhibitors are stillpresent pancreas size can be expected to increaseby 50-100%. While processed beans should beperiodically tested for trypsin inhibitor or ureaselevels, a simple on-going test is to taste thebeans. Under-heated beans have a character-istic ‘nutty’ taste, while over-heated beans havea much darker color and a burnt taste. Theproblem with overheating is potential destruc-tion of lysine and other heat-sensitive amino acids.

Heat-treated soybeans can be easily groundin a hammer mill, even though they are high infat, and the ground product is a relatively free-flowing material. Because of the high oil content, ground beans should not be stored forany length of time due to potential for oxidativerancidity. However, it is important that beans be

well ground because it is necessary to release fatfrom the plant cells in order to aid digestion.Coarsely ground beans have lower fat digestibil-ity than do more finely ground material. Heatingbeans by whatever means usually results inconsiderable ‘shrinkage’ which is mainly due toloss of water. In many situations, shrinkagewill be up to 7%, but of this, less than 1% willbe real loss of dry matter.

Recently there has been growing interestin processing beans through extruders orexpanders. The heat necessary to destroy trypsininhibitors and other hemagglutinins found in rawbeans is dependent upon exposure time, and sohigh temperatures for a shorter time period areas effective as lower temperatures for longertimes. Because both expanders and extrudersare fast throughput, the beans have a relativelyshort dwell time in the conditioning chamber.Consequently, slightly higher temperatures arenecessary, and depending upon design, suchmachines are best operated at 140-155ºC.Again, the effectiveness of expanding and extrusion can be measured by tests for urease andavailable lysine content.

Potential Problems:

Under-heating of soybeans is detected as ahigh urease or KOH protein solubility. If broilerfinisher diets contain > 30% soybeans, thentheir body fat will become less saturated and moreprone to oxidative rancidity. This latter problemcan be resolved to some extent by using higherlevels of vitamin E (75-100 IU/kg).







Bulk Density:


QA Schedule:

kg/m3 lb/ft3 lb/bushel

750 47 60

Bird age Min. Max. Comments

0-4 wk 15 In broiler finisher diets, > 30% may cause ‘oily’ fat depots.

4-8 wk 20Adult 30


All deliveries 1 mos 1 mos 6 mos 12 mos Monthly analyses for urease or KOH solubility



11. Canola mealNutritional Characteristics:

Canola is a widely grown crop in westernCanada and production is increasing in other partsof the world. Production has been influencedby the marked increase in the demand forcanola oil as well as the ability of this highprotein oilseed to grow in northern climateswhere the short growing season is not suitablefor the production of soybeans.

While canola was derived from varieties ofrapeseed, its composition has been alteredthrough genetic selection. The level of goitrogensand erucic acid, two of the more detrimental con-stituents of the original rapeseed cultivars, havebeen markedly reduced. Erucic acid levels arenow negligible while goitrogen levels are downto less than 20 µg/g and these levels are lowenough to be of little or no problem to poultry.Varieties containing such levels of toxins are classified as canola and are often referred to as‘double zero varieties’.

Canola still has enough goitrogen activity toresult in measurable increases in thyroid weight,although this does not appear to be a problemaffecting the performance of poultry. The tanninlevels in canola can also be relatively high,with up to 3% for some cultivars. Again, researchhas shown that the canola tannins have little influence in the utilization of the protein indiets containing appreciable levels of the meal.

Canola meal also contains significant quantities (1.5%) of sinapine. While this compound poses no problem to most classes ofpoultry, a significant percent of brown egg layersproduce eggs with a fishy and offensive odourwhen fed canola sinapines. One of the end products of the degradation of sinapine in the intestinal tract is trimethylamine and it is this com-

pound, which is involved in the production offishy- flavored eggs. A small proportion oftoday’s brown egg laying birds lack the ability toproduce trimethylamine oxidase which effectivelybreaks down the compound and so the intacttrimethylamine is deposited into the egg. Even1% sinapine in canola can result in off-flavoredeggs. It should be pointed out that brown eggsproduced by broiler breeders, are not affectedby canola sinapines.

While canola meal has been accepted by thefeed industry as a high quality feedstuff forpoultry, there continues to be isolated reports ofincreased leg problems with broilers and turkeys,smaller egg size with layers and in some cases,reports of increased liver hemorrhages when dietscontain significant amounts of canola meal.There are several reports which suggest thatincreased leg problems resulting from feedingcanola may be due to its having a differentmineral balance than does soybean meal. Theaddition of dietary K, Na and in some cases Clhave, under certain conditions, altered birdperformance. Canola is also high in phyticacid and so there is speculation that the high levelof this compound may be sequestering zincand this affects bone development. The smalleregg size reported with canola meal diets seemsto be a direct result of lower feed intake. Canolameal levels should therefore be limited in dietsfor very young laying hens, or at least until feedintake plateaus at acceptable levels.

Within the past few years, there have beenreports suggesting that high levels of sulfur in canolameal may be responsible for some of the leg problems and reduced feed intake noted withcanola meal diets. Canola meal contains 1.4% sul-fur while soybean meal contains around 0.44%.



Up to 75% of the sulfur in soybean meal iscontributed by the sulfur amino acids com-pared to around only 20% for canola meal.High levels of dietary sulfur have been report-ed to complex intestinal calcium and lead toincreased calcium excretion. This could explainthe reports suggesting low availability of calci-um in canola meal, and so possibly contributeto more leg problems. While lower weightgain has periodically been reported with canoladiets, it is usually noted that feed:gain ratios arelittle affected. This situation suggests that the reduc-tion in gain was not the result of reduced nutrient availability but rather a direct effecton appetite, resulting in reduced feed intake.Recent work demonstrates quite clearly that a soy-bean meal diet containing the same level of sul-

fur as that in canola diets results in comparableweight gain and feed intake in young broilers (Table2.4). In this study, the unsupplemented canoladiet contained 0.46% sulfur while the soy dietcontained 0.14%. Adding sulfur to the soy-bean meal diet resulted in a decrease in weightgain. The level of sulfur in the unsupplementedcanola diet (0.46%) lies part way between thelevels found in the 0.26 and 0.39% sulfur sup-plemented soybean meal diet. Weight gain forthe unsupplemented canola meal diet was 424g while the average for the two soybean meal dietswas 426 g. Higher dietary calcium levels par-tially overcame the growth depressing effect ofhigh dietary sulfur thus demonstrating the neg-ative effect of sulfur on calcium retention.

Protein Suppl. S Total S Calcium Weight source (%) (%) level (%) gain (g)

- .46 .37 424Canola meal .26 .72 .37 371

- .46 1.32 560.26 .72 1.32 481- .14 .37 525

.13 .27 .37 519

.26 .40 .37 479

.39 .53 .37 373Soybean meal - .14 1.32 635

.13 .27 1.32 598

.26 .40 1.32 559

.39 .53 1.32 451

Table 2.4 Interaction of sulfur and calcium in canola andsoybean meal diets



In view of the reductions in appetite and cal-cium retention resulting from high dietary sul-fur levels, these need to be closely monitored ifsubstantial levels of canola meal are used. Highlevels of methionine or sulphate salts, alongwith ingredients with significant amounts ofsulfur, such as phosphate supplements, can addconsiderable sulfur to a diet. Some sources ofwater can also be high in sulfur. Broilers can tolerate dietary sulfur levels of up to around 0.5%without any effect on performance while layinghens can handle even higher levels. There arereports which suggest that part of the responseto increased levels of dietary sulfur is due to itsinfluence in dietary acid-base balance. WhileMongin, in his original work, suggested consideringNa, K, and Cl in the dietary acid-base balance

equation, S, being a strong anion, should also beconsidered in this equation if > 8% canolameal is used in poultry diets.

Potential Problems:

Canola meal contains less lysine than doessoybean meal but slightly more sulfur amino acidsper unit of dietary protein. It is also lower in energy than is soybean meal. Levels of up to 8%canola meal can be used in laying diets withoutany adverse effects on performance although egg size may be reduced by up to 1 g. Energycontent is the factor that usually limits inclusionlevel. Levels of toxic goitrogens should be assayedperiodically, together with tannins. Canola mealshould not be fed to brown egg layers.






625 39 50

Bulk Density:



12. Corn gluten mealNutritional Characteristics:

Corn gluten meal contains around 60% CPand is a by-product of wet milling of corn, mostof which is for manufacture of high-fructosecorn syrup. Being high in protein, it is often com-pared to animal protein ingredients during for-mulation. The protein is merely a concentrationof the original corn protein component broughtabout by removal of the starch in the endosperm.There are, in fact, two products often manufacturedduring wet milling, the alternate being corngluten feed which contains only 20% CP, due todilution with various hull material. In certainregions of the world, the two products are mere-ly called ‘corn gluten’ and so this must be dif-ferentiated based on protein content. Corn

gluten meal is very deficient in lysine, althoughwith appropriate use of synthetic lysine sources,the product is very attractive where high nutri-ent density is required. Gluten meal is alsovery high in xanthophylls pigments (up to 300mg/g) and is a very common ingredient wherethere is a need to pigment poultry products.

Potential Problems:

Periodically corn gluten feed (20% CP) is inad-vertently formulated as corn gluten meal (60%CP). Using much more than 10% corn glutenmeal will produce a visible increase in pigmen-tation of broilers and egg yolks.


0-4 wk 5% Potential problems with tannins,

4-8 wk 8% low energy and high sulfur.

Adult 8% Not for brown egg layers.


QA Schedule:

Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 12 mos 12 mos 12 mos Tannins, sulfur and goitrogens

each 6 mos.







Bulk Density:


QA Schedule:


578 36 46.1

Bird age Min. Max. Comments0-4 wk 15% Pigmentations increases with 4-8 wk 20% > 10% inclusion.8 wk+ 20%


All deliveries 3 mos 6 mos 6 mos 12 mos -



13. Cottonseed mealNutritional Characteristics:

Cottonseed meal is not usually consideredin diets for poultry, although for obvious economicreasons it is often used in cottonseed producingareas. A high fiber content and potential con-tamination with gossypol are the major causesfor concern. Gossypol is a yellow polyphenolicpigment found in the cottonseed ‘gland’. In mostmeals, the total gossypol content will be around1%, although of this, only about 0.1% will befree gossypol. The remaining bound gossypol isfairly inert, although binding can have occurredwith lysine during processing, making both thegossypol and the lysine unavailable to the bird.So-called ‘glandless’ varieties of cottonseed arevirtually free of gossypol.

Birds can tolerate fairly high levels of gossypol before there are general problemswith performance although at much lower levels there can be discoloration of the yolkand albumen in eggs. Characteristically thegossypol causes a green-brown-black discoloration in the yolk depending upon gossypol levels, and the duration of egg storage.As egg storage time increases, the discolorationintensifies, especially at cool temperatures (5ºC)where there is more rapid change in yolk pH.Gossypol does complex with iron, and thisactivity can be used to effectively detoxify the meal.Adding iron at a 1:1 ratio in relation to free

gossypol greatly increases the dietary inclusionrate possible in broiler diets and also the levelat which free gossypol becomes a problem withlaying hens. Because most cottonseed samplescontain around 0.1% free gossypol, detoxifica-tion can be accomplished by adding 0.5 kgferrous sulphate/tonne feed. With addition of iron,broilers can withstand up to 200 ppm freegossypol, and layers up to 30 ppm free gossypolwithout any adverse effects.

If cottonseed meal contains any residualoil, then cyclopropenoid fatty acids may contributeto egg discoloration. These fatty acids aredeposited in the vitelline membrane, and alterits permeability to iron that is normally found onlyin the yolk. This leached iron complexes withconalbumin in the albumen producing a characteristic pink color. Addition of iron saltsdoes not prevent this albumen discoloration, andthe only preventative measure is to use cottonseedmeals with very low residual fat content.

Potential Problems:

Yolk discoloration is the main concern, andso ideally, cottonseed meal should not be usedfor laying hens or breeders. The lysine in cotton-seed is particularly prone to destruction due tooverheating of meals during processing.



Dry Matter 90 Methionine 0.49Crude Protein 41.0 Methionine + Cystine 1.11Metabolizable Energy: Lysine 1.67




Bulk Density:


QA Schedule:


644 40.1 51.3


0-4 wk 10% Maximum levels dependent upon levels of free gossypol. Inadvisable for layers if alternative ingredients available.4-8 wk 15%

8-18 wk 20%18 wk+ 10%

Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 6 mos 12 mos 12 mos Gossypol 2-3 times each year



Dry Matter 90 Methionine 0.49Crude Protein 41.0 Methionine + Cystine 1.11Metabolizable Energy: Lysine 1.67




Bulk Density:


QA Schedule:


644 40.1 51.3


0-4 wk 10% Maximum levels dependent upon levels of free gossypol. Inadvisable for layers if alternative ingredients available.4-8 wk 15%

8-18 wk 20%18 wk+ 10%

Moisture CP Fat Ca/P AA’s OtherAll deliveries 6 mos 6 mos 12 mos 12 mos Gossypol 2-3 times each year



14. FlaxseedOther Names: Linseed

Nutritional Characteristics:Flax is grown essentially for its oil content,

although in Europe there is still some productionof special varieties for linen production. Fat-extracted flax, which is commonly called linseedmeal, has traditionally been used for ruminantfeeds. Over the last few years, there has beeninterest in feeding full-fat flaxseed to poultry,because of its contribution of linolenic acid. Flaxoil contains about 50% linolenic acid (18:3w3)which is the highest concentration of omega-3fatty acids within vegetable oils. It has recent-ly been shown that 18:3w3, and its desaturation products docosahexaenoic acid and eicos-apentaenoic acid are important in human health,and especially for those individuals at risk fromchronic heart disease. Government agencies inmany countries now recognize the importanceof linolenic acid in human health, suggesting theneed to increase average daily intake, and especially intake in relation to that of linoleic acid.

Feeding flaxseeds to poultry results in directincorporation of linolenic acid into poultrymeat and also into eggs. Feeding laying hens 10%flax results in a 10-fold increase in egg yolklinolenic acid content and eating two suchmodified eggs each day provides adults with mostof their daily recommended allowance oflinolenic acid. For each 1% of flaxseed addedto a layer diet, there will be a +40 mg increasein total omega-3 fatty acids per egg. Likewise,in broilers, each 1% flaxseed addition willincrease total omega-3 fats in the carcass by +2%of total fat. Feeding layers 8% flaxseed will resultin an egg with about 320 mg total omega-3fatty acids. For broiler chickens, there is no need

to feed flaxseed for the entire grow-out period.Feeding 10% flaxseed to broilers for only the last14 d of grow-out, results in significant incorporationof omega-3 fatty acids in the meat. With cookedbreast + skin there is an increase in omega-3 con-tent from 150 675 mg/100 g cooked product.

Linolenic acid enriched eggs and poultry meatare therefore an attractive alternative to con-sumption of oily fish. Linolenic acid is essentiallyresponsible for the characteristic smell of ‘fish oils’and undoubtedly flax oil does have a ‘paint-type’smell. There is some concern about the taste andsmell of linolenic acid-enriched poultry meat andthis topic needs more careful study with controlledtaste panel work. There is often discussionabout the need to grind flaxseed. The seeds arevery small, and for birds with an ‘immature’ gizzard it seems likely that some seeds willpass directly through the bird. Flaxseeds are quitedifficult to grind, and are usually mixed 50:50with ground corn before passing through ahammer mill. Perhaps the greatest benefit to grinding is seen with mash diets. Table 2.5shows digestible amino acid values, determinedwith adult roosters for whole and ground flaxseed.

These digestibility values were determinedusing the force-feeding method, and so the birdis fed only the flaxseed, which is a novel situation to the bird. Over time gizzard activity may increase and so digestibility ofwhole seeds may improve. Using a classical AMEnbioassay, we have shown a consistent increasein AMEn of flaxseed when diets are steam crumbled (Table 2.6).



Table 2.5 Amino acid digestibilityof flaxseed (%)

Flaxseed Whole Ground

Methionine 68 85Cystine 68 87Lysine 72 88Threonine 65 82Tryptophan 85 95Arginine 71 92Isoleucine 66 86Valine 65 84Leucine 67 87

Courtesy Novus Int.

Table 2.6 Effect of steam crumblingon AMEn of flaxseed (kcal/kg)Bird Type Mash Steam

Crumble �

Broiler chicken 3560 4580 +31%

Rooster 3650 4280 +17%

Laying hen 3330 4140 +24%Adapted from Gonzalez (2000) and Bean (2002)

These assays were conducted at differenttimes and with different samples of flaxseed. Inanother study there was an 18% improvementin AMEn for layers when flaxseed was extruded.Conventional pelleting seems sufficient to weaken the seed structure so as to allow greaterdigestibility of amino acids and energy.

With laying hens, there may be transitory problems with suddenly incorporating 8-10%flaxseed in the diet, usually manifested asreduced feed intake and/or wet sticky manure.

These problems can usually be overcome by gradual introduction of flaxseed, using for ex -ample, 4% for one week, followed by 6% foranother week and then the final 8-10% inclusion.It usually takes 15-20 d in order for omega-3 content of eggs to plateau at the desired level of300 mg/egg. With prolonged feeding there is oftengreater incidence of liver hemorrhage in layers,even though mortality is rarely affected. Suchhemorrhaging occurs even in the presence of 100-250 IU vitamin E/kg diet, which is a regular addition to flax-based diets. Disruptionto liver function may become problematic ifother stressors occur.

Potential Problems:

Flaxseed should be introduced graduallywhen feeding young layers. Weekly incrementsusing 4-6 and 8-10% over 3 weeks are ideal to pre-vent feed refusal. Ground flaxseed is prone to oxida-tive rancidity, and so should be used within 2-3 weeks of processing. There seem to beadvantages to steam pelleting diets contain-ingflaxseed. Flaxseed contains a number of antinutrients including mucilage, trypsin inhibitor,cyanogenic glycosides and considerable quantities of phytic acid. The mucilage is main-ly pectin, found in the seed coat and can be 5-7%by weight. The mucilage undoubtedly con-tributes to more viscous excreta, and there issome evidence that ß-glucanase enzymes may beof some benefit, especially with young birds.Flaxseed may contain up to 50% of the level oftrypsin inhibitors found in soybeans, and this ispossibly the basis for response to heat treatmentand steam pelleting of flaxseed. The main glucosidesyield hydrocyanic acid upon hydrolysis, and thishas an adverse effect on many enzyme systemsinvolved in energy metabolism.




(kcal/kg) 35001-42002 Tryptophan 0.29(MJ/kg) 14.64–17.60 Threonine 0.82

Calcium 0.25 Arginine 2.10Av. Phosphorus 0.17Sodium 0.08 Dig Methionine 0.281-0.352

Chloride 0.05 Dig Meth + Cys 0.56-0.70Potassium 1.20 Dig Lysine 0.64-0.78Selenium (ppm) 0.11 Dig Tryptophan 0.25-0.27Fat 34.0 Dig Threonine 0.53-0.67Linoleic acid 5.2 Dig Arginine 1.49-1.93Crude Fiber 6.0


Bulk Density:


1 Mash; 2 Pellets


Bird age Min. Max. Comments0-4 wk 84-8 wk 8> 8 wk 10

Gradual introduction suggestedto prevent feed refusal.


All deliveries 6 mos 6 mos 12 mos 12 mos Fatty acid profile each 12 mos.

QA Schedule:



15. Meat mealOther names: Meat and bone meal

Nutritional Characteristics:Meat meal is a by-product of beef or swine pro-

cessing, and this can be of variable composition.For each 1 tonne of meat prepared for human con-sumption, about 300 kg is discarded as inedibleproduct, and of this, about 200 kg is rendered intomeat meal. In the past, meat meal referred onlyto soft tissue products, while meat and bonemeal also contained variable quantities of bone.Today, meat meal most commonly refers to ani-mal by-products with bone where protein levelis around 50% and calcium and phosphorus areat 8% and 4% respectively. Because the miner-al comes essentially from bone, the calciumphosphorus ratio should be around 2:1 and devi-ations from this usually indicate adulterationwith other mineral sources.

Variation in calcium and phosphorus contentis still problematic, and the potential for over-feeding phosphorus is a major reason for upperlimits of inclusion level. Meat meals usually contain about 12% fat and the best qualitymeals will be stabilized with antioxidants suchas ethoxyquin. Some of the variability in composition is now being resolved by so-called‘blenders’ that source various meat meal products and mix these to produce more consistent meat meals.

Meat meals are currently not used in Europebecause of the problems they have had with BSE(Bovine Spongiform Encephalopathy). It seemsas though conventional rendering treatmentsdo not inactivate the causative prions. However,pressure treatment to 30 psi (200 kPa) for about30 minutes during or after rendering seems todestroy prions. Parsons and co-workers at theUniversity of Illinois have shown that such pressure treatment can reduce lysine digestibility

from 75% to 55% and cystine from 65% downto 30%. If extreme pressure treatment becomesstandard during rendering of meat meal, it willobviously be necessary to carefully re-evaluatenutrient availability.

Recent evidence suggests that the metabolizableenergy content of meat meal, and other animalprotein by-products, is higher than the mostcommon estimates used in the past. In bioassays,ME values determined at inclusion levels of 5 –10%are much higher than those determined at moreclassical levels of 40 – 50% inclusion. The reasonfor the higher values is unclear, although it mayrelate to synergism between protein or fat sources,and these are maximized at low inclusion levels.Alternatively, with very high inclusion levels of meatmeal, the high calcium levels involved maycause problems with fat utilization due to soap formation, and so energy retention will be reduced.Another reason for change in energy value, is thatcommercial samples of meat meal today containless bone than occurred some 20 – 30 years ago.Dale suggests that the TMEn of meat meal frombeef is around 2,450 kcal/kg while that frompork is closer to 2,850 kcal/kg.

Another concern with meat meal is microbialcontent, and especially the potential for con-tamination with salmonella. Due to increasingawareness and concern about microbial quality,surveys show that the incidence of contaminationhas declined, but remains at around 10%. Proteinblends are at highest risk, because obviously a singlecontaminated source can lead to spread of salmonella in various blended products. One meansof reducing microbial load is to treat freshlyprocessed meals with organic acids. In many stud-ies, it is shown that meals are virtually sterile when



15. Meat mealOther names: Meat and bone meal

Nutritional Characteristics:Meat meal is a by-product of beef or swine pro-

cessing, and this can be of variable composition.For each 1 tonne of meat prepared for human con-sumption, about 300 kg is discarded as inedibleproduct, and of this, about 200 kg is rendered intomeat meal. In the past, meat meal referred onlyto soft tissue products, while meat and bonemeal also contained variable quantities of bone.Today, meat meal most commonly refers to ani-mal by-products with bone where protein levelis around 50% and calcium and phosphorus areat 8% and 4% respectively. Because the miner-al comes essentially from bone, the calciumphosphorus ratio should be around 2:1 and devi-ations from this usually indicate adulterationwith other mineral sources.

Variation in calcium and phosphorus contentis still problematic, and the potential for over-feeding phosphorus is a major reason for upperlimits of inclusion level. Meat meals usually contain about 12% fat and the best qualitymeals will be stabilized with antioxidants suchas ethoxyquin. Some of the variability in composition is now being resolved by so-called‘blenders’ that source various meat meal products and mix these to produce more consistent meat meals.

Meat meals are currently not used in Europebecause of the problems they have had with BSE(Bovine Spongiform Encephalopathy). It seemsas though conventional rendering treatmentsdo not inactivate the causative prions. However,pressure treatment to 30 psi (200 kPa) for about30 minutes during or after rendering seems todestroy prions. Parsons and co-workers at theUniversity of Illinois have shown that such pressure treatment can reduce lysine digestibility

from 75% to 55% and cystine from 65% downto 30%. If extreme pressure treatment becomesstandard during rendering of meat meal, it willobviously be necessary to carefully re-evaluatenutrient availability.

Recent evidence suggests that the metabolizableenergy content of meat meal, and other animalprotein by-products, is higher than the mostcommon estimates used in the past. In bioassays,ME values determined at inclusion levels of 5 –10%are much higher than those determined at moreclassical levels of 40 – 50% inclusion. The reasonfor the higher values is unclear, although it mayrelate to synergism between protein or fat sources,and these are maximized at low inclusion levels.Alternatively, with very high inclusion levels of meatmeal, the high calcium levels involved maycause problems with fat utilization due to soap formation, and so energy retention will be reduced.Another reason for change in energy value, is thatcommercial samples of meat meal today containless bone than occurred some 20 – 30 years ago.Dale suggests that the TMEn of meat meal frombeef is around 2,450 kcal/kg while that frompork is closer to 2,850 kcal/kg.

Another concern with meat meal is microbialcontent, and especially the potential for con-tamination with salmonella. Due to increasingawareness and concern about microbial quality,surveys show that the incidence of contaminationhas declined, but remains at around 10%. Proteinblends are at highest risk, because obviously a singlecontaminated source can lead to spread of salmonella in various blended products. One meansof reducing microbial load is to treat freshlyprocessed meals with organic acids. In many stud-ies, it is shown that meals are virtually sterile when



they emerge from the cooking chambers, and thatproblems most often occur with recontamination.Certainly most feed ingredients contain salmonella,however, because of the relative proportion of meatmeals used in a diet, the actual chance of contamination for a single bird may, in fact,come from corn (Table 2.7).

The relative risk to an individual bird is,therefore, claimed to be higher from cerealsbecause, even though they are not usually contaminated, their much higher inclusion levelresults in a greater potential risk. However,this type of argument is open to the real criticismthat meat meals are much more likely to con-taminate the feed, trucks, equipment etc., andthat salmonella numbers will likely increaseafter feed manufacture. Pelleted and extruded/

expanded diets will have much lower microbialcounts than corresponding mash diets.

Unfortunately, there is variability in nutrientavailability of conventionally rendered meatmeal, where lysine digestibility, for example, canvary from 70 to 88%. Such variability is not highly correlated with simple in vitro assayssuch as pepsin digestibility and KOH solubility.

Potential problems:

Meat meal should contain no more than4% phosphorus and 8% calcium, since higherash content will reduce its energy value. Nutrientavailability is variable across suppliers, and soit is important to have adequate quality controlprocedures in place, and especially when thereis a change in supplier.

Salmonella Diet

RelativeContamination Risk Factor

(%) (%)

Corn 1 60 60Vegetable proteins 8 30 24Meat meals 10 5 50

Table 2.7 Relative risk due to salmonella from various ingredients




(kcal/kg) 2450 - 2850 Tryptophan 0.36(MJ/kg) 10.25 - 11.92 Threonine 1.52

Calcium 8.0 Arginine 3.50Av. Phosphorus 4.0Sodium 0.50 Dig Methionine 0.62Chloride 0.90 Dig Meth + Cys 0.95Potassium 1.25 Dig Lysine 2.09Selenium (ppm) 0.4 Dig Tryptophan 0.26Fat 11.5 Dig Threonine 1.17Linoleic acid 1.82 Dig Arginine 2.78Crude Fiber -



Bulk Density:


QA Schedule:

Bird age Min. Max. Comments0-4 wk 6% Main concern is4-8 wk 8% level of Ca and

> 8 wk 8% P, and ash

Moisture CP Fat Ca/P AA’s OtherAll deliveries Yearly Fatty acid profile yearly.

Salmonella each 3 months.



As for meat meal, poultry by-product mealis produced essentially from waste generated during poultry meat processing. Because onlyone species is used, PBM should be a moreconsistent product than is meat meal, and certainly calcium and phosphorus levels will belower. Variability in composition relates towhether or not feathers are added during processingor kept separate to produce feather meal. PBMand feathers are best treated using differentconditions, because feathers require moreextreme heat in order to hydrolyze the keratinproteins. PBM with feathers may thereforemean that either the feather proteins are under-cooked or that the offal proteins are overcooked.Overcooking usually results in a much darker colored product. PBM contains more unsaturatedfats than does meat meal, and so if much morethan 0.5% fat remains in the finished product,it should be stabilized with an antioxidant.

Because of problems of disposal of spent layers, there is now some production of ‘spenthen meal’ which is essentially produced byrendering the whole body, including feathers. Suchspent hen meal contains around 11% fat and 20%ash, with 70% crude protein. Methionine,TSAA and lysine in such samples are around 1.2%,2.5% and 3.5% respectively, with digestibilityof methionine and lysine at 85%, while cystineis closer to 60% digestible. As with poultry by-product meal, the ME of spent hen meal isinfluenced by content of ash, fat and protein, witha mean value around 2,800 kcal/kg.

There is also current interest in ensiling various poultry carcasses and/or poultry by-

products prior to heat processing. Ensilingallows for more control over microbial con-tamination prior to processing, and allows the poten-tial to better utilize smaller quantities of poultrycarcasses on-farm or from sites more distant tothe PBM processing plant. Ensiling is also beingconsidered as a means of handling spent layersprior to production of PBM. Poultry carcasses oroffal do not contain sufficient fermentable car-bohydrate to allow lactic acid fermentationwhich will quickly reduce pH to about 4.2 andstabilize the product. These lactic acid produc-ing microbes can therefore be encouraged to pro-liferate by adding, for example, 10% molasses or 10% dried whey to ground carcasses. These mixtures quickly stabilize at around pH 4.2 – 4.5,and can be held for 10 – 15d prior to manufac-ture of PBM. Carcasses from older birds may requireslightly higher levels of theses carbohydrates, andbecause of their inherently high fat content,may be mixed with products such as soybean mealin order to improve handling characteristics.Ensiled whole carcasses, as is now being producedwith spent fowl, may present problems withavailability of feather proteins for reasons outlinedpreviously in terms of ideal processing conditionsfor tissue versus feathers. In the future, thisproblem may be resolved by adding feather-degrading enzymes to the ensiling mixture.

Potential problems:

Nutritive value will be positively correlatedwith protein and fat content and negatively correlated with ash. Cystine content will givean indication if feathers were included during processing, which will detract from amino aciddigestibility.

16. Poultry by-product mealOther Names: Poultry Meal, PBM Nutritional Characteristics:







Bulk Density:


FormulationConstraints:

Bird age Min. Max. Comments0-4 wk 8% No major concerns other 4-8 wk 10% than fat stability

> 8 wk 10%

QA Schedule:


All samples Weekly Weekly Weekly Yearly Digestible amino acids, including cystine, yearly







Bulk Density:


FormulationConstraints:

Bird age Min. Max. Comments0-4 wk 8% No major concerns other 4-8 wk 10% than fat stability

> 8 wk 10%

QA Schedule:


All samples Weekly Weekly Weekly Yearly Digestible amino acids, including cystine, yearly



17. Feather mealNutritional Characteristics:

Feather meal can be an excellent source ofcrude protein where this is needed to meet regulatory requirements. However, its use is severe-ly limited by deficiencies of several amino acids,including methionine, lysine and histidine.Feather meal usually contains about 4.5 – 5.0%cystine, and this should be around 60% digestible.The energy value of feather meal is quite high,being around 3300 kcal ME/kg, and Dale and co-workers at the University of Georgia suggestsTMEn of feather meal is highly correlated withits fat content (2860 + 77 x % fat, kcal/kg).Variability in quality is undoubtedly related tocontrol over processing conditions. Feathers arepartially dried and then steam-treated to inducehydrolysis, and within reason, the higher the temperature and/or longer the processing time,the better the chance of complete hydrolysis.Obviously extreme processing conditions will causedestruction of heat-labile amino acids such aslysine. As a generalization, the lower the pro-cessing and drying temperatures, the lower thelevel of cystine digestibility. Research has shownprocessing conditions to result in digestiblecystine levels as low as 45% with low cookingtemperature, to as high as 65% with highertemperatures for longer durations. Becausefeather meal is an important contributor toTSAA in the diet, the level of digestible cystineis a critical factor in evaluating nutritive value.

High pressure, unless for a short duration,seems to reduce amino acid digestibility, and againthis is especially critical for cystine. Underextreme processing conditions it seems as thoughsulfur can be volatilized, likely as hydrogensulfide, and so another simple test for protein quality, is total sulfur content. Sulfur levelshould be just over 2%, and any decline is like-

ly a reflection of higher than normal processingtemperature, time and/or pressure, all of whichwill adversely affect amino acid digestibility.

Feather meal also contains an amino acidcalled lanthionine, which is not normally foundin animal tissue. Total lanthionine levels can there-fore be used in assaying meat meal products forpotential contamination with feathers. Lanthioninecan occur as a breakdown product of cystine, andthere are some research results which indicatea very good correlation between high lanthio-nine levels and poor digestibility of most otheramino acids. In most feather meal samples, lanthionine levels should be at 20 – 30% of totalcystine levels. A potential problem in using lanthionine assays in quality control programs,is that it is readily oxidized by performic acid,which is a common step used in preparation ofsamples for amino acid analysis and particularlywhere cystine levels are of interest.

As with other animal proteins, there is currentinterest in alternate methods of processing.Treating feathers with enzyme mixtures that pre-sumably contain keratinase enzyme togetherwith NaOH has been shown to improve overallprotein digestibility and bird performance. Morerecently, it has been shown that a pre-fermenta-tion with bacteria such as Bacillus licheniformisfor 5 d at 50ºC, produces a feather lysate that iscomparable in feeding value to soybean meal whenamino acid balance is accounted for.

Potential problems:

Amino acid digestibility, and especially cystine digestibility is greatly influenced by processing conditions. Monitoring total sulfurlevels may be a simple method of assessingconsistency of processing conditions.







Bulk Density:



Bird age Min. Max. Comments0-4 wk 2% Amino acid 4-8 wk 3% digestibility the > 8 wk 3% main concern

QA Schedule:

Moisture CP Fat Ca/P AA’s OtherAll deliveries Weekly Monthly 6 mos 6 mos Total sulfur each 3 months







Bulk Density:



Bird age Min. Max. Comments0-4 wk 2% Amino acid 4-8 wk 3% digestibility the > 8 wk 3% main concern

QA Schedule:

Moisture CP Fat Ca/P AA’s OtherAll deliveries Weekly Monthly 6 mos 6 mos Total sulfur each 3 months



Because of the decline in activities of mostfisheries directed at human consumption, fish mealsare now almost exclusively produced fromsmaller oily fish caught specifically for mealmanufacture. Menhaden and anchovy are themain fish species used for meal manufacture, withlesser quantities of herring meal produced inEurope. Fish meal is usually an excellent sourceof essential amino acids, while energy level islargely dependent upon residual oil content.Because of variable oil and protein content,expected ME value can be calculated basedon knowledge of their composition in the meal.

ME (kcal/kg) = 3000 ± (Deviation in % fat x8600) ± (Deviation in % CP x 3900) Where standard fat content is 2%, and CP is 60%.

Therefore, a 4% fat, 63% CP sample isexpected to have an ME of 3289 kcal/kg, whilea 1% fat, 58% CP sample will have ME closerto 2836 kcal/kg. The ash content of fishmeal willbe predominantly calcium and phosphorus andthe latter can be around 90% available, as is phosphorus from any quality animal protein.

All fish meals should be stabilized withantioxidants. This is especially true for high oilcontent samples, but even with only 2% residual oil, there is good evidence to showreduced oxidation (in terms of production of oxidation products and free fatty acids, as wellas reduced heat production) by adding 100ppm ethoxyquin during manufacture.

Potential problems in feeding fish meal aretaint of both eggs and meat, and gizzard erosionin young birds. With inadequately heat-treated

fishmeal, especially from fresh water fish, thereis also the potential problem of excessive thiaminase activity. Depending upon geographicallocation, taint in eggs and meat can be detectedby consumers when birds are fed much more than4 – 5% fish meal. Problems of taint will bemore acute with high fat samples, and of course,the problems are most acute if fish oil per se is used.Even at levels as low as 2.5% fish meal, some brownegg birds produce tainted eggs which may be relat-ed to the trimethylamine content of fish meal, andthe genetic predisposition of certain birds failingto produce sufficient trimethylamine oxidase.Excess trimethylamine is shunted to the egg, pro-ducing a characteristic fishy taint (see also canolameal). The trimethylamine content of fish mealis around 50 – 60 mg/kg, and assuming a 2.5%inclusion level, and feed intake of such brown egglayers of 115 g/day, means that the bird is takingin about 0.2 mg/day. Each affected egg con-tains around 0.8 mg, and so, it is obvious that thediet contains sources of trimethylamine otherthan fish meal, or that there is microbial synthe-sis in the intestine.

For young chicks, and especially the broil-er chicken, a major concern with feeding fish meal,is gizzard erosion. A proportion of chicks fedalmost any level of fish meal develop gizzardlesions, although there is a strong dose-response.Affected birds have signs ranging from small localized cracks in the gizzard lining, throughto severe erosion and hemorrhage which ultimatelyleads to total destruction of the lining. Thethick lining is required for preventing degradingeffects of acid and pepsin produced by theproventriculus. Because of disrupted protein

18. Fish mealOther names: Herring meal; White Fish meal; Menhaden meal




degradation, the affected birds show very slowgrowth rate. The condition is most common whenfish meal is included in the diet, although similar signs are seen with birds fed a high levelof copper (250 ppm) or vitamin K deficientdiets, or simply induced by starvation. Gizzarderosion was initially thought to be associated withhistamine levels in fish meal. Feeding histamineto birds simulates the condition, as does feed-ing a heated semi-purified diet containing his-tidine. Fish meals contain histamine, and followingmicrobial degradation during pre-cooking stor-age, bacteria possessing histidine decarboxy-lase will convert variable quantities from histi-dine to histamine. Histamine has the effect ofstimulating excessive acid production by theproventriculus, and it is this acid environmentthat initiates breakdown of the gizzard lining. Aproduct known as gizzerosine has been isolated from fish meal, and this has histamine-type properties in terms of stim-ulating acid secretion. Gizzerosine is formed byheating histidine and a protein during manufactureof fish meal. The most common components arelysine and histidine. Gizzerosine is almost 10xas potent as is histamine in stimulating proven-tricular acid production and some 300x more

potent in causing gizzard erosion. Currently theonly useful screening test is to feed high levels (25 – 50%) to young chicks and score the degreeof gizzard lesions (see ingredient quality controlSection 2.2 i).

Because the mode of action of gizzerosineis via acid production and a change in gizzardpH, there have been attempts at adding buffersto prevent the problem. For example adding sodium bicarbonate has been reported to lessenthe severity of gizzard erosion. However, levels as high as 10 kg/tonne are required to changegizzard pH by only 0.3 units. Variable levels ofgizzerosine in fish meals likely relate to pre-processing holding time and storage temperature, and also to the time and temper-ature of the cooking and oil extraction procedures.

Potential Problems:

Taint of meat or eggs can occur with muchmore than 2% fish meal in the diet. Fish mealshould be stabilized with an antioxidant, and thisfactor is critical when residual fat contentexceeds 2%. With young chicks, gizzard erosionis a consequence of using poorly processed, orinadequately stored fish meal.



degradation, the affected birds show very slowgrowth rate. The condition is most common whenfish meal is included in the diet, although similar signs are seen with birds fed a high levelof copper (250 ppm) or vitamin K deficientdiets, or simply induced by starvation. Gizzarderosion was initially thought to be associated withhistamine levels in fish meal. Feeding histamineto birds simulates the condition, as does feed-ing a heated semi-purified diet containing his-tidine. Fish meals contain histamine, and followingmicrobial degradation during pre-cooking stor-age, bacteria possessing histidine decarboxy-lase will convert variable quantities from histi-dine to histamine. Histamine has the effect ofstimulating excessive acid production by theproventriculus, and it is this acid environmentthat initiates breakdown of the gizzard lining. Aproduct known as gizzerosine has been isolated from fish meal, and this has histamine-type properties in terms of stim-ulating acid secretion. Gizzerosine is formed byheating histidine and a protein during manufactureof fish meal. The most common components arelysine and histidine. Gizzerosine is almost 10xas potent as is histamine in stimulating proven-tricular acid production and some 300x more

potent in causing gizzard erosion. Currently theonly useful screening test is to feed high levels (25 – 50%) to young chicks and score the degreeof gizzard lesions (see ingredient quality controlSection 2.2 i).

Because the mode of action of gizzerosineis via acid production and a change in gizzardpH, there have been attempts at adding buffersto prevent the problem. For example adding sodium bicarbonate has been reported to lessenthe severity of gizzard erosion. However, levels as high as 10 kg/tonne are required to changegizzard pH by only 0.3 units. Variable levels ofgizzerosine in fish meals likely relate to pre-processing holding time and storage temperature, and also to the time and temper-ature of the cooking and oil extraction procedures.

Potential Problems:

Taint of meat or eggs can occur with muchmore than 2% fish meal in the diet. Fish mealshould be stabilized with an antioxidant, and thisfactor is critical when residual fat contentexceeds 2%. With young chicks, gizzard erosionis a consequence of using poorly processed, orinadequately stored fish meal.







Bulk Density:



Bird age Min. Max. Comments0-4 wk 8% Taint problems likely in most 4-8 wk 10% markets at levels much in excess > 8 wk 10% of 2%

QA Schedule:


All deliveries Monthly 12 mos Fat oxidation, gizzerosine each 6 mos.



19. Fats and oilsNutritional Characteristics:

Fats provide a concentrated source of energy,and so relatively small changes in inclusionlevels can have significant effects on diet ME. Mostfats are handled as liquids, and this means heating of most fats and fat blends that containappreciable quantities of saturated fatty acids.

Depending upon the demands for pelletdurability, 3 – 4% is the maximum level of fat thatcan be mixed with the other diet ingredients. Tothis, up to 2 – 3% can be added as a spray-oncoat to the formed pellet. Alternate technologyof spraying fat onto the hot pellet as it emergesfrom the pellet die means that much higherinclusions are possible since the hot pelletseems better able to adsorb the fat. Underthese conditions, there is concern for manufacturerswho demand extreme pellet durability, since fineswill already be treated with extra fat, prior to their recycling through the pellet mill.

All fats and oils must be treated with anantioxidant which ideally should be added at thepoint of manufacture. Fats held in heated tanksat the mill must be protected from rancidity. Themore unsaturated a fat, the greater the chanceof rancidity. Fats also provide varying quantitiesof the essential nutrient linoleic acid. Unless adiet contains considerable quantities of corn, itmay be deficient in linoleic acid, because all dietsshould contain a minimum of 1%. A major prob-lem facing the industry at the moment is the increasing use of restaurant grease in feed-gradefats. These greases are obviously of variable composition in terms of fatty acid profile and

content of free fatty acids. Also, dependentupon the degree of heating that they have beensubjected to, these greases can contain significantquantities of undesirable break-down products.

In order to ensure adequate levels of linole-ic acid, and to improve palatability and reduce dustiness of diets, all diets require a minimumof 1% added fat, regardless of other economicor nutritional considerations. There is consid-erable information published on factors thatinfluence fat digestibility, but in most instances,this knowledge is not used during formulation.In large part variability is due to the fact thatdigestibility is not a static entity for any fat, butrather its utilization is variable with such factorsas bird age, fat composition and inclusion level.Unfortunately, these variables are difficult tofactor into formulation programs. Other concernsabout fats are their potential for rancidity and effecton carcass composition. Following are descrip-tions of the major types of fat used in the feedindustry. Table 2.8 summarizes the fatty acid profile and ME of the most common fat sourcesused in poultry nutrition. An attempt has beenmade to predict fat ME based on bird age.

19a. TallowTallow has traditionally been the principle fat

source used in poultry nutrition. However, over thelast 10 years, there has been less use of pure tallowand greater use of blended fats and oils. Tallow issolid at room temperature and this presents someproblems at the mill, especially when heated



19. Fats and oilsNutritional Characteristics:

Fats provide a concentrated source of energy,and so relatively small changes in inclusionlevels can have significant effects on diet ME. Mostfats are handled as liquids, and this means heating of most fats and fat blends that containappreciable quantities of saturated fatty acids.

Depending upon the demands for pelletdurability, 3 – 4% is the maximum level of fat thatcan be mixed with the other diet ingredients. Tothis, up to 2 – 3% can be added as a spray-oncoat to the formed pellet. Alternate technologyof spraying fat onto the hot pellet as it emergesfrom the pellet die means that much higherinclusions are possible since the hot pelletseems better able to adsorb the fat. Underthese conditions, there is concern for manufacturerswho demand extreme pellet durability, since fineswill already be treated with extra fat, prior to their recycling through the pellet mill.

All fats and oils must be treated with anantioxidant which ideally should be added at thepoint of manufacture. Fats held in heated tanksat the mill must be protected from rancidity. Themore unsaturated a fat, the greater the chanceof rancidity. Fats also provide varying quantitiesof the essential nutrient linoleic acid. Unless adiet contains considerable quantities of corn, itmay be deficient in linoleic acid, because all dietsshould contain a minimum of 1%. A major prob-lem facing the industry at the moment is the increasing use of restaurant grease in feed-gradefats. These greases are obviously of variable composition in terms of fatty acid profile and

content of free fatty acids. Also, dependentupon the degree of heating that they have beensubjected to, these greases can contain significantquantities of undesirable break-down products.

In order to ensure adequate levels of linole-ic acid, and to improve palatability and reduce dustiness of diets, all diets require a minimumof 1% added fat, regardless of other economicor nutritional considerations. There is consid-erable information published on factors thatinfluence fat digestibility, but in most instances,this knowledge is not used during formulation.In large part variability is due to the fact thatdigestibility is not a static entity for any fat, butrather its utilization is variable with such factorsas bird age, fat composition and inclusion level.Unfortunately, these variables are difficult tofactor into formulation programs. Other concernsabout fats are their potential for rancidity and effecton carcass composition. Following are descrip-tions of the major types of fat used in the feedindustry. Table 2.8 summarizes the fatty acid profile and ME of the most common fat sourcesused in poultry nutrition. An attempt has beenmade to predict fat ME based on bird age.

19a. TallowTallow has traditionally been the principle fat

source used in poultry nutrition. However, over thelast 10 years, there has been less use of pure tallowand greater use of blended fats and oils. Tallow issolid at room temperature and this presents someproblems at the mill, especially when heated



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fats are added to very cold ingredients originatingfrom unheated outside silos. Being highly saturated, tallow is not well digested by young chickens, although there is some evidence of better utilization by young turkeys. The digestibil-ity of tallow can be greatly improved by the addition of bile salts suggesting this to be alimiting feature of young chicks. However, theuse of such salts is not economical and so inclusion of pure tallow must be severelyrestricted in diets for birds less than 15 – 17 d of age.

19b. Poultry FatThis fat source is ideal for most types and ages

of poultry in terms of its fatty acid profile. Dueto its digestibility, consistent quality and residualflavor, it is in high demand by the pet foodindustry, and this unfortunately reduces its supply to the poultry industry. As occurs with poul-try meal, there is a concern with integratedpoultry operations that fat-soluble contaminantsmay be continually cycled (and concentrated)through the birds. This can obviously be resolvedby breaking the cycle for a 1 or 2 bird cycle.

19c. Fish OilThere is current interest in the use of fish oils

in diets for humans and animals, since its distinctivecomponent of long chain fatty acids is thoughtbeneficial for human health. Feeding moderatelevels of fish oils to broiler chickens has beenshown to increase the eicosapentaenoic acid content of meat. However, with dietary levels inexcess of 1%, distinct fish type odour is often present in both meat and eggs, which is due mainly to the contribution of the omega-3 fatty acids.

19d. Vegetable OilA large range of vegetable oils is available as

an energy source, although under most situations,competition with the human food industry

makes them uneconomic for animal feeds.Most vegetable oils provide around 8700 kcalME/kg and are ideal ingredients for very youngbirds. If these oils are attractively priced asfeed ingredients, then the reason(s) for refusal bythe human food industry should be ascertainede.g. contaminants.

19e. Coconut OilCoconut oil is a rather unusual ingredient in

that it is a very saturated oil. Coconut oil is moresaturated than is tallow. It contains 50% ofsaturated fatty acids with chain length less than12:0. In many respects, it is at the opposite endof the spectrum to fish oil in terms of fatty acidprofile. There has been relatively little work conducted on the nutritional value of coconutoil, although due to its saturated fatty acid contentit will be less well digested, especially by youngbirds. However recent evidence suggests veryhigh digestibility by young birds of mediumchain triglycerides, such as C:8 and C:10 asfound in coconut oil. These medium length fattyacids do not need bile for emulsification orprior incorporation within a micelle prior toabsorption.

19f. Palm OilPalm oil production is now only second to

soybean oil in world production. Palm oil is produced from the pulpy flesh of the fruit, whilesmaller quantities of palm kernel oil are extractedfrom the small nuts held within the body of thefruit. Palm oil is highly saturated, and so will havelimited usefulness for very young birds. Also, soap-stocks produced from palm oil, because of theirfree fatty acid content, will be best suited for olderbirds. There is potential for using palm andcoconut oils as blends with more unsaturated oilsand soapstocks, so as to benefit from potentialfatty acid synergism.



19g. Soapstock (Acidulated soapstock)As a by-product of the vegetable oil refining

industry, soapstocks provide a good source of energy and essential fatty acids. Soapstockscan be quite high in free fatty acids, and so stabilization with an antioxidant is essential.Soapstocks may also be acidulated, and thismay pose problems with corrosion of metallicequipment. Some impurities may be added tosoapstocks as a means of pollution-free disposal by refineries, and therefore qualitycontrol becomes more critical with these products. Moisture level may also be high in somesamples, and this simple test is worthwhile foreconomic evaluation.

19h. Animal-Vegetable Blend FatSome manufacturers mix animal and vegetable

based fats, to give so-called blended products.The vegetable source is usually soapstock material. The blend has the advantage of allowingfor some synergism between saturated fattyacids of animal origin and unsaturates from thesoapstock. Animal-vegetable blends are there-fore ideally suited for most classes of poultry without the adverse problem of unduly increasingthe unsaturates in meat which can lead to increasedrate of oxidative rancidity (reduced shelf life).

19i. Restaurant GreaseAn increasing proportion of feed fats is

now derived from cooking fats and oils, and thegeneric product is termed restaurant grease. Itsuse has increased mainly due to problems of alternate disposal. Traditionally restaurant greases were predominately tallow or lard basedproducts and this posed some problems in collection and transportation of the solid material. In recent years, due to consumer concerns about saturated fats, most major fast food

and restaurant chains have changed to hydro-genated vegetable cooking fats and oils. The fatsare hydrogenated to give them protection againsthigh-temperature cooking. Today, restaurantgreases contain higher levels of oleic acid, andmuch of this will be trans-oleate. Assuming therehas not been excessive heating, and that the greasehas been cleaned and contains a minimum ofimpurities, then the energy value will be comparable to that of poultry fat. Future use ofnon-fat ‘cooking fats’ will lead to considerablevariation in the nutrient profile of these products.

19j. Conjugated Linoleic Acid (CLA)CLA is an isomer of conventional linoleic acid,

but unlike linoleic, there are numerous healthbenefits claimed for CLA. It is claimed to helpcontrol glucose metabolism in diabetic mammals,and more importantly to prevent and/or controlthe growth of certain cancerous tumors. CLA isnormally found in dairy products, represent-ing around 0.3% of total fat. Turkey meat is alsohigh in CLA. Feeding CLA to layers results in bioaccumulation in the egg, much as for any fattyacid, and so there is potential for producing CLAenriched designer eggs. It seems as though theAMEn of CLA is comparable to that of linoleicacid, suggesting that the two fatty acids arecomparably metabolized.

It is possible that CLA is not elongated as inlinoleic acid during metabolism and so this hasposed questions about adequacy of prostaglandinsynthesis, and hence immune function. Thereare some reports of altered lipid metabolism inembryos and young chicks from eggs hatched fromhens fed 1 g CLA daily. There is some discussionabout whether or not synthetic sources of CLAactually mimic the beneficial anti-cancerousproperties of ‘natural’ CLA found in dairy products.



Important Considerations:

Fats and oils are probably the most problem-atic of all the ingredients used in poultry feeds. Theyrequire special handling and storage facilitiesand are prone to oxidation over time. Their fattyacid profile, the level of free fatty acids and degreeof hydrogenation can all influence digestibility. Unlikemost other ingredients, fat digestion can be agedependent, since young birds have reduced abil-ity to digest saturated and hydrogenated fats.

a. Moisture, Impurities, UnsaponifiablesFeed grade fats will always contain some

non-fat material that is generally classified as M.I.U.(moisture, impurities and unsaponifiables).Because these impurities provide no energy orlittle energy, they act as diluents. A recent survey indicated M.I.U’s to range from 1 – 9%.Each 1% MIU means a loss in effective value ofthe fat by about $3 - $4/tonne, and more importantly, energy contribution will be lessthan expected. The major contaminants aremoisture and minerals. It seems as thoughmoisture can be quickly detected by Near InfraRed Analysis. Moisture and minerals also leadto increased peroxidation.

b. Rancidity and OxidationThe feeding value of fats can obviously be

affected by oxidative rancidity that occurs priorto, or after feed preparation. Rancidity caninfluence the organoleptic qualities of fat, as wellas color and ‘texture’ and can cause destructionof other fat soluble nutrients, such as vitamins,both in the diet and the bird’s body stores.Oxidation is essentially a degradation process thatoccurs at the double-bond in the glyceridestructure. Because presence of double-bonds infersunsaturation, then naturally the more unsaturateda fat, the greater the chance of rancidity. The initial step is the formation of a fatty free radicalwhen hydrogen leaves the -methyl carbon inthe unsaturated group of the fat. The resultant

free radical then becomes very susceptible to attackby atmospheric oxygen (or mineral oxides) to formunstable peroxide free radicals. These peroxidefree radicals are themselves potent catalysts,and so the process becomes autocatalytic andrancidity can develop quickly. Breakdownproducts include ketones, aldehydes and shortchain fatty acids which give the fat its characteristic‘rancid’ odour. Animal fats develop a slightrancid odour when peroxide levels reach 20meq/kg while for vegetable oils problems startat around 80 meq/kg.

Oxidative rancidity leads to a loss in energyvalue, together with the potential degradation ofthe bird’s lipid stores and reserves of fat-soluble vitamins. Fortunately we have some control over these processes through the judicioususe of antioxidants. Most antioxidants essentiallyfunction as free radical acceptors – these radical-antioxidant complexes are, however,stable and do not cause autocatalytic reactions.Their effectiveness, therefore, relies on adequatedispersion in the fat immediately after process-ing. As an additional safety factor, most diets willalso contain an antioxidant added via the premix.The Active Oxygen Method (AOM) is most com-monly used to indicate potential for rancidity. After20 h treatment with oxygen, quality fats shoulddevelop no more than 20 meq peroxides/kg.

Time is a very important factor in the AOMtest, because peroxides can break down and disappear with extended treatment. For thisreason, some labs will provide peroxide valuesat 0, 10 and 20 hr. A newer analytical techniqueis the Oil Stability Index (OSI). This is similar toAOM, but instead of measuring initial peroxideproducts, measures the accumulation of secondarybreakdown compounds. The assay is highly auto-mated and records the time necessary to producea given quantity of breakdown products such asshort chain volatile fatty acids.



Important Considerations:

Fats and oils are probably the most problem-atic of all the ingredients used in poultry feeds. Theyrequire special handling and storage facilitiesand are prone to oxidation over time. Their fattyacid profile, the level of free fatty acids and degreeof hydrogenation can all influence digestibility. Unlikemost other ingredients, fat digestion can be agedependent, since young birds have reduced abil-ity to digest saturated and hydrogenated fats.

a. Moisture, Impurities, UnsaponifiablesFeed grade fats will always contain some

non-fat material that is generally classified as M.I.U.(moisture, impurities and unsaponifiables).Because these impurities provide no energy orlittle energy, they act as diluents. A recent survey indicated M.I.U’s to range from 1 – 9%.Each 1% MIU means a loss in effective value ofthe fat by about $3 - $4/tonne, and more importantly, energy contribution will be lessthan expected. The major contaminants aremoisture and minerals. It seems as thoughmoisture can be quickly detected by Near InfraRed Analysis. Moisture and minerals also leadto increased peroxidation.

b. Rancidity and OxidationThe feeding value of fats can obviously be

affected by oxidative rancidity that occurs priorto, or after feed preparation. Rancidity caninfluence the organoleptic qualities of fat, as wellas color and ‘texture’ and can cause destructionof other fat soluble nutrients, such as vitamins,both in the diet and the bird’s body stores.Oxidation is essentially a degradation process thatoccurs at the double-bond in the glyceridestructure. Because presence of double-bonds infersunsaturation, then naturally the more unsaturateda fat, the greater the chance of rancidity. The initial step is the formation of a fatty free radicalwhen hydrogen leaves the -methyl carbon inthe unsaturated group of the fat. The resultant

free radical then becomes very susceptible to attackby atmospheric oxygen (or mineral oxides) to formunstable peroxide free radicals. These peroxidefree radicals are themselves potent catalysts,and so the process becomes autocatalytic andrancidity can develop quickly. Breakdownproducts include ketones, aldehydes and shortchain fatty acids which give the fat its characteristic‘rancid’ odour. Animal fats develop a slightrancid odour when peroxide levels reach 20meq/kg while for vegetable oils problems startat around 80 meq/kg.

Oxidative rancidity leads to a loss in energyvalue, together with the potential degradation ofthe bird’s lipid stores and reserves of fat-soluble vitamins. Fortunately we have some control over these processes through the judicioususe of antioxidants. Most antioxidants essentiallyfunction as free radical acceptors – these radical-antioxidant complexes are, however,stable and do not cause autocatalytic reactions.Their effectiveness, therefore, relies on adequatedispersion in the fat immediately after process-ing. As an additional safety factor, most diets willalso contain an antioxidant added via the premix.The Active Oxygen Method (AOM) is most com-monly used to indicate potential for rancidity. After20 h treatment with oxygen, quality fats shoulddevelop no more than 20 meq peroxides/kg.

Time is a very important factor in the AOMtest, because peroxides can break down and disappear with extended treatment. For thisreason, some labs will provide peroxide valuesat 0, 10 and 20 hr. A newer analytical techniqueis the Oil Stability Index (OSI). This is similar toAOM, but instead of measuring initial peroxideproducts, measures the accumulation of secondarybreakdown compounds. The assay is highly auto-mated and records the time necessary to producea given quantity of breakdown products such asshort chain volatile fatty acids.



c. Fatty Acid ProfileFat composition will influence overall fat

utilization because different components aredigested with varying efficiency. It is generallyrecognized that following digestion, micelleformation is an important prerequisite to absorp-tion. Micelles are complexes of bile salts, fattyacids, some monoglycerides and perhaps glycerol. The conjugation of bile salts withfatty acids is an essential prerequisite for transportation to and absorption through the microvilli of the small intestine. Polar unsaturated fatty acids and monoglyceridesreadily form this important association. However,micelles themselves have the ability to solubilize non-polar compounds such as satu-rated fatty acids. Fat absorption is, therefore,dependent upon there being an adequate supply of bile salts and an appropriate balanceof unsaturates:saturates.

Taking into account the balance of saturatedto unsaturated fatty acids can be used to advan-tage in designing fat blends. This type of synergisticeffect is best demonstrated using pure fatty acids(Table 2.9). In this study, the metabolizable

energy of the 50:50 mixture of the unsaturatedoleic acid with the saturated palmitic acid, is 5%higher than the expected value based on the meanvalue of 2710 kcal/kg. We therefore have a boostof 5% in available energy that likely comesfrom greater utilization of the palmitic acidbecause of the presence of the unsaturatedoleic acid.

This type of synergism can, however, have aconfounding effect on some research results. Ifwe want to measure the digestibility of corn, itis possible to feed just corn for a short period oftime and conduct a balance study. For obviousreasons, it is impossible to feed only fats, and wehave to conduct studies involving graded fat additions to a basal diet, with extrapolation ofresults to what would happen at the 100% feeding level. In these studies, we assume thedifference in digestibility between any two dietsis due solely to the fat added to the diet. If, becauseof synergism, the added fat improved digestibilityof basal diet components, then this ‘boost’ indigestibility is attributed to the fat and an erro-neously high value is projected. However, it canbe argued that this ‘boost’ to fat’s value occursnormally when fats are added to diets, and thatthese higher values more closely reflect thepractical value of fat in a poultry diet. We haveproposed this synergism to account for some ofthe so-called ‘extra-caloric’ effect of fat often seenin reported values, where metabolizable energy can sometimes be higher than corresponding gross energy values (which theoretically cannot occur). Table 2.10 showsresults from this type of study where corn oil wasassayed using different types of basal diet.

Table 2.9 Metabolizable energy oflayer diets containing various fattyacids

(Atteh and Leeson, 1985)

Determined Expected ME (kcal/kg)

Oleic 2920Palmitic 250050:50 mixture 2850 (+5%) 2710



When the basal diet contains saturated fattyacids, there is an apparent increase in the ME ofcorn oil. This effect is possibly due to the unsat-urates in corn oil aiding in utilization of the basaldiet saturates. However, because of methods ofdiet substitution and final ingredient ME calculation, any such synergism is attributedto the test ingredient (corn oil).

ME values of fats will therefore vary with inclusion level, although this effect will be influenced by degree of fat saturation. A ratioof 3:1, unsaturates:saturates is a good compro-mise for optimum fat digestibility for all ages ofbird. However, this ratio may not be the mosteconomical type of fat to use, because of theincreased cost of unsaturates relative to saturates.

d. Level of Free Fatty Acids and FattyAcid Hydrogenation

Concern is often raised about the level of freefatty acids in a fat, because it is assumed theseare more prone to peroxidation. Acidulated soapstocks of various vegetable oils containthe highest levels of free fatty acids, which canreach 80 – 90% of the lipid material. For youngbirds there is an indication that absorption of fattyacids is highest in birds fed triglycerides ratherthan free fatty acids and this may relate to lessefficient micelle formation or simply to lessbile production. Wiseman and Salvadore (1991)demonstrated this effect in studying the MEvalue of tallow, palm oil and soy oil that contained

various levels of free fatty acids (soapstock of therespective fat). Table 2.11 shows a summary ofthese results, indicating energy values for therespective fats containing the highest and lowest levels of free fatty acids used.

Table 2.10 Variation in ME value ofcorn oil attributed to fatty acid saturation of the basal diet

Basal diet Corn oil ME (kcal/kg)

Predominantly unsaturated 8390a

Predominantly saturated 9380b

Corn-soy diet 8510a

Table 2.11 Effect of level of freefatty acid and bird age on fat MEvalue (kcal/kg)

Age10 d 54 d

Tallow 13% FFA 7460 794095% FFA 4920 6830

Palm 6% FFA 6690 780092% FFA 3570 6640

Soy 14% FFA 9290 930068% FFA 8000 8480

Adapted from Wiseman and Salvador (1991)

These data suggest that free fatty acids are moreproblematic when the fat is predominantly saturated and this is fed to young birds. Contraryto these results, others have shown comparableresults with broilers grown to market weightand fed tallows of varying free fatty acid content.

Hydrogenation of fats becomes an issuewith the general use of these fats in restaurants,and the fact that restaurant grease is now acommon, and sometimes the major compo-nent of feed-grade fat blends. Hydrogenationresults in a high level of trans oleic acid (40 – 50%)and such vegetable oils have physical characteristicssimilar to those of lard. There seems to be no problem in utilization of these hydrogenated fatsby poultry with ME values of restaurant greasesbeing comparable to those of vegetable oils. Thelong-term effect of birds eating trans fatty acidsis unknown at this time.



e. Bird Age and Bird TypeYoung birds are less able to digest saturated

fats, and this concept has been known for sometime. With tallow, for example, palmitic aciddigestibility increases from 50 to 85% through14 to 56 d of age, which together with corre-sponding changes for other fatty acids means thattallow ME will increase by about 10% over thistime period. The reason why young birds are lessable to digest saturated fats is not well understood,although it may relate to less bile salt production,less efficient recirculation of bile salt or lessproduction of fatty acid binding protein.

f. Soap FormationWhen fats have been digested, free fatty

acids have the opportunity of reacting withother nutrients. One such possible associationis with minerals to form soaps that may or maynot be soluble. If insoluble soaps are formed, thereis the possibility that both the fatty acid and themineral will be unavailable to the bird. There issubstantial soap formation in the digesta ofbroiler chicks and this is most pronounced withsaturated fatty acids, and with increased levelsof diet minerals. Such increased soap productionis associated with reduced bone ash and bonecalcium content of broilers. Soap production seemsto be less of a problem with older birds. This isof importance to laying hens that are fed high levels of calcium. In addition to calcium, otherminerals such as magnesium can form soaps withsaturated fatty acids. In older birds and some otheranimals, there is an indication that while soapsform in the upper digestive tract, they are subsequently solubilized in the lower tract dueto changes in pH. Under these conditions boththe fatty acid and mineral are available to the bird.Control over digesta pH may, therefore, be animportant parameter for control over soap formation.

g. Variable ME ValuesIt seems obvious that the use of a single

value for fat ME during formulation is a com-promise, considering the foregoing discussion onfactors such as inclusion level, bird age, soap formation etc. Table 2.8 gives different ME values for birds younger or older than 21 d, andthis in itself is a compromise. Following is anattempt to rationalize the major factors affectingME of a given fat, although it is realized that suchvariables are not easily incorporated within a formulation matrix (Table 2.12).

Table 2.12 Factors affecting fat MEvalues

Relative fat ME28 d+ 100%

Bird age: 7 - 28 d 95%1 – 7 d 88%

(esp. for saturates)

0 – 10% 102%Free fatty 10 – 20% 100%acids: 20 – 30% 96%

30%+ 92%(esp. for saturates)

1% 100%2% 100%

Inclusion level: 3% 98%4% 96%

5%+ 94%<1% 100%

Calcium level: >1% 96%(esp. for birds <56 d

of age)



h. Trans Fatty AcidsTrans fatty acids are isomers of naturally

occurring cis fatty acids. Trans fatty acids are oftenproduced by the process of hydrogenation, as commonly occurs in production of margarine andother cooking fats. Hydrogenated (stabilized) soybean oil, which is a common component ofcooking oils, contains around 20% trans fatty acids.With increasing use of restaurant grease in animal fats and fat blends, it seems inevitable that

fats used in the feed industry will contain higherproportions of trans fatty acids than occurred some20 years ago. It is thought that ‘overused’ fryingoil, that contains trans fatty acids as well as oxidized and polymerized materials, is harmfulto human health. These trans fatty acids can befound in human adipose tissue, and have beenassociated with immune dysfunction and unusual lipid metabolism in heart tissue. Thereis very little information available on the effectof trans fatty acids on health of broilers or layers.

OTHER INGREDIENTS

20. OatsOats are grown in cooler moist climates

although they are of minor importance on a glob-al scale, representing only about 1.5% of totalcereal production. Most oats are used for ani-mal feed, and about 85% of this quantity isused locally and there is little trade involved. Thehull represents about 20% of the grain by weight,and so this dictates the high fiber – low energycharacteristics of oats. The amino acid profileis however quite good, although there is somevariation in protein and amino acid levels dueto varietal and seasonal effects. The best predictorof the energy value of oats, is simply the crudefiber content which is negatively correlatedwith ME. Oat lipids are predominantly oleic andlinoleic acid, although a relatively high pro-portion of palmitic acid leads to a ‘harder’ fat beingdeposited it the bird’s carcass.

As for other small grains, oats contain an appre-ciable quantity of ß-glucans, and these cause prob-lems with digesta and excreta viscosity. Most oatscontain about 3-7% ß-glucans and so withmoderate inclusion levels of oats in a poultry dietit may be advantageous to use supplemental ß-glucanase enzyme. There has been some inter-est in development of so-called naked oats,which are similar in composition to oat groats.Naked oats contain up to 17% CP with 0.68%

lysine and 1% methionine plus cystine. The MEvalue is around 3200 kcal/kg, making theseoats comparable to wheat in most characteristics.As with regular oats, ß-glucans can still beproblematic and their adverse effect can beovercome with use of exogenous enzymes, andto a lesser extent antibiotics such as neomycin.Much of the phosphorus in naked oats is asphytic acid, and so availability is very low.There have been some reports of reduced skeletal integrity in birds fed naked oats unlessthis reduced phosphorus availability is takeninto account. There are reports of broilers performing well with diets containing up to40% naked oats, and with layers, up to 50% hasbeen used successfully.

21. RyeAlthough the nutrient content of rye is essen-

tially similar to that of wheat and corn, its feeding value for poultry is poor due to thepresence of various antinutritional factors. Ryecontains a water insoluble fraction, which ifextracted, improves its feeding value. Various othertreatments such as water soaking, pelleting,irradiation and the dietary supplementation ofvarious antibiotics all help to improve the growthof chicks fed rye.



h. Trans Fatty AcidsTrans fatty acids are isomers of naturally

occurring cis fatty acids. Trans fatty acids are oftenproduced by the process of hydrogenation, as commonly occurs in production of margarine andother cooking fats. Hydrogenated (stabilized) soybean oil, which is a common component ofcooking oils, contains around 20% trans fatty acids.With increasing use of restaurant grease in animal fats and fat blends, it seems inevitable that

fats used in the feed industry will contain higherproportions of trans fatty acids than occurred some20 years ago. It is thought that ‘overused’ fryingoil, that contains trans fatty acids as well as oxidized and polymerized materials, is harmfulto human health. These trans fatty acids can befound in human adipose tissue, and have beenassociated with immune dysfunction and unusual lipid metabolism in heart tissue. Thereis very little information available on the effectof trans fatty acids on health of broilers or layers.

OTHER INGREDIENTS

20. OatsOats are grown in cooler moist climates

although they are of minor importance on a glob-al scale, representing only about 1.5% of totalcereal production. Most oats are used for ani-mal feed, and about 85% of this quantity isused locally and there is little trade involved. Thehull represents about 20% of the grain by weight,and so this dictates the high fiber – low energycharacteristics of oats. The amino acid profileis however quite good, although there is somevariation in protein and amino acid levels dueto varietal and seasonal effects. The best predictorof the energy value of oats, is simply the crudefiber content which is negatively correlatedwith ME. Oat lipids are predominantly oleic andlinoleic acid, although a relatively high pro-portion of palmitic acid leads to a ‘harder’ fat beingdeposited it the bird’s carcass.

As for other small grains, oats contain an appre-ciable quantity of ß-glucans, and these cause prob-lems with digesta and excreta viscosity. Most oatscontain about 3-7% ß-glucans and so withmoderate inclusion levels of oats in a poultry dietit may be advantageous to use supplemental ß-glucanase enzyme. There has been some inter-est in development of so-called naked oats,which are similar in composition to oat groats.Naked oats contain up to 17% CP with 0.68%

lysine and 1% methionine plus cystine. The MEvalue is around 3200 kcal/kg, making theseoats comparable to wheat in most characteristics.As with regular oats, ß-glucans can still beproblematic and their adverse effect can beovercome with use of exogenous enzymes, andto a lesser extent antibiotics such as neomycin.Much of the phosphorus in naked oats is asphytic acid, and so availability is very low.There have been some reports of reduced skeletal integrity in birds fed naked oats unlessthis reduced phosphorus availability is takeninto account. There are reports of broilers performing well with diets containing up to40% naked oats, and with layers, up to 50% hasbeen used successfully.

21. RyeAlthough the nutrient content of rye is essen-

tially similar to that of wheat and corn, its feeding value for poultry is poor due to thepresence of various antinutritional factors. Ryecontains a water insoluble fraction, which ifextracted, improves its feeding value. Various othertreatments such as water soaking, pelleting,irradiation and the dietary supplementation ofvarious antibiotics all help to improve the growthof chicks fed rye.



One of the most noticeable effects of feedingrye, other than reduced performance is the production of a very sticky and wet excreta.The sticky droppings are due to the pectin-like components present in rye. Structural arabinoxylans,present in rye endosperm cell walls, are respon-sible for creating the viscous digesta. These viscous products reduce the rate of diffusion ofother solutes in the digesta so affecting nutrientuptake from the gut. In recent years enzyme preparations have been developed that markedlyreduce the antinutritional factor and eliminate thewet-sticky fecal problem with rye based diets.

22. TriticaleTriticale is a synthetic small grain cereal

resulting from the intergeneric cross of wheat andrye. Its higher yield per acre, as compared to ryeor wheat, make it of agronomic interest in areasof the world not suitable for corn production.Numerous cultivars have been developed withprotein contents varying from 11 to 20% andamino acid balance comparable to wheat andsuperior to that of rye. Energy content is also similar to that of wheat and superior to that ofrye. Like wheat, triticale has a significant phytase content and so is a better source ofavailable phosphorus than other cereals such ascorn or milo. There are reports of increasedenhancement of other dietary phosphorus withtriticale supplementation. The starch content oftriticale is as digestible as that of wheat and presents no wet litter or sticky manure problem.Where triticale is available, high levels can be usedin poultry diets without any adverse problems. Similar to wheat and rye it contains little or no xanthophylls and with fine grinding canresult in beak impaction with young birds. Alsolike wheat its feeding value can be increased byappropriate enzyme supplementation of the diet.

23. MolassesMolasses is a by-product of the sugar refining

industry, where either sugar beet or sugar caneare used as raw materials. Because of a high watercontent and concomitantly low energy value, itis only used extensively in poultry diets in areasclose to sugar refineries. The molasses usuallyavailable for animal feeding is so called final orblackstrap molasses, which is the productremaining after most of the sugar has beenextracted for human consumption. Dependingupon local conditions, high-test and type A andB molasses are sometimes available. The high-test product is basically unrefined caneor beet juice that has had its sugars inverted toprevent crystallization. Type A and B molassesare intermediate to final molasses. As expected,the energy level of molasses decreases as moreand more sugar is extracted. Molasses is usuallyquantitated with a Brix number, measured indegrees, and these numbers relate very closelyto the sucrose concentration in the product.Both cane and beet molasses contain about 46 - 48% sugar.

Although molasses contains relatively littleenergy and protein, it can be used to advantage tostimulate appetite and to reduce dustiness of feed.For example, feed intake is usually increased in birdssuch as young Leghorn pullets, if molasses ispoured directly onto feed in the feed trough. It isdoubtful that molasses improves ‘taste’ of feedunder these conditions, rather it presents a novelfeed texture to the bird. A major problem withmolasses is a very high potassium content, at 2.5– 3.5%, which has a laxative effect on birds.While most birds perform well on balanced dietscontaining up to 2% molasses, inclusion levels muchabove 4% will likely result in increased waterintake and increased manure wetness.



24. Dehydrated AlfalfaDehydrated alfalfa meal can be quite high in

protein (18 – 20%) although because the product is heated during drying, availability ofessential amino acids such as lysine is often 10to a 20% below expected values. Alfalfa isvery high in fiber content, and is most often addedto poultry diets as a source of xanthophylls forpigmentation, or as a source of so-called unidentified growth factors.

Alfalfa products should contain a minimumof 200,000 IU vitamin A activity per kg, althoughin most cases this will only be 70% available. Inorder to achieve intense yellow skin color in broilers or egg yolk color of � 10 on the Rochescale, diets should contain 5% alfalfa as one sourceof xanthophylls in the diet. Alfalfa levels muchin excess of 5% have only a moderate effect onpigmentation and so other natural or syntheticsources must be used to ensure consistentlyhigh levels of pigmentation. At high levels of inclusion (20%) problems can arise due to thesaponins and phenolic acids normally presentin alfalfa. If alfalfa contains any appreciable moldcount, then estrogen level can be high. Fresh grassis thought by some nutritionists to contain anunidentified growth factor which is of particularsignificance to turkeys, although much of this factor is destroyed by the dehydrating process.Even so, many nutritionists still insist on adding1 – 2% dehydrated alfalfa to turkey feeds, especially pre-starter and starter diets. Theaddition of small quantities of alfalfa also imparta darker color to diets which helps mask any minorfluctuations in appearance due to regular changesin formulations. The quality of alfalfa productshas been improved considerably in recent yearsdue to the use of inert gas storage, pelleting andaddition of antioxidants.

25. Full-fat Canola SeedsThe nutrient profile of canola seed makes it an

ideal ingredient for high nutrient dense diets.Periodically, grades unfit for oil extraction are available for animal feeding. Canola seed suffersfrom the same problems as described for canolameal, although obviously most harmful elementsare diluted by the high oil content. Seeds must beground adequately to ensure normal digestion, andthis is best accomplished by mixing with groundcorn prior to passing through a hammer mill.The oil provides considerable energy, and is an excel-lent source of linoleic acid. The ground seed is nottoo oily, and so provides a practical way of addingconsiderable quantities of fat to a diet. Due to earlyfrost damage, some samples of canola contain oilthat is contaminated with chlorophyll – while unac-ceptable to the human food industry, this contaminantdoes not seem to pose any major problems to poultry.

26. Groundnut (Peanut) MealThe peanut is an underground legume, and

because of warm moist conditions in the soil, isvery susceptible to fungal growth with aspergilluscontamination being of most concern. Grown essentially for their oil, peanuts yield a solvent extracted meal containing 0.5 – 1% fat with about47% protein. As with soybeans, peanuts con-tain a trypsin inhibitor that is destroyed by theheating imposed during oil extraction. Potential aflatoxin contamination is the major problem withgroundnut meal. Being a potent carcinogen, aflatoxin causes rapid destruction of the liver, evenat moderate levels of inclusion. Peanut meal thatis contaminated with aflatoxin can be treated byammoniation which seems to remove up to95% of the toxin. Alternatively, products suchas sodium-calcium aluminosilicates can beadded to the diet containing contaminatedgroundnut because these minerals bind with afla-toxin preventing its absorption.



24. Dehydrated AlfalfaDehydrated alfalfa meal can be quite high in

protein (18 – 20%) although because the product is heated during drying, availability ofessential amino acids such as lysine is often 10to a 20% below expected values. Alfalfa isvery high in fiber content, and is most often addedto poultry diets as a source of xanthophylls forpigmentation, or as a source of so-called unidentified growth factors.

Alfalfa products should contain a minimumof 200,000 IU vitamin A activity per kg, althoughin most cases this will only be 70% available. Inorder to achieve intense yellow skin color in broilers or egg yolk color of � 10 on the Rochescale, diets should contain 5% alfalfa as one sourceof xanthophylls in the diet. Alfalfa levels muchin excess of 5% have only a moderate effect onpigmentation and so other natural or syntheticsources must be used to ensure consistentlyhigh levels of pigmentation. At high levels of inclusion (20%) problems can arise due to thesaponins and phenolic acids normally presentin alfalfa. If alfalfa contains any appreciable moldcount, then estrogen level can be high. Fresh grassis thought by some nutritionists to contain anunidentified growth factor which is of particularsignificance to turkeys, although much of this factor is destroyed by the dehydrating process.Even so, many nutritionists still insist on adding1 – 2% dehydrated alfalfa to turkey feeds, especially pre-starter and starter diets. Theaddition of small quantities of alfalfa also imparta darker color to diets which helps mask any minorfluctuations in appearance due to regular changesin formulations. The quality of alfalfa productshas been improved considerably in recent yearsdue to the use of inert gas storage, pelleting andaddition of antioxidants.

25. Full-fat Canola SeedsThe nutrient profile of canola seed makes it an

ideal ingredient for high nutrient dense diets.Periodically, grades unfit for oil extraction are available for animal feeding. Canola seed suffersfrom the same problems as described for canolameal, although obviously most harmful elementsare diluted by the high oil content. Seeds must beground adequately to ensure normal digestion, andthis is best accomplished by mixing with groundcorn prior to passing through a hammer mill.The oil provides considerable energy, and is an excel-lent source of linoleic acid. The ground seed is nottoo oily, and so provides a practical way of addingconsiderable quantities of fat to a diet. Due to earlyfrost damage, some samples of canola contain oilthat is contaminated with chlorophyll – while unac-ceptable to the human food industry, this contaminantdoes not seem to pose any major problems to poultry.

26. Groundnut (Peanut) MealThe peanut is an underground legume, and

because of warm moist conditions in the soil, isvery susceptible to fungal growth with aspergilluscontamination being of most concern. Grown essentially for their oil, peanuts yield a solvent extracted meal containing 0.5 – 1% fat with about47% protein. As with soybeans, peanuts con-tain a trypsin inhibitor that is destroyed by theheating imposed during oil extraction. Potential aflatoxin contamination is the major problem withgroundnut meal. Being a potent carcinogen, aflatoxin causes rapid destruction of the liver, evenat moderate levels of inclusion. Peanut meal thatis contaminated with aflatoxin can be treated byammoniation which seems to remove up to95% of the toxin. Alternatively, products suchas sodium-calcium aluminosilicates can beadded to the diet containing contaminatedgroundnut because these minerals bind with afla-toxin preventing its absorption.



27. PeasPeas are a medium energy-protein ingredient

that can be used effectively in poultry dietsdepending upon local economical conditions.The major limitation to using peas is low levelsof sulfur amino acids and moderate energylevel. With high-tannin peas, there may be anadvantage to some type of heat treatment,although such processing is of little value for regular pea varieties. Protein digestibility isreduced by about 6% for each 1% increase intannin content. Peas do have some of theircarbohydrate as oligosaccharides, and so enzymesystems being developed to improve the digestibil-ity of soybean meal may be of use with peas.Peameal is a very dense material and bulk density of the final diet should be taken into consideration for diets containing > 15% peas.

28. SafflowerSafflower is grown mainly for its oil content

which, although variable, can be as high as40%. The residual meal contains in excess of 20%fiber and is referred to as undecorticated safflowermeal. It is possible to commercially remove alarge portion of the hull resulting in a mealcontaining 42 to 44% protein with a fiber content of around 14%. This product is referredto as decorticated meal. Safflower meal is verydeficient in lysine, although with appropriate lysinesupplementation the protein quality of safflowermeal is similar to that of soybean meal. However,with the high fiber content the available energyis still relatively low and so its value does not equalthat of soybean meal. Where safflower meal isavailable, relatively large quantities can be usedin poultry diets if proper consideration is givento nutrient availability.

29. Sesame MealSesame meal is very deficient in available

lysine, and this is sometimes used to advantage

in formulating lysine-deficient diets for experi-mental reasons. Sesame also contains highlevels of phytic acid which can cause problemswith calcium metabolism leading to skeletaldisorders or poor eggshell quality. If diets contain >10% sesame, then the diet should beformulated to contain an extra 0.2% calcium.

30. LupinsLow alkaloid lupins are being increasingly

used as an alternative feedstuff for poultry in certain areas of the world. These new cultivars havebeen reported to contain low levels of the toxic alka-loids (less than .01%) normally found in wild vari-eties. These low alkaloid lupin seeds are often referredto as sweet lupins and can vary in seed color.The high level of fiber in the seeds (up to 25%) resultsin low metabolizable energy values compared tosoybean meal. Mature lupin seeds contain little orno starch, the bulk of their carbohydrate beingoligosaccharides (sugars) and non-starch poly-saccharides. Many reports suggest that sweetlupins are comparable to soybeans in terms of pro-tein quality although they are much lower inmethionine and lysine. Their low oil content (6 to10%) and absence of antinutritive factors means thatthey can be inexpensively processed. Recentstudies have shown that dehulling lupins results ina marked increase in nutritive value. Also with prop-er dietary enzyme supplement the feeding value ofraw lupins is improved. Fine grinding also aidsdigestibility.

31. Blood MealBlood meal is very high in crude protein, and

while it is an excellent source of lysine, it is verydeficient in isoleucine and this imbalance needscorrecting if any substantial quantity is used ina diet. Blood meal is essentially the solids of theblood from processing plants, and consistsmainly of hemoglobin, cell membranes, cellu-lar electrolytes and a small quantity of lipid.



Historically, the level of blood meal used indiets has been severely limited, mainly becauseof problems of palatability, poor growth rateand abnormal feathering. All these problems relateto inherent amino acid balance and also to lowdigestibility induced by overheating of the bloodduring processing. With less harsh drying treatments, the amino acids are more stable, andthere are few problems with palatability. Ifblood meal is overheated, it has a much darker color, tending to be black rather than reddish-brown. The amino acid balance ofblood meal can be ‘improved’ by combining itwith other ingredients. For example, a 50:50 mixture of blood meal and hydrolyzed hairmeal gives a product with a reasonable aminoacid balance, and certainly a balance that is preferable to either product alone. Such a mixture may be used in least-cost formulation,whereas either ingredient is unlikely to be usedindependently because of amino acid balance.

32. Sources of Calcium,Phosphorus and Sodium Calcium

Constraints are not usually imposed on theseingredients because there should be fairly stringent constraints imposed on minimum andmaximum levels of calcium and phosphorus ina diet. There has been considerable controversyin the past concerning the relative potency of limestone vs oyster shell as sources of calcium,especially for the laying hen. Perhaps of moreimportance than the source of calcium, is particle size. Usually the larger the particlesize, the longer the particle will be retained inthe upper digestive tract. This means that the larger particles of calcium are released more slowly, and this may be important for the continuity of shell formation, especially in thedark period when birds are reluctant to eat.Oyster shell is a much more expensive ingredient

than limestone, but it offers the advantage of beingclearly visible in the diet to the egg producer andso there is less chance of omission during feedmanufacture. Birds also have some opportunityat diet self-selection if oyster shell is given, andthis may be of importance in maintaining optimum calcium balance on egg-forming vs nonegg-forming days. There are current limitationson oystershell dredging in the Chesapeakeregion of the U.S.A., due to environmentalissues, and this may add to the discrepency inprice between oystershell and limestone.

Limestone should be in as large a particle sizeas can be readily manipulated by the bird’sbeak. For laying hens, this means a fairly coarsecrumble consistency. There has been someconcern in recent years regarding the variabil-ity in solubility of limestone from various sources.This can easily be checked by measuring pHchanges when limestone is added to hydro -chloric acid at initial pH of 4.0. Obviously100% solubility is desirable, yet ideally thisshould be achieved over a prolonged period oftime which hopefully correlates with the slowrelease of calcium into the blood stream.

Periodically, dolomitic limestone is offeredto the feed industry. Dolomitic limestone contains at least 10% magnesium, and this com-plexes with calcium or competes with calcium for absorption sites. The consequence offeeding dolomitic limestone is induced calcium deficiency, usually manifested by poor skele-tal growth or egg shell quality. The major user ofdolomitic limestone is the steel industry and so prob-lems with this ingredient seem to mirror the eco-nomic malaise in steel production. Dolomitic lime-stone should never be used in poultry diets.

Phosphorus

A considerable number of inorganic phosphorus sources are used around the world.



Most naturally occurring phosphate sources areunavailable to the bird unless they are heat-treated during processing. As with limestone, thesolubility in HCl at pH 4 can be used as a meas-ure of quality. Insoluble phosphate sources areunlikely to be available to the bird – however solubility is not a guarantee of subse-quent availability. Solubility tests are thereforeonly useful in screening out insoluble sources. Testsfor biological availability are much more com-plex, because they necessarily require a chick bioas-say where growth and bone ash are measured.

The phosphorus in most phosphate sourceswith the exception of soft phosphate, can be regarded as close to 100% available. Rockphosphate and Curaco phosphate are the majorexceptions because these sources may only be60 – 65% available to the bird. Anhydrousdicalcium phosphate is about 10% less availablethan the hydrated form, and this seems to relateto solubility. In this context, ingredients that stimulate gastric secretion, and hence HCl production, seem to result in improved utiliza-tion of the anhydrous form. Some rock phosphatescontain various contaminants of concern forpoultry. The most common of these is vanadium.At just 7 – 10 ppm of the diet, vanadium will causeloss in internal egg quality and hatchability. Atslightly higher levels (15 – 20 ppm), there is achange in the shell structure where the shell takeson a somewhat translucent appearance, andappears more brittle. Rock phosphates canalso contain as much as 1.5% fluorine. Becausefluorine can influence calcium metabolism,there are often regulations governing the maximum permissible levels in feed. Only de-fluorinated rock phosphates are recommendedalthough it must be remembered that this product usually contains about 5% sodium.Most mineral sources are detrimental to thepelleting process because they create significant

friction at the pellet die. With phosphates,there is a distinct advantage to using rock phosphates rather than mono- or dicalciumphosphate in terms of pelleting efficiency, whereup to +10% throughput is achieved.

Sodium Sources

Most diets will contain some added salt,usually in the form of sodium chloride. Whereiodine is not added as a separate ingredient, iodizedsalt must be used. In most countries the varioussalt forms are differentiated by color, with common salt being a natural white color andiodized salt being red. Cobalt iodized salt is oftenused in diets for swine and ruminants, and thiscan be used without any problems for poultry.This type of salt is usually colored blue. Becausehigh levels of sodium chloride can lead toincreased water intake, then a substitution of sodium bicarbonate for a portion of this chloridesalt has been shown to be beneficial. Under thesecondition, up to 30% of the supplemental saltcan be substituted with sodium bicarbonatewithout loss in performance, and such birdsoften produce drier manure. For substitutions ofsodium bicarbonate for sodium chloride above30%, care must be taken to balance dietarychloride levels, since under commercial conditionsit is often difficult to add inexpensive sources ofchloride other than salt. Chloride contributedby ingredients such as choline chloride andlysine-HCl should be accommodated duringformulation. There is a trade-off when substitutingsodium bicarbonate for sodium chloride underheat-stress conditions. Birds will drink lesswhen NaHCO3 is used, and this is the reasonfor substitution. However, we really have to question this scenario, since higher levels of waterintake are correlated with survival under extremeheat stress conditions. Sources of calcium,phosphorus and sodium are given in Table 2.13.



Table 2.13 Calcium, phosphorus and sodium sources

Ingredient % Ca % PLimestone 38.0 -Oyster shell 38.0 -Calcium carbonate 40.0 -Bone meal 26.0 13.0Monocalcium phosphate 17.0 25.0Dicalcium phosphate 21.0 20.0Tricalcium phosphate 23.0 19.0Defluorinated rock phosphate 34.0 19.0Curaco phosphate 35.0 16.0Phosphoric acid (75%) - 25.0

Ingredient % Na % ClPlain salt 39.0 60.0Iodized salt 39.0 60.0 (I, 70 mg/kg)Cobalt iodized salt 39.0 60.0 (I, 70 mg/kg; Co, 40 mg/kg)Sodium bicarbonate 27.0 -

33. Trace Minerals Trace minerals are available in a variety of

forms, and periodically problems arise due to lackof knowledge of the composition, and/or stabilityof mineral salts. Most research into mineral availability has been conducted with so-calledreagent-grade forms of minerals, which are verypure and of known composition and purity.Unfortunately, the feed industry cannot afford theluxury of such purity, and so obviously, feed gradeforms are used.

One of the most important factors to ascertain prior to formulation is the state ofhydration of a mineral. Many mineral forms

contain ‘bound’ water which obviously dilutesthe effective mineral concentration. For example, hydrated cupric sulphate (white crystal) contains about 40% copper, whereas themore common pentahydrate (blue) contains26% copper. It should also be emphasizedthat the various processing conditions used in manufacturing will likely influence mineralbioavailability. A combination of these twofactors can mean a substantially lower potencyof trace mineral sources relative to chemical stan-dard values (Table 2.14). For this reason, feedmanufacturers are encouraged to take great



care in ordering trace minerals based on valency,hydration and purity. All minerals sourcesshould be analyzed, on an ‘as is’ basis for the majormineral component.

Because feed manufacturers are often concerned about ‘space’ in the diet during formulation, there is a trend towards makingvery concentrated mineral and vitamin premixes. In considering concentration of min-eral sources, oxides appear attractive, since theyinvariably contain the highest mineral concen-tration. Oxides however, are potent oxidizingagents, and if stored with premixed vitaminsfor any length of time, can cause the destructionof vitamins that are susceptible to oxidation.Since oxides are generally less available than othermineral salts, they should not be used exclusivelyin mineral premixes.

Cobalt

The major source of cobalt is cobalt sulphateor cobalt carbonate. Both products are goodsources of cobalt, with the cobalt as sulphate beingslightly more available than in the carbonate form. Cobalt oxide has very low availability, and should not usually be considered during formulation.

Copper

Copper oxide, sulphate and carbonate are usedby the feed industry. Copper oxide can be of verylow biological availability, especially with poorquality samples that contain significant amountsof metallic copper. Good quality copper oxide canbe considered as available as is copper sulphate.As previously mentioned, the degree of hydrationof copper sulphate must be specified.

Table 2.14 Trace mineral sources

1 Cupric; 2 Ferrous; 3 Ferric

Ingredient% of

major mineral

oxide 71.0

Cobalt chloride 24.0sulphate 21.0carbonate 46.0oxide1 79.0

Copper chloride 37.0sulphate 25.5carbonate 55.0oxide2 77.0

Iron chloride3 34.0sulphate2 32.0carbonate2 40.0oxide 56.0

Magnesiumcarbonate 30.0

% of Ingredient major

mineraloxide 77.0

Manganesechloride 27.5sulphate 32.5carbonate 47.0oxide 78.0

Zincchloride 48.0sulphate 36.0carbonate 52.0

Seleniumsodium selenite 46.0sodium selenate 42.0

Iodinepotassium iodine 77.0calcium iodate 65.0



Iron

Ferrous salts should be used in feed manu-facture. As with copper, the major contaminantcan be the metal itself, and this has a very lowbiological availability. Ferrous carbonate and fer-rous sulphate are the preferred forms of iron.Ferrous salts are prone to chemical change dur-ing storage, such that 10 – 20% of ferric salts canbe produced from original ferrous forms after 3–6 months storage at around 25ºC.

Magnesium

Magnesium carbonate and oxide are bothavailable in feed grade form. The oxide can takeup both water and carbon dioxide when storedfor any length of time, and such activity obviouslyreduces the relative potency of magnesium.

Manganese

The major source of manganese used in thefeed industry is manganese oxide. Sulphateand carbonate sources both have higher biologicalavailability, yet these are usually uneconomicalto use. Manganese oxide has a biological availability of 50 – 70%, yet this can be greatlyinfluenced by its major contaminant, namely manganese dioxide. Manganese dioxide isonly 50% as bioavailable as is the oxide, and soan appreciable content of dioxide can lead to amarked reduction in effectiveness of manganeseoxide. Oxides should not contain more than 10%dioxides, and undoubtedly the range of availabilityquoted in research findings is usually a reflection of dioxide contamination.

Zinc

Zinc oxide and zinc sulphate are the most common forms of zinc used in the feed industry. Zinc is often used as a catalyst in various industrial processes, and unfortunately cat-alysts sometimes find their way into the feedindustry and are of low biological availability. Zinc sources can be contaminated with

aluminum, lead and cadmium. If good quality sourcesare considered, then zinc oxide and zinc sulphateappear to be of comparable biological availability.

Selenium

Selenium is most often added to feeds as sodium selenite or sodium selenate. The mostcommon naturally occurring form of seleniumis selenomethionine, and this seems to have a muchlower potency than either of the salt forms.There seems to be a greater availability of selenium within low protein diets, althoughthis may be related to the fact that when birdsare growing at a slower rate, their absolute selenium requirement is reduced. Seleniumavailability, from whatever source, is improvedwhen diets contain antioxidants.

Selenite is more readily reduced to elementalselenium, and for this reason selenate is some-times preferred. Selenium metal is less availableand can form insoluble complexes with otherminerals. Whichever form of selenium is used,it must be remembered that the final diet inclusionsare extremely low in relation to the other minerals, and so some degree of premixing is essential prior to incorporation in diets or premixes.

Iodine

If iodine is added to a mineral premix, ratherthan supplied with salt, then potassium iodideand calcium iodate are the preferred sources.Potassium iodide is very unstable and deterio-rates rapidly with moderate exposure to heat, lightand/or moisture. Calcium iodate is the most common source of supplemental iodine.

Mineral chelates

Chelates are mixtures of mineral elementsbonded to some type of carrier such as anamino acid or polysaccharide. These carriers,or ligands, have the ability to bind the metal,



usually by covalent bonding through aminogroups or oxygen. The formed chelate is usuallya ring structure with the divalent or multivalentmetal held strongly or weakly through two or morecovalent bonds. Iron in hemoglobin is the classical example of a chelate. The covalent bond-ing is such that the chelate has no electrical charge.

Chelated, or complexed minerals are usuallymuch more expensive than inorganic minerals,and so one expects improved bird perform-ance through either enhanced absorption orbetter utilization in some way. It is difficult torationalize the cost of chelated minerals basedsolely on improved absorption in the intestine.Even a 50% difference in absorption can be mosteconomically resolved by doubling the level ofinorganic mineral used. However, there arelimits to the level of any one mineral to beused, because of potential negative effects ofabsorption and utilization of other mineralsand other nutrients. The mineral availability fromsome inorganic sources can be very low. For exam-ple, the manganese in some samples of manganesesulfate has been reported at just 5%, and inthis instance a 20 fold increase in inclusionlevel, while correcting the potential manganeseabsorption problem, will likely have adverse effectson utilization of phosphorus, calcium and iron.

Factors affecting the uptake of heme iron areoften used to support the concept of usingchelated minerals. There are a number of othertrace minerals, such as copper, manganese andphosphorus that can affect absorption of inorganiciron, while uptake of heme iron will be little affected. The uptake of chelated minerals is there-fore expected to be more consistent and less affected by adverse (or enhanced) environmentsin the gut lumen. Bioavailability of minerals fromchelates should also be consistent because of standardization during manufacture versus lessstandard conditions with some supplies of

inorganic salts. There are also claims of chelatedminerals being used more effectively at the cellular level following absorption. There are fewclassical supporting claims for these suppositions,and so enhanced performance of meat birds andlayers is discussed in terms of stimulation of various biological processes by the mineraland/or that the chelated mineral enters certainpools with greater affinity or efficiency.

Inorganic minerals are likely to contain tracequantities of heavy metals such as arsenic, leadand cadmium. Such levels of heavy metals arenot problematic to poultry, although the EEC hasrecently imposed limits of these metals in mineral premixes and complete feeds. While itis challenging to consistently achieve minimumlevels using conventional mineral salts, most chelat-ed minerals are very pure and usually containno heavy metals.

Ultimately the choice of using inorganicversus chelated minerals is one of economics,which obviously relates to cost benefit. Such resultsmay vary depending upon the levels and spectrum of trace minerals used and the bioavail-ability to be expected from inorganic sources thatare available.

34. Synthetic Amino AcidsSynthetic sources of methionine and lysine

are now used routinely in poultry diets and tryptophan and threonine will likely be usedmore frequently as future prices decline. Inmost situations, the use of synthetic amino acids(Table 2.15) is an economic decision, and so theirprice tends to shadow that of soybean meal,which is the major protein (amino acid) sourceused world-wide. By the year 2010, lysine usein North America is estimated to be at 150,000tonnes while that for methionine will be around85,000 tonnes, of which the poultry industries use30 – 65%.



Lysine is usually produced as the hydrochlo-ride salt, and consequently, the commercial products have 79% lysine activity on a weightbasis. Liquid lysine products are now also avail-able. In North America, lysine tends to be con-sidered a commodity, and as such its use isdirectly related to that of other ingredients. Ingeneral, there is greater L-lysine HCl usagewhen soybean meal price increases, or when cornprice declines. In Europe however, because ofinherently higher commodity prices, L-lysine HCltends to be used less as a commodity, and moreas a means of improving performance. Care mustbe taken therefore, in interpretation of cost benefit of lysine use in research results reportedfrom these two regions.

Tryptophan is not usually a limiting aminoacid in most poultry diets, and so the move to

greater synthetic tryptophan use comes from theswine industry. Tryptophan will become a limiting nutrient as crude protein levels of dietsare reduced, although currently its efficient useis somewhat hampered by complexity involvedin diet analysis. Tryptophan levels in ingredientsand feed are much more difficult to assay thanare the other common amino acids, and inpart, this situation leads to variability in researchresults aimed at quantitating response to tryptophan.This amino acid is most likely to be consideredwhen diets contain appreciable quantities of meator poultry by-product meal.

Methionine is available in a number of formsand also as an analogue. Over the years there hasbeen considerable research into the potency anduse of these various sources. There are essentiallyfour different sources of methionine (Table 2.16).

Table 2.15 Synthetic amino acids

CrudeAmino acid Relative protein

activity equivalent(%)

DL-Methionine 100 59Methionine hydroxy analogue (liquid) 88 0L-Lysine 100 120L-Lysine HCL 79 96L-Arginine 100 200L-Arginine HCL 83 166L-Tryptophan 100 86L-Threonine 100 74Glycine 100 117Glutamic acid 100 117



Lysine is usually produced as the hydrochlo-ride salt, and consequently, the commercial products have 79% lysine activity on a weightbasis. Liquid lysine products are now also avail-able. In North America, lysine tends to be con-sidered a commodity, and as such its use isdirectly related to that of other ingredients. Ingeneral, there is greater L-lysine HCl usagewhen soybean meal price increases, or when cornprice declines. In Europe however, because ofinherently higher commodity prices, L-lysine HCltends to be used less as a commodity, and moreas a means of improving performance. Care mustbe taken therefore, in interpretation of cost benefit of lysine use in research results reportedfrom these two regions.

Tryptophan is not usually a limiting aminoacid in most poultry diets, and so the move to

greater synthetic tryptophan use comes from theswine industry. Tryptophan will become a limiting nutrient as crude protein levels of dietsare reduced, although currently its efficient useis somewhat hampered by complexity involvedin diet analysis. Tryptophan levels in ingredientsand feed are much more difficult to assay thanare the other common amino acids, and inpart, this situation leads to variability in researchresults aimed at quantitating response to tryptophan.This amino acid is most likely to be consideredwhen diets contain appreciable quantities of meator poultry by-product meal.

Methionine is available in a number of formsand also as an analogue. Over the years there hasbeen considerable research into the potency anduse of these various sources. There are essentiallyfour different sources of methionine (Table 2.16).

Table 2.15 Synthetic amino acids

CrudeAmino acid Relative protein

activity equivalent(%)

DL-Methionine 100 59Methionine hydroxy analogue (liquid) 88 0L-Lysine 100 120L-Lysine HCL 79 96L-Arginine 100 200L-Arginine HCL 83 166L-Tryptophan 100 86L-Threonine 100 74Glycine 100 117Glutamic acid 100 117



Dow Chemical was the first to produce pow-dered DL-methionine in commercial quantitiesin the 1940’s, while Monsanto introduced the calcium salt of methionine hydroxy analogue in the1950’s. Since this time, the market has establisheddemand for both DL-methionine and the analogue,in both powdered and liquid forms.

It has been known for some time that mostessential amino acids can be replaced by the corresponding -keto acid (analogue). With theexception of lysine and threonine, which are notinvolved in transamination processes, it is therefore possible to replace amino acids withtheir keto acid-analogues. Presumably the birdproduces the corresponding amino acid bytransamination involving mainly non-essentialamino acids such as glutamic acid. Suchtransamination can occur in various tissues,and some bacteria in the intestine may alsosynthesize amino acids prior to absorption. Thequestion of relative potency of products such as

liquid MHA (eg. Alimet®) often arises in selec-tion of methionine sources. Liquid MHA has avalue of 88% methionine based on normalchemical structure. Availability of this 88%value has then been shown to vary from 60 –100%. It seems inconceivable that any nutrientcould have such variable efficacy, and so one mustlook at experimental conditions and diet for-mulation in assessing such results. Potency ofMHA relates to variable uptake in the intes-tine, degradation in body tissues and/or degreeof elimination by the kidney. Another major vari-able in response to MHA under commercialconditions is ingredient methionine levels usedin formulation and diet specifications for methio-nine and cystine. There are usually logical reasonswhy nutritionists use different potency values. Thebottom line is cost per kg of meat/eggs produced,and the value of products such as MHA quick-ly establish themselves over time within anintegrated operation. In most situations MHA isused at 85-88% relative to DL-methionine.

MethionineDL- Methionine hydroxy

DL- methionine hydroxy analogue-methionine Na analogue Ca

CH3 CH3 CH3 CH3

S S S S

CH2 CH2 CH2 CH2

CH2 CH2 CH2 CH2

H-C-NH2 H-C-NH2 H-C-OH H-C-OH

COOH COONa+ COOH COOCa+

Powder Liquid Liquid Powder

Table 2.16 Methionine sources


SECTION 2.2Ingredient testing

I ngredients must be continuously moni-tored to ensure consistency of nutrientprofile and presence of potential contam-

inants. The number and frequency of assays willdepend upon the class of ingredient, historicalresults of analysis and to some extent the seasonof the year. Ingredients from new suppliersshould be tested the most rigorously, and number and frequency of testing reduced onlywhen consistency of nutrient profile is established.Examples of the type and frequency of testing aregiven previously with the description of all themajor ingredients.

The frequency of sampling will obviously varywith the significance of a particular ingredientin the feed. For example, where fish meal is usedextensively, and represents a significant pro-portion of dietary amino acids, then amino acidanalyses may be done more frequently, and it mayalso be advisable to screen more often for gizzard erosion factors. On the other hand, wherea history of consistent analyses is developed, thentesting can be less frequent.

For assay results to be meaningful, ingredientsmust be sampled accurately. For bagged ingre-dients, at least 4 bags per tonne, to a maximumof 20 samples per delivery, should be taken, andthen these sub-samples pooled to give one or twosamples that are sent for assay. It is alwaysadvisable to retain a portion of this mixed sample,especially when assays are conducted by outsidelaboratories. For bulk ingredients, there shouldbe about 10 sub-samples taken from each truckor rail car load and again this mixed to give a representative composite for assay.

There are a number of rapid tests availablefor evaluating ingredients. In some instances, these

tests are specific to certain ingredients and to spe-cific nutrients and/or antinutrients within aningredient. Alternatively, some tests are more gener-ic and can be applied across a number of ingre-dients. The decision to carry out any of these testsis based on significance of the ingredient inthe diet, and so the relative contribution of con-stituents under test. Developing historical dataon ingredients is also a useful way of deter-mining the need and frequency of various testing procedures. The following testsor methodologies are assumed to be in additionto more extensive chemical testing that will routinely be used for the most important nutrients.

a. Bulk densityBulk density of individual cereals is correlated

with energy value and protein content. In NorthAmerica, the usual measurement is bushelweight, while the common metric equivalent iskg/hl. Weight of 100 kernels of cereal is also usedas an indicator of bulk density. Under normalgrowing conditions, as bulk density declines, thereis usually a reduction in energy level, mainly associated with reduction in starch content of theendosperm. Concurrently protein content oftenincreases since protein is commonly found in theouter bran or pericarp layers. Bulk density is alsoa useful measure for calculation of needs for storage space within the mill.

Bulk density will vary with moisture content,and this should be taken into account during measurement. Density is easily measured byweighing the cereal or feed into a container ofknown volume. The smaller the container, thegreater the care needed in standardizing thefilling and especially the packing of the ingredient. Bulk density values are not always

2.2 INGREDIENT TESTING



additive and so the density of a mash feed cannot always be predicted from knowledge ofbulk density of component ingredients. This situation arises, because of ‘mixing’ of particlesof different size within a feed, so affecting the empty space common with low bulk density ingredients such as wheat shorts or alfalfa meal.

b. Proximate analysisProximate analysis is still the most widely used

system for monitoring the quality of ingredi-ents. At a time when we formulate diets basedon digestible or metabolizable nutrients, itsvalue is often questioned, since proximate com-ponents are very broad and encompass what canbe both digestible and indigestible components.However, proximate analysis is quite rapid andinexpensive, and does give an idea of continu-ity of composition. Proximate analyses canalso be used to predict the content of nutrientssuch as total and digestible amino acids. This typeof information is essentially regression analysesof simple proximate components versus analyticalvalues for amino acids.

For proximate analysis an ingredient is partitioned into six fractions, namely water,ether extract, crude fiber, nitrogen-free extract,crude protein and ash. Some of the informationfrom proximate analyses (usually the protein, etherextract, fiber and ash values) are shown ondescriptive feed labels, which accompany feed-stuffs and complete feeds. These values represent the guarantees of quality used by thefeed manufacturing industry.

Water is usually determined by the loss in weightthat occurs in a sample upon drying to constantweight in an oven. Although water is considereda nutrient, it effectively is a diluent for othernutrients. Increase in moisture, therefore, reducesthe total nutritional value of a feedstuff. Becausewater content can vary, ingredients should be com-

pared for their nutrient content on a dry matter basis.Moisture much in excess of 12 – 13% is cause forconcern regarding potential for mold growth.

Fat is determined by extracting the dry sample with ether. The weight of the extract isdetermined after distilling the ether and weigh-ing the residue. Although this is the usualmethod for determining fat in feeds, ether extraction does not remove all the fats, especiallyphospholipids or fats bound to protein. Often acidhydrolysis followed by extraction of the hydrolysatewith chloroform:methanol or ether is necessaryto obtain ‘total’ lipid values. Acid hydrolysis alsoliberates fat present as soap, and is more likelyto liberate fat from bacterial cell walls.

Crude protein is determined by measuring thenitrogen content of the feed and multiplying thisby 6.25. This factor is based upon the fact that onaverage, a pure protein contains 16% nitrogen.Thus 100/16 = 6.25. For most ingredients, thisassumption is fairly accurate, and allows us to esti-mate protein (which is a very complex assay) basedsimply on assay for nitrogen, which is quitestraightforward and inexpensive. The nitrogen con-tent of a feedstuff is determined usually by theKjeldahl or heco methods. The Kjeldahl involvesconversion of the nitrogen in feedstuffs to anammonium salt by digestion with concentratedsulfuric acid in the presence of a suitable catalyst.The ammonia is distilled from the digestion mix-ture into a collecting vessel after the sample is madealkaline. The amount of ammonia is determinedby titration with standard acid, and then nitrogen,and hence crude protein are calculated.

Ashing of an ingredient combusts all organicconstituents, leaving behind only the mineral elements. Some elements such as seleniumand arsenic form volatile oxides at this temper-ature. These losses can be avoided if the ash ismade alkaline by addition of known quantitiesof calcium oxide prior to ashing.



Crude fiber refers to the organic residue ofa feed that is insoluble after successive boilingwith H2SO4 and NaOH solutions according tospecified procedures. The determination ofcrude fiber is an attempt to separate the more readily digestible carbohydrates from those lessreadily digestible. Boiling with dilute acid andalkali is an attempt to imitate the process that occursin the digestive tract. This procedure is based onthe supposition that carbohydrates, which are readily dissolved by this procedure, also will be read-ily digested by animals, and that those not solubleunder these conditions are not readily digested. Atbest, this is an approximation of the indigestible mate-rial in feedstuffs. Nevertheless, it is used as a gen-eral indicator in estimating the energy value of feeds.Feeds high in fiber will be low in ME.

Nitrogen-free extract (NFE) is determined bysubtracting from 100 the sum of the percentagesof ash, crude protein, crude fiber, ether extractand water. The NFE is considered to be a measureof the digestible carbohydrates. A criticism of theproximate analysis system, is that its major contributor, namely NFE, is calculated by difference,and not actually determined directly.

Proximate analysis gives some indicationof the nutritive value of an ingredient. Forexample, a material very high in crude fiber islikely to have a low energy value, while feedstuffslow in crude fiber and high in ether extract arelikely to be of high energy value. The crude pro-tein content of material is a good indicator of itspotential value as a protein source. Unless theamino acid composition is known, however, theactual quality of the protein cannot be determined.Certain ingredients such as meat meal normallycontain a high quantity of ash. In meat meal andfish meal, calcium and phosphorus may beestimated from the ash value since it consists main-ly of bone ash. Thus a determination of the ashof these materials may be very useful.

Proximate analyses should perhaps be bettertermed ‘approximate analyses’, especially since itsmain component, NFE, is determined by difference. However, it is a useful starting point fornecessity to conduct other more specific analyses.

c. Amino acid analysesDetermination of total amino acids is time

consuming and expensive and so tends not to bea routine procedure. The most common proceduretoday is gas-liquid chromatography, which canbe highly automated to give relatively speedyanalyses. However, the major time factor residesin preparation of the sample for analysis, since thecomponent amino acids have to be freed from with-in protein structures. This pre-analysis procedureis usually termed hydrolysis, and unfortunatelycare must be taken during this process, since twoimportant amino acids can be destroyed by inap-propriate processing. Tryptophan is almost com-pletely destroyed by acid hydrolysis and can onlybe determined following alkaline or enzymatichydrolysis. The acid buffers used in amino acidanalyses also cause loss of tryptophan. Special pre-cautions also must be taken against loss of methio-nine and cystine during hydrolysis. Perfomicacid oxidation is usually carried out prior tohydrolysis, such that methionine is converted tomethionine sulfone and cystine to cysteic acid.Amino acids are then liberated from the proteinsby hydrolysis with HCl. In the case of tryptophan,further precautions against destruction by acids andalkalis are essential. Such problems in prepara-tion of samples are often the reason that tryptophanis omitted from published data.

For measurement of digestible (available)amino acids, it is necessary to feed birds and meas-ure total amino acids in the feed and excreta. Thedifference between amino acid input and output is assumed to be digestible or availableamino acids. The bioassay is most easily achieved



by the TME precision force-feeding system,because the ingredient can be considered alone.In a classical bioassay, the bird voluntarily eatsfeed and only the test ingredient can supply aminoacids. This situation means that semi-purified diets(containing other basal ingredients such assugar, starch, sand and oils) are necessarilyused and the practicality of such diets are oftenquestioned. Today, virtually all estimates ofamino acid digestion are derived from the force-feeding method, and values are often termed TAAA(True Amino Acid Availability).

d. Metabolizable Energy (AME or TME)

Metabolizable energy is the most costly nutrient in an ingredient or diet, yet unfortunate-ly it is the most difficult to measure. As fordigestible amino acids, estimates of AME or TMErequire a bioassay involving live animals. Theonly lab assay for energy is gross energy and thisis merely a starting point used in AME or TME determinations. Gross energy is the total heatevolved when an ingredient or diet is burned in anatmosphere of oxygen. Wood and corn haveapproximately the same gross energy.

In an energy bioassay, birds are fed diets containing a given quantity of the ingredient, andfeed intake and excreta output measured over a 3–5 d balance period. Gross energy is determined on feed and dried excreta and calculations madeto determine the metabolizable energy derived fromthe ingredient under test. In the TME assay, the birdis force-fed only the ingredient under test, and sothe estimate of ME is simplified. With all the laboratory and sample preparation necessary forthe test, it is challenging to generate results within a 2–3 week period, at a cost approaching$1,000 USD per sample.

Because of the complexity and cost involvedin measuring AME or TME, various chemical or invitro systems have been developed. Essentially thesemethods attempt to correlate more easily measurablecomponents, with available energy. One of the firstsuch calculations was applied by Carpenter andClegg (1956) and their equation is still as good asanything developed in the last 50 years.

ME (kcal/kg) = 53 + 38(%CP + 2.25 x % fat+ 1.1 x % starch + % sugar)

This type of prediction equation is accurate towithin ± 200 kcal/kg and so is useful for giving anestimate of AME for a novel ingredient. There havealso been ME assays based on enzyme digestion. Themost successful uses duodenal fluid taken from a pig,and measuring the gross energy of solubilized components after 1 – 2 hr of incubation. AME hasalso been predicted by NIRA (see next section).

e. Near Infra Red Analysis(NIRA)

NIRA offers the possibility for very rapidanalyses of ingredients and feeds. The techniquehas the potential to assay many organic com-pounds. The system has the capability to measuremetabolizable energy as well as more simple components such as fat, moisture, protein andfiber. Analysis relies on measuring how muchlight energy is absorbed when the sample is bombarded with light at very specific wavelengths.

The basis of NIRA is chemometrics, whichis the application of mathematics to analyticalchemistry. The technique is an integration of spectroscopy, statistics, and computer sciences.Mathematical models are constructed that relatechemical composition (active chemical groups)to energy changes in the near infra red region ofthe spectrum which ranges from 700 to 2500 nmin wavelength. In this region of the spectrum we



measure mainly vibrations of chemical bonds inwhich hydrogen is attached to atoms such as nitro-gen, oxygen, or carbon. Because most feedstuffsare opaque, NIRA uses reflectance instead of transmittance. The reflected light of a sample isused to indirectly quantify the amount of energyabsorbed in a sample. NIRA measures theabsorption of infra red radiation by variouscomponents, for example, peptide bonds atspecific wavelengths in the near infra red spectrum.Other components of the sample absorb energyas well, however, and have the effect of interfer-ing. This effect is eliminated by mathematical treat-ment of the spectral data and by multiple linearregression or other statistical procedures.

Because each molecule usually exists in its low-est energy state, absorption of energy will raise itsenergy state to some degree. Such energy absorp-tion occurs at a wavelength that is characteristic forthat particular molecule. Energy absorption in thefundamental infra red region is very strong, but alsovery specific for certain molecular groups. For exam-ple, water has a characteristic absorption at the samewavelength as does starch. Strong, but specific fundamental wavelengths, would be difficult to dif-ferentiate for these two components. This does notmean to say that infra red analysis does not havea place in feed analysis. For example, with purenutrients (amino acids, vitamins) the use of lightreflectance in the fundamental range may offer poten-tial for very specific analysis of purity. With sam-ples of mixed composition, whether it be ingredientsor complete feeds, then a more subtle analysis mustbe used to differentiate all the various chemical group-ings. In the weaker absorbing NIR range of wave-lengths, it is secondary absorption wavelengths thatare considered – these are most often referred toas ‘overtones’. By considering a spectrum ofwavelengths, a characteristic pattern of absorptionenergy is given for each major component of thesample. Chemometrics then involves calculation

of correlation coefficients at each wavelength andsimultaneously selecting both the best fit with thenutrient under study, and also the best fit at all otherabsorption frequencies so as to remove all interferenceproblems with application of a correction factor.

The usefulness of NIRA, therefore dependsentirely on the careful and conscientious calibrationof the equipment. To some extent this exercisehas been simplified through introduction of so-called scanning machines that cover a wideband of NIR. Prior to this technology, only fixedwavelength equipment was available, and soprior knowledge of likely absorption bands ortedious testing of numerous wavelengths was essential in order to develop useful calibrations.

Developing calibrations for componentssuch as moisture, fat, crude protein and fiber isa very straightforward procedure. These calibrationscan be combined within a single program suchthat from each ingredient scan, these various analyses are conducted concurrently. For mostcommercial machines, ensuring consistent fine-ness of grind and controlling moisture contentof samples eliminates much of the variationassociated with operating procedure.

Determination of ME with NIRA provides aconsiderable challenge. Firstly, there is a needfor an extensive range of diets of determined analy-sis to be used for calibration. The conventionalbioassay for ME is both time consuming and veryexpensive, and these facts have undoubtedly limited investigation to date. Secondly, ME perse provides a complex problem for NIRA,because energy contribution is not confined toone nutrient but rather is represented by a rangeof molecular bondings and configurations.Usefulness of NIRA to predict ME thereforedepends upon careful bioassay of a range of dietspreselected in terms of anticipated ME, nutrient



contribution and ingredient composition. Theselatter parameters are of importance if ‘universal’calibrations are to be developed. Similarly,great care must be taken in the mathematicalmanipulation of spectral coefficients. Over thelast few years Valdes and Leeson (1992, 1994)have developed a number of such calibrationsfor feeds and ingredients. Table 2.17 shows someof these results for ingredients.

Table 2.17 Prediction of metaboliz-able energy by NIRA (kcal/kg)

Ingredient Determined NIRAprediction

Corn 3380 3370Barley 2720 2670Wheat 3275 3225

Soybean meal 2340 2320Bakery meal 2990 3005

Tallow 8690 8680Poultry fat 9020 8840

Corn oil 9660 9530Palm oil 7300 7700

Adapted from Valdes and Leeson (1992, 1994)

There is also potential for NIRA to predictamino acids in ingredients (Table 2.18) as wellas antinutrients such as glucosinolates or trypsininhibitors. As with NIRA analyses, the accuracy

Table 2.18 Prediction of aminoacids in fish meal

%Amino AcidAssay NIRA prediction

Methionine 1.5 1.6 ± 0.06Cystine 0.6 0.6 ± 0.07Lysine 3.7 4.0 ± 0.30Tryptophan 0.6 0.5 ± 0.03Threonine 2.2 2.3 ± 0.09Arginine 3.4 3.4 ± 0.09

Valdes and Leeson (unpublished)

f. Urease testing of soybeans andsoybean meal

Levels of the enzyme urease are used as anindicator of trypsin inhibitor activity. Urease ismuch easier to measure than is trypsin inhibitorand both molecules show similar characteristicsof heat sensitivity. A rapid qualitative screeningtest for urease can be carried out using conversion of urea to ammonia in the presenceof an indicator.

A qualitative test for urease activity can becarried out using a simple colorimetric assay. Urea-phenol-red solution is brought to an ambercolor by using either 0.1 N HCl or 0.1 N NaOH.About 25 g of soybean meal is then added to 50ml of indicator in a petri dish. After 5 minutes,the sample is viewed for the presence of red particles. If there are no red particles showing,the mixture should stand another 30 minutes, andagain if no red color is seen, it suggests overheatingof the meal. If up to 25% of the surface is covered in red particles, it is an indication of accept-able urease activity, while 25 – 50% coveragesuggest need for more detailed analysis. Over50% incidence of red colored particles sug-gests an under-heated meal.

g. Protein solubilityPlant proteins are normally soluble in weak

alkali solution. However, if these proteins areheat-treated, as normally occurs during pro-cessing of many ingredients, the solubility of protein will decline. Dale and co-workers atGeorgia have developed a fairly rapid test whichseems to give a reasonable estimate of proteinsolubility and hence protein quality in soybeanmeal. The assay involves adding just 1.5 g of soy-bean meal to 75 ml of 0.2% potassium hydrox-

of such predictions is greatly influenced bythe time and precision involved in calibration usingsamples of known composition.



ide solution, and stirring for 20 minutes. Solubleproteins will be in the liquid phase and so all ora portion of the centrifuged liquid is assayed forcrude protein, and protein content relative to theoriginal 1.5 g sample calculated accordingly. Byknowing the crude protein content of the orig-inal sample of soybean meal, percentage solu-bility can easily be calculated. Typical results,as shown by Dale and Araba are given in Table2.19. As heating time is increased, there is adecrease in protein solubility. Values of 75–80%solubility seem to be ideal, with higher values sug-gesting under-heating, and lower values over-heat-ing of the protein. A variation of this test is to assessprotein solubility in water. Sometimes termedProtein Solubility Index, the results of water sol-ubility are said to be more highly correlated withfeeding value than are estimates of urease indexor protein solubility in KOH.

h. Protein and amino acid dye-binding

Proteins will bind with a number of dyes andso this provides the basis for colorimetric assays.These dye-binding techniques can be used to test protein per se or used to test for protein in various extractions involved in assays of solubilityor digestibility. Dye-binding can thereforereplace the Kjeldahl analysis depending upon sensitivity needs. The most commonly usedmethods are as follows:

Cresol Red J. Amer. Assoc. Anal. Chem. 43:440

Orange G J. Nutr. 79:239

Coomassie Blue Anal. Biochem. 72:248

Lysine also reacts with certain dyes to givea colorimetric assay. Carpenter suggested thatif the e-amino group of lysine is free to react with dye, then the lysine can be considered as ‘available’. The most commonly used dye is Fluoro-

2,4 dinitrobenzene (FDNB), which gives a yellow/orange color when combined with lysine.

Table 2.19 Protein solubility ofsamples of soybean meal heated forvarious times

Urease Protein Wt Heating (ph solubility gain Feed:Gaintime change) (%) (g)0 (Raw) 2.40 99.2 343d 2.44c

5 min 2.04 87.7 429c 2.29bc

10 min 0.23 79.1 481ab 2.00a

15 min 0 74.9 496a 2.09ab

20 min 0 71.8 500a 2.03a

Dale and Araba (1987)

i. Fish meal gizzard erosion factorIn some countries, fish meal is an econom-

ical feed ingredient to use in poultry diets. Aspreviously described, some samples of fish mealwill cause severe gizzard erosion in young birds.Where fish meal is an integral part of a broiler diet,then it is common to carry out a chick growthtest with each shipment of fish meal. About 50chicks are fed a broiler starter diet, usually without any fish meal, for 5 – 7 days. At this time,the diet is mixed with 40 – 50% of the test fishmeal, and this diet fed for another 7 – 10 days.Birds are then sacrificed and the gizzard exam-ined for erosion, often using a subjective scaleas follows:

1. very mild erosion, with good gizzard color

2. mild erosion, with evidence of destruction of the lining in some areas

3. erosion in localized areas, with cracks in the thinner lining

4. severe erosion, cracking, thinning and discoloration

5. sloughing of the gizzard lining withhemorrhage



ide solution, and stirring for 20 minutes. Solubleproteins will be in the liquid phase and so all ora portion of the centrifuged liquid is assayed forcrude protein, and protein content relative to theoriginal 1.5 g sample calculated accordingly. Byknowing the crude protein content of the orig-inal sample of soybean meal, percentage solu-bility can easily be calculated. Typical results,as shown by Dale and Araba are given in Table2.19. As heating time is increased, there is adecrease in protein solubility. Values of 75–80%solubility seem to be ideal, with higher values sug-gesting under-heating, and lower values over-heat-ing of the protein. A variation of this test is to assessprotein solubility in water. Sometimes termedProtein Solubility Index, the results of water sol-ubility are said to be more highly correlated withfeeding value than are estimates of urease indexor protein solubility in KOH.

h. Protein and amino acid dye-binding

Proteins will bind with a number of dyes andso this provides the basis for colorimetric assays.These dye-binding techniques can be used to test protein per se or used to test for protein in various extractions involved in assays of solubilityor digestibility. Dye-binding can thereforereplace the Kjeldahl analysis depending upon sensitivity needs. The most commonly usedmethods are as follows:

Cresol Red J. Amer. Assoc. Anal. Chem. 43:440

Orange G J. Nutr. 79:239

Coomassie Blue Anal. Biochem. 72:248

Lysine also reacts with certain dyes to givea colorimetric assay. Carpenter suggested thatif the e-amino group of lysine is free to react with dye, then the lysine can be considered as ‘available’. The most commonly used dye is Fluoro-

2,4 dinitrobenzene (FDNB), which gives a yellow/orange color when combined with lysine.

Table 2.19 Protein solubility ofsamples of soybean meal heated forvarious times

Urease Protein Wt Heating (ph solubility gain Feed:Gaintime change) (%) (g)0 (Raw) 2.40 99.2 343d 2.44c

5 min 2.04 87.7 429c 2.29bc

10 min 0.23 79.1 481ab 2.00a

15 min 0 74.9 496a 2.09ab

20 min 0 71.8 500a 2.03a

Dale and Araba (1987)

i. Fish meal gizzard erosion factorIn some countries, fish meal is an econom-

ical feed ingredient to use in poultry diets. Aspreviously described, some samples of fish mealwill cause severe gizzard erosion in young birds.Where fish meal is an integral part of a broiler diet,then it is common to carry out a chick growthtest with each shipment of fish meal. About 50chicks are fed a broiler starter diet, usually without any fish meal, for 5 – 7 days. At this time,the diet is mixed with 40 – 50% of the test fishmeal, and this diet fed for another 7 – 10 days.Birds are then sacrificed and the gizzard exam-ined for erosion, often using a subjective scaleas follows:

1. very mild erosion, with good gizzard color

2. mild erosion, with evidence of destruction of the lining in some areas

3. erosion in localized areas, with cracks in the thinner lining

4. severe erosion, cracking, thinning and discoloration

5. sloughing of the gizzard lining withhemorrhage



Because 40 –50% fish meal is used, some gizzard erosion is expected with most samples.Scores of 4 – 5 are often used to reject samples,although this decision will to some extentdepend upon the level of fish meal to be usedin the commercial diet.

j. Sorghum tanninsTannins are detrimental to protein utilization,

and so levels should be minimized in poultry diets.Sorghum is a potential source of tannin, and thisis usually found in the outer seed coat.Unfortunately, there is not a clear relationshipbetween seed coat color and tannin content. Hightannin sorghums are usually darker in color,but some dark colored sorghums are also low intannin. The tannins are present in the testa, whichis the layer immediately beneath the outer peri-carp. One quick test is therefore to cut into theseed and observe for presence of a pigmented(tannin) testa. More recently, a bleach test hasbeen developed which again shows presence,or not, of a pigmented testa. About 20 g ofsorghum is mixed with 5 g potassium hydroxidecrystals and 75 ml of household bleach. The mixture is shaken until the KOH dissolves, andthen set aside for 20 minutes. Sorghum grainsare then strained, rinsed with water and placedon a paper towel. The KOH will remove the outerpericarp, and expose the testa. High tannin grainswill appear dark brown/black while low tanninsorghum will be bleached white/yellow.

k. Gossypol in eggsFeeding gossypol to laying hens can result in

discoloration of both the yolk (green-brown)and albumen (pink). Gossypol is usually foundin cottonseed meal and, as described previ-ously for this ingredient, there are ways to minimize the effects of this compound by dietmodification. However, egg discoloration occursperiodically, and cottonseed meal or cotton-

seed oil is often suspected. Placing egg yolks ina petri dish with ammonia quickly causes vary-ing degrees of brown discoloration dependingupon gossypol content.

l. Fat assaysFat quality is best assessed by measurement

of moisture, impurities and individual fattyacids. However, there are a number of lessextensive tests that can be used to give some ideaof fat composition and quality. Fat titre is a measure of hardness, and simply relates to melting point. The break-point between tal-lows and greases is about 40˚C. The higher themelting point, the more saturated the fat. Titreshould obviously be consistent for an individualclass of fat or fat blend from any one supplier.Iodine value can also be used as a measure ofhardness. Each double bond (unsaturated) willtake up a molecule of iodine, and so higher val-ues mean a greater degree of unsaturation,which in turn should relate to lower titre (Table2.20). Iodine value is greatly influenced bylevels of palmitic, oleic and linoleic acid inmost fats and oils. Generally, as titre increasesby 10 units over the range of 50 – 100, thenpalmitic acid content decreases by about 2%. Alsoas a rule of thumb iodine value = 0.9 x % oleicacid + 1.8% x linoleic acid.

Table 2.20 Iodine value and titre ofcommon fats

Iodine Value TitreºC

Tallow 45 45

Lard 65 40

Poultry fat 80 35

Vegetable oil 120 15



A major concern with the quality of fats andoils, is rancidity or the potential for rancidity.Rancidity is an irreversible oxidative process, thatis autocatalylic, meaning that breakdown productsfuel further degradation. Rancid fats will be lesspalatable, less digestible, and in extreme cases, theprocess of oxidative rancidity can continue inthe body of the bird following consumption of thesefats. The Initial Peroxide Value (IPV) is often usedto measure degree of rancidity upon delivery of afat. An IPV in excess of 18 – 20 meq is cause forconcern. If a fat is not stabilized with an antiox-idant, there is potential for subsequent rancidityduring storage. This potential can be measured bycreating extreme conditions for rancidity, name-ly bubbling pure oxygen through the heated sample for 24 hr, and re-measuring peroxidevalue. As a word of caution, peroxide build-up istime dependent, since after reaching a peak, thereis a breakdown of peroxides to other indigestiblecompounds. Therefore fats that have finished oxidizing can show a low peroxide value, but havevery poor nutritive value. Such samples are bestdetected by their ‘rancid smell’.

m. Hulls in rice by-productsRice bran, sometimes called rice pollard, is

used extensively in rice growing areas of the world.The major variable affecting nutritive value, is thecontent of hulls, which are essentially indi-gestible for poultry. A major component of hullsis lignin, and this reacts with the reagent phloroglu-cinol to produce a color reaction. The reagentis produced by combining 1 g of phloroglucinolwith 80 ml 2M HCl and 20 ml ethanol. The riceby-product is mixed 1:2 with reagent and heldat about 25ºC for 10 minutes. Development ofred color will be directly proportional to hull content. Actual hull content and a color score-card are necessary to ‘calibrate’ the assay.

n. Mineral solubilityNeutralizing mineral salts with various acids

can be used to give some idea of mineral avail-ability, and when an assay is monitored over timethen information on rate of solubility is alsoobtained. Hopefully, all mineral sources will betotally available to the bird, although, at least withcalcium sources, there is concern about solubility.Slow solubilization is preferable to very rapid solubilization, because the former more closelymatches the prolonged duration of need for calcium supply to the shell gland in laying hens.

Limestone solubility can easily be meas-ured by monitoring pH of the mineral in diluteacid. After recording the original pH of a 90 mlaliquot of 0.1 N HCl, 10 g of limestone is grad-ually added, and without stirring, pH measuredafter time intervals of say 10, 20, 30 and 60 minutes. Limestone will result in an increase inpH, as H+ ions are liberated from solution. ApH change of +0.1 relates to a 20% solubility,while changes of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9 and 1.0 relate to about 37, 50, 60, 70, 75,80, 84, 87 and 90% solubility respectively. A pHchange of +2.0 means 99% solubility. A high solubility after 60 minutes is expected from a quality limestone, whereas the rate of achieving95 – 99% solubility will give an indication of therate of calcium release in the proventriculus.Particle size and particle porosity are the factorsmost likely to affect rate of change of solubility.Optimum eggshell quality, and perhaps bone devel-opment in young birds, are dependent upon aconsistent pattern of calcium solubility.

Neutralization of ammonium citrate hasbeen used to assess solubility of phosphatesources and also of manganese and zinc salts.

SECTION 2.3Feed additives


2.3 FEED ADDITIVES

Anumber of additives are often used in poul-try diets and most of these do not con-tribute any nutrients per se. Most

additives are used to improve physical dietcharacteristics, feed acceptability or bird health.The following discussion is not intended toemphasize efficacy of the various products butrather to highlight various implications of theiruse in terms of diet formulation, ingredientcompatibility and/or general feeding management.

a. Pellet bindersWhen pellet quality is of concern, a pellet

durability index is often ascribed to ingredientsand this is considered during formulation. Thisindex may range from 55 – 60 for corn soy dietsthat are notoriously difficult to pellet, to 90 – 95for wheat-based diets. With corn-based diets, itis often necessary to use synthetic pellet bindersin order to achieve desirable pellet quality. In mostinstances, the need for a good pellet is necessaryto placate the purchaser of the feed, because thebird per se is often tolerant of a range of qualityin terms of growth rate and feed efficiency. Theturkey poult is perhaps the most sensitive topellet or crumble quality, where growth ratecan be markedly influenced by both pellet sizeand the proportion of fines. The pelleting processis discussed in more detail in the following section on Feed Mixing and Pelleting.

A number of pellet binders are available,although they are used at considerably differentinclusion levels, and such levels should beclearly specified for each product. When wheator wheat by-products are used at less than 10%of the diet, then a binder will often be necessaryif high pellet durability is desired. The twomajor types of binders have lignosulfonate or colloidal clays as the base product, with inclu-

sion levels of around 5 – 12 kg/tonne. There havebeen reports of colloidal-clay type productsbinding some B-vitamins and pigments in the gut,and so making them unavailable to the bird. Thecolloidal-clay products may also aid in reduc-ing apparent moisture content of the bird’s exc-reta and more recently, some forms of clay havebeen shown to have activity in binding aflatoxin.The lignosulfonate pellet binders often contain20 – 30% sugars, and so contribute to dietenergy level. Studies show lignosulfonatebinders to have ME values of 900 – 2200 kcal/kgdepending upon sugar content. Because thesebinders are often used at 1 – 1.2% of the diet,then energy contribution is meaningful at 10 –25kcal/kg of diet.

b. AnticoccidialsAnticoccidials are used in diets for most

meat birds and young breeding stock that are rearedon litter floors. Over the past 20 years, the so-called ionophore anticoccidials have predom-inated and they have proved most efficacious incontrolling clinical signs of coccidiosis. Froma nutritional viewpoint, some care must betaken in selection of these products as they caninfluence metabolism of the bird under certainsituations.

Monensin has been a very successful anticoccidial, and seems to work well withboth broiler chickens and turkeys. Monensin,like most ionophores, has an affinity to bind metalions, the most important in terms of bird metab-olism being sodium and potassium. Lasalocidalso binds metals, although its major affinity isfor potassium and secondly, sodium. Mostionophores also increase the permeability of membranes to H+ ions, a factor that may be of significance in acid-base balance. For this



reason, there needs to be more work conductedon ionophores for heat-stressed birds. Ionophoreshave been shown to alter mineral availability,although this should not be of concern under commercial conditions where most mineralsare present in excess of requirements. Studiesshow that the effect of ionophores on mineralmetabolism is not always consistent for variousminerals. For example, monensin may lead toincreased tissue level of certain minerals, whilelasalocid has the opposite effect, yet for anothermineral these effects could be reversed.

Ionophores, and monensin in particular,seem to have an adverse effect when used in con-junction with low protein (methionine) diets. Whenlow protein diets or feed restriction are employedfor birds less than 21 d of age, alternatives toionophores should be considered in an attemptto alleviate potential growth depression, loss ofuniformity and poor feathering. However, withnormal diet protein levels, the ionophores do nothave a measurable effect on TSAA requirement.Ionophores and monensin in particular doimpart some growth depression in young birds,although this seems to be completely overcomewith compensatory growth during the with-drawal or finisher period. For monensin, a 5 – 7 dwithdrawal is optimum for compensatory gain,assuming that no major coccidiosis challenge willoccur during this time. With minimal challenge,a non-medicated withdrawal diet is recom-mended, while in situations of high challenge,an alternative anticoccidial may be necessary.

There has also been some controversy on therelationship between wet litter and certainionophore products. Lasalocid in particularhas been associated with wet litter, and as such,recommendations are often given for reducingdiet sodium levels when this anticoccidial is used.Under such conditions adjustment of chloride

levels is often ignored, and as a consequence performance is sub-optimal. The relationshipbetween ionophores and water intake has not beenfully resolved other than the fact that birds fedmonensin do seem to produce drier manure.

Non-ionophore anticoccidials are not usedextensively in chicken broiler production,although their use is often recommended inshuttle programs. Nicarbazin is an anticoccidialthat seems to work well in such shuttle programs,although again there are some potential problems with this product. Nicarbazin seemsto accentuate the undesirable effects of heatstress, and if inadvertently added to layer orbreeder diets at normal anticoccidial levels,can cause loss in reproductive performance.Nicarbazin fed to brown egg birds turns theireggshells white within 48 hr although this is completely reversible when the product is with-drawn from the feed. Even low levels of nicarbazin can cause some loss in shell color,and mottling of egg yolks, and loss in fertility andhatchability of breeders.

Amprolium is used extensively in diets forgrowing breeder pullets, because unlike theionophores, it allows some build-up of immunity. Amprolium induces a thiamin deficiencyin the developing oocysts, and as such, hasbeen queried with respect to thiamin status of thebird. In most instances thiamin deficiency willnot occur in birds, although cases have been reported of combinations of amprolium andpoorly processed fish meal that is high in thiaminase enzyme, leading to thiamin deficiency in young birds.

Coccidial vaccines are now commonly usedin breeders, and their use will likely increase forbroilers. There has been some discussion aboutdiet manipulation so as to improve the immune



response. Oocysts start to cycle when birds are10 d of age, and if the litter is exceptionally drythis important cycling is less effective. Under suchextreme conditions, it may be advisable to temporarily increase diet or water sodium levels, so as to stimulate water intake.

c. Antibiotics, GrowthPromoters

There has been a gradual reduction in the useof antibiotics per se, although growth promot-ing agents are still used extensively in mostregions. The mode of action of growth promotingagents is comparable to that of antibiotics in termsof beneficial modification of gut microflora. Inthis context, the type of dietary ingredients usedmay influence the efficacy of these productsbecause microbial activity is influenced bydigesta composition. There has been insuffi-cient work conducted in this area, e.g. the beneficial effect seen when antibiotics are usedwith ingredients such as rye. It is unlikely thatgrowth promoters result in increased digestibil-ity of feed, rather improvements in feed efficiencyare a consequence of increased growth rateand hence reduced days to market. Over the pastfew years, there has been criticism about the useof antibiotics in poultry feeds, especially withrespect to the potential for build-up of microor-ganisms resistant to a specific antibiotic, and subsequent transfer of this resistance to knownpathogens. In this context, the use of antibioticssuch as penicillin, that are also used in human-medicine, come under very close scrutiny.

It is very difficult to grow broilers without theuse of growth promoters, since clostridial organ-isms often proliferate and clinical necroticenteritis develops. While some countries havea ban on sub-therapeutic growth promoters inthe feed, their use is escalating as water additives.

Without the use of such ‘antibiotics’, there willundoubtedly be greater risk of bacterial overgrowthin the bird’s digestive tract and especially when‘poorly’ digested ingredients are used sincethese provide substrates for microbial fermentationin the lower gut. Such enhanced microbialgrowth can have various consequences for thebird. If the microbes are pathogens, then diseasecan occur. With proliferation of non-pathogensthere can still be effective loss of nutrients to the bird and undoubtedly such conditions contribute to ‘feed passage’ where feed particlescan be seen in the excreta. Using germ-free (gnotobiotic) birds, there is invariably a decreasein diet AMEn, since there is no ‘digestion’ bymicrobes.

There will undoubtedly be future interest in developing nutritional strategies aimed at reducing our reliance on sub-therapeutic antimicrobials. In general, such strategies revolvearound limiting the nutrient supply to the intestinalmicrobes, altering the lumen environment so asto hinder microbial growth and/or priming orimproving the bird’s immune response (Table 2.21).

If diets are made more digestible, then theoretically, there should be fewer substrates available for microbial growth. The greatestsuccess in this area will likely occur from developments in feed processing and greater application of exogenous feed enzymes. Thereseems great potential for modifying gut pH,either with use of feed or water source acids, orsimply by stimulating gizzard activity. Many organic acids are bactericidal, and while someare corrosive, there are few limitations in addingthem to diets in terms of stability of most othernutrients. While such acids may not have a dra-matic effect on pH of the small intestine, products such as lactic acid are bactericidalover quite a range of pH.



89

Laying hens and especially broiler chickenstoday have very rudimentary gizzards. Withincreased gizzard activity, there will be greater HClproduction from the proventriculus and this is obvi-ously bactericidal. Stimulating gizzard growth andactivity may, therefore become more important,and contribute to health management of thebirds There are often reports of higher digestibil-ity of broiler feeds when particle size of feed isreduced. However, in most of these trials, the‘young’ broilers likely have a rudimentary gizzard.For birds that have previously been fed larger sizeparticles and/or more fiber, such that gizzardactivity is increased, then there is greater digestibil-ity of feed with a larger particle size. Gizzard func-tion is generally a factor of fiber content of the feed, together with consideration of feed particle size.

As detailed in Table 2.21 another potentialsubstitute for antibiotics is mannanoligosac-

charides (MOS). Gram-negative bacteria havemannose specific fimbriae that are used forattachment to the gut wall. Mannan derivatesfrom the cell wall of yeast offer the bacterial fimbriae an alternate binding site, and consequentlyare excreted along with the undigested mann -anoligosaccarhride. Adding 1 – 3 kg of MOS pertonne feed, depending on bird age, will likely bepart of future strategies for growing birds on‘antibiotic-free’ diets.

The other issue involving use of antibioticsand growth promoters in poultry feeds is the potential for tissue or egg accumulation of thesecompounds. Adherence to regulated withdrawalperiods eliminates these problems, as doesscheduling of mixing non-medicated and med-icated feeds in the mill. Most countries arenow establishing GMP and HACCP programs at

Table 2.21 Nutritional strategies to reduce reliance on sub-therapeuticgrowth promoters

Areas of study Examples

1. Limit microbial growth by 1. Use more digestible Corn vs small grainslimiting their nutrient ingredientssupply 2. Feed processing Pelleting, expansion etc.

3. Use of feed enzymes NSP, lipase?4. Reduce diet nitrogen Increased use synthetic AA’s

2. Limit microbial growth by 1. Feed/water acids Phosphoric, propionic, lactic acidsmanipulating digesta pH 2. Stimulate gizzard Feed whole grain or large feed

activity particles.

3. Improve immunity to 1. Vaccines Coccidiosisinfection 2. Prime the immune Fatty acids, Vitamin E

system

4. Interfering with sites of 1. sugars Mannanoligosaccharidesbacterial attachment



feed mills to eliminate any potential for antibiotic residues in poultry products.

A number of ingredients are still referred toas having ‘unidentified growth factors’. Onthis basis, ingredients such as alfalfa meal, distiller’s solubles, bakery yeasts and animalproteins are often added at 1 – 2% of the diet.Any ‘unexplained’ response to these ingredientsmost often relates to their containing trace levels of vitamin or natural antibiotic residues.

d. Antifungal agentsIn many regions of the world, molds and

associated mycotoxins are major problems,affecting both growth and reproductive performance. Mycotoxins produced by both aerobic field molds and anaerobic storage moldscan accumulate, often undetected, in a range ofingredients. A number of antifungal agents areavailable, most of which are based on organic acids.By altering the pH of the feed, it is hoped to con-trol mold growth, although it must be rememberedthat any mycotoxin already present in feed willnot be destroyed by these antifungal agents.Apart from their cost, these organic acids can beproblematic in accelerating the corrosion ofmetal feeders and mill equipment.

Gentian violet is also used in many countriesas an antifungal agent, and in this context, its effi-cacy is governed by factors that determine theefficacy of organic acids (i.e.: time, tempera-ture, moisture and feed particle size). Gentian vio-let also has some bacteriostatic activity and as such,is often used to maintain a beneficial gut microflo-ra, comparable to an antibiotic. In recent years,there has been some interest in use of alumi-nosiliacate (zeolites) as an ‘adsorbent’ of aflatoxin,and also products based on yeast cell walls.

Unfortunately, relatively high levels of alumi-nosilicates must be used and these provide noother nutrients and may, in fact, act as chelatingagents for some essential minerals. However,where aflatoxin contamination is common, thenadding up to 15 kg aluminosilicates per tonneof feed may be necessary in order to minimizethe effect of this mycotoxin.

In addition to, or as an alternative to using suchantifungal agents, there is a potential for minimizing mold growth through formulation,diet preparation and feeding management. Thereseems little doubt that the feed surface area is direct-ly related to potential fungal activity since the greaterthe surface area of feed exposed to the atmosphere,the greater the possibility of fungal spore colonization.This fact is the most likely cause for the increasein mold growth often seen with feed as it travelsfrom the mill to the feed trough because particlesize is invariably reduced. Up to a 50% increasein fines can occur with high-fat pelleted broiler dietsbetween the time of pelleting and consumption bythe bird. At the same time, there is a 100%increase in the potential (and most often theoccurrence) of fungal activity. In areas of poten-tial mycotoxin contamination, there is obviouslyan advantage to maintaining as large a pellet or crum-ble size as possible. The heat generated during pel-leting has been shown to sterilize feed to some extent,because fresh pellets have low fungal counts.However, pelleting will not destroy mycotoxins alreadyformed prior to pelleting, and warm moist pelletsare an ideal medium for fungal growth. Researchhas shown increased fungal activity in feed takenfrom trough vs tube feeders with the former hav-ing more feed exposed to the atmosphere.

With toxins such as aflatoxin, there is abenefit to increasing the protein content of thediet, and in particular, sulfur amino acids. It ispossible that sulphates may also be beneficial in



91

helping to spare sulfur amino acids that arecatabolized during aflatoxicosis. Due to thespecific enzyme system involved with aflatox-icosis, selenium at up to 0.4 ppm may be beneficial in overcoming major adverse effectsof this mycotoxin. There have also been reportsof niacin increasing the catabolism of aflatoxinB1, and so decreasing overall toxicity.

It appears that diet modification and feed management can be manipulated to minimizechances of mycotoxicosis. However, suchmeasures will not likely be 100% effective, andit should always be remembered that most fungal growth can be reduced if moisture content of grains and feeds is kept below 14 – 15%.

e. Probiotics and PrebioticsProbiotics, unlike antibiotics, imply the use

of live microorganisms rather than specific products of their metabolism. Not being specificmolecules therefore, they are difficult to quantitate and even more difficult to describe interms of proposed modes of action. Probioticscan be classified into two major types – viablemicrobial cultures and microbial fermentationproducts. Most research has centered onLactobacilli species, Bacillus subtilis and someStreptococcus species. Similar to the situationwith antibiotics, the mode of action is stillunclear although the following have been suggested: a) beneficial change in gut flora withreduction in population of E. Coli; b) lactateproduction with subsequent change in intestinalpH; c) production of antibiotic-like substances;d) reduction of toxin release (suppression of E. coli). With these varied potential routes of activity, it is perhaps not too surprising thatresearch results are inconsistent. In mostinstances, the feeding of live cultures modifiesthe gut microflora of birds usually with increases

in number of Lactobacilli at the expense of coliforms. A healthy animal has a preponder-ance of lactic acid producing bacteria, and soit is only under situations of ‘stress’, when coliforms often increase in numbers, that probioticswill be of measurable benefit. In this context thereis interest in the use of live cultures administered(orally) to day-old poultry as a means of preventingharmful bacteria such as salmonella from colonizing the gut.

The term ‘competitive exclusion’ is oftenused synonymously with probiotics. It is assumedthat the probiotic will have a competitive advan-tage over any inherent pathogen, and eitherreplace it, or prevent its colonization. Bacterialantagonism may arise due to synthesis ofinhibitors by the probiotic organism. Lacticacid from Lactobacilli and other species is an example of such a product. Probiotic organismsmay also stimulate mucosal immunity. Whileundefined mixtures of bacteria, usually derivedfrom cecal contents of healthy adult birds, seemto be effective probiotics, regulatory agencies areoften concerned about dosing animals withunknown organisms. Defined synthetic mixturesof bacteria seem less efficacious at this time, possibly because we have only scant knowledgeof the normal (beneficial) microbial populationwithin a healthy bird. However, this approachto developing a probiotic probably has the bestlong-term chance of success. With potential instability in most feeds for many Lactobacillusspecies, there has been recent interest in probioticsbased on Bacillus subtilis species, because theypossess a viable spore that has greater stabilitythan do most lactic acid producing cultures.

Regardless of somewhat inconclusive results,it appears that probiotic use is increasing, andthat the animal industry looks to such productsas the substitutes for conventional antibiotics. These



91

helping to spare sulfur amino acids that arecatabolized during aflatoxicosis. Due to thespecific enzyme system involved with aflatox-icosis, selenium at up to 0.4 ppm may be beneficial in overcoming major adverse effectsof this mycotoxin. There have also been reportsof niacin increasing the catabolism of aflatoxinB1, and so decreasing overall toxicity.

It appears that diet modification and feed management can be manipulated to minimizechances of mycotoxicosis. However, suchmeasures will not likely be 100% effective, andit should always be remembered that most fungal growth can be reduced if moisture content of grains and feeds is kept below 14 – 15%.

e. Probiotics and PrebioticsProbiotics, unlike antibiotics, imply the use

of live microorganisms rather than specific products of their metabolism. Not being specificmolecules therefore, they are difficult to quantitate and even more difficult to describe interms of proposed modes of action. Probioticscan be classified into two major types – viablemicrobial cultures and microbial fermentationproducts. Most research has centered onLactobacilli species, Bacillus subtilis and someStreptococcus species. Similar to the situationwith antibiotics, the mode of action is stillunclear although the following have been suggested: a) beneficial change in gut flora withreduction in population of E. Coli; b) lactateproduction with subsequent change in intestinalpH; c) production of antibiotic-like substances;d) reduction of toxin release (suppression of E. coli). With these varied potential routes of activity, it is perhaps not too surprising thatresearch results are inconsistent. In mostinstances, the feeding of live cultures modifiesthe gut microflora of birds usually with increases

in number of Lactobacilli at the expense of coliforms. A healthy animal has a preponder-ance of lactic acid producing bacteria, and soit is only under situations of ‘stress’, when coliforms often increase in numbers, that probioticswill be of measurable benefit. In this context thereis interest in the use of live cultures administered(orally) to day-old poultry as a means of preventingharmful bacteria such as salmonella from colonizing the gut.

The term ‘competitive exclusion’ is oftenused synonymously with probiotics. It is assumedthat the probiotic will have a competitive advan-tage over any inherent pathogen, and eitherreplace it, or prevent its colonization. Bacterialantagonism may arise due to synthesis ofinhibitors by the probiotic organism. Lacticacid from Lactobacilli and other species is an example of such a product. Probiotic organismsmay also stimulate mucosal immunity. Whileundefined mixtures of bacteria, usually derivedfrom cecal contents of healthy adult birds, seemto be effective probiotics, regulatory agencies areoften concerned about dosing animals withunknown organisms. Defined synthetic mixturesof bacteria seem less efficacious at this time, possibly because we have only scant knowledgeof the normal (beneficial) microbial populationwithin a healthy bird. However, this approachto developing a probiotic probably has the bestlong-term chance of success. With potential instability in most feeds for many Lactobacillusspecies, there has been recent interest in probioticsbased on Bacillus subtilis species, because theypossess a viable spore that has greater stabilitythan do most lactic acid producing cultures.

Regardless of somewhat inconclusive results,it appears that probiotic use is increasing, andthat the animal industry looks to such productsas the substitutes for conventional antibiotics. These



products seem ideal candidates for geneticmanipulation which has been inferred by anumber of researchers in this area. By using genetic engineering, some researchers suggestthat bacteria can be reformed to carry moredesirable gene characteristics, including theproduction of digestive enzymes and antimicrobialsubstances.

Prebiotics are aimed at supplying probi-otics with an advantageous source of nutrients,implying that their needs are different to thoseof the host and/or different to those of potentialpathogens. Certain oligosaccharides, whichresist endogenous enzyme degradation, seem topromote a more favorable microflora in thelower small intestine and also the large intestine.However, certain pathogenic bacteria, such asClostridium perfringens are also able to fermentsome of the oligosaccharides. There is some preliminary work with pigs suggesting synergismfor certain combinations of prebiotics and probiotics, which is expected if both are efficacious.

f. YeastsYeast, or single-celled fungi, have been used in

animal feed and the human food industry formany years. Brewer’s yeast was a common feedingredient in diets for monogastric animals prior tothe identification of all the B-vitamins. Today,some nutritionists still incorporate these inactivated microbes as a source of so-called‘unidentified growth factor’. More recently therehas been an interest in the use of live yeast cultures. These cultures most often contain the yeastthemselves and the medium upon which theyhave been grown. Yeast cultures are usually derivedfrom Saccharomyces species, in particular,Saccharomyces cerevisiae. As with probiotics, theirmode of action in enhancing animal perform-

ance is not fully understood. Yeasts may beneficiallyalter the inherent gut microflora, possibly throughcontrolling pH. The presence of living yeastcells may also act as a reservoir for free oxygen,which could enhance growth of other anaerobes.At the present time, there does not seem to be anymove to manipulate yeast for specific purposesrelated to animal nutrition. To some extent, thisrelates to scant knowledge on mode of action, andso should more facts be uncovered in this areaso-called ‘designer’ yeast may be considered.

g. EnzymesEnzymes have been added to poultry diets ever

since workers at Washington State Universityshowed improvement in digestibility of barley andrye-based diets when various enzymes wereused. In the 1950’s, corn-soybean diets pre-dominated, and these were assumed to be highly digestible and so there was little interestin feed enzyme application. Over the past fewyears, this area of nutrition has gained interest andactivity due to economics of small grain useand also because of a better understanding of modeof action and availability of various enzymes.Enzymes are now being manufactured specificallyfor feed use, and can be broadly categorized ascarbohydrases, proteinases and lipases. Increasingthe digestibility of various carbohydrate fractions of cereals and plant proteins has receivedmost attention, although there is growing interest in the potential for improving digesti-bility of both plant and animal proteins, and of saturated fatty acids for young birds. Currently,enzymes are used most commonly to aid digestion of diets containing wheat, barley andrye where improvements are seen in dry matterdigestibility and also in consistency of the excreta. There is also current interest in enzymesdesigned specifically to improve soybean mealdigestibility.



The term non-starch polysaccharides (NSP)is now frequently used to describe what in thepast has been referred to as fiber. Birds have avery limited ability to digest fiber because theylack the enzymes necessary to cleave theselarge and complex molecules. In animals suchas the pig, and in ruminants, it is the resident micro-bial populations that synthesize cellulase typeenzymes that allow for varying degrees of fiberdigestion. If we can improve digestion of the complex carbohydrates, we not only increasepotential energy utilization, but also removeany negative impact that these products may haveon gut lumen activity and excreta consistency.

The NSP content of cereals and other by-product feeds is usually inversely proportionalto their conventional energy level. These NSPcomponents are most often associated with thehull and underlying aleurone layers. In order fornormal endogenous enzymes to contact thestarch endosperm, these outer layers must be disrupted or chemically degraded. Although manycompounds fit into the category of NSP’s, thereare three main types of importance in poultry nutrition. These are the ß-glucans in barley, thearabinoxylans or pentosans in wheat and the raf-finose group of oligosaccharides in soybeans. Barleyß-glucans are polymers of glucose while arabi-noxylans contain long chains, and cross chainsof fructose. The oligosaccharides in soybean are

polymers of sucrose. Most cell wall NSP’seither exist alone or as structural material oftencomplexed with protein and lignin. Solubility ofNSP’s usually relates to the degree of binding tolignin and other insoluble carbohydrates. In water,most NSP’s produce a very viscous solution, andthis has a predictably negative effect on diges-ta flow and interaction of all substrates withtheir endogenous enzyme systems. Some NSP’ssuch as pectins, have a three-dimensional struc-ture that can chelate certain metal ions. Anyincrease in digesta viscosity causes an increasein thickness of the unstirred water layer adjacentto the mucosal villi. Consequently, there isreduced solubilization and uptake of most nutri-ents. Digesta retention time increases, butbecause of the increased viscosity there is lessopportunity for substrates to contact enzymes.There are also more endogenous secretions andthese contain proportionally more bile acids. Inaddition to reduced digestibility, there are alsoreports of reduced net energy of diets due to NSP’s.The reduced NE may be a consequence ofincreased energy expended by the digestivesystem in simply moving digesta through the sys-tem. The increased digesta viscosity also influ-ences the gut microflora and there is an indicationthat their overgrowth may, in fact, add to the over-all deleterious effects. To the poultry producer,the most notable effect of NSP’s will be wetter,more sticky and viscous excreta. Table 2.22 details

Ingredient Cellulose Arabinoxylan Pectin ß-glucans

Corn 2.5 5.0 0.1 -

Wheat 2.5 6.0 0.1 1.0

Barley 4.8 7.0 0.2 4.0 – 5.0

Soybean meal 5.01 0.5 12.0 -1 depending on hull fraction returned

Table 2.22 Non-starch polysaccharides in selected ingredients (%)



The term non-starch polysaccharides (NSP)is now frequently used to describe what in thepast has been referred to as fiber. Birds have avery limited ability to digest fiber because theylack the enzymes necessary to cleave theselarge and complex molecules. In animals suchas the pig, and in ruminants, it is the resident micro-bial populations that synthesize cellulase typeenzymes that allow for varying degrees of fiberdigestion. If we can improve digestion of the complex carbohydrates, we not only increasepotential energy utilization, but also removeany negative impact that these products may haveon gut lumen activity and excreta consistency.

The NSP content of cereals and other by-product feeds is usually inversely proportionalto their conventional energy level. These NSPcomponents are most often associated with thehull and underlying aleurone layers. In order fornormal endogenous enzymes to contact thestarch endosperm, these outer layers must be disrupted or chemically degraded. Although manycompounds fit into the category of NSP’s, thereare three main types of importance in poultry nutrition. These are the ß-glucans in barley, thearabinoxylans or pentosans in wheat and the raf-finose group of oligosaccharides in soybeans. Barleyß-glucans are polymers of glucose while arabi-noxylans contain long chains, and cross chainsof fructose. The oligosaccharides in soybean are

polymers of sucrose. Most cell wall NSP’seither exist alone or as structural material oftencomplexed with protein and lignin. Solubility ofNSP’s usually relates to the degree of binding tolignin and other insoluble carbohydrates. In water,most NSP’s produce a very viscous solution, andthis has a predictably negative effect on diges-ta flow and interaction of all substrates withtheir endogenous enzyme systems. Some NSP’ssuch as pectins, have a three-dimensional struc-ture that can chelate certain metal ions. Anyincrease in digesta viscosity causes an increasein thickness of the unstirred water layer adjacentto the mucosal villi. Consequently, there isreduced solubilization and uptake of most nutri-ents. Digesta retention time increases, butbecause of the increased viscosity there is lessopportunity for substrates to contact enzymes.There are also more endogenous secretions andthese contain proportionally more bile acids. Inaddition to reduced digestibility, there are alsoreports of reduced net energy of diets due to NSP’s.The reduced NE may be a consequence ofincreased energy expended by the digestivesystem in simply moving digesta through the sys-tem. The increased digesta viscosity also influ-ences the gut microflora and there is an indicationthat their overgrowth may, in fact, add to the over-all deleterious effects. To the poultry producer,the most notable effect of NSP’s will be wetter,more sticky and viscous excreta. Table 2.22 details

Ingredient Cellulose Arabinoxylan Pectin ß-glucans

Corn 2.5 5.0 0.1 -

Wheat 2.5 6.0 0.1 1.0

Barley 4.8 7.0 0.2 4.0 – 5.0

Soybean meal 5.01 0.5 12.0 -1 depending on hull fraction returned

Table 2.22 Non-starch polysaccharides in selected ingredients (%)



levels of NSP’s commonly found in cerealsand soybean meal. Oligosaccharides as foundin soybean meal are perhaps the most complexstructures within the NSP’s and to date have provendifficult to digest with exogenous enzymes.Depending upon variety, growing conditionsand oil extraction procedures, soybeans willcontain 4 – 7% of oligosaccharides mainly as raffinose and stachyose. Because of the absenceof -galactosidase in chickens, these oligosac-charides remain undigested, and again contributeto increased digesta viscosity, especially in youngbirds. Soybean oligosaccharides can be extracted using ethanol. Such treatment of soy-beans is not commercially viable at this time,although the residual meal has an AMEn valueapproaching 3,000 kcal/kg, and the meal seemsan interesting ingredient for very young birds. Sincethe oligosaccharides are removed by ethanol, thenthere is a corresponding loss of dry matter in theresidual soybean meal.

Addition of feed enzymes could thereforeimprove NSP availability, and just as important,reduce the negative impact that these undi-gested residues have on digesta viscosity. Normaldigestion requires unimpeded movement ofenzyme, substrate and digestion productsthroughout the digesta and especially close tothe absorptive gut wall. As the viscosity of thedigesta increases, the rate of diffusion decreas-es, and this causes reduced digestibility of all substrates. The undigested viscous digesta subsequently translates to very sticky excreta whichcauses problems of litter management. Reductionin digesta viscosity is therefore highly correlatedwith efficacy of enzymes that can digest substratessuch as ß-glucans. In oats and barley the bulkof the NSP’s are ß-glucans, whereas in wheat andrye, arabinoxylans predominate. Enzymes tailored for barley therefore contain ß-glucanase

enzymes, while those designed to improvewheat digestibility should contain cellulaseand arabinoxylanase enzymes.

There is potential for adding lipase enzymesto feeds or fats, to improve digestibility.Improvement in digestion of saturated fats for youngbirds seems to have the greatest potential.Although there are no lipase enzymes currentlydesigned for use in animal feeds, preliminary studies with enzymes obtained from other industries suggest that a 7 – 10% improvementis possible, with a corresponding increase in dietAME. Since the young chick does not efficientlyre-cycle its bile salts, there have also been indications that fat digestion can be improvedby adding synthetic bile salts to the feed. Again,these are not commercially available, but itdoes suggest some potential for the developmentof emulsifying agents or detergents.

The most widely used feed enzyme is phy-tase. Phytase cleaves the phytic acid in soybeanmeal and cereals, to release phosphorus and calcium. Phytic acid is a complex structurethat tightly binds phosphorus, and is the main storage source of phosphorus in plant material(Fig. 2.1). Few animals possess the phytaseenzyme necessary to cleave the molecule andso phytic acid is largely undigested. Interest inthe phytase enzyme arose because phosphorushas become an expensive nutrient, as well as thefact that undigested phytic acid adds greatly tomanure loading of phosphorus. Phytate also bindsother trace minerals and may conjugate with proteins and carbohydrates. Digestion of the molecule therefore can potentially release traceminerals, amino acids and energy, as well as calcium and phosphorus.

Phytase enzymes are commonly found in plantmaterials, and especially for wheat and wheat



by-products the values are quite high. Corn, forexample, contains just 15 FTU/kg while wheatshorts can contain as much as 10,000 FTU/kg.However, such endogenous phytase may haveonly limited usefulness in the digestive tract, sincemost plant phytases are effective only at aroundpH 5, whereas exogenous phytases, usually ofmicrobial origin, seem efficacious from pH 3 to7. There are variable results reported for efficacyof phytase in commercial diets. It has been suggested that diet calcium level is perhaps themajor factor in such variance, since high levelsof calcium seem to reduce the effectiveness ofphytase enzyme. However, if this concept is true,then one wonders why phytase enzymes seemso efficacious in layer diets that contain from 4– 4.5% calcium. If phytase is used in formulation,there are a number of different approaches toaccount for increased phytate availability. Wherefew ingredients are used, the available phosphoruslevel of these ingredients can be increasedaccordingly. Alternatively, the specification foravailable phosphorus in the diet can be reducedor phytase enzyme can be included as an ingredient with specifications for available

phosphorus and calcium. Each 500 units of phytase activity are equivalent to about 1 g of phosphorus as provided by sources such as di-calcium phosphate. Using 500 FTU of phytase/kg feed therefore provides the equiva-lent of 0.1% P.

Phytase also liberates some trace minerals andso theoretically, supplemental levels can bereduced. As described previously for calcium,there is an indication that phytase is more effec-tive when moderate, rather than high, levels ofsupplemental zinc are used. The release ofenergy and amino acids by phytase is a more contentious issue. Some research suggests up to2% improvement in AMEn and digestible aminoacids, although more conservative estimatesare for 15 kcal ME/kg release of energy, with noincrease in amino acid availability. Some commercial sources of phytase are sensitive toheat, and pelleting at 85 – 90ºC can cause significant loss in phytase. In pelleted feeds, thesesources of phytase are most appropriately usedas post-pelleting additives. Other sources of phytase seem more heat stable, and can beadded to the mix prior to pelleting.

Figure 2.1 Phytic acid



by-products the values are quite high. Corn, forexample, contains just 15 FTU/kg while wheatshorts can contain as much as 10,000 FTU/kg.However, such endogenous phytase may haveonly limited usefulness in the digestive tract, sincemost plant phytases are effective only at aroundpH 5, whereas exogenous phytases, usually ofmicrobial origin, seem efficacious from pH 3 to7. There are variable results reported for efficacyof phytase in commercial diets. It has been suggested that diet calcium level is perhaps themajor factor in such variance, since high levelsof calcium seem to reduce the effectiveness ofphytase enzyme. However, if this concept is true,then one wonders why phytase enzymes seemso efficacious in layer diets that contain from 4– 4.5% calcium. If phytase is used in formulation,there are a number of different approaches toaccount for increased phytate availability. Wherefew ingredients are used, the available phosphoruslevel of these ingredients can be increasedaccordingly. Alternatively, the specification foravailable phosphorus in the diet can be reducedor phytase enzyme can be included as an ingredient with specifications for available

phosphorus and calcium. Each 500 units of phytase activity are equivalent to about 1 g of phosphorus as provided by sources such as di-calcium phosphate. Using 500 FTU of phytase/kg feed therefore provides the equiva-lent of 0.1% P.

Phytase also liberates some trace minerals andso theoretically, supplemental levels can bereduced. As described previously for calcium,there is an indication that phytase is more effec-tive when moderate, rather than high, levels ofsupplemental zinc are used. The release ofenergy and amino acids by phytase is a more contentious issue. Some research suggests up to2% improvement in AMEn and digestible aminoacids, although more conservative estimatesare for 15 kcal ME/kg release of energy, with noincrease in amino acid availability. Some commercial sources of phytase are sensitive toheat, and pelleting at 85 – 90ºC can cause significant loss in phytase. In pelleted feeds, thesesources of phytase are most appropriately usedas post-pelleting additives. Other sources of phytase seem more heat stable, and can beadded to the mix prior to pelleting.

Figure 2.1 Phytic acid



h. PigmentsThe yellow to orange color in avian fatty

tissue is caused by various carotenoid pigments.These pigments control the color of the eggyolk, as well as the shanks and beaks of layers,and also the skin color that may be important inmeat birds. The xanthophylls are the mostimportant carotenoids in poultry nutrition, andnatural ingredients rich in these compoundsare alfalfa meal, corn gluten meal and marigoldpetal (Table 2.23).

Table 2.23 Xanthophyll content ofselected ingredients (mg/kg)

Ingredient XanthophyllCorn 20Wheat 4Milo 1Alfalfa meal 175Corn gluten meal 275Marigold petal 7,000

Corn contains much more xanthophylls thando other cereals, although high levels of pig-mentation can only be achieved from natural ingredients by including other products such asalfalfa and corn gluten meal.

The various xanthophylls differ in their effecton skin and yolk pigmentation. ß-carotene haslittle pigmenting value, although pigments suchas zeaxanthin as found in corn, is more easilydeposited, while there is a very high incorporationrate of synthetic products such as ß-apo-8-carotenoic ethyl ester. The zeaxanthin in corntends to impart the darker orange-red colors, where-as the luteins, as found in alfalfa, cause a moreyellow color. Pigments are destroyed by oxidation,and so addition of antioxidants to feed, andgeneral feed management applied to fat protection

also apply to preservation of pigments. Coccidiosis,malabsorption and certain mycotoxins will allreduce pigment absorption. Pigmentation in theyoung meat bird is directly proportional to pigments fed throughout growth. For the layinghen however, yolk color is a consequence of pigments consumed in the layer feed, and alsothe transfer of pigments accumulated in theskin and shanks when the bird was immature.This transfer of pigments to the ovary occurs regardless of diet pigments, and is responsiblefor the ‘bleaching’ effect of the shanks and beakof yellow-skinned birds over time.

Because many of the naturally carotenoid-rich ingredients are low in energy, it is difficultto achieve high levels of pigmentation of meatbirds without using various synthetic sources.Canthaxanthin, astaxanthin and ß-apo-8-carotenoic acid (where allowable in poultrydiets) can be used to impart the spectrum fromyellow to orange/red coloration in either skin oregg yolk. As described more fully in Chapter 4,there is now interest in enriching eggs withlutein, since this carotenoid is known to beimportant in maintenance of eye health inhumans. Future designer eggs may well containconcentrated levels of lutein.

i. Flavoring agentsThe chicken is not usually considered to

have the ability to select feed based on flavor, ororganoleptics per se. The chicken has onlyabout 24 taste buds in comparison to 9,000 inhumans and 25,000 in cattle. Relatively few studies have been conducted with flavoringagents for poultry, and for this reason, caremust be taken in extrapolating data from otherspecies. For example, sucrose octa-acetate solution is reported to be readily accepted by birds,but universally rejected by humans. Thereseems little scope for use of flavoring agents withbroiler chickens and turkeys that already seem



to be eating at near physical capacity. However,there may be some potential with breeders foridentification of agents that are distasteful to birds,as an aid in limiting their feed intake.

We have studied the effect of feeding cinnamamide to young broilers, as a means ofregulating feed intake. Cinnamamide is relatedto the spice known as cinnamon and is a naturally occurring product in some weed seedsthat is thought to impart bird resistance characteristics as do tannins. Table 2.24 showsthe effect of feeding cinnamamide on growth andfeed intake of young broilers. At the highest inclusion level, cinnamamide reduced voluntaryfeed intake by around 50%.

Table 2.24 Effect of cinnamamideon feed intake and body weight ofyoung broilers

Body Weight Feed Intake(gms) 4-12 day

(gms/bird)Day 4 Day 12

Control 82.2 266.4 257.3

Cinnamamide 81.4 170.8 159.2

(0.2%)

Cinnamamide 82.8 122.7 104.4

(0.42%)

Flavor agents may be beneficial in maskingany unpalatable ingredients, and for maintaininga constant feed flavor during formulation changes.Flavors may also be useful tools in masking any undesirable changes in drinking water dur-ing medication. It is conceivable that use of a sin-gle flavor agent in both feed and medicatedwater may prevent some of the refusals seenwith medicated water, especially for turkey poults.

j. Worming compoundsMost floor grown birds are exposed to infec-

tion from various species of worms. In manyinstances such challenge can be prevented or minimized with the use of antihelmintic agents.Products based on piperazine and hygromycinhave been used most commonly over the last 15– 20 years. Piperazine used in diets for layingbirds has been shown to result in discolorationof the yolk. When administered at 28 d intervals,one report indicated about 4% incidence ofdiscolored yolks which appeared as irregular areasof olive to brownish discoloration. Such yolk discoloration is most pronounced in summermonths especially after prolonged storage atregular egg cooler temperatures. The mottlingof yolks seen with another commercial producthas been compared to the mottling seen with calcium-deficient birds, suggesting a similar modeof action. However, we are unaware of any pub-lished reports relating worming compounds to calcium deficiency and problems with shell quality.

k. Ammonia controlVarious extracts of the yucca plant are

claimed to reduce ammonia levels in poultry houses. A soluble component of the yuccaplant seems able to bind ammonia, preventingits release from manure, which is especiallyimportant in confinement housing systems.Most poultry will react adversely to 50 ppmammonia, and this is in contrast to the level of20 – 30 ppm which is the usual detection rangefor humans. Products such as Deodorase® addedto feed at 100 – 150 g/tonne have been shownto reduce environmental ammonia levels by20 – 30%, and this has been associated withimproved growth rate and reduced mortality.

SECTION 2.4Feed toxins and contaminants


P roducing poultry feed that is free of toxins and contaminants is obviouslythe goal of all feed mills. However, this

is difficult to achieve because many natural feedingredients will contain toxins that are inherentin the feedstuff or have ‘naturally’ contaminatedthe feedstuff prior to feed preparation. Mycotoxinsare perhaps the best example of such ‘natural’ toxins, and together with many plant lectins cancause poor bird growth and reduced egg production.In addition to these biological contaminants,there is also concern about accidental inclusionof such products as polychlorinated biphenyls, pesticides, fungicides etc.

a. MycotoxinsMycotoxins are now virtually ubiquitous in

poultry diets, and with ever increasing sophis-tication of testing sensitivity, they are routinelyisolated as contaminants of most grains andsome vegetable protein ingredients. We still donot know the cause of high levels of moldgrowth occurring in pre-harvest grains. Certainlysuch aerobic molds are more prevalent in hothumid conditions, and insect damage to thestanding crop seems to provide a route of entryfor the mold. Unfortunately, visual inspectionof harvested grains can be misleading in regardto mycotoxin content. Likewise, merely becausegrains appear moldy, does not mean to say thatthey are contaminated with harmful toxins. Instorage, the major factors affecting mold growthare again temperature and humidity. The higherthe temperature, the greater the chance of moldgrowth. However such mold growth rarelyoccurs in grains containing less than 14 – 15%moisture. Unfortunately, many grain silos are notwaterproof, or grains are not aerated, and so

pockets of moisture can cause microclimatesideal for mold growth. The following is a reviewof the major mycotoxins affecting meat birds andegg layers.

Aflatoxin - Produced by the Aspergillus flavus mold,aflatoxin is one of the most potent carcinogensknown. Usually present in cereals in ppb lev-els, acute toxicity will occur at 1.2 ppm. AflatoxinB1 is the most common form of the toxin, the Bdesignation relating to the fact that the toxin flu-oresces a blue color when exposed to ultravio-let light, and so this can be used in the screen-ing of ingredients. Blue fluorescence occurs withother components, and so this simple test screensout negative samples, but needs subsequentchemical analysis for confirmation. Aflatoxin isfound in most cereals, although corn and miloare the most common hosts. As with any mold,Aspergillus growth is greatly reduced whencorn or milo moisture levels are less than 15%.

Aflatoxin is a potent hepatotoxin, and so varying degrees of liver breakdown occur. As toxicity develops, normal liver function declines,and reduced growth rate is quickly followed bydeath. Toxicity is enhanced by the presence ofother toxins such as ochratoxin and T2 toxin. Theeffects of aflatoxin are also much worse if birdsare infected with aspergillosis. There also seemsto be a nutrient interaction, because toxicity ismore severe when diets are low in either crudeprotein or methionine or when the diet containsmarginal levels of riboflavin, folic acid or vitamin D3. There is no treatment for acuteaflatoxicosis, although because of the liver disruption, giving higher levels of antioxidantsand/or selenium seems to slow the onset ofsymptoms and speed up recovery if aflatoxin isremoved from the diet.

2.4 FEED TOXINS and CONTAMINANTS



There are a number of effective preventativemeasures, although not all of these are economical. Treating infected grains withammonia, hexane or hydrogen peroxide have allbeen shown to reduce aflatoxin levels. Undercommercial conditions adding binding agents tothe feed seems to reduce the adverse effects ofaflatoxin. To date, aluminosilicates, bentoniteclays and yeast cell walls have proven effective.For example adding 10 – 15 kg/tonne of hydrat-ed sodium-calcium aluminosilicate has beenshown to drastically reduce mortality in broilersand turkeys fed diets containing 0.5 – 1.0 ppmaflatoxin. Such aluminosilicates have limited effectson other mycotoxins.

Tricothecenes - Three mycotoxins, namely T2, DAS(diacetoxyscirpenol) and DON (Deoxynivalenolor vomitoxin) are included in this group. All ofthese mycotoxins are produced by Fusariumspecies molds such as Fusarium graminearum andFusarium roseum. The tricothecenes affect protein metabolism and have the characteristicfeature of causing mouth lesions in most animals.However DON does not seem to be particularlyharmful to poultry. Unlike the situation in pigsand other mammals, birds can tolerate up to 20ppm of this mycotoxin. T2 and DAS however aremore toxic, causing problems at 2 – 4 ppm.The adverse effect of tricothecenes is made evenworse by the presence of aflatoxin or ochratoxin,and seems to be worse in young broilers fedionophore vs non-ionophore anticoccidials.There are no really effective treatments, andwhile the addition of relatively high levels of antioxidants may slow the disruption of proteinsynthesis, they are not effective long-term.Adsorbents and binding agents are being devel-oped that specifically bind these toxins.

Ochratoxin - As with other mycotoxins, there area number of forms of ochratoxin, although ochra-

toxin A (OA) is by far the most significant for poul-try. OA is produced by a number of molds,with Aspergillus and Penicillium species being mostcommonly involved. OA is toxic at 2 ppm andas with tricothecenes, it has an adverse effect onprotein synthesis. However, OA also affectskidney function and so the classical signs areswollen kidneys and associated increased waterintake with wet excreta. Secondary visceralgout, which appears as urate deposits over the vis-cera, is common with OA toxicity, due essentially to failure of uric acid clearance by thekidney tubules. OA toxicity is compounded bythe presence of aflatoxin, DON and T2 toxicosis,and also made worse by feeding diets high in vanadium (usually as a contaminant of phosphatesor limestone). There are no effective preventa-tive measures, although birds sometimes respondto diet manipulation in the form of increasing crudeprotein levels. There are also reports of benefi-cial response to increasing diet vitamin C levels,especially in egg layers.

Other mycotoxins - There are a diverse group ofother mycotoxins that periodically cause problemsfor poultry. Their occurrence is less frequent than the major mycotoxins already dis-cussed, and in some instances exact toxicity lev-els have not been clearly established.Table 2.25summarizes these mycotoxins in terms of effect onpoultry and their probable threshold for toxicity.

b. Plant toxinsA number of cereals and vegetable protein

crops contain natural toxins that can affect birdperformance.

Cyanides - While there are a number of poten-tial feed ingredients that contain natural cyanides,cassava (manioc), is probably the most commonand contains relatively high levels of this toxin.



Cassava meal is derived from the tuberous rootof the cassava plant. Ingestion of this materialby animals can result in enlarged thyroids, dueto the presence in the meal of cyanogenic glu-cosides, the main one being linamarin. Theseglucosides are concentrated in the peel of the root.On hydrolysis by the enzyme linamarase, the glu-cosides produce hydrocyanic acid (HCN), whichis highly toxic. In addition to the enzyme in theroot, glucosidic intestinal enzymes and HClcan also hydrolyze the glucosides.

Hydrocyanic acid inhibits animal tissue res-piration by blocking the enzyme cytochrome-oxi-dase. HCN is detoxified to produce thiocyanatein the liver which is then excreted via the urine.This detoxification system utilizes sulfur frommethionine in the conversion of cyanate tothiocyanate, thus increasing the bird’s require-

ment for this amino acid. Thiocyanate is respon-sible for the goitrogenic effect of cassava, due toits effect on iodine uptake and metabolism in thethyroid, resulting in reduced output of thyroxine,which regulates tissue oxidative functions.Cyanate is known to alleviate the toxicity of anexcess of dietary selenium by complexing withselenium, thus making it less available to the bird.Linseed meal, which has been known for sometime to alleviate selenium toxicity in animals, hasbeen shown to contain two cyanogenic gluco-sides, namely linustatin and neolinustatin. Thesecompounds are closely related in structure to linamarin and thus on hydrolysis yield HCN.

The cyanide content of cassava varies withvariety and can range from 75 to 1000 mg/kg ofroot. Crushing the root releases the enzyme linamarase which acts on the glucosides to

Mycotoxin Effect Toxicity Comments

Fumonisin Degeneration of nerve > 80 ppm Diet thiamin levelscell lipids important

Cyclopiazonic acid Mucosal inflammation 50 – 100 ppm Often present along with aflatoxin

Oosporin Kidney damage, gout > 200 ppm Most commonly found in corn

Citrinin Kidney damage > 150 ppm Commonly associated with ochratoxin

Ergot Tissue necrosis > 0.5% Wheat and rye

Fusarochromanone Tibial > 50 ppm Fusarium speciesdyschondroplasia

Moniliformin Acute death > 20 ppm Mechanism unknown

Zearalenone Reproduction, vitamin > 200 ppm Can affect shell qualityD3 metabolism

Table 2.25 Effect of minor mycotoxins on poultry



produce volatile HCN which is then eliminatedduring drying. Rate of drying in commercial forcedair driers is important as it has been reported thatat 80 to 100ºC, only 10 to 15% of cyanide isremoved compared to 80 to 100% detoxifica-tion occurring at 47 to 60ºC but with a longertime. Steam pelleting can also assist in thevolatization of free HCN.

While there are differing reports as to how muchcassava meal can be incorporated into poultry dietswithout reducing performance, this will obviouslydepend on the concentration of cyanide in themeal. Cassava meals containing up to 50 mg totalcyanide/kg have been fed successfully up to50% inclusion in broiler diets.

Glucosinolates – These belong to a group of anti-nutritive compounds of which over 100 differ-ent types are known to occur in members of theCruciferae family. The genus Brassica is a mem-ber of this family which includes many impor-tant feeds and foods such as, rapeseed, mustard, kale, radish, cabbage, cauliflower,etc. In individual species, usually around 12 to20 glucosinolates are found, although most ofthese are present in small amounts. Hydrolysisof these glucosinolates is brought about by theenzyme myrosinase, which is usually present inmost glucogenic plants. In the intact plant, theenzyme and its substrate are separated, butwith cellular rupture (grinding, insect damage,etc.) these components are combined andhydrolysis can occur.

For many plants including rapeseed, glucosinolates can be readily divided into threemain groups, based on physiological effectsand hydrolysis products. By far the largest of thesegroups are glucosinolates that yield isothio-cyanates on hydrolysis. These compounds arevolatile and possess a range of antimicrobial,

antifungal and antibacterial properties, andhave a very pungent taste (mustard, horseradish,etc.). A second, but much smaller group, formpotent anti-thyroid compounds on hydrolysis with5-vinyloxazolidine-2-thione being the mostcommon. If present in large amounts thesecompounds can impart an intense bitterness.Glucosinolates in the third group all contain anindole side chain, and on hydrolysis yield thiocyanate ions which are anti-thyroid or goitrogenic. The glucosinolate contents of thevarious rapeseed cultivars ranges from a high of100 to 200 µM/g to less than 30 µM/g, while newvarieties are claimed to be glucosinolate-free.

A significant research program was initiatedin Canada in the early 60’s to develop rapeseedvarieties low in glucosinolates and erucic acid,a fatty acid known to result in detrimental meta-bolic problems with certain animals. In 1968,the first low erucic acid variety was licensed andshortly thereafter a low glucosinolate varietyappeared. In 1974, the first double low variety,very low in erucic acid and glucosinolates waslicensed. A number of improved varieties weredeveloped and in 1979 the name canola wasadopted in Canada to apply to all double low rapeseed cultivars. For reasons not yet completelyunderstood, reduction of total glucosinolatehad little effect on the content of the indole group.Thus, when expressed as a percent of total glucosinolates, this group increases from around5 to 40% in the low glucosinolate varieties.

While the feeding value of canola meal hasbeen markedly increased for poultry, as comparedto the older rapeseed varieties, there are still someproblems encountered. The occurrence of liverhemorrhages with the feeding of rapeseed mealis well documented. Unlike the fatty liver hem-orrhagic syndrome, these hemorrhages are notassociated with increased liver or abdominal fat



produce volatile HCN which is then eliminatedduring drying. Rate of drying in commercial forcedair driers is important as it has been reported thatat 80 to 100ºC, only 10 to 15% of cyanide isremoved compared to 80 to 100% detoxifica-tion occurring at 47 to 60ºC but with a longertime. Steam pelleting can also assist in thevolatization of free HCN.

While there are differing reports as to how muchcassava meal can be incorporated into poultry dietswithout reducing performance, this will obviouslydepend on the concentration of cyanide in themeal. Cassava meals containing up to 50 mg totalcyanide/kg have been fed successfully up to50% inclusion in broiler diets.

Glucosinolates – These belong to a group of anti-nutritive compounds of which over 100 differ-ent types are known to occur in members of theCruciferae family. The genus Brassica is a mem-ber of this family which includes many impor-tant feeds and foods such as, rapeseed, mustard, kale, radish, cabbage, cauliflower,etc. In individual species, usually around 12 to20 glucosinolates are found, although most ofthese are present in small amounts. Hydrolysisof these glucosinolates is brought about by theenzyme myrosinase, which is usually present inmost glucogenic plants. In the intact plant, theenzyme and its substrate are separated, butwith cellular rupture (grinding, insect damage,etc.) these components are combined andhydrolysis can occur.

For many plants including rapeseed, glucosinolates can be readily divided into threemain groups, based on physiological effectsand hydrolysis products. By far the largest of thesegroups are glucosinolates that yield isothio-cyanates on hydrolysis. These compounds arevolatile and possess a range of antimicrobial,

antifungal and antibacterial properties, andhave a very pungent taste (mustard, horseradish,etc.). A second, but much smaller group, formpotent anti-thyroid compounds on hydrolysis with5-vinyloxazolidine-2-thione being the mostcommon. If present in large amounts thesecompounds can impart an intense bitterness.Glucosinolates in the third group all contain anindole side chain, and on hydrolysis yield thiocyanate ions which are anti-thyroid or goitrogenic. The glucosinolate contents of thevarious rapeseed cultivars ranges from a high of100 to 200 µM/g to less than 30 µM/g, while newvarieties are claimed to be glucosinolate-free.

A significant research program was initiatedin Canada in the early 60’s to develop rapeseedvarieties low in glucosinolates and erucic acid,a fatty acid known to result in detrimental meta-bolic problems with certain animals. In 1968,the first low erucic acid variety was licensed andshortly thereafter a low glucosinolate varietyappeared. In 1974, the first double low variety,very low in erucic acid and glucosinolates waslicensed. A number of improved varieties weredeveloped and in 1979 the name canola wasadopted in Canada to apply to all double low rapeseed cultivars. For reasons not yet completelyunderstood, reduction of total glucosinolatehad little effect on the content of the indole group.Thus, when expressed as a percent of total glucosinolates, this group increases from around5 to 40% in the low glucosinolate varieties.

While the feeding value of canola meal hasbeen markedly increased for poultry, as comparedto the older rapeseed varieties, there are still someproblems encountered. The occurrence of liverhemorrhages with the feeding of rapeseed mealis well documented. Unlike the fatty liver hem-orrhagic syndrome, these hemorrhages are notassociated with increased liver or abdominal fat



contents. Certain strains of laying hens were moresusceptible than others, however, with moststrains it was not uncommon to see signs of thecondition. While liver hemorrhages have beensignificantly reduced in laying hens with intro-duction of canola meal, isolated cases are seenwhen feeding 10% or more of this product.Research to date suggests that this is the resultof intact glucosinolates, rather than any of theirproducts of hydrolysis. However, it is stillunclear how glucosinolates function in the etiology of hemorrhagic liver.

An increase in weight of the thyroid stilloccurs following feeding of canola meal, althoughseverity is much reduced from that seen with theolder rapeseed varieties. Thiocyanate is respon-sible for the goitrogenic effect noted with theseproducts due to their effect on iodine uptake andmetabolism, and so increase in thyroid size is seen.Because thiocyanate is the end product of indoleglucosinolate hydrolysis and levels of this compound are still high in canola, then thisproduct probably accounts for the enlargedthyroids still seen with low glucosinolate meals.

Another major problem with the feeding ofrapeseed or canola meal is egg taint which is experienced in certain flocks of layers, andespecially brown egg layers containing RhodeIsland Red ancestory. This is the result of a singlemajor autosomal semi-dominant gene beingpresent which is responsible for the bird lackingthe ability to oxidize trimethylamine (TMA) to TMAoxide which is the odorless excretory product ofTMA. While the double low varieties of canolacontain very low levels of glucosinolates, thereis still sufficient present, along with the soluble tan-nins, to impair TMA oxidation and thus tainted eggs can result. Because brown-egg layers are quitecommon in many parts of the world, canola meal,in such regions is used sparingly for layers.

Nitrates – The nitrate content of cereals and plantproteins can vary from 1-20 ppm. While havinglittle affect on the bird per se, reduction tonitrite, usually by intestinal microbes, can leadto toxicity. Nitrite is readily absorbed from thegut and diffuses into red blood cells where it oxi-dizes the ferrous iron of oxyhemoglobin to theferric state, forming methemoglobin, which isunable to transport oxygen. Because there hasbeen an interest in the role of dietary nitrite inthe incidence of pulmonary hypertension and spon-taneous turkey cardiomyopathy. Feeding broil-ers nitrite up to 1600 ppm had no effect on pul-monary hypertension. However, turkey poults fed1200 ppm nitrite had a numerically higher inci-dence of STC than did controls (20 vs. 5%).Interestingly, both chicks and poults developedanemia; poults appeared to be more sensitive tothe adverse effects of nitrite on hemoglobincontent since the minimum dietary level-caus-ing anemia was 800 ppm in poults and 1200 ppmin chicks. Decreased perormance was observedwith the highest dietary concentration. Theresults of this study indicate that the dietarylevels causing methemoglobinemia, anemia,and decreased body weight are not likely to beencountered in cereal grains and legume seeds.However, nitrate and nitrite may also be presentat significant levels in water sources.

Tannins – These are water soluble polyphenolicplant metabolites that are known to reduce theperformance of poultry when fed at moderate lev-els in a diet. Grain sorghum is probably the mostcommon feedstuff which contains relativelyhigh levels of tannin. However, faba beans, rape-seed and canola meal all contain sufficient tan-nins to affect poultry performance.

The growth depressing effect of tannins isundoubtedly due to their ability to bind proteins.Tannic acid is hydrolyzed by the chick to gallic



acid, its major hydrolytic product, and to alesser extent to the somewhat toxic compounds,pyroacetol and pyrogallol. A large portion of thegallic acid is methylated and excreted in the urineas methyl gallic acid. This pathway offers apossible explanation as to why additions ofmethionine, choline and other methyl donors havebeen reported to be beneficial when includedin diets containing tannic acid.

Much of the work on toxicity of tannins hasinvolved purified tannic acid. Legume andcereal tannins are of a condensed type while tannic acid is of a hydrolyzable type. Since thereare conflicting reports on the degree of growthdepression and the role of methionine in alleviatingtannin toxicity, it follows that the predominantdetoxification process may differ between thesetwo compounds. More recent work suggests thatwhile gallic acid is the breakdown product of bothcondensed tannins and tannic acid, and can bedetoxified by methyl groups, the stability ofcondensed tannins is such that this route ofdetoxification may be of little importance.

i) Sorghum tannins - The nutritive value ofsorghum is usually considered to be 90 to 95%that of corn, due in large part, to its tannin content.There are a number of varieties of sorghum on themarket which are usually classified as bird resist-ant or non-bird resistant varieties. These have eithera low (less than 0.5%) or high (1.5% or higher)level of tannins. A number of toxic effects havebeen reported with the feeding of high tanninsorghum. These include depressed growth andfeed utilization, reduced protein digestibility,lower egg production and leg abnormalitieswith broilers.

A number of procedures have been tried inan attempt to reduce the toxicity of the tanninsin sorghum. These include soaking in water oralkali solution, which are reported to deactivatetannins and thus improve the nutritive value of

the cereal. Besides the addition of the methyldonors which have been reported to improve thefeeding value of high tannin sorghum, productssuch as polyvinylpyrrolidone, and calciumhydroxide, or a slurry of sodium carbonate havealso been reported to give positive responses.However, several crude enzyme preparations thathave been tried were not effective in enhancingthe feeding value of high tannin sorghum.

Tannins have also been implicated in egg yolkmottling. Yolk mottling is a condition which periodically appears in a flock and without a directinvolvement of nicarbazin, gossypol or certainworming compounds, there is usually no readyexplanation for its appearance. While severalreports have suggested tannic acid and its derivatives as possible causes, other than the addition of commercial tannic acid at levelsabove 1%, there appears to be no mottling seenwith diets containing up to 2.5% tannins.

There are reports suggesting that tanninsare bound tightly to a fraction of the nitrogen insorghum and that this reduces protein digestibil-ity. However, because the tannins are relativelyinsoluble they appear to have little influence incomplexing with protein. In a recent studywith turkeys, a high tannin sorghum varietywhen used at 40% in the diet, resulted indepressed performance to 8 weeks of age.However, the feeding of a similar level to turkeysbeyond 8 weeks of age had no detrimentaleffects. The authors suggest that a more fully developed digestive system of the older birds maybe able to overcome the anti-nutritional effectsof the tannins.

While dark colored varieties of sorghumseed usually contain higher levels of tanninthan do lighter colored varieties, seed color, ingeneral, is a poor indicator of the tannin contentof sorghum.



acid, its major hydrolytic product, and to alesser extent to the somewhat toxic compounds,pyroacetol and pyrogallol. A large portion of thegallic acid is methylated and excreted in the urineas methyl gallic acid. This pathway offers apossible explanation as to why additions ofmethionine, choline and other methyl donors havebeen reported to be beneficial when includedin diets containing tannic acid.

Much of the work on toxicity of tannins hasinvolved purified tannic acid. Legume andcereal tannins are of a condensed type while tannic acid is of a hydrolyzable type. Since thereare conflicting reports on the degree of growthdepression and the role of methionine in alleviatingtannin toxicity, it follows that the predominantdetoxification process may differ between thesetwo compounds. More recent work suggests thatwhile gallic acid is the breakdown product of bothcondensed tannins and tannic acid, and can bedetoxified by methyl groups, the stability ofcondensed tannins is such that this route ofdetoxification may be of little importance.

i) Sorghum tannins - The nutritive value ofsorghum is usually considered to be 90 to 95%that of corn, due in large part, to its tannin content.There are a number of varieties of sorghum on themarket which are usually classified as bird resist-ant or non-bird resistant varieties. These have eithera low (less than 0.5%) or high (1.5% or higher)level of tannins. A number of toxic effects havebeen reported with the feeding of high tanninsorghum. These include depressed growth andfeed utilization, reduced protein digestibility,lower egg production and leg abnormalitieswith broilers.

A number of procedures have been tried inan attempt to reduce the toxicity of the tanninsin sorghum. These include soaking in water oralkali solution, which are reported to deactivatetannins and thus improve the nutritive value of

the cereal. Besides the addition of the methyldonors which have been reported to improve thefeeding value of high tannin sorghum, productssuch as polyvinylpyrrolidone, and calciumhydroxide, or a slurry of sodium carbonate havealso been reported to give positive responses.However, several crude enzyme preparations thathave been tried were not effective in enhancingthe feeding value of high tannin sorghum.

Tannins have also been implicated in egg yolkmottling. Yolk mottling is a condition which periodically appears in a flock and without a directinvolvement of nicarbazin, gossypol or certainworming compounds, there is usually no readyexplanation for its appearance. While severalreports have suggested tannic acid and its derivatives as possible causes, other than the addition of commercial tannic acid at levelsabove 1%, there appears to be no mottling seenwith diets containing up to 2.5% tannins.

There are reports suggesting that tanninsare bound tightly to a fraction of the nitrogen insorghum and that this reduces protein digestibil-ity. However, because the tannins are relativelyinsoluble they appear to have little influence incomplexing with protein. In a recent studywith turkeys, a high tannin sorghum varietywhen used at 40% in the diet, resulted indepressed performance to 8 weeks of age.However, the feeding of a similar level to turkeysbeyond 8 weeks of age had no detrimentaleffects. The authors suggest that a more fully developed digestive system of the older birds maybe able to overcome the anti-nutritional effectsof the tannins.

While dark colored varieties of sorghumseed usually contain higher levels of tanninthan do lighter colored varieties, seed color, ingeneral, is a poor indicator of the tannin contentof sorghum.



ii) Faba Bean Tannins - Raw faba beans areknown to result in depressed performance ofpoultry while autoclaving results in a significantimprovement in bird performance. Dehulling alsoresults in improved energy value with this effectbeing greater than can be accounted for byreduction in fiber content. The growth depressingproperties of faba beans are due to two water-acetone soluble fractions, one containing low weightpolyphenolic compounds, the other containingcondensed tannins, the latter being the major growthinhibiting substance. These condensed tanninsare similar to those found in sorghum and are concentrated in the hull fraction.

While proper heat treatment of faba beanscan markedly increase their nutritive value,there appears to be some detrimental effect onintestinal villi structure regardless of the degreeof heat treatment or the fraction of seed consumed.This has led to reports that factors other than thoseusually considered, such as protease inhibitors,phytates and lectins, may be contributing tothe low nutritional value of faba beans. Tannin-free varieties of faba beans are available that contain less than 0.1% condensed tannins in theirhulls compared to over 4% in the high tannin varieties. These lighter colored seeds are ofimproved nutritive value. Regardless of tannincontent, appropriate heat treatment improves thenutritive value of faba beans.

iii) Rapeseed and Canola Tannins - Rapeseed andcanola meal have been reported to contain 2 to3% tannin, which is concentrated in the hull. Thesetannins have been shown to contribute to the eggtaint problem of these meals, when fed tobrown-egg layers, due to their inhibitory effecton trimethylamine oxidase. The original methodfor assaying tannin also included sinapine. Because the sinapine content ofcanola is around 1.5%, a value of 1.5% fortotal tannins is more realistic than earlier

reported values of around 3%. With tannins concentrated in the hull of both rapeseed andcanola, the amount of extractable tannins has beeninvestigated and appears to range from 0.02 to2%. The ability of these tannins to inhibit amylase in-vitro was not detected. Hence, it hasbeen assumed that the tannins in rapeseed andcanola are bound in such a manner that their influence on digestibility of other ingredients isnegligible.

Lathyrism - As with many species of animals, poul-try are susceptible to lathyrism, a metaboliccondition caused by the consumption of legumeseeds of the genus Lathyrus, of which sweetpeas are a member. The seeds are rich in protein (25 to 27%) and their availability and relatively low cost in many Asian and mid-Eastern countries often results in their use in poultry feeds. The causative agents for lathyrismare the lathyrogens, of which lathyrogen beta-aminopropionitrile (BAPN) is the principletoxin found. However, there are some syntheticlathyrogens available that have been used in studying the condition.

Lathyrism manifests itself in two distinctiveforms. Firstly, there is a disorder of the nervoussystem leading to a crippling condition andreferred to as neurolathyrism, and secondly a disorder of the collagen and elastin componentof connective tissue resulting in a skeletal and/orvascular disease and referred to as osteolathyrism.Typical symptoms seen with poultry consumingsignificant quantities of toxins are depressedperformance, ruffled feathers, enlarged hocks,curled toes, ataxia, leg paralysis and eventuallymortality.

Most of the poultry research involves specificsynthesized lathyrogens rather than natural seeds.BAPN has been shown to inhibit cross-linking



compounds in elastin and collagen by inhibitingthe enzyme lysyl oxidase, an important componentin the synthesis of these compounds. It has alsobeen reported to reduce growth rate of chicks, poultsand ducklings and to reduce egg production ofadults of these species. BAPN can result indefective shell membranes, so ultimately affectingshell calcification, leading to malformed andsoft-shelled eggs. This effect is similar to that seenwith copper deficiency since the enzyme lysyl oxidase is a metalloenzyme that requires copper.Consequently, there are reports of copper alleviating the symptoms of BAPN toxicity.

While recommended maximum levels ofinclusion of the various lathyrus seeds, to avoidmetabolic problems, varies with the type ofseed and the lathyrogen content of the seed, ageneral recommendation would be to keep thedietary level of BAPN below 50 mg/kg of diet.While the addition of lathyrogens to a laying dietresults in a decrease in production after 4 to 5days, hens seem to return to normal productionin 10 to 14 days after receiving a normal diet.Interestingly there has been some research interest on the ability of BAPN to tenderizemeat from spent hens. This is obviously relatedto its effect in altering collagen cross-linking byinhibiting the enzyme lysyl oxidase.

Gossypol - The use of cottonseed products in dietsfor laying hens has long been a problem for nutri-tionists as well as producers. As early as 1891there were reports of mottled egg yolks result-ing from the feeding of cottonseed meal to lay-ers. In the early 1930’s gossypol was identified asthe compound involved in discoloration of eggyolks when hens were fed cotton seed meal. Itsoon became evident that there were two problems that could occur with the feeding ofcottonseed meal to layers: the albumen of stored eggs developed a pink color and thus the

disorder became known as pink egg white; andsecondly there was brown or olive pigment inthe yolks. This later defect was the result of gossy-pol from the cottonseed pigment glands interactingwith iron in the egg yolk.

Although pink albumen discoloration isknown to occur spontaneously, it is usually seenwith ingestion of products from plants of the botanical order, Malvales. Two naturally occurringcyclic fatty acids have been isolated from plantsknown to cause the unusual color. These com-pounds were called malvalic and sterculic acids.A color test developed many years ago byHalpen, can be used to identify cottonseed oil invegetable oil mixtures. The test has been shownto be very specific to cyclopropenoid compounds,especially malvalic and sterculic fatty acids.The pink-white albumen condition noted instored eggs, which is common with the ingestionof either malvalic or sterculic fatty acids, resultsfrom a combination of conalbumen and eggwhite protein mixing with iron that diffuses fromthe yolk. This is due, in part, to changes inmembrane permeability and an increase in yolkpH. The amount of these compounds fed, storage conditions and breed of hen, have all beenshown to influence the degree and incidence ofthe condition.

Yolk discoloration is also caused by theingestion of gossypol and/or malvalic or sterculicacid. However, there is a difference in incidenceand degree of discoloration and mottling depend-ing on whether intact gossypol or the fatty acidsare involved. Changes in membrane permeabilityand a shift in yolk and albumen pH result in waterand albumen protein migrating to the yolks.The severity of the condition will depend on theamount of gossypol ingested and can lead to pastycustard-like or viscous yolks being observed. Thesecan be seen at ovulation but the condition can



compounds in elastin and collagen by inhibitingthe enzyme lysyl oxidase, an important componentin the synthesis of these compounds. It has alsobeen reported to reduce growth rate of chicks, poultsand ducklings and to reduce egg production ofadults of these species. BAPN can result indefective shell membranes, so ultimately affectingshell calcification, leading to malformed andsoft-shelled eggs. This effect is similar to that seenwith copper deficiency since the enzyme lysyl oxidase is a metalloenzyme that requires copper.Consequently, there are reports of copper alleviating the symptoms of BAPN toxicity.

While recommended maximum levels ofinclusion of the various lathyrus seeds, to avoidmetabolic problems, varies with the type ofseed and the lathyrogen content of the seed, ageneral recommendation would be to keep thedietary level of BAPN below 50 mg/kg of diet.While the addition of lathyrogens to a laying dietresults in a decrease in production after 4 to 5days, hens seem to return to normal productionin 10 to 14 days after receiving a normal diet.Interestingly there has been some research interest on the ability of BAPN to tenderizemeat from spent hens. This is obviously relatedto its effect in altering collagen cross-linking byinhibiting the enzyme lysyl oxidase.

Gossypol - The use of cottonseed products in dietsfor laying hens has long been a problem for nutri-tionists as well as producers. As early as 1891there were reports of mottled egg yolks result-ing from the feeding of cottonseed meal to lay-ers. In the early 1930’s gossypol was identified asthe compound involved in discoloration of eggyolks when hens were fed cotton seed meal. Itsoon became evident that there were two problems that could occur with the feeding ofcottonseed meal to layers: the albumen of stored eggs developed a pink color and thus the

disorder became known as pink egg white; andsecondly there was brown or olive pigment inthe yolks. This later defect was the result of gossy-pol from the cottonseed pigment glands interactingwith iron in the egg yolk.

Although pink albumen discoloration isknown to occur spontaneously, it is usually seenwith ingestion of products from plants of the botanical order, Malvales. Two naturally occurringcyclic fatty acids have been isolated from plantsknown to cause the unusual color. These com-pounds were called malvalic and sterculic acids.A color test developed many years ago byHalpen, can be used to identify cottonseed oil invegetable oil mixtures. The test has been shownto be very specific to cyclopropenoid compounds,especially malvalic and sterculic fatty acids.The pink-white albumen condition noted instored eggs, which is common with the ingestionof either malvalic or sterculic fatty acids, resultsfrom a combination of conalbumen and eggwhite protein mixing with iron that diffuses fromthe yolk. This is due, in part, to changes inmembrane permeability and an increase in yolkpH. The amount of these compounds fed, storage conditions and breed of hen, have all beenshown to influence the degree and incidence ofthe condition.

Yolk discoloration is also caused by theingestion of gossypol and/or malvalic or sterculicacid. However, there is a difference in incidenceand degree of discoloration and mottling depend-ing on whether intact gossypol or the fatty acidsare involved. Changes in membrane permeabilityand a shift in yolk and albumen pH result in waterand albumen protein migrating to the yolks.The severity of the condition will depend on theamount of gossypol ingested and can lead to pastycustard-like or viscous yolks being observed. Thesecan be seen at ovulation but the condition can



be accentuated with storage. There are reportsof increased embryo mortality during the first weekof incubation when breeders are fed high levelsof malvalic or sterculic acid, however, the levels fed must be much higher than those normally present in laying hen diets.

Although varieties of cottonseed have beendeveloped that are gossypol free, their low yieldhas meant that they are not widely used incommercial production. Consequently, muchof the cottonseed grown world-wide still containsappreciable quantities of gossypol. Processingmethod can markedly reduce the gossypol content of the meal to levels less than 0.04% freegossypol. In addition, soluble iron salts can beadded to diets containing cottonseed meal. Theiron will complex with gossypol reducing its toxiceffects. In a recent report, broilers fed a diet withup to 30% cottonseed meal, with soluble ironadded (to provide a 2:1 ratio of iron to freegossypol) resulted in no detrimental effect on weightgain or liveability.

Alkaloids - Alkaloids are found in a number offeedstuffs but by far the most important are thelupine legumes. Seeds of the plant Crotalaria retusaL., contain up to 4.5% of the pyrolizidine alkaloidmonocrotaline and these can be a problem in cereal contamination in some areas of Asia andAustralia. The older varieties of lupines were oftenreferred to as bitter lupines, due to the presenceof significant quantities of quinolizidine alkaloids,mainly lupanine. These alkaloids affect thecentral nervous system causing depressedlaboured breathing, convulsions and death fromrespiratory failure. Newer varieties of lupines nowbeing grown are very low in alkaloids (less than0.02%) and have been shown to be well toler-ated by poultry.

One of the most common sources of alkaloidsfinding its way into animal feeds is grain con-taminated with ergot. Samples of ergot canrun as high as 0.4% total alkaloids. Chickensreceiving 1 to 2% of ergot in their diet canshow symptoms ranging from depressed growthto necrosis of the extremities, staggers, ataxia,tremors and convulsions.

c. AutointoxicationAutointoxication could be defined as self-

poisoning as it is endogenous in origin andresults from the absorption of waste products ofmetabolism or from products of decompositionin the intestine. High fiber diets fed to young chickscan cause obstruction of the digestive tract withsubsequent absorption of products of decompositionor metabolic wastes. Litter consumed by chicksor over-consumption of green grass or plantscan also lead to gut impaction problems.

The chilling or overheating of chicks can leadto vent pasting and occlusion resulting in stasisof the intestine contents with autointoxicationbeing the end result. Birds suffering from autoin-toxication are anorexic, and show increasedwater consumption, followed by weakness andprostration. A generalized toxaemia may resultleading to nervous symptoms prior to death.

d. Bacterial toxinsAlthough losses in birds due to bacterial

toxins are not of great economic importance, theydo occasionally result in heavy losses in a par-ticular flock. The main organism affecting poul-try is Clostridium botulinum. No significantlesions are found in botulism poisoning and a positive diagnosis is usually based on identificationof the organism and its toxin.



Botulism is caused by the toxin produced fromthe C. botulinum organism under anaerobicconditions. C. botulinum is a saprophyte foundin soil and dirt and can also be found in intestinalcontents and feces. The mere presence of theorganism is sufficient to cause disease or to beof diagnostic significance. Growth of the organ-ism, in anaerobic conditions, results in the production of toxins. Botulism can result frombirds eating carcasses of birds which have diedfrom the disease and also fly larvae from suchcarcasses. The toxins present in the meat are ingested by larva rendering them extremelypoisonous. Symptoms may appear within afew hours to a day or two after contaminated feedis eaten. The common symptom noted is paral-ysis, with the leg and wing muscles first affected.If the neck muscles are affected the head hangslimp, hence the name ‘limberneck’ which hasbeen used to refer to the disease. In mild cases,leg weakness, ruffled feathers and soft pastyfeces may be noted. The severity of the diseasedepends on the amount of toxin consumed.However, death usually occurs as this toxin is verypotent. Losses in birds are most commonly dueto type A and C toxins. Type A, is common in themountainous regions of North and South American,while type C is world-wide in distribution.

For many years, a disease of wild ducks andother aquatic birds was common in the westernpart of North America. It is now known that thisis due to botulism poisoning. Insect larvae in anaquatic environment may die as the result ofanaerobic conditions caused by decaying vegetation.When these larvae are eaten by birds, botulism organ-isms invade tissues and produce toxins. Preventionrelates to proper management procedures that elim-inate dead and decomposed carcasses around apoultry house. A good rodent and fly control pro-gram is also essential as is screening of the build-ing to eliminate entry of wild birds.

e. Chemotherapeutic drugsWhile the use of various pharmaceutical

compounds has contributed significantly to thedevelopment of the modern poultry industry, theirmisuse can result in toxicity. Some of the morecommon drugs that can result in problems if usedat toxic levels are:

i. Sulfonamides – Toxicity is manifested by signsof ruffled feathers, paleness, poor growth andincreased blood clotting time. Hemorrhages inskin and muscle may be noted and necrosis of theliver, spleen, lungs and kidney are often seen.

ii. Nitrofurans – Toxicity results in depressedgrowth and hyperexcitability, where chickscheep and dash about. Enteritis and congestionof the kidneys and lungs, along with bodyedema and cardiac degeneration may be noted.

iii. Nicarbazin – Toxicity in chicks results inbirds being listless and showing signs of ataxia,with incoordination and a stilted gait especial-ly in hot weather. Fatty degeneration of the livermay be noted. The most common problemwith nicarbazin is its effect on laying hens.Brown eggs will be depigmented and yolk mot-tling may be noted with white and brown eggs.

f. Toxic seedsPhytotoxins can be considered as any toxic

substance derived from plants including roots,stems, leaves, flower and seeds. Some plants aretoxic throughout the whole growing seasonwhile others are only toxic during certain stagesof development. The majority of toxic plants arerelatively unpalatable and are usually avoidedby birds. However, with the absence of succulentfeed, range birds will consume sufficient foliageor seeds to result in poisoning. Some of the morecommon poisonous plants are as follows:



i) Black locust (Robinia pseudoacacia) – The toxinis the glycoside robitin-alectin (hemagglutinin).It has been reported that the leaves of black locustare toxic during early July and August in the N.Hemisphere and cause mortality with chick-ens if consumed at this period. Symptomsnoted are listlessness, diarrhea, anorexia and paral-ysis with death occurring within several days.Hemorrhagic enteritis may also be seen.

ii) Castor bean (Ricinus communis) – Manylegume seeds contain a protein fraction whichis capable of agglutinating red blood cells.These compounds are referred to as lectins andthey vary widely in their degree of specificity totypes of red blood cells and also their degree oftoxicity. Such legumes must be degraded by heattreatment in order to detoxify them and soenhance their nutritive value. Castor bean wasone of the first such legumes to be investigatedand a lectin called ricin was isolated which isextremely poisonous. However, the steaming ofcastor meal for 1 hour will reduce the toxicityof the meal to 1/2000 of its original level.Toxicity is seen as progressive paralysis startingwith the legs and progressing to complete prostration. With the exception of blood-stainedmucus in the droppings, clinical signs are indis-tinguishable from those of botulism. A paleswollen mottled liver is often seen with petechialhemorrhages present on the heart and visceral fat.

iii) Coffee bean seed (Cassia occidentalis; C. obtusi-folia) – Mechanical harvesting methods haveincreased the danger of contamination of cornand soybeans with coffee bean plants which arefrequently found in relatively large numbers inthe southern USA. At all levels of incorporationof the anthraquinone lectins from coffee seeds,egg production and weight gain are reduced.Platinum colored yolks and profuse diarrhea arealso noted with layers. Birds fed 2 to 4% of the

coffee seeds become ataxic or partially paralysedbefore death. Muscle lesions are similar tothose seen with vitamin E deficiency. Death oftenoccurs due to a hyperkalemic heart failure.Production will return to normal with the removalof the contaminated feed.

iv) Corn cockle (Argostemma githago) – Corncockle is often harvested with wheat and socan become incorporated into poultry feeds. Thediet must contain 5% or more of corn cockle toshow toxic symptoms, which are caused bygithagenin, a plant saponin. General weakness,with decreased respiration and heart rate may benoted often associated with diarrhea.Hydropericardium and edema of the intestine canbe seen along with petechial hemorrhages in themyocardium and congestion and degenerationof the liver.

v) Coyotillo (Karwinskia humboldtiana) – Thisplant is indigenous to southwest Texas andMexico. The fruit and seed are toxic to poultryand 3 to 4 days after ingestion generalized tox-aemia signs can be noted, followed by paraly-sis and death.

vi) Cacao (Theobroma cacao) – High levels of cacaobean wastes (in excess of 7% of the diet) arerequired to show toxic symptoms caused by the toxintheobromine. Such symptoms include nervous andexcitable birds. Birds die in convulsions and usually are on their back with legs drawn tightly against their body. The comb is often cyanotic.

vii) Crotalaria seed – A few species are toxic topoultry the most problematic being C. spectabilisand C. giant (striata). The toxin is a pyrolizidinealkaloid, designated, monocrotaline. Crotalariais a small black or brownish seed and is a con-taminant in corn and soybeans in the southeastUSA. One percent in a chick diet can result indeath by 4 weeks of age. Birds become huddled



having a pale comb and diarrhea and mayexhibit a duck-like walk. With young birdsabdominal fluid and edema, similar to that seenwith ascites may be noted. With mature birds, thereis a reduced egg production and massive liver hem-orrhages may be noted. The lesions are similarto those reported for toxic fat and salt poisoning.

viii) Daubentonia seed (Daubentonia longifolia) –This seed can be a problem in the southernUSA. As little as 9 seeds can cause death in 24– 72 hours. The comb can be cyanotic, with thehead hanging to one side. Emaciation anddiarrhea may also be noted. Severe gastroenteritis,ulceration of the proventriculus and degenera-tion of the liver are not uncommon.

ix) Glottidium seed (Glottidium vesicarium) – Thisseed is often found in the southeastern USA.Clinical symptoms are a cyanotic comb andwattles, ruffled feathers, emaciation and yellow diarrhea. Necrotic enteritis as well as liverand kidney degeneration are also commonobservations.

x) Death camas (Zygadenus) – This is a green rangeplant with an alkaloid toxin called nuttallii.Consumption of 5 to 10 g by a chicken can resultin clinical symptoms in 12 hours that include incoordination, diarrhea and prostration fol-lowed by death.

xi) Vetch (Vicia sativa) - Vetch belongs to theLeguminosae family which is related to thelegumes Lathyrus, Pisum and Ervum. It is com-

mon in the northwest USA and produces acyanogenic glucoside called viciana, which isconverted by the enzyme vicianase into hydro-cyanic acid. Problems comparable to lathyrismare observed, including excitability, incoordination,respiratory problems and convulsions.

xii) Milkweed – Two common species areAsclepias tuberosa and A. incarnata. They con-tain the bitter glucoside, asclepdin, which is toxicto birds. Symptoms vary widely depending onthe quantity of material consumed. The first signis usually lameness, developing quickly intocomplete loss of muscle control. The neckbecomes twisted with the head drawn back. Insome cases symptoms gradually subside. Infatal cases, symptoms become more progressiveand prostration, coma and death result. No char-acteristic lesions are seen on necropsy.

xiii) Algae – Certain types of algae, includingMicrocystis aeruginosa, which readily grows inmany lakes, can become concentrated by windand deposited on shore or in shallow water.Degradation of this material produces toxins whichhave been responsible for losses in wild anddomestic birds. The condition is usually notedin summer months. Toxicity is proportional tothe amount of toxin consumed. Death canresult in 10 to 45 minutes for mature ducksand chickens. Clinical symptoms include rest-lessness, twitching, muscle spasms, convul-sions and death. These symptoms are similar to those seen with strychnine poisoning.



having a pale comb and diarrhea and mayexhibit a duck-like walk. With young birdsabdominal fluid and edema, similar to that seenwith ascites may be noted. With mature birds, thereis a reduced egg production and massive liver hem-orrhages may be noted. The lesions are similarto those reported for toxic fat and salt poisoning.

viii) Daubentonia seed (Daubentonia longifolia) –This seed can be a problem in the southernUSA. As little as 9 seeds can cause death in 24– 72 hours. The comb can be cyanotic, with thehead hanging to one side. Emaciation anddiarrhea may also be noted. Severe gastroenteritis,ulceration of the proventriculus and degenera-tion of the liver are not uncommon.

ix) Glottidium seed (Glottidium vesicarium) – Thisseed is often found in the southeastern USA.Clinical symptoms are a cyanotic comb andwattles, ruffled feathers, emaciation and yellow diarrhea. Necrotic enteritis as well as liverand kidney degeneration are also commonobservations.

x) Death camas (Zygadenus) – This is a green rangeplant with an alkaloid toxin called nuttallii.Consumption of 5 to 10 g by a chicken can resultin clinical symptoms in 12 hours that include incoordination, diarrhea and prostration fol-lowed by death.

xi) Vetch (Vicia sativa) - Vetch belongs to theLeguminosae family which is related to thelegumes Lathyrus, Pisum and Ervum. It is com-

mon in the northwest USA and produces acyanogenic glucoside called viciana, which isconverted by the enzyme vicianase into hydro-cyanic acid. Problems comparable to lathyrismare observed, including excitability, incoordination,respiratory problems and convulsions.

xii) Milkweed – Two common species areAsclepias tuberosa and A. incarnata. They con-tain the bitter glucoside, asclepdin, which is toxicto birds. Symptoms vary widely depending onthe quantity of material consumed. The first signis usually lameness, developing quickly intocomplete loss of muscle control. The neckbecomes twisted with the head drawn back. Insome cases symptoms gradually subside. Infatal cases, symptoms become more progressiveand prostration, coma and death result. No char-acteristic lesions are seen on necropsy.

xiii) Algae – Certain types of algae, includingMicrocystis aeruginosa, which readily grows inmany lakes, can become concentrated by windand deposited on shore or in shallow water.Degradation of this material produces toxins whichhave been responsible for losses in wild anddomestic birds. The condition is usually notedin summer months. Toxicity is proportional tothe amount of toxin consumed. Death canresult in 10 to 45 minutes for mature ducksand chickens. Clinical symptoms include rest-lessness, twitching, muscle spasms, convul-sions and death. These symptoms are similar to those seen with strychnine poisoning.

SECTION 2.5Feed manufacture


2.5 FEED MANUFACTURE

I n the early days of poultry nutrition feeds con-tained relatively few synthetic ingredients andthe smallest amount of any addition amount-

ed to 0.5% or more. Some natural ingredients, how-ever, have been gradually replaced and supplementedby extremely small quantities of synthetic and puri-fied ingredients, especially the vitamins, traceminerals, pigments and various pharmacologicalcompounds. Consequently, the proper mixing offeed requires ever increasing technical knowledge.Improper mixing can result in variation in thequality of feed and vitamin or mineral deficienciesresulting in lack of protection against disease or chem-ical or drug toxicity.

a. Vitamin-Mineral PremixesMicro-ingredients should be properly premixed

before being added to a feed. It is desirable tohave similar physical characteristics amongingredients to be premixed. The diluent suggestedfor use in the vitamin-mineral premixes is groundyellow corn or wheat middlings, both being ofmedium grind for best results. If the carrier is too coarse, it is not possible to obtaingood distribution of the supplements, while toofine a carrier leads to dustiness and caking.For mineral mixes, limestone or kaolin (china clay)make satisfactory carriers. Where premixes arebeing stored for relatively short periods of time,the vitamin and mineral premix can be combined.However, where mixes are to be stored formore than 6 weeks in a warm moist environment,it may be advisable to make separate vitamin andmineral mixes. Also, if premixes are to beshipped long distances and thus subjected to agreat deal of handling, and perhaps high tem-perature, it is advisable to make separate vitaminand mineral mixes. This helps to reduce the physical separation of nutrients and leads toless vitamin deterioration.

When vitamin-mineral premixes are pre-pared in quantity ahead of time, they should beclearly labeled and stored in a cool dry place forfuture use. With the addition of an antioxidant andthe margins of safety provided in most premixes, they can be held for two to threemonths under ideal conditions. Rather than sug-gesting the use of products with specific poten-cies to supply the vitamins and other nutrients (Table2.26) the units or weights of the compoundshave been indicated and the decision as to prod-uct use is left to the individual. Some feed man-ufacturers are capable of making premixes frommore concentrated vitamin and mineral preparations,since this usually results in a cost saving com-pared with the use of more dilute preparations.The choice of potency of products for use in thepremixes should be governed, to a large extent,by personnel and the facilities available. Becausevitamin and mineral supplements represent a rel-atively small part of the total cost of a diet,margins of safety are being added in most cases.Lower levels can be used with satisfactory resultsunder ideal conditions.

The direct addition of vitamin premixes or othersupplements to the feed, at a usage rate less than1 kg/tonne, is not usually recommended. Thesemicro-ingredients should be suitably premixedfirst, so that at least 1 kg/tonne is added. It is gen-erally recommended that vitamin-mineral pre-mixes be added to the mixer after about one-halfof the other ingredients have been included. Thetime required for a satisfactory mix is very importantand varies considerably depending upon the equipment used. Usually 2 – 3 minutes is the opti-mum for horizontal mixers and up to 5 minutes for vertical machines although mixing times are being continually reduced with newer equipment. This canvary with the type of mixer and manufacturer’sspecifications should always be followed.



Tab

le 2

.26

Vit

amin

-min

eral

pre

mix

es (

wit

hou

t ch

olin

e)–

all p

rem

ixes

sho

uld

be m

ade

up to

1 –

5 k

g by

the

addi

tion

of a

car

rier

suc

h as

whe

at m

iddl

ings

.Th

e am

ount

s sh

own

belo

w a

re th

e le

vels

of n

utri

ents

to b

e ad

ded

per t

onne

of f

inis

hed

feed

.

CH

ICK

EN

TU

RK

EY

WA

TE

RFO

WL

VIT

AM

INS

Star

ter

Gro

wer

Lay

ing

Bre

eder

Star

ter

Gro

wer

Bre

eder

Star

ter

Gro

wer

Bre

eder

Vit

amin

A(M

.IU)

10.0

8.0

7.5

11.0

10.0

8.0

11.0

10.0

8.0

10.0

Vit

amin

D3

(M.IU

)3.

53.

33.

33.

33.

53.

33.

32.

52.

53.

0V

itam

in E

(T.

IU)

30.0

20.0

50.0

70.0

40.0

30.0

100.

020

.015

.040

.0R

ibof

lavi

n (g

)6.

05.

05.

08.

06.

05.

08.

05.

04.

05.

5T

hiam

in (

g)4.

04.

04.

04.

04.

04.

04.

04.

04.

04.

0P

yrid

oxin

e (g

)3.

33.

33.

35.

03.

33.

35.

03.

33.

33.

3P

anto

then

ic a

cid

(g)

15.0

10.0

10.0

15.0

15.0

12.0

15.0

12.0

10.0

10.0

Vit

amin

B12

(g)

.015

.012

.015

.015

.015

.012

.015

.015

.010

.015

Nia

cin

(g)

50.0

30.0

40.0

50.0

50.0

40.0

50.0

50.0

40.0

50.0

Vit

amin

K (

g)2.

02.

02.

03.

02.

02.

03.

01.

51.

51.

5Fo

lic a

cid

(g)

1.0

1.0

1.0

1.0

1.0

0.5

1.0

1.0

0.5

0.5

Bio

tin1

(g)

0.15

0.10

0.10

0.15

0.2

0.15

0.2

0.1

0.1

0.1

MIN

ER

AL

S

Man

gane

se (

g)70

.070

.070

.070

.070

.070

.070

.070

.070

.070

.0Z

inc

(g)

60.0

60.0

60.0

60.0

60.0

60.0

60.0

60.0

60.0

60.0

Cop

per

(g)

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

8.0

Sele

nium

(g)

0.3

0.3

0.3

0.3

0.3

0.3

0.3

0.3

0.3

0.3

Iron

(g)

5040

3040

5040

4040

3030

All

vita

min

pre

mix

es s

houl

d co

ntai

n E

thox

yqui

n to

pro

vide

125

g/to

nne

feed

.1

Incr

ease

if d

iet

cont

ains

> 1

0% w

heat

.



The segregation of ingredients in a mixed feedcan occur due to improper handling after mixing.This can be a problem when mash feeds containingno added fat are blown into bulk bins. However,care in unloading and a cyclone on top of thebulk tank will help overcome the problem. Thisis usually not a great problem when the feed ispelleted or crumbled.

b. Vitamin StabilityNaturally occurring vitamin E is quite unstable,

particularly in the presence of fat and traceminerals, however, vitamin E added as a sup-plement usually is in a highly stable form (e.g.gelatin coated beadlet containing an antioxidant).

Vitamin A in fish oil and pro-vitamin A compounds in yellow corn are easily destroyedin the typical mixed ration. Most dehydrated greenfeeds are now treated with an antioxidant thathelps prevent the destruction of the pro-vitaminA compounds during storage. Today, most poultry feeds contain supplementary gelatin-or starch-coated synthetic vitamin A which is quitestable. The inclusion of antioxidants in the feedhelps to retain the potency of vitamins A and Ein mixed feed.

Vitamin D3 is the only form of the productto be used in poultry diets, since birds cannotmetabolize vitamin D2. Vitamin D3 supple-ments are available in a dry, stabilized form. Theseproducts are reported to be stable when mixed withminerals. Hy-D®, a commercial form of 24(OH)D3is also very stable within premixes and mixed feed.

Calcium pantothenate may be destroyed in the presence of supplements containing acidingredients such as niacin, arsenilic acid and 3-nitro. The calcium chloride complex of calcium pantothenate is more stable than is conventionalcalcium pantothenate under acid conditions.

Recent work has shown that thiamin, folic acid,pyridoxine and some vitamin K supplements canbe relatively unstable in the presence of trace mineral supplements. This is especially truewhere the minerals are supplied as sulphatesalts, hence special consideration must be givento the above mentioned vitamins when premixes contain both vitamins and minerals, andstorage is for 4 – 6 weeks.

Most of the other vitamins are fairly stable.However, care should be taken in storing vita-mins to ensure their potency. Always store in acool, dry, lightproof space or container. Whilevitamin supplements are an extremely importantpart of a well balanced diet, animals usually havesufficient body stores to meet their require-ments for several days. Modern poultry farmsreceive feed deliveries on a weekly or evenmore frequent basis. Failure to incorporate thevitamin premix in a delivery of feed will likelyhave little or no effect on the performance of mostclasses of poultry, assuming the ‘next delivery’contains the vitamin supplement. For breedingbirds, this may not be true, especially forriboflavin, which could well affect hatchabilityif hens are fed a deficient diet for 5 to 7 days.

c. PelletingThe pelleting process usually involves treat-

ing ground feed with steam and then passing thehot, moist mash through a die under pressure. Thepellets are then cooled quickly and dried bymeans of forced air. Sufficient water should beapplied so that all feed is moistened. Pelleting attoo low a temperature, or with too little steam, resultsin a ‘shiny pellet’, due to increased friction on thepellet going through the die. Often such pelletsare only the original mash enclosed in a hard cap-sule and have not benefited from the ‘cooking’process brought about by moisture and heat.



Optimum moisture content of a feed requiredfor good pelleting will vary with the composi-tion of the feed, however, a range of 15 to 18%moisture is usually desirable. Feeds containingliberal quantities of high fiber ingredients willrequire a higher level of moisture while feeds lowin fiber will require less moisture. A good pellet,when hot, can be reduced to two-thirds of its lengthwithout crumbling. Such feed has been ‘steam-cooked’ and holds together well. Rations canbe pelleted at any temperature up to 88ºC thatwill allow for maximum production per hour without any major fear of vitamin destruction.

Feed mills sometimes experience difficulty inobtaining good pellets when manufacturingcorn-soybean diets containing added fat. Productssuch as lignosol or bentonite are reasonablyeffective as binding agents, however, they ahave little nutritive value, and so one should con-sider whether the advantage of introducing suchmaterial into pelleted or crumbled diets warrantsthe cost. The inclusion of 10 to 15% of wheat,wheat middlings or to a lesser extent barley willoften give a pellet of satisfactory hardness. Whenthese ingredients are too expensive, the additionof about 2% of extra water to the mash will aidin producing a better pellet. If this procedure isfollowed, however, extra drying of the pellets isrequired so that mold growth does not occur dur-ing storage. Work in our laboratory has indicatedthat molasses may be used as a pellet binder. Inaddition to aiding in pelleting, molasses unlikeother binders, also contributes energy to thediet and so inclusion levels of 1 to 2% in certaindiets may be beneficial.

In addition to the advantages of less feedwastage and ease of handling, pelleted diets aremore efficiently utilized by poultry. While someof this improvement is due to chemical changesbrought about by heat, moisture and pressure,

a significant part of the enhanced efficiency isdue to birds spending less time when eating pellets resulting in a reduction in maintenanceenergy requirements by the bird. This situationwas demonstrated in the classical study byJensen et al. (Table 2.27).

Table 2.27 Time spent eating mashand pelleted diets

Av. time spent Av. feedAGE eating consumed

(min/12 hr day) (g/bird/12 hr)Mash Pellets Mash Pellets

Turkeys(38-45 d) 136 16 62 57Chickens(21-28 d) 103 34 38 37

Jensen et al. (1962)

The need for good quality pellets is often questioned by feed manufacturers since regrinding of pellets or crumbles and feeding theseto birds has little apparent effect on performance.

There seems little doubt that good quality crumbles and pellets can be advantageous forimproving the growth rate of turkeys. However,pellet quality seems of less importance withbroiler chickens, especially where high-energydiets are considered. More important in the pelleting process is the treatment of feed with steamand pressure, although it is realized that in certainmarkets it is difficult to sell feed that is not of ‘ideal’pellet quality.

d. Expanding, extrusion andthermal cooking

Extrusion has been used for a number of yearsto produce dry cereal snack foods and more recent-ly, various pet foods. Extrusion usually involveshigher temperatures and pressure than doesconventional steam pelleting, and so there is greater



potential for starch gelatinization and theoreti-cally higher digestibility. Extrusion is howevermuch slower than conventional pelleting, andinitial capital cost is very high.

Thermal cooking offers the most extreme processing conditions, where high temperaturescan be maintained for very long periods oftime, relative to pelleting, extrusion or expansion.Thermal cooking will result in the best possiblestarch gelatinization etc. and will also give thebest control over microbial content.

While all heat processing conditions aregoing to reduce microbial counts in feed therewill be a concomitant loss of heat-sensitive

nutrients such as some vitamins and aminoacids. In this context synthetic amino acidsmay be more susceptible to heat processingthan those naturally present in other ingredi-ents. One recent study suggested some 6% lossof total methionine in an extruded broiler starterthat contained 0.18% supplemental methionine.For most vitamins, other than vitamin C andMSBC, normal pelleting conditions are expect-ed to result in 8 – 10% loss of potency. Extrusionhowever, which usually employs much higher temperatures, can lead to 10 – 15% loss of most vitamins. Under any heat treatment conditionsthere will always be significant loss (� 50%) ofregular forms of vitamin C, and up to 30 – 50%loss of MSBC (Table 2.28).

Table 2.28 Effect of steam pelleting, extrusion and expansion on loss of vitamin potency

Loss of Vitamin Potency (%)Pelleting Expander Extrusion

VITAMIN (82ºC, 30 sec) (117ºC, 20 sec) (120ºC, 60 sec)Vitamin A (beadlet) 7 4 12Vitamin D3 (beadlet) 5 2 8Vitamin E 5 3 9MSBC 18 30 50Thiamin 11 9 21Folic acid 7 6 14Vitamin C 45 40 63Choline chloride 2 1 3

Adapted for Coehlo, (1994)


SECTION 2.6Water

Fig. 2.2 Water consumption of laying hensin relation to time of oviposition.(from Mongin and Sauveur, 1974)

2.6 WATER

W ater, is the most critical nutrient thatwe consciously supply to birds, yetin most instances, it is taken completely

for granted and often receives attention only whenmechanical problems occur. Water is by far thelargest single constituent of the body, and rep-resents about 70% of total body weight. Of thisbody water, about 70% is inside the cells of thebody and 30% is in the fluid surrounding the cellsand in the blood. The water content of the bodyis associated with muscle and other proteins.This means that as a bird ages, and its body fat con-tent increases, then its body water contentexpressed as a percent of body weight willdecrease. The bird obtains its water by drinking,from the feed and by catabolism of body tissueswhich is a normal part of growth and development.

a. Water intakeWater intake of a bird increases with age,

although it decreases per unit of body weight.Drinking behaviour is closely associated with feedintake, and so most factors affecting feed intakewill indirectly influence water intake. At moderate temperatures, birds will consumealmost twice as much water by weight as theyeat as feed. Any nutrients that increase mineralexcretion by the kidney will influence water intake.For example, salt, or an ingredient high in sodium, will increase water intake.

Similarly, feeding an ingredient high inpotassium such as molasses or soybean meal, orcalcium/phosphorus sources contaminated withmagnesium, will result in increased water intake.Such increases in water intake are of no majorconcern to the bird itself, but obviously result inincreased water excretion and so wetter manure.Table 2.29 indicates average water consumptionof various poultry species maintained at 20 or32ºC. These figures indicate approximate waterusage values and will vary with the stage of

production, health and feed composition. Asa generalization, for any bird up to 8 weeks ofage, an approximation of water needs can be calculated by multiplying age in days x 6 (e.g.42 d = 252 ml/d).

In calculating the water needs of egg producingstock, it should be realized that water intake isnot constant throughout the day, rather it variesdepending upon the stage of egg formation (Fig2.2). These data clearly show a peak in water con-sumption immediately following egg laying,and again, at the time just prior to the end of anormal light cycle. This means that water needsmust be accommodated during these peak times(around 10 – 11 a.m. and 6 – 8 p.m.) within a6 a.m. – 8 p.m. light cycle, because most birdswill be in the same stage of egg formation as direct-ed by the light program.

SECTION 2.6Water


Table 2.29 Daily ad-lib water consumption ofpoultry (litres per 1,000 birds)

20ºC 32ºCLeghorn pullet 4 wk 50 75

12 wk 115 18018 wk 140 200

Laying hen 50% prod. 150 25090% prod. 180 300

Non-laying hen 120 200Broiler breeder pullet 4 wk 75 120

12 wk 140 22018 wk 180 300

Broiler breeder hen 50% prod 180 30080% prod 210 360

Broiler chicken 1 wk 24 403 wk 100 1906 wk 240 5009 wk 300 600

Turkey 1 wk 24 504 wk 110 20012 wk 320 60018 wk 450 850

Turkey breeder hen 500 900Turkey breeder tom 500 1100Duck 1 wk 28 50

4 wk 120 2308 wk 300 600

Duck breeder 240 500Goose 1 wk 28 50

4 wk 250 45012 wk 350 600

Goose breeder 350 600These figures indicate approximate water usage values and will vary with the stage ofproduction, health and feed consumption.


SECTION 2.6Water

The contribution of feed is not usually considered in calculating water balance, yetmost feeds will contain around 10% of freewater. Other bound water may become available during digestion and metabolism,such that 7 – 8% of total requirements can originate from the feed.

Water is created in the body as a by-productof general metabolism. If fats are broken down,then about 1.2 g of water are produced from eachgram of fat. Likewise protein and carbohydratewill yield about 0.6 and 0.5 g per gram respec-tively. Total metabolic water can be more easily estimated from the bird’s energy intakebecause on average 0.14 g of water is producedfor each kcal of energy metabolized. This meansthat for a laying hen, consuming 280 kcalME/day, about 39 g of metabolic water will beproduced. Feed and metabolic water togethertherefore account for about 20% of total waterneeds, and so are very important in the calcu-lation of water balance.

b. Water outputThe quantities of water excreted in the feces

and urine are dependent on water intake. Broilerchickens produce excreta containing about 60– 70% moisture, while that produced by the laying hen contains about 80% moisture. For thelaying hen at least, the quantity of water excreted in the feces is about four times that excreted as urine. Undoubtedly, this loss issubject to considerable variation with the amountand nature of undigested feed.

Evaporation is one of four physical routes bywhich poultry can control their body tempera-ture. Due to its molecular structure and bonding,water has an unusually high latent heat of vaporization. Some 0.5 kcals of heat are requiredto vaporize one gram of water. Evaporative

heat loss takes place mainly through the respiratory tract. The fowl has no sweat glands,consequently evaporation via the skin is minimal. Evaporation overwhelmingly occursvia the moist surface layer of the respiratorytract to the inspired air which is ‘saturated’ withwater vapor at body temperature. Evaporationrate is therefore proportional to respiratory rate.Heat loss through evaporation represents onlyabout 12% of total heat loss in the broiler chickenhoused at 10ºC, but this increases dramaticallythrough 26 – 35ºC where it may contribute asmuch as 50% of total heat loss from the body.At high temperatures, evaporative water loss willapproximate water intake and so this obviouslyimposes major demands on the ventilation systems.

c. Water balance and dehydration

Under normal physiological conditions foradult birds, water intake and output are controlledto maintain a constant level of water in thebody. A positive water balance is found in thegrowing bird to accommodate growth. Withdrinking water being supplied ad libitum undermost commercial conditions, dehydration dueto lack of drinking water should not occur. Theadverse effects of short term reduced waterintake are often a result of a concomitant reduction in feed intake.

The turkey poult is most susceptible to dehy-dration resulting from drinking water deprivation,and mortality occurs when drinking water is re-introduced to the poults. Poults 11 days of age,subjected to a 48-hour period of water deprivation,showed 83% mortality following reintroductionof ad libitum cold water, and in most casesdeath occurred within 30 minutes. Poults 18 daysof age showed less mortality which was some-what delayed (2 –34 hours) while older turkeyssubjected to the same conditions showed no

SECTION 2.6Water


mortality. The exact reason for this mortality isnot fully understood. Poults deprived of watershow reduced body temperature, and whenwater is introduced, body temperature continuesto decrease for 30 minutes or so. Poults oftendrink large amounts of water following dehydration,and it has been suggested that the problemrelates to simple water intoxication and associateddilution of electrolytes in the body. If young poultsare dehydrated for whatever reason, then administration of electrolytes in the water maybe beneficial. This problem does not seem to occurwith chickens.

d. Drinking water temperatureWater offered to birds is usually at ambient

temperature. This means that for laying birdshoused under controlled environmental condi-tions, the temperature of drinking water is heldfairly constant, while for broiler chickens, watertemperature decreases with age correspondingto a reduction in brooding temperature. It is onlyfor the first few days of a chick’s life that drinkingwater temperature is specified, where traditionalmanagement recommendations suggest the useof ‘warm’ water. However, there is little documentedevidence supporting this recommendation.Birds drink more water at higher environmentaltemperatures, yet the cooling of water mayresult in even higher intakes. Table 2.30 outlinesthe results of a small scale study conductedwith layers housed at 33ºC.

Table 2.30 Layer performance at 33ºCwith hot vs cold drinking water

Water temperature

33ºC 2ºCFeed/bird/day (g) 63.8 75.8Egg production (%) 81.0 93.0Egg weight (g) 49.0 48.5

When birds received cool water for a 4-weekperiod, they were able to maintain peak egg pro-duction, possibly due to higher feed intake.Under commercial conditions, with long runs ofwater pipe, it is obviously very difficult to dupli-cate these conditions. However, it does show theimportance of trying to keep the water as cool aspossible, and in this regard, the usual practice ofplacing water tanks on high towers in direct sun-light should be seriously questioned.

e. Water restrictionMost birds should have continuous access to

water. Some breeders recommend water restric-tion of laying hens as a means of preventing wetmanure, especially in hot climates, although serious consideration should be given to other pre-ventative measures prior to this last resort.Production may drop as much as 30% whenhens are deprived of water for 24 hours, and it maytake as long as 25 to 30 days before productionreturns to normal. Similar results have been reported for broilers where decreases in water sup-ply have resulted in marked depressions in weightgain. Table 2.31 shows the results of a con-trolled test where water restriction was imposedon broilers. There was a marked drop in feed intake-with the greatest reduction occurring with the first10% reduction in water intake, causing a 10%decline in feed intake.

Table 2.31 Effect of water restric-tion on relative weekly feed con-sumption of broilersAge (weeks) Degree of water restriction (%)

0 10 20 30 40 502 100 84 84 75 84 714 100 99 102 90 85 806 100 88 81 78 73 718 100 86 83 79 74 67Total 100 90 87 81 77 73* All birds receive water ad libitum for first week.(Data from Kellerup et al. 1971)


SECTION 2.6Water

The effect of an accidental 48-hour cut inwater supply to layers is shown in Fig. 2.3.Production dropped off very quickly to virtu-ally 0%, although interestingly a few birdsmaintained normal production. Most birdsthat resumed production within 28 d achievednormal output for their age, and there was anindication of improved shell quality.

For certain classes of stock, intentional waterrestriction is used as a management tool. To date,this is most common with broiler breeders fedon a skip-a-day program. Water restriction mayoccur on both feed-days and off-feed days.Restriction on off-feed days is done because itis assumed that birds will over-consume wateron these days due to hunger or boredom.However, it seems as though breeders do not drinkthat much water on an off-feed day (Table 2.32).

All birds drank the same average amount ofwater over a 2 day feeding schedule regardlessof water treatment. When birds are given free-choice water, they obviously over-consumeon a feed-day, but drink little on an off-feed day.These data suggest the need for water restrictionof skip-a-day fed birds, although special attention on feed-days rather than off-feed dayswill be most advantageous in preventing wet litter.

Table 2.32 Water intake of 13week-old broiler breeders(ml/bird/day)

Water restrictedAd-lib

each only on waterday feed days

Feeding day 175 182 270Non-feed day 108 109 36Average 141 145 153

Fig. 2.3 Effect of a 48-hour period of waterdeprivation on egg numbers.

f. Water qualityWater quality should be monitored with

assays conducted at least each 6 months.Chemical contaminants are the most seriousproblem affecting water quality. However,poultry usually adjust to high levels of certain minerals after a period of time, and so only in arelatively small number of cases does the mineral content of water significantly affect theperformance of a flock. There are certain areaswhere water salinity is high enough to adverselyaffect flock performance. In such cases, it maybe necessary to remove some of the supplementalsalt from the diet. However, this should bedone only after careful consideration to ensurethat there will be a sufficient salt intake becauseperformance can be severely reduced if saltintake is too low.

Any bacterial contamination of water is anindication that surface water is entering thewater supply and steps should be taken to cor-rect the situation. Alternatively, the water maybe chlorinated to eliminate contamination.Another problem that can exist with water is a

SECTION 2.6Water


build-up of nitrates or nitrites. Such contaminationis usually an indication of run-off from animalwastes or fertilizers leaching into the water system. Although the standard for human watersupply is 10 to 20 ppm of nitrate nitrogen, higherlevels can usually be tolerated by animals.Levels beyond 50 ppm need to be present beforewater is suspected as a factor in the poor per-formance of poultry. As nitrites are 10 times moretoxic than nitrates, and because bacteria in theintestinal tract and in the water supply can convert nitrates to nitrites, levels of these two contaminants in the water supply must be keptto a minimum. Superchlorination of the waterwill quickly oxidize nitrites to nitrates thereby reducing their toxicity. Before initiating a super-chlorination program, check with a local pathologist to ensure a proper level of chlorinationin order not to interfere with the performance orefficiency of vaccines or other drugs.

Table 2.33 Concentration of waterminerals above which problemsmay occur with poultry (ppm)

Total soluble salts (hardness) 1500Chloride 500Sulphate 1000Iron 50Magnesium 200Potassium 500Sodium 500Nitrate 50Arsenic 0.01pH 6.0 – 8.5

Table 2.33 outlines standards for drinking waterin terms of mineral levels. Toxicity and loss ofperformance will vary dependent upon bird

age and class of stock, but in general these values can be used as guidelines to indicate thepossibility of toxicity with birds consumingsuch water over prolonged periods.

In the last few years, there has been aninterest in the treatment of water for poultry. Inlarge part, this is carried out in an attempt to prevent problems of mineral deposits occurringin pipelines, boilers and automatic waterers,rather than preventing toxicity problems perse. Such treatments involves orthophosphates,which sequester calcium and magnesium, there-by preventing precipitation in the water supply.In most situations, these systems will not unduly alter the water composition in terms ofthe bird’s nutritional requirements. As a last resort,some producers use water softeners, and inthese situations, there is some cause for concern,regarding the bird’s health. These softenerscontain an active column of resin, that has the ability to exchange one ion (mineral) for another. Over time, the resin column becomes saturated with the absorbed minerals (usually calcium and magnesium salts) that are extractedfrom the water, and so it must be flushed and re-charged with the donor mineral. In mostsofteners, this recharging process involves sodium from NaCl. This means that sodium isreplacing other minerals in the water, becausesodium salts readily dissolve, and will not leavemineral scale in the equipment. The amount ofsodium that is pumped into the water supply istherefore in direct proportion to the hard minerals extracted from the water. In areas of veryhard water, one can expect higher levels ofsodium in water reaching the birds, and vice-versain areas of lower water hardness. Problems inwater sodium will likely occur if softener salt useexceeds 40 kg/40,000 litres of water.


SECTION 2.6Water

g. General management considerations with water

Where continuous flow water troughs are usedfor caged birds, one must be sure that birds atthe end of the trough obtain sufficient water. A rise in house temperature will result inincreased water consumption, and unless the watersupply can be adjusted accordingly, shortagesof water may result for the birds at the far end ofthe line. It has also been demonstrated that poor-ly beak-trimmed birds may not be able to drink

sufficient water to sustain maximum production.When the lower beak of the bird is too long, upto 20% loss in egg production can occur, com-pared with properly beak-trimmed birds. Whendisease or stress occur, a decrease in water con-sumption is usually noted a day or two before adecrease in feed consumption. For this reason,managers should consider installing water meterson all water lines to each pen or cage row andhave the attendant keep a daily record of waterconsumption. Such records can give early warn-ing of potential problems with the flock.


SECTION 2.6Water

g. General management considerations with water

Where continuous flow water troughs are usedfor caged birds, one must be sure that birds atthe end of the trough obtain sufficient water. A rise in house temperature will result inincreased water consumption, and unless the watersupply can be adjusted accordingly, shortagesof water may result for the birds at the far end ofthe line. It has also been demonstrated that poor-ly beak-trimmed birds may not be able to drink

sufficient water to sustain maximum production.When the lower beak of the bird is too long, upto 20% loss in egg production can occur, com-pared with properly beak-trimmed birds. Whendisease or stress occur, a decrease in water con-sumption is usually noted a day or two before adecrease in feed consumption. For this reason,managers should consider installing water meterson all water lines to each pen or cage row andhave the attendant keep a daily record of waterconsumption. Such records can give early warn-ing of potential problems with the flock.


Suggested Reading

Angel, R. et al. (2002). Phytic acid chemistry:Influence on phytin phosphorus availability andphytase efficacy. J. Appl. Poult. Res. 11:471-480.

Bedford, M.R., (2002). The foundation of conductingfeed enzyme research and the challenges of explain-ing the results. J. Appl. Poultry Res. 11:464-470.

Coelho, M.B., (1994). Vitamin stability in premixesand feeds: A practical approach. BASF TechnicalSymposium. Indianapolis. May 25. pp 99-126.

Dale, N., (1997). Metabolizable energy of meat andbone meal. J. Appl. Poultry Res. 6:169-173.

Kersey, J.H. et al., (1997). Nutrient composition ofspent hen meals produced by rendering. J. Appl.Poultry Res. 6:319-324.

Lane, R.J. and T.L. Cross, (1985). Spread sheetapplications for animal nutrition and feeding.Reston Publ., Reston, Virginia.

Leeson, S., G. Diaz and J.D. Summers, (1995). In:Poultry Metabolic Disorders and Mycotoxins. Publ.University Books, Guelph, Ontario, Canada

Mateos, G.G., R. Lazaro and M.I. Garcia, (2002).The feasibility of using nutritional modification toreplace drugs in poultry feeds. J. Appl. Poult. Res.11:437-452.

McDowell, L.R., (1989). In: Vitamins in AnimalNutrition. Academic Press, N.Y.

Moritz, J.S. and L.D. Latshaw, (2001). Indicators ofnutritional value of hydrolysed feather meal.Poultry Sci. 80:79-86.

National Academy of Sciences, (1973). In: Effect ofProcessing on the Nutritional Value of Feeds. NASWashington, D.C.

National Academy of Sciences, (1974). In: Nutrientsand Toxic Substances in Water for Livestock andPoultry. NAS Washington, D.C.

National Academy of Sciences, (1980). In: MineralTolerances of Domestic Animals. NAS Washington, D.C.

National Academy of Sciences, (1987). In: VitaminTolerance of Animals. NAS Washington, D.C.

National Academy of Sciences, (1994). In: NutrientRequirements of Poultry. 9th Rev. Ed. NAS Washing-ton, D.C.

Novus, (1994). In: Raw Material Compendium. 2nd

Edition. Publ. Novus Int., Brussels.

Pesti, G.M. and B.R. Mitter, (1993). In: Animal FeedFormulation. Publ. Van Nostrand Reinhold, N.Y.

Shirley, R.B. and C.M. Parsons, (2000). Effect of pres-sure processing on amino acid digestibility of meatand bone meal for poultry. Poult. Sci. 79:1775-1781.

Sibbald, I.R., (1983). The TME system of feed eval-uation. Agriculture Canada 1983-20E. AnimalResearch Centre, Ottawa, Canada.

Sibbald, I.R., (1987). Examination of bioavailableamino acids in feedstuffs for poultry and pigs. Areview with emphasis on balance experiments. Can.J. Anim. Sci. 67:221-301.

Valdes, E.V. and S. Leeson, (1992). Near infraredreflectance analysis as a method to measure metabo-lizable energy in complete poultry feeds. Poult. Sci.71:1179-1187.

Wiseman, J., F. Salvador and J. Craigon, (1991).Prediction of the apparent metabolizable energy con-tent of fats fed to broiler chickens. Poult. Sci.70:1527-153.

CHAPTER 2INGREDIENT EVALUATION AND DIET FORMULATION

FEEDING PROGRAMSFOR GROWING EGG-STRAIN PULLETS

123

33.1 Diet specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

3.2 Strain specific nutrient requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

3.3 Feeding management of growing pullets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

a. General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137

b. Manipulating nutrient intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141

c. Suggested feeding program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143

d. Manipulation of body weight at sexual maturity . . . . . . . . . . . . . . . . . . . .146

e. Nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148

f. Prelay nutrition and management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149

i. considerations for calcium metabolism ii. prelay body weight and composition iii. early eggsize iv. pre-pause v. urolithiasis

g. Lighting programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

h. Feed restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

Page

CHAPTER

3.1 Diet specifications

T able 3.1 shows diet specificationsfor Leghorn pullets, while Table 3.2provides comparable data for brown

egg birds. These nutrient specifications areintended for guidelines in diet formulationwhen general growth and development (asoutlined by the primary breeders) is the goalof the rearing program. Pullets are grown undera range of environmental conditions andhousing systems and these can influencenutrient needs. In most situations, variablemanagement conditions influence energyneeds, and so it is important to relate all othernutrients to energy level. In hot climates for

example, the pullet will eat less and sonutrients, such as amino acids, will have tobe increased accordingly. Pullets grownon the floor, rather than in cages, will eat morefeed, and so amino acid levels can bereduced. The diet specifications are basedon using conventional ingredients wherenutrient digestibility is fairly predictable.When non-standard ingredients are used, itis essential to formulate to more stringent stan-dards of digestibility, such as for digestibleamino acids. Tables 3.3 – 3.6 show exam-ples of diet formulations using corn, wheator sorghum with and without meat meal.

SECTION 3.1Diet specifications

124 CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS


Starter Grower Developer Pre-layAge (weeks) (0 to 6) (6 to 10) (10 to 16) (16 to 18)Crude Protein (%) 20.0 18.5 16.0 16.0Metabolizable Energy (kcal/kg) 2900. 2900. 2850. 2850.Calcium (%) 1.00 0.95 0.92 2.25Available Phosphorus (%) 0.45 0.42 0.40 0.42Sodium (%) 0.17 0.17 0.17 0.17

Methionine (%) 0.45 0.42 0.39 0.37Methionine+cystine (%) 0.78 0.72 0.65 0.64Lysine (%) 1.10 0.90 0.80 0.77Threonine (%) 0.72 0.70 0.60 0.58Tryptophan (%) 0.20 0.18 0.16 0.15Arginine (%) 1.15 0.95 0.86 0.80Valine (%) 0.75 0.70 0.65 0.60Leucine (%) 1.30 1.10 0.92 0.88Isoleucine (%) 0.70 0.60 0.51 0.48Histidine (%) 0.35 0.32 0.29 0.26Phenylalanine (%) 0.65 0.60 0.53 0.49

Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 2500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (µg) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 12

Trace minerals (per kg of diet):Manganese (mg) 60Iron (mg) 30Copper (mg) 6Zinc (mg) 60Iodine (mg) 0.5Selenium (mg) 0.3

Table 3.1 Diet specifications for leghorn pullets

125CHAPTER 3FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS


Starter Grower Developer PrelayAge (wks) (0 to 5) (5 to 10) (10 to 15/16) (15/16 to 17)Crude Protein (%) 20.0 18.0 15.5 16.0Metabolizable Energy (kcal/kg) 2900 2850 2800 2850Calcium (%) 1.00 0.95 0.90 2.25Av. Phosphorus (%) 0.45 0.42 0.38 0.42Sodium (%) 0.17 0.17 0.17 0.17

Methionine (%) 0.45 0.41 0.35 0.34Methionine+cystine(%) 0.78 0.71 0.63 0.61Lysine (%) 1.10 0.90 0.75 0.73Threonine (%) 0.72 0.68 0.60 0.57Tryptophan (%) 0.20 0.18 0.15 0.15Arginine (%) 1.15 0.95 0.86 0.80Valine (%) 0.75 0.70 0.65 0.60Leucine (%) 1.30 1.10 0.92 0.88Isoleucine (%) 0.70 0.60 0.51 0.45Histidine (%) 0.35 0.32 0.27 0.24Phenylalanine (%) 0.65 0.60 0.50 0.45

Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 2500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (µg) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 12


Table 3.2 Diet specifications for brown egg pullets



1 2 3 4 5 6Corn 544 555Wheat 628 643Sorghum 578 568Wheat shorts 100 105 100 100 100 100Meat meal 50 30 50Soybean meal 310 258 227 191 27 250Fat 10 10 10 10 10 10DL-Methionine* 1.1 1.3 1.5 1.6 1.7 1.6Salt 3.1 2.8 2.7 2.3 3.4 2.9Limestone 18 13.2 19.3 16.1 18.5 13.3Dical Phosphate 12.8 3.7 10.5 5 11.4 3.2Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 21.0 21.0 20.6 20.6 20.0 21.0ME (kcal/kg) 2930 2930 2900 2930 2930 2930Calcium (%) 1.05 1.05 1.00 1.05 1.05 1.05Av. Phos. (%) 0.47 0.47 0.45 0.45 0.45 0.47Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.46 0.47 0.45 0.46 0.45 0.45Meth + Cys. (%) 0.78 0.78 0.78 0.78 0.81 0.81Lysine (%) 1.16 1.17 1.10 1.10 1.10 1.20Threonine (%) 0.89 0.87 0.76 0.74 0.78 0.80Tryptophan (%) 0.29 0.28 0.31 0.30 0.27 0.27

* or eqivalent MHA** with choline

Table 3.3 Examples of chick starter diets (kg)



1 2 3 4 5 6

Corn 550 555Wheat 620 590Sorghum 568 558Wheat shorts 150 165 150 160 150 150Meat meal 50 20 20Soybean meal 256 200 188 180 238 234Fat 10 10.5 10 23.5 10 10DL-Methionine* 1.2 1.3 1.3 1.3 1.7 1.6Salt 3.3 2.7 2.7 2.5 3.4 3.2Limestone 17.3 12.5 18 15.6 17.9 15.4Dical Phosphate 11.2 2 9 6.1 10 6.8Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000


* or eqivalent MHA

** with choline

Table 3.4 Examples of pullet grower diets



1 2 3 4 5 6Corn 534 535Wheat 648 649Sorghum 572 580Wheat shorts 239 240 197 200 205 203Meat meal 20 20 20Soybean meal 186 167 114 96 181 161Fat 10 10 10 10 10 10DL-Methionine* 1.1 1.2 1.4 1.4 1.3 1.3Salt 3.3 3.1 2.7 2.4 3.5 3.2Limestone 16 16.4 17.5 15.4 17 15Dical Phosphate 9.6 6.3 8.4 4.8 9.2 5.5Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000


* or eqivalent MHA

** with choline

Table 3.5 Examples of pullet developer diets


SECTION 3.2Strain specific nutrient requirements

T here are often questions about the needfor strain-specific diets in growing whiteor brown egg pullets. Such differences

would most likely be induced by differential growthrate and/or different mature body weight. As shownin Table 3.12 there are differences in growth rateof commercial pullets throughout the 18 weekgrow-out period. At 4 weeks of age, there is a14% difference in body weight between thelightest and heaviest strain, while at 18 weeks thisdifference is 10%. This differential growth rateis reflected in nutrient needs, where for exam-

ple, amino acid levels in the starter diet are10-15% higher for this smaller strain.

Starter diets are shown in Table 3.7 where thereis a fairly consistent energy base for all strains,although the diet for the smallest body weightstrain, namely Lohmann, is much higher inlysine and threonine. This same trend continuesfor the grower diets (Table 3.8). Interestingly, forthe developer diets (Table 3.9), the highestamino acid needs are for the heaviest pullet

Table 3.6 Examples of prelay diets

1 2 3 4 5 6Corn 527 481Wheat 615 629Sorghum 574 593Wheat shorts 227 306 180 180 180 180Meat meal 50 34 60Soybean meal 168 100 122 90 167 105Fat 10 10 16.7 11 11 10DL-Methionine* 1.4 1.6 1.4 1.4 1.6 1.5Salt 3 2.4 2.5 2 3.2 2.7Limestone 51.6 46.6 51.5 48.2 51.3 46.8Dical Phosphate 11 1.4 9.9 3.4 10.9Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 16.0 16.0 16.6 17.0 16.0 16.2ME (kcal/kg) 2850 2850 2850 2850 2850 2900Calcium (%) 2.25 2.25 2.25 2.25 2.25 2.30Av Phosphorus (%) 0.42 0.42 0.42 0.42 0.42 0.42Sodium (%) 0.17 0.17 0.17 0.17 0.17 0.18Methionine (%) 0.41 0.42 0.38 0.39 0.37 0.37Meth + Cystine (%) 0.64 0.64 0.64 0.64 0.66 0.65Lysine (%) 0.78 0.78 0.81 0.84 0.82 0.84Threonine (%) 0.66 0.63 0.58 0.58 0.60 0.58Tryptophan (%) 0.22 0.20 0.25 0.24 0.21 0.20* or eqivalent MHA** with choline

3.2 Strain specific nutrient requirements



Shaver Hyline 36 Hyline 98 Lohmann BovanAge fed (wks) (0 to 6*) (0 to 6) (0 to 6) (0 to 3) (0 to 6)

Protein (%) 19.5 20 20 21 20ME (kcal/kg) 2900 2960 2960 2900 2980Calcium (%) 1.0 1.0 1.0 1.05 1.0Av. Phosphorus (%) 0.47 0.50 0.5 0.48 0.5Sodium (%) 0.16 0.19 0.19 0.16 0.18Linoleic acid (%) 1.2 1.0 1.0 1.4 1.3

Methionine (%) 0.42 0.48 0.48 0.48 0.45Methionine+cystine (%) 0.73 0.8 0.8 0.83 0.8Lysine (%) 0.95 1.1 1.1 1.2 1.1Tryptophan (%) 0.20 0.20 0.20 0.23 0.21Threonine (%) 0.68 0.75 0.75 0.8 0.75

* Extrapolated from Management Guide Information

Table 3.7 Starter diets for white egg pullets

Table 3.8 Grower diets for white egg pullets

Shaver Hyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (6 to 12*) (6 to 8) (6 to 8) (3 to 8) (6 to 10)

Protein (%) 17.5 18 18 19 18ME (kcal/kg) 2800 3025 2960 2800 2970Calcium (%) 0.95 1.0 1.0 1.03 1.0Av Phosphorus (%) 0.47 0.47 0.48 0.46 0.48Sodium (%) 0.16 0.18 0.18 0.16 0.17Linoleic acid (%) 1.0 1.0 1.0 1.44 1.3





Shaver Hyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (12 to 17) (8 to 15) (8 to 16) (8 to 16) (10 to 15)

Protein (%) 16.5 16.0 16.0 14.9 16.0ME (kcal/kg) 2750 3075 2940 2800 2960Calcium (%) 1.15 1.0 1.0 0.92 1.0Av Phosphorus (%) 0.45 0.45 0.46 0.38 0.45Sodium (%) 0.16 0.17 0.17 0.16 0.17Linoleic acid (%) 1.0 1.0 1.0 1.03 1.3


Table 3.9 Developer diets for white egg pullets

Table 3.10 Prelay diets for white egg pullets

Hyline 36 Hyline 98 Lohmann BovanAge fed (weeks) (15 to 19*) (16 to 18) (16 to 18*) (15 to 17)

Protein (%) 15.5 15.5 18 15ME (kcal/kg) 3040 2940 2800 2930Calcium (%) 2.75 2.75 2.05 2.25Av Phosphorus (%) 0.4 0.45 0.46 0.45Sodium (%) 0.18 0.18 0.16 0.18Linoleic acid (%) 1.0 1.0 1.03 1.2

Methionine (%) 0.36 0.36 0.37 0.36Methionine+cystine (%) 0.60 0.60 0.70 0.63Lysine (%) 0.75 0.75 0.87 0.8Tryptophan (%) 0.15 0.15 0.21 0.16Threonine (%) 0.55 0.55 0.62 0.55




Week Shaver Hyline 36 Hyline 98 Lohmann Bovan1 70 65 65 70 702 135 110 110 115 1053 205 180 180 170 1754 280 250 260 240 2505 365 320 350 320 3206 450 400 450 400 3957 535 500 550 470 4758 620 590 650 540 5609 700 680 750 614 650

10 775 770 850 682 73511 845 870 930 749 82012 915 950 1000 816 90013 975 1030 1070 878 97514 1035 1100 1130 941 104515 1095 1160 1180 998 111016 1165 1210 1230 1056 117017 1235 1250 1270 1118 122518 1300 1280 1320 1181 1270

Shaver1 Hyline 36 Hyline 98 Lohmann BovanStarter 1099 1085 1141 350 931Grower 2072 621 665 1258 1239Developer 2702 2645 3241 3327 2023Pre-lay 860 980 1048 924Layer 448 476Total (to 18wks) 5873 5659 6027 5983 55931 No prelay diet.

(Shaver) while the smaller Lohmann apparent-ly need much lower amino acid intake. Thereis considerable variation in the specifications forstrain-specific prelay diets (Table 3.10).

To some extent, variable diet specifications forprelay diets relate to age of bird. Prelay diets aremost beneficial in terms of optimizing calcium accre-

tion, and so it is somewhat surprising that there isa considerable range of calcium (2.05 to 2.75%)and available phosphorus (0.4 to 0.5%) given forthe various strains. At this time, the Lohmann seemsto have higher amino acid needs. The various strainsof pullets consume anywhere from 5.6 to 6.0 kgof feed to 18 weeks, and this is somewhat influ-enced by diet energy level (Table 3.11).

Table 3.11 Feed intake for white egg pullets (grams)

Table 3.12 Body weight of white egg pullets (grams)



Body weight of pullets are shown in Table 3.12.

There are significant differences in vitamin-mineral premixes suggested for the variousstrains of commercial pullets (Table 3.13). In someinstances, the breeding companies do not givea specification for a certain nutrient, and pre-sumably this means that the natural ingredi-ents provide adequate levels for this strain of bird.

For critical nutrients such as vitamin E there aresix-fold differences in suggested specifications.

Comparable diet specifications for brown eggpullets are shown in Tables 3.14 to 3.20. Thereseems to be more consistency in strain specif-ic specifications for brown egg pullets, althoughit should be emphasized that the feeding schedule in terms of bird age is more variable.

units/kg Shaver Hyline 36,98 Lohmann Bovanfeed

Vitamin A IU 12000 8000 12000 8000Vitamin D3 IU 2500 3300 2000 2500Vitamin E IU 30 66 20* 10Vitamin K IU 3 5.5 3 3

Thiamin mg 2.5 0 1 1Riboflavin mg 7 4.4 4 5Pantothenic acid mg 12 5.5 8 7.5Niacin mg 40 28 30 30Pyridoxine mg 5 0 3 2Biotin µg 200 55 50 100Folic acid mg 1 0.22 1 0.5Vitamin B12 µg 30 8.8 15 12Choline mg 1000 275 200* 300

Iron mg 80 33 25 35Copper mg 10 4.4 5 7Manganese mg 66 66 100 70Zinc mg 70 66 60 70Iodine mg 0.4 0.9 0 1Selenium mg 0.3 0.3 0.2 0.25


Table 3.13 Vitamin-mineral premix for white egg pullets



Shaver ISA Hyline Lohmann BovanAge fed (wks) (4 to 10) (5 to 10) (6 to 9) (0 to 8) (6 to 10)

Protein (%) 19.0 20.0 16.0 18.5 18.0ME (kcal/kg) 2850 2850 2890 2775 2940Calcium (%) 1.0 1.0 1.0 1.0 1.0Av Phosphorus (%) 0.42 0.44 0.46 0.45 0.5Sodium (%) 0.16 0.17 0.18 0.16 0.17Linoleic acid (%) 1 1.4 1.3


Shaver ISA Hyline BovanAge fed (weeks) (0 to 4) (0 to 5) (0 to 6) (0 to 6)

Protein (%) 20.5 20.5 19.0 20.0ME (kcal/kg) 2950 2950 2870 2980Calcium (%) 1.07 1.07 1.0 1.0Av Phosphorus (%) 0.48 0.48 0.48 0.5Sodium (%) 0.16 0.16 0.18 0.18Linoleic acid (%) 1.0 1.3

Methionine (%) 0.52 0.52 0.48 0.45Methionine+cystine (%) 0.86 0.86 0.8 0.8Lysine (%) 1.16 1.16 1.1 1.1Tryptophan (%) 0.21 0.21 0.2 0.21Threonine (%) 0.78 0.78 0.75 0.75

Table 3.14 Starter diets for brown egg pullets

Table 3.15 Grower diets for brown egg pullets



Shaver ISA Hyline Lohmann BovanAge fed (wks) (16 to 17) (16 to 17*) (16 to 18*) (16 to 18*) (15 to 17)

Protein (%) 17.0 17.0 16.5 17.5 14.8ME (kcal/kg) 2750 2750 2850 2775 2820Calcium (%) 2.05 2.05 2.75 2.0 2.25Av Phosphorus (%) 0.45 0.45 0.44 0.45 0.45Sodium (%) 0.16 0.16 0.18 0.16 0.18Linoleic acid (%) 1.0 1.0 1.2



Shaver ISA Hyline Lohmann BovanAge fed (wks) (10 to 16) (10 to 16) (9 to 16) (8 to 16) (10 to 15)

Protein (%) 16.0 16.8 15.0 14.5 15.5ME (kcal/kg) 2750 2750 2830 2775 2840Calcium (%) 0.95 1.0 1.0 0.9 1.0Av Phosphorus (%) 0.36 0.38 0.44 0.37 0.45Sodium (%) 0.16 0.17 0.16 0.16 0.17Linoleic acid (%) 1.0 1.0 1.2


Table 3.16 Developer diets for brown egg pullets

Table 3.17 Prelay diets for brown egg pullets



All poultry breeding companies recommendprelay diets for their brown egg pullets, andwhile most nutrient specifications are similar, thereare again major differences in recommendationsfor calcium. These brown egg pullets weigh from1475g to 1580g at 18 weeks, and consume any-

where from 6.3 to 6.8 kg feed (Tables 3.18 and3.19). As for the white egg pullets, the strain spec-ifications for vitamin-mineral premixes for the brownpullets show tremendous variation, and again forsome strains, certain nutrients are not deemed essen-tial within these premixes (Table 3.20).

Table 3.18 Feed intake1 for brown egg pullets (grams)

Shaver ISA Hyline Lohmann BovanStarter 600 840 1099 1148Grower 2100 1694 966 1764 1351Developer 3000 2758 3346 3577 2170Pre-lay 588 525 1163 1029 1015Layer 600 480 539

Total (to 18 wks) 6888 6297 6574 6370 62231Dependent on diet energy level

Table 3.19 Body weight of brown egg pullets (grams)

Week Shaver ISA Hyline Lohmann Bovan1 60 50 70 75 70*2 100 100 115 130 110*3 200 190 190 195 180*4 300 280 280 275 2905 380 380 380 367 3706 480 480 480 475 4507 570 580 580 580 5308 650 675 680 680 6109 760 770 770 780 69010 850 850 870 875 77011 940 950 960 960 85012 1030 1040 1050 1040 93513 1120 1130 1130 1120 102014 1220 1220 1210 1200 111015 1320 1300 1290 1265 120016 1400 1390 1360 1330 130017 1490 1475 1430 1400 140018 1580 1560 1500 1475 1500* Extrapolated from Management Guide Information


SECTION 3.3Feeding management of growing pullets

units/kg Shaver ISA Hyline Lohmann Bovanfeed

Vitamin A IU 13000 13000 8800 12000 8000Vitamin D3 IU 3000 3000 3300 2000 2500Vitamin E IU 25 25 66 10-30 10Vitamin K IU 2 2 5.5 3 3

Thiamin mg 2 2 0 1 1Riboflavin mg 5 5 4.4 6 5Pantothenic acid mg 15 15 5.5 8 7.5Niacin mg 60 60 28 30 30Pyridoxine mg 5 5 0 3 2Biotin µg 200 200 55 50 100Folic acid mg 0.75 0.75 0.22 1.0 0.5Vitamin B12 µg 20 20 8.8 15.0 12Choline mg 600 600 275 300 300

Iron mg 60 60 33 25 35Copper mg 5 5 4.4 5 7Manganese mg 60 60 66 100 70Zinc mg 60 60 66 60 70Iodine mg 1 1 0.9 0.5 1Selenium mg 0.2 0.2 0.3 0.2 0.25

a) General considerations

D iet formulation and feeding managementare now critical aspects of growingpullets to the onset of sexual maturity.

Age at maturity is getting earlier although it is ques-tionable that this has changed suddenly in justa few years. In fact, what has been happeningis that age at maturity has slowly been decreas-ing by almost 1 d per year, and this is especial-ly true for many strains of brown egg pullets.Moving birds to laying cages at 19-20 weeks isno longer feasible and often results in manage-

ment problems. Similarly, first egg appearing at15-17 weeks means that we must criticallyreview our rearing programs. The key to successfulnutritional management today is through opti-mizing (maximizing) body weight of the pullet.Pullets that are on-target or slightly above targetweight at maturity will inevitably be the best pro-ducing birds for the shell egg market.

The traditional concern with early maturityhas been too small an egg size. Results from ourearly studies indicate the somewhat classical

Table 3.20 Vitamin-mineral premix for brown egg pullets

3.3 Feeding management of growing pullets



effect of early maturity in Leghorns withoutregard to body weight (Table 3.21).

There seems little doubt that body weight andperhaps body composition at this time are themajor factors influencing egg size both at matu-rity and throughout the remainder of the layingperiod. Summers and Leeson (1983) conclud-ed that body weight is the main factor control-ling early egg size (Table 3.22).

Table 3.22 Effect of body weight onegg size

18 wk wt (g) Early egg wt (g)1100 46.91200 48.41280 48.81380 49.7

Although there is some evidence to indicatethat nutrients such as protein, methionine and linole-ic acid can influence egg size throughout the lay-ing cycle, these nutrients have only moderate effectson early egg size. This is probably related to thepullet producing at maximum capacity at least upto the time of peak egg mass.

Although it is fairly well-established thatbody weight is an important criterion for adequateearly production, there is still insufficient evidenceregarding optimum body structure and com-position. Frame size is still discussed, although

standards are now rarely given in the breeder man-agement guides. It is known that most (90%) ofthe frame size is developed early, and so by 12-16 weeks of age, the so-called ‘size’ of the pul-let is fixed. While this parameter is useful as anoth-er monitoring tool, we have had little success inaffecting frame size without also affecting bodyweight. It therefore seems very difficult to pro-duce, by nutritional modification, pullets that arebelow target weight, yet above average frame sizeand vice versa. Since shank length and ‘framesize’ are so highly correlated with body weight,their measurement or monitoring is no longer con-sidered necessary. However, an exception to thisrule occurs in hot weather conditions where hightemperatures seem to stimulate leg bone growthindependent of body weight. It is not clearwhy birds held at higher temperatures havelonger shank bones, although there is a possibilityof altered hormone balance. For example, thy-roid hormones are known to influence bone devel-opment through mediation of somatomedinsand it has been shown that even though birds heldat 30 vs. 22ºC have reduced thyroid size, theircirculating T4 levels are increased by 100%.Another factor that may be of importance isblood flow to the feet and legs during heatstress. It is well known that birds divert more bloodto the legs during heat stress as a means ofcountercurrent cooling between the arterialand venous supply. In some types of birds,heat loss from the legs can be the largest con-tributor to overall heat loss, and it is interestingthat this has been recorded to occur at 30ºC since

Table 3.21 Pullet maturity and egg characteristics

Age at Lighting Egg production (%) Egg size (% large)(wk) 18-20 wk Mean 30 wk 63 wk

(to 35 wk)15 32 92 17 4418 12 92 21 6521 0 91 37 69



at higher tempertures evaporative losses becomemore important. Since the hind limbs are appar-ently more heavily supplied with blood at 30 vs.18ºC, and even though nutrient intake is reducedat higher temperatures, it is conceivable that theactive growth plate receives a greater supply ofnutrients related simply to increased blood flow.It would be interesting to see if environmentaltemperature influences development of other partsof the skeleton and especially the keel.

While pullets are maturing earlier, there hasbeen little change in body weight at time of firstegg. As will be discussed in section 3.3g), light-ing program is the most important stimulus to matu-rity. Pullets as young as 8 weeks of age will beinfluenced by light stimulation, and regardlessof body weight or composition, will produce eggsearlier than normal. Without any light stimulation,then a minimum threshold body weight and/or

body composition is most likely the stimulus tomaturity. There may, in fact, be a need forattainment of a minimum lean body mass priorto sexual maturation. With most mammals,attainment of minimum fat reserves are essen-tial for puberty, and so it seems likely that bodycomposition is as important as total body massin influencing the onset of egg production. Instudies involving a relatively small number of birds,we have seen no correlation between age at firstegg and either percentage or absolute levels ofbody fat. While no clear picture has yet emergedwith respect to body composition and maturi-ty, it seems likely that birds having some ener-gy reserve, as they approach peak egg produc-tion, are less prone to subsequent productionproblems. A production curve as shown inFigure 3.1 is often observed in flocks, related toinadequate body size or energy reserves at thetime of maturity.

Fig. 3.1 Reduction in egg production after peak, associated with smallappetite and body weight.



When this type of production loss is not dueto an identifiable disease and/or management prob-lem, then it most likely relates to birds beingdeficient in energy. It is perhaps not too surpris-ing that birds are in such a precarious situation withrespect to energy balance. Dairy cows and sowsinvariably lose body weight during peak lactationin order to meet energy requirements. Perhaps themost classical case of energy deficiency at this timeis seen with the turkey breeder. Due to a declinein feed intake from time of first lighting throughto peak egg production, the turkey breeder nec-essarily loses considerable body mass in anattempt to maintain energy balance. It is likelythat the same situation applies to Leghorn pulletsand in some cases, to brown egg birds. Obviously,the effect is most pronounced for underweight flockswith small appetites where energy intake is min-imal. In fact, with many flocks exhibiting productioncharacteristics as shown in Figure 3.1, it is bodyweight at housing that deserves immediate inves-tigation rather than factors occurring at the actu-al time of the production loss.

The key to optimizing layer performancewould seem to be attainment of body weight goalsat time of maturity. It is likely that body condi-tion will be a factor of the flock in question, beinginfluenced by stocking density, environmentaltemperature, feather cover, etc. Unfortunatelyattainment of desired weight for age is notalways easy to achieve especially where earli-

er maturity is desired or when adverse environmental conditions prevail. Leeson andSummers (1981) suggested that energy intake ofthe pullet is the limiting factor to growth rate, sinceregardless of diet specifications, pullets seem toconsume similar quantities of energy (Table3.23). In this study, all pullets had a similar bodyweight at 15 weeks even though diet specificationswere dramatically variable. As seen in Table 3.23,birds consumed similar quantitities of energy eventhough protein intake varied by 85%. These datasuggest that if protein and amino acid intake are adequate, additional diet protein does little to stimulate growth rate.

In other studies, we have reared Leghorn pul-lets on diets varying in protein or energy, and again,energy intake seems to be the major factorinfluencing body weight (Tables 3.24 and 3.25).These studies indicate that growth rate is morehighly correlated with energy intake than withprotein intake. This does not mean to say thatprotein (amino acid) intake is not important tothe growing pullet. Protein intake is very impor-tant, but there does not seem to be any measurablereturn from feeding more than 800 g of proteinto the pullet through 18 weeks of age. On theother hand, it seems as though the more ener-gy consumed by the pullet, the larger the bodyweight at maturity. Obviously, there must be afine line between maximizing energy intakeand creating an obese pullet.

Table 3.23 Nutrient intake of pullets (8-15 weeks)

Diet energy-protein 15 wk Body wt. Energy intake Protein (g) (Mcal) intake (g)

2950 kcal – 15% CP 1272 9.77 464c

3100 kcal – 24% CP 1267 9.17 718a

3200 kcal – 20% CP 1291 9.51 597b



b) Manipulating nutrient intakeIf one calculates expected energy output in terms

of egg mass and increase in body weight, and relatesthis to feed intake, then it becomes readily appar-ent that the Leghorn must consume at least 90g/bird/day and the brown egg bird close to 100g/bird/day at peak production. Because feedingis ad-libitum, management programs must begeared at stimulating early appetite. The practi-cal long-term solution is to rear birds with opti-mum body weight and body reserves at maturity.This situation has been aggravated in recentyears, with the industry trend of attempting to rearpullets on minimal quantitites of feed. Unfortunately,this move has coincided with genetically smaller body weights and hence smaller appetites,together with earlier sexual maturity.

In order to maximize nutrient intake, one mustconsider relatively high nutrient dense diets,although these alone do not always ensure opti-mum growth. Relatively high protein (16-18%CP) with adequate methionine (2% CP) andlysine (5% CP) levels together with high energylevels (2800-3000 kcal/kg) are usually given toLeghorn pullets, especially in hot weather situations. However, there is some evidence tosuggest that high energy diets are not always help-ful under such warm conditions. (Table 3.26)

Leghorn pullets were heavier at 126 d whenfed the high energy diet in the cool environment,but diet had no effect at 30ºC. As expected, pul-lets ate less of the high energy diet, and because

Table 3.24 Effect of diet protein level (0-20 wks) on pullet growth and nutrient intake

Diet Protein Body wt. Energy intake Protein intake(%) (g) (Mcal) (kg)15 1445 24.3 1.28d

16 1459 22.9 1.28d

17 1423 22.9 1.37cd

18 1427 22.0 1.39c

19 1444 22.9 1.53b

20 1480 23.0 1.62a

All diets 2850 kcal ME/kg

Table 3.25 Effect of diet energy level (0-20 wks) on pullet growth and nutrient intake

Diet energy Body wt. Energy intake Protein intake(kcal ME/kg) (g) (Mcal) (kg)

2650 1320c 20.6c 1.40a

2750 1378bc 21.0bc 1.37a

2850 1422ab 21.8ab 1.37a

2950 1489a 22.1ab 1.35ab

3050 1468a 21.4abc 1.26c

3150 1468a 22.5a 1.29bc

All diets:18% CP, 0.36% methionine aand 0.9% lysine



all other nutrient levels were fixed, this result-ed in reduced intake of all nutrients exceptenergy. Pullets therefore ate less protein and aminoacids when fed 3000 vs. 2500 kcal ME/kg, andthis can be critical where intake per se is less at30ºC. The pullets fed 3000 kcal/kg are border-line in intake of balanced protein at 870 g vs. ourrequirement for 800 g to this age. High energydiets may therefore not always be beneficialunder heat stress conditions, and intake of othernutrients such as protein and amino acids mustbe given priority during formulation. The Leghornpullet eats for energy requirement, albeit with someimprecision, and so energy:protein balance is crit-ical. All too often there is inadequate amino acidintake when high energy corn-based diets are used,the result of which is pullets that are both smalland fat at maturity.

One of the most important concepts todayin pullet feeding, is to schedule diets accordingto body weight and condition of the flock, ratherthan according to age. For example, tradition-al systems involve feeding starter diets for about6 weeks followed by grower and then developerdiets. This approach does not take into accountindividual flock variation, and this will be inap-propriate for underweight flocks. It is becom-ing more difficult to attain early weight for age.This means that flocks are often underweight rel-

ative to management guide values (Table 3.12)at 4-6 weeks of age. This situation can arise fora variety of reasons such as sub-optimal nutri-tion, heat stress, disease, etc. For such flocks itis inappropriate to change from starter to grow-er diet, merely because the flock has reached somearbitrary age. It is more appropriate to feed thehigher nutrient dense starter until the targetweight is reached. For example, Figure 3.2shows an underweight flock at 6 weeks. For thisflock to receive a grower at 6 weeks of age willcause problems because the flock will likely staysmall until maturity, be late maturing, and thenproduce a sub-optimal number of eggs that willalso be small. This type of flock can most effec-tively be ‘corrected’ in growth by prolongedfeeding of the starter diet. In this situation, thebirds reach the low end of the guide weight atalmost 10 weeks of age (Figure 3.2). At this time,a grower diet could be introduced. Since the flockis showing a growth spurt, then feeding toalmost 12 weeks could be economical. The flockis now slightly over-weight and so ideally suit-ed to realizing maximum genetic potential dur-ing peak production. Some producers, andespecially contract pullet growers, are sometimesreluctant to accept this type of program, since theycorrectly argue that feeding a high protein starterdiet for 10-12 weeks will be more expensive.Depending upon local economic conditions,

Table 3.26 Influence of diet energy on growth and nutrient intake ofleghorn pullets maintained at 30 or 18ºC to 18 weeks of age

Body wt 126 d Total feed intake ME intake Protein intake (g) (kg) (Mcal) (g)

Temperature 18ºC2500 kcal ME/kg 1398 7.99 20.04 13303000 kcal ME/kg 1434 6.98 21.07 1160

Temperature 30ºC2500 kcal ME/kg 1266 6.05 15.17 10103000 kcal ME/kg 1218 5.19 15.69 870



feeding an 18% protein starter diet for 12 vs. 6weeks of age, will cost the equivalent of 2 eggs.A bird in ideal condition at maturity will producefar in excess of these 2 eggs relative to a bird thatis underweight at maturity.

c) Suggested feeding programDiet specification, together with approximate

ages for feeding, are given in Tables 3.1 and 3.2for Leghorns and brown egg birds respectively.In practice, flocks may not grow according toexpected standards, and for Leghorns at least, theyare more likely to be underweight than on tar-get. Brown egg strains on the other hand,because of their inherently higher feed intake,sometimes achieve weights that are greater thanstandard goals. For these reasons, there needsto be flexibility in time of change from, forexample, starter to grower etc. Table 3.27shows various scenarios for the feeding sched-uling of a Leghorn strain to 17 weeks of age.

According to the standard schedule, the starterand grower are each fed for 6 weeks, followedby developer. In Scenario #1, the body weightis below standard at 3 weeks, and pullets are only400 g at 6 weeks relative to the standard of450 g at this time. If this flock is changed to thelower nutrient dense grower diet at 6 weeks, thebirds will not likely achieve target weight atmaturity. For this reason in Scenario #1, the starterdiet is continued until weight-for-age is achievedat 9 weeks of age. In Scenario #2 there is evengreater cause for concern since the flock suddenlyslows down in growth at 9 weeks of age. Thistype of growth depression is seen in situationsof disease challenge, with severe beak trim-ming or when there is sudden increase in envi-ronmental temperature. For this flock, it isessential to re-introduce the higher nutrientdense starter diet in order to stimulate growth.In this extreme situation, the grower diet isintroduced at 12 weeks since the pullets seemto be making acceptable weekly gains in growth.

Fig. 3.2 Pullet growth in relation to feeding program.



However, grower is fed for two weeks longer thannormal, during weeks 13 and 14, to ensure idealweight at 17 weeks.

Table 3.28 shows examples for feed sched-uling of brown egg birds where increased growthis the problem. In Scenarios 1 and 2, the pul-lets are overweight at various ages according tothe standard. In Scenario #1, pullets are over-weight at 5 weeks and so the lower nutrient densegrower diet is introduced a week early. Likewisedeveloper diet type is used from 10 rather than11 weeks. In Scenario #2, pullet growth ismuch higher than standard. This growth is tem-pered somewhat by earlier introduction of grow-er and developer diets, yet pullets are still over-weight at 16 weeks. Because such rapid growthwill result in earlier maturity it may be advisable

to light stimulate this flock a week earlier thanscheduled, with appropriate early introductionof the layer diet.

The examples shown in Table 3.27 and Table3.28 emphasize the need for flexibility in feedscheduling. For most flocks, the end goal willlikely be the breeder’s recommended targetweight at 16-18 weeks or whenever light stim-ulation occurs. In certain situations it may be nec-essary to manipulate mature body weight accord-ing to economics of manipulating egg size andegg grade (see Section d). As a generalization,the smaller the body weight of the pullet, the small-er the size of the egg throughout the entire lay-ing cycle. Conversely, a larger pullet will alwaysproduce a bigger egg and this is little influ-enced by layer nutrition.

Table 3.27 Feeding scenarios for White pullets according to growth (g)

Standard Scenario #1 Scenario #2Week(s) Body Feed type Body Feed type Body Feed type

wt. wt. wt.

1 70 Starter 70 Starter 70 Starter2 135 Starter 130 Starter 135 Starter3 205 Starter 190 Starter 205 Starter4 280 Starter 255 Starter 280 Starter5 365 Starter 320 Starter 365 Starter6 450 Starter 400 Starter 450 Starter7 535 Grower 500 Starter* 535 Grower8 620 Grower 600 Starter* 620 Grower9 700 Grower 700 Starter* 650 Starter*10 775 Grower 775 Grower 720 Starter*11 845 Grower 845 Grower 800 Starter*12 915 Grower 915 Grower 870 Grower13 975 Developer 975 Developer 950 Grower*14 1035 Developer 1035 Developer 1000 Grower*15 1095 Developer 1095 Developer 1095 Developer16 1165 Developer 1165 Developer 1165 Developer17 1235 Developer 1235 Developer 1235 Developer

* different from standard



An argument that is often heard about the roleof body weight at maturity, is that it is not in fact,too important because the pullet will showcatch-up growth prior to first egg. In otherwords, if the pullet is small, it will take a few dayslonger to mature, and start production at the ‘sameweight’. However, this does not seem to hap-pen, as small birds at 18 weeks are smaller at timeof laying their first egg (Table 3.29).

For the smaller pullet there is a degree of com-pensatory growth up to the time of the first egg,although this is insufficient to allow for total ‘catch-up’ growth. It is also interesting to note the rela-tionship between body weight and age at first eggand also between body weight and size of firstegg. In other studies, we have monitored thegrowth of pullets through a production cycle inrelation to 18 week body weight which is the ageof light stimulation. Again, there is a remarkably

Body weight (g) Age at first Weight of 18 wks 1st egg Change egg (d) first egg (g)

1100 1360 +260 153 40.71200 1440 +240 150 42.01280 1500 +220 149 43.71380 1590 +210 148 42.5

Standard Scenario #1 Scenario #2Week(s) Body Feed type Body Feed type Body Feed type

wt. wt. wt.1 50 Starter 50 Starter 50 Starter2 100 Starter 110 Starter 110 Starter3 190 Starter 200 Starter 210 Starter4 280 Starter 290 Starter 320 Grower*5 380 Starter 420 Grower* 460 Grower*6 480 Grower 510 Grower 550 Grower7 580 Grower 600 Grower 650 Grower8 675 Grower 700 Grower 780 Developer*9 770 Grower 790 Grower 900 Developer*10 850 Grower 870 Developer* 980 Developer*11 950 Developer 960 Developer 1050 Developer12 1040 Developer 1040 Developer 1200 Developer13 1130 Developer 1130 Developer 1260 Developer14 1220 Developer 1220 Developer 1320 Developer15 1300 Developer 1300 Developer 1350 Developer16 1390 Developer 1390 Developer 1430 Layer*

* different from standard

Table 3.29 Effect of immature body weight on development to sexual maturity

Table 3.28 Feeding scenarios for ISA Brown pullets according to growth (g)



similar pattern of growth for all weight groupsindicating that immature weight seems to ‘set’the weight of the bird throughout lay (Figure 3.3).

More importantly from a production viewpoint,is the performance of birds shown in Figure 3.3.When the lightest weight birds were fed diets ofvery high nutrient density (20% CP, 3000 kcalME/kg) they failed to match egg production andegg size of the largest weight pullets that were fedvery low nutrient dense diets (14% CP, 2600 kcalME/kg). These results emphasize the impor-tance of mature body weight in attaining maxi-mum egg mass output.

The actual body weight achieved will obvi-ously vary with strain and bird type (Tables3.12, 3.19). For Leghorns, weight should be around400-450 g at 6 weeks, 850-1000 g at 12 weeksand 1200-1300 g at 18 weeks. The brown eggstrains will be 450-480 g at 6 weeks, 1000 g at12 weeks and 1500-1600 g at 18 weeks. The

brown egg strains will likely mature 7-10 d ear-lier than the Leghorn strains.

d) Manipulation of body weightat sexual maturity

In the previous section, the main emphasiswas on attaining the breeder’s recommendedweight at time of sexual maturity. Under certainconditions, some tempering of mature bodysize may be economically advantageous. Becausebody size has a dramatic effect on egg size, largebirds at maturity can be expected to produce largeeggs throughout their laying cycle. Dependingupon the pricing of various egg grades, a very largeegg may be uneconomical to produce, and in mostinstances tempering of egg size of birds from 40-65 weeks of age is often difficult to do withoutassociated loss in egg numbers. Because bodyweight controls feed intake and egg size, an eas-ier way of manipulating life-cycle egg size isthrough the manipulation of mature body size.

Fig. 3.3 Effect of immature body weight on subsequent body weight during lay.



If the maximum possible egg size is desired, thenefforts must be made to realize the largest pos-sible mature weight. However, where a small-er overall egg size is economical then a small-er pullet is desirable. Such lightweight pulletscan be obtained by growing pullets more slow-ly or most easily by light-stimulating pullets atan earlier age. Figure 3.4 gives a schematic rep-resentation of the above concept. In this scenario,birds are on the heavy side of the breeder’sweight guide, and so if moved at 18 weeks, wouldbe heavier than the ideal weight and be expect-ed to produce very large eggs. If this situationis not economical in the laying house, thenthese birds should be moved at the ‘ideal weight’

which in this scenario means moving at 17 ratherthan 18 weeks of age. Moving the bird, andlight stimulating at 17 vs. 18 weeks will have noadverse effect on performance, as light stimulationis still at the desired body weight standard (that hasbeen achieved one week earlier than anticipated).

Early maturity is not a problem for flocks thathave ideal body weight and condition. Early matu-rity and light stimulation will only result in sub-sequent small egg size and increased incidenceof prolapse if the bird is small at this age. Thisconcept is preferred over attempts at trying to slowthe bird down during growth in an attempt to delaymaturity (Figure 3.5).

Fig. 3.4 Light stimulation at target weight rather than age.



Such adjustments are invariably brought aboutby use of very low nutrient dense diets and/or useof restricted feeding. Both of these practices havethe desired ‘effect’ of slowing down mean growth,but at the great cost of loss of pullet uniformity.

e) Nutrient managementAlthough growing pullets do not produce large

quantities of manure in relation to adult layers,nutrient loading of manure will likely be a man-agement consideration. Under average condi-tions of feeding and management, pullets will retainabout 25% of nitrogen and 20% of phosphorusconsumed. Most of the remaining phosphoruswill be retained in the manure while around 30%of the excreted nitrogen will be lost as ammo-nia, either in the pullet house or during storageprior to land disposal. Based on these values fornutrient balance, Table 3.30 provides informa-

tion on nutrient flow for pullets through to 18weeks. On a per pullet basis therefore, each birdproduces about 0.1 kg N and 0.03 kg P in themanure to 18 weeks of age.

Manure nutrient loading is in direct pro-portion to corresponding diet nutrient levels. Usinglower protein or lower phosphorus diets will invari-ably result in less of these elements appearingin the manure. Attempts at reducing crudeprotein levels in pullet diets, as a means ofreducing feed cost and/or manure N loading, oftenresults in poor growth rate (Table 3.31). Regardlessof constant levels of the most important aminoacids in these diets, pullets responded adverse-ly to any reduction in crude protein. This datasuggests that pullets have minimal needs fornon-essential amino acids and/or that require-ments for amino acids such as threonine and arginine are of more importance than normally

Fig. 3.5 Potentially harmful adjustment to pullet weight.



estimated. Regardless of mode of action, itseems that there is only limited potential toreduce the crude protein levels in pullet diets asa means of reducing manure nitrogen loading.There does seem to be potential for reducing dietphosphorus levels in pullet diets, to limit manureloading. Keshavarz (2000) shows acceptable pul-let growth with diet levels as low as 0.2% in thestarter diet (Table 3.32). There was an indicationof slightly lower egg production to 30 weeks ofage in pullets fed the lowest level of diet P,although growth characteristics were little affect-ed. The P loading of manure of 28 kg/1000 agrees

well with the prediction shown in Table 3.30. Itseems as though there is potential for at least 30%reduction in manure P output of pullets throughdiet formulation.

f) Prelay nutrition and managementi) Considerations for calcium metabolism –Prelay diets and prelay management are designedto allow the bird the opportunity to establish ade-quate medullary bone reserves that are neces-

Table 3.30 Nitrogen and phosphorus balance for 50,000 pullets to 18 weeksof age

Intake (kg)1 Body retention Excretion Gas Loss Manure (kg) (kg) (kg) (kg)

Nitrogen 7680 1920 5760 1760 5000Phosphorus 1950 390 1560 - 15601Assumes 6 kg feed per pullet, averaging 16% CP (2.56% N) and 0.65% total phosphorus

Table 3.31 Body weight of Leghorn and brown egg pullets fed low proteindiets with constant levels of TSAA, lysine and tryptophan

Diet CP (%) Brown bird weight (g) Leghorn weight (g)Starter1 Grower2 56d 98d 126d 56d 98d 126d

20 16 746a 1327a 1524a 592a 1086a 1291a

18 14 720b 1272b 1471b 576b 1046b 1235b

16 12 706b 1144c 1301c 546c 921c 1085c

14 10 540c 989d 1175d 434d 781d 932d

1 0.66% TSAA: 0.90% lysine; 0.24% tryptophan2 0.55% TSAA; 0.72% lysine; 0.19% tryptophan

Table 3.32 Effect of dietary phosphorus on pullet development and phophorus excretion

Diet available P (%) Body weight (g) Feed intake Tibia Manure PStarter Grower Developer 6 wk 18 wk (kg) ash (kg/1000)

(%)0.40 0.35 0.30 345 1210 5.94 50.7 280.30 0.25 0.20 340 1260 5.98 49.3 240.20 0.15 0.10 330 1200 5.85 48.8 18

Adapted form Keshavarz (2000)



sary for calcifying the first egg produced. In prac-tice, there is considerable variation in formula-tion and time of using prelay diets, and to someextent this confusion relates to defining sexualmaturity per se. Historically, prelay diets werefed from about 2 weeks prior to expected matu-rity, up to the time of 5% egg production. Withearly, rapid and hopefully synchronized matu-ration with today’s strains, we rarely have the oppor-tunity to feed for 2 weeks prior to maturity.Likewise, it is unwise to feed inadequate levelsof calcium when flocks are at 5% production.One of the major management decisions todayis the actual need for prelay diets, or whether pul-lets can sustain long-term shell quality when movedfrom grower diet directly to a high calciumlayer diet.

The bird’s skeleton contains around 1 g ofmedullary calcium that is available for shell cal-cification on any one day. This calcium is con-tinually replenished between successive ovula-tions, and in times of inadequate calcium repletion,the medullary reserve may be maintained at theexpense of structural cortical bone. Around 60-70% of the medullary calcium reserves are locat-ed in the long bones, and so long-term problemsof calcium deficiency can lead to lameness andcage layer fatigue.

Prelay diets normally contain 2-2.5% calcium,and when fed over a 10-14 d period provide thebird with the opportunity to deposit medullarybone. This bone deposition coincides with fol-licular maturation and is under the control of bothestrogens and androgens. The latter hormoneseems essential for medullary bone growth,and its presence is manifested in growth of the

comb and wattles. Consequently, there willbe little medullary deposition, regardless of dietcalcium level, if the birds are not showing comband wattle development and this stage of matu-rity should be the cue for increasing the bird’scalcium intake.

Because egg production is an ‘all or none’event, the production of the first egg obviouslyplaces a major strain on the bird’s metabolismwhen it has to contend with a sudden 2 g lossof calcium from the body. Some of this calciumwill come from the medullary bone, and sothe need to establish this bone reserve prior tofirst egg. The heaviest pullets in a flock will like-ly be the first to mature, and so it is these birdsthat are most disadvantaged if calcium metab-olism is inadequate. If these early maturingpullets receive a 1% calcium grower diet atthe time they are producing their first few eggs,they will only have a sufficient calcium reserveto produce 2-3 eggs. At this time, they will like-ly stop laying, or less frequently continue tolay and exhibit cage layer fatigue. If these ear-lier maturing birds stop laying, they do so for 4-5 days, and then try to start the process again.The bird goes through very short clutches, whenat this time she is capable of a very prolonged30 – 40 egg first clutch. Advocates of pro-longed feeding of grower diets suggest that it makesthe bird more efficient in the utilization orabsorption of calcium, such that when she is even-tually changed to a layer diet, improved efficiencycontinues for some time, with the bird having morecalcium available for shell synthesis. Figure3.6 indicates that percentage calcium absorptionfrom the diet does decline with an increased levelof calcium in the diet.



However, with 40% retention of 5 g of cal-cium consumed daily, there will be greaterabsolute calcium retention (2 g/d) than the birdconsuming 2.5 g Ca/d and exhibiting 60% effi-ciency of retention (1.5 g retained/d). There isalso no evidence to support the suggestion of carryover of this higher efficiency during early egg pro-duction. If 1% calcium grower diets are usedaround the time of maturity, then these diets shouldnot be used after the appearance of first egg, andto 0.5% production at the very latest. It must beremembered that under commercial conditions,it is very difficult to precisely schedule dietchanges, and so decisions for diet change needto precede actual time of diet change, suchthat production does not reach 5 – 10% beforebirds physically receive the calcium enriched diets.

Prelay diets provide more calcium than domost grower diets, but still not enough Ca for sus-tained production. Prelay diets should allow the

build up of medullary reserves without adverse-ly influencing general mineral metabolism.However, as previously discussed for grower diets,2 – 2.5% calcium prelay diets are inadequate forsustained egg production, and should not be fedbeyond 1% egg production. The main disad-vantage of prelay diets is that they are used fora short period of time, and many producers donot want the bother of handling an extra diet atthe layer farm. There is also a reluctance by someproducers with multi-age flocks, at one site, touse prelay diets where delivery of diets with 2%calcium to the wrong flock on site can have dis-astrous effects on production.

Simply in terms of calcium metabolism, themost effective management program is earlyintroduction of the layer diet. Such high calci-um diets allow sustained production of even theearliest maturing birds. As previously men-tioned, higher calcium diets fed to immature birds,

Fig. 3.6 Relationship between calcium intake and calcium retention.



lead to reduced percentage retention, althoughabsolute retention is increased (Table 3.33).

Feeding layer diets containing 3.5% calcium,prior to first egg, therefore results in a slightincrease in calcium retention of about 0.16 g/drelative to birds fed 0.9% calcium grower dietsat this time. Over a 10 d period, however, thisincreased accumulation is equivalent to theoutput in 1 egg. Since there is only about 1 g ofmobile medullary calcium reserve in the maturebird, then the calcium retention values shownin Table 3.33 suggest accumulation of somecortical bone at this time.

Early introduction of layer diets is thereforean option for optimizing the calcium retentionof the bird. However, there has been somecriticism leveled at this practice. There is the argu-ment that feeding excess calcium prior to layimposes undue stress on the bird’s kidneys,since this calcium is in excess of her immediaterequirement and must be excreted. In the studydetailed in Table 3.33, there is increased excretacalcium. However, kidney histology from thesebirds throughout early lay revealed no changedue to prelay calcium feeding. Recent evi-dence suggests that pullets must be fed a layerdiet from as early as 6 – 8 weeks of age before

any adverse effect on kidney structure is seen (seefollowing section on urolithiasis). It seems like-ly that the high levels of excreta calcium shownin Table 3.33 reflect fecal calcium, suggesting thatexcess calcium may not even be absorbed intothe body, merely passing through the bird withthe undigested feed. This is perhaps too simplistica view, since there is other evidence to suggestthat excess calcium may be absorbed by the imma-ture bird at this time. Such evidence is seen inthe increased water intake of birds fed layerdiets prior to maturity (Figure 3.7).

Early introduction of a high calcium layer dietseems to result in increased water intake, and aresultant increase in excreta moisture.Unfortunately this increased water intake and wet-ter manure seems to persist throughout the lay-ing cycle of the bird, (Table 3.34). These data sug-gest that birds fed high calcium layer dietsduring the prelay period will produce manure thatcontains 4 – 5% more moisture than birds fed 1%calcium grower or 2% calcium prelay diets.There are reports of this problem being most pro-nounced under heat stress conditions. A 4-5%increase in manure moisture may not be prob-lematic under some conditions, although for thosefarms with a chronic history of wet layer manure,this effect may be enough to tip the balance and

Diet Ca (%) Daily Ca Excreta Caretention (g) (% dry matter)

0.9 0.35 1.41.5 0.41 3.02.0 0.32 5.72.5 0.43 5.93.0 0.41 7.53.5 0.51 7.7

Table 3.33 Effect of % diet calcium fed to birds immediately prior to lay oncalcium retention



produce a problem. The current trend of feedingeven higher calcium levels to laying hens may accen-tuate this problem, and so dictate the need for prelaydiets with more moderate levels of calcium.

In summary, the calcium metabolism of theearliest maturing birds in a flock should be thecriterion for selection of calcium levels duringthe prelay period. Prolonged feeding of low-cal-cium diets is not recommended. Early introductionof layer diets is ideal, although where wet

manure may be a problem, a 2% calcium prelaydiet is recommended. There seems to be no prob-lem with the use of 2% calcium prelay diets, aslong as birds are consuming a high calciumlayer diet no later than at 1% egg production.

ii) Prelay body weight and composition –Prelay diets are often formulated and used on theassumption that they will improve body weightand/or body composition, and so correct problemsarising with the prior growing program. Body weight

Fig. 3.7 Effect of introducing a 4% calcium layer diet at 112 days ( _____ ) andat 138 ( _ _ _ _ ) on daily water intake.

Prelay diet Ca (%) Bird age (d)(16 – 19 weeks)1 147 175 196 245

1.0 71.4 78.7 75.3 65.52.0 71.6 77.2 73.9 63.93.0 72.1 77.7 74.1 63.94.0 77.0 80.0 76.0 69.4

1 All birds fed 4.0% Ca after 20 weeks of age

Table 3.34 Effect of prelay calcium level on excreta moisture (%)



and body condition should not really be consideredin isolation, although at this time, we do not havea good method of readily assessing body con-dition in the live pullet. For this reason our mainemphasis at this time is directed towards body weight.

Pullet body weight is the universal criterionused to assess growing program. Each strain ofbird has a characteristic mature body weight thatmust be reached or surpassed for adequate eggproduction and egg mass output. In general, prelaydiets should not be used in an attempt to manip-ulate mature body size. The reason for this is thatfor most flocks, it is too late at this stage ofrearing to meaningfully influence body weight.

However, if underweight birds are necessarilymoved to a layer house, then there is perhapsa need to manipulate body weight prior tomaturity. With black-out housing, this cansome-times be achieved by delaying photo-stimulation – this option is becoming less use-ful in that both Leghorns and brown egg strainsare maturing early without any light stimulation.If prelay diets are used in an attempt to correctrearing mismanagement, then it seems as thoughthe bird is most responsive to energy. This factfits in with the effect of estrogen on fat metab-olism, and the significance of fat used for liverand ovary development at this time. While usinghigh nutrient density prelay diets may have a minoreffect in manipulating body weight, it must beremembered that this late growth spurt (if it occurs)will not be accompanied by any meaningfulchange in skeletal growth. This means that inextreme cases, where birds are very light weightand of small stature at say, 16 weeks of age, thenthe end result of using high nutrient denseprelay diets may well be pullets of correct bodyweight, but of small stature. Pullets with ashort shank length seem more prone to pro-lapse/pick-out, and so this is another example

of the limitations in the use of high nutrient denseprelay diets.

While body composition at maturity maywell be as important as body weight at this age,it is obviously a parameter that is difficult toquantitate. There is no doubt that energy is like-ly the limiting nutrient for egg production of allstrains of bird, and at peak egg numbers, feed maynot be the sole source of energy. Labile fatreserves seem essential to augment feed sourcesthat are inherently limited by low feed intake. Theselabile fat reserves become critical during situationsof heat stress or general hot weather conditions.Once the bird starts to produce eggs, then its abil-ity to build fat reserves is greatly limited. Obviously,if labile fat reserves are to be of significance,then they must be deposited prior to maturity. Aswith most classes of bird, the fat content of the pul-let can best be manipulated through changing theenergy:protein balance of the diet. If labile fatreserves are thought necessary, then high energy,high fat prelay diets should be considered. As pre-viously stated, this scenario could well be ben-eficial if peak production is to coincide withperiods of high environmental temperature.

The requirement for a specific body com-position at the onset of maturity has not been ade-quately established. With mammals, onset andfunction of normal estrus activity is dependenton attainment of a certain body fat content. Inhumans, for example, onset of puberty will notoccur if body fat content is much less than14%. No such clear cut relationship has emergedwith egg layers. Work conducted with broilerbreeders, in fact, indicates a more definite rela-tionship between lean body mass and maturity,rather than fat content and maturity.

iii) Early egg size – Egg size is greatly influ-enced by the size of the yolk that enters the oviduct.In large part this is influenced by body weight



of the bird and so factors described previouslyfor mature body weight can also be applied toconcerns with early egg size. There is a gener-al need for as large an early egg size as is pos-sible. Most attempts at manipulating early eggsize have met with limited success. Increasedlevels of linoleic acid in prelay diets may be ofsome use, although levels in excess of the usual1% found in most diets produce only marginaleffects on early egg size. From a nutritional stand-point, egg size can best be manipulated with dietprotein, and especially methionine concentra-tion. It is logical, therefore to consider increas-ing the methionine levels in prelay diets.

iv) Pre-pause – In some countries, and most notablyJapan, pre-pause feeding programs are used tomaximize early egg size. The idea behind theseprograms is to withdraw feed, or feed a very low

nutrient dense diet at the time of sexual matu-rity. This somewhat unorthodox program isdesigned to ‘pause’ the normal maturation pro-cedure, and at the same time to stimulate greateregg size when production resumes after about10-14 days. This type of prelay program istherefore most beneficial where early small eggsize is economically undesirable.

Pre-pause can be induced by simply with-drawing feed, usually at around 1% egg pro-duction. Under these conditions, pullets imme-diately lose weight, and fail to realize normalweight-for-age when refed. Egg productionand feed intake normalize after about 4 weeks,although there is 1-1.5 g increase in egg size.Figure 3.8 shows the production response ofLeghorn pullets fed only wheat bran from 18 weeks(or 1% egg production) through to 20 weeks of age.

Fig. 3.8 Early egg production of pullets fed wheat bran at 1% egg productionor at 18 weeks of age.



The most noticeable effects resulting from useof a pre-pause diet such as wheat bran, are a veryrapid attainment of peak egg production and anincrease in egg size once refeeding commences.This management system could therefore beused to better synchronize onset of production(due to variance in body weight), to improve earlyegg size or to delay production for various man-agement related decisions. The use of suchpre-pause management will undoubtedly beaffected by local economic considerations, andin particular the price of small vs. medium vs.large grade eggs.

v) Urolithiasis – Kidney dysfunction often leadsto problems such as urolithiasis that some-timesoccurs during the late growing phase of thepullet or during early egg production. While infec-tious bronchitis can be a confounding factor,urolithiasis is most often induced by diet min-eral imbalance in the late growing period. At post-mortem, one kidney is often found to be enlargedand contain mineral deposits known as uroliths.Some outbreaks are correlated with a largeincrease in diet calcium and protein in layer vs.grower diets, coupled with the stress of physicallymoving pullets at this time, and being subject-ed to a change in the watering system (usuallyonto nipples in the laying cages). The urolithsare most often composed of calcium-sodium-urate.

The occurrence is always more severe whenimmature pullets are fed high calcium diets foran extended period prior to maturity. For exam-ple, urolithiasis causing 0.5% weekly mortali-ty often occurs under experimental conditionswhen pullets are fed layer diets from 10-12weeks of age (relative to maturity at 18-19weeks). However, there is no indication that earlyintroduction of a layer diet for just 2-3 weeks priorto maturity is a causative factor.

Because diet electrolytes can influence waterbalance and renal function, it is often assumedthat electrolyte excess or deficiency may bepredisposing factors in urolithiasis or gout.Because salts of uric acid are very insoluble, thenthe excretion of precipitated urate salts could serveas a water conservation mechanism, especial-ly when cations are excreted during salt loadingor when water is in short supply. When roost-ers are given saline water (1% NaCl) and fed highprotein diets, uric acid excretion rates are dou-bled compared to birds offered the high proteindiet along with non-saline drinking water.Because uric acid colloids are negatively charged,they attract cations such as Na, and so when theseare in excess, there is an increased excretion viaurates, presumably at the expense of conventionalNH4 compounds. There is some evidence of animbalance of Na+K:Cl levels influencing kidneyfunction. When excess Na+K relative to Cl is fed,a small percentage of the birds develop urolithi-asis. It is likely that such birds are excreting amore alkaline urine, a condition which encour-ages mineral precipitation and urate formation.

As previously described, Urolithiasis occursmore frequently in laying hens fed high levels ofcalcium well in advance of sexual maturity.Feeding prelay (2-2.5% Ca) or layer diets con-taining 4-5% calcium for 2-3 weeks prior to firstegg is usually not problematic, and surprising-ly, uroliths rarely form in adult male breeders fedhigh calcium diets. High levels of crude proteinwill increase plasma uric acid levels, and poten-tially provide conditions conducive to urateformation.

In humans, urolith formation (gout) can becontrolled by adding urine acidifiers to the diet.Studies with pullets show similar advantages.Adding 1% NH4Cl to the diet results in a more



acidified urine, and uroliths rarely form underthese conditions. Unfortunately, this treatmentresults in increased water intake, and associat-ed wet manure. One of the potential prob-lems in using NH4Cl once the birds start layingis that the metabolic acidosis is detrimental toeggshell quality especially under conditions ofheat stress. Such treatment also assumes the kid-ney can clear the increased load of H+, and fora damaged kidney, this may not always be pos-sible. As a potential urine acidifier withoutsuch undesirable side effects, several researchershave studied the role of Alimet® a methionineanalogue. In one study, pullets were fed diets con-taining 1 or 3% calcium with or without Alimet®from 5-17 weeks. Birds fed the 3% calcium dietexcreted alkaline urine containing elevated cal-cium concentrations together with urolith formationand some kidney damage. Feeding Alimet® acid-ified the urine, but did not cause a generalmetabolic acidosis. Alimet® therefore reducedkidney damage and urolith formation without caus-ing acidosis or increased water consumption.Urine acidification can therefore be used as a pre-vention or treatment of urolithiasis, and thiscan be accommodated without necessarilyinducing a generalized metabolic acidosis.From a nutritional viewpoint, kidney dysfunction

can be minimized by not oversupplying nutri-ents such as calcium, crude protein and electrolytesfor too long a period prior to maturity.

g) Lighting programsPhotoperiod has a dramatic influence on the

growth and body composition of the growing pul-let and so light programs must be taken intoaccount when developing feeding programs. Interms of pullet management, day length has twomajor effects, namely the development of repro-ductive organs and secondly a change in feed intake.It is well known that birds reared on a step-up ornaturally increasing day length will mature ear-lier than those reared on a constant day length.Similarly, if birds are subjected to a step-down daylength much after 12 weeks of age, they willlikely exhibit delayed sexual maturity. The longerthe photoperiod, the longer the time that birds haveto eat feed, and so usually this results in heavierbirds. Table 3.35 shows the growth rate andfeed intake of pullets reared on constant daylengths of 6, 8, 10 or 12 hours to 18 weeks of age.For Leghorn pullets, each extra hour of day lengthduring rearing increased body weight by about 20g and feed intake by 100 g. For brown egg pul-lets there was a 13 g increase in weight and 70g increase in feed intake for each hour of extra light.

Table 3.35 Effect of day length during rearing on growth and feed intake ofpullets

Hours of Leghorn Brown egg

light/d 18 wk Feed 17 wk egg 18 wk Feed 17 wk egg

7d-18 wkswt (g) intake production wt (g) intake production

(kg) (%) (kg) (%)6 1328c 6.14 0 1856b 7.53 128 1376b 6.00 1.2 1930ab 7.83 1210 1425a 6.30 2.0 1889ab 7.60 1012 1455a 6.71 3.4 1953a 8.06 12



Longer photoperiods may be beneficial in hotweather situations where feed intake of pulletsis often depressed. As the day length for the grow-ing pullet is increased, there is a reduction in ageat maturity. Research data suggests earlier matu-rity with constant rearing day lengths up to 16-18 hours per day, although longer daylengths suchas 20-22 hours per day seem to delay maturity.Another potential problem with longer daylength during rearing is that it allows less poten-tial for light stimulation when birds are moved tolaying facilities. However, in equatorial regionswhere maximum day length fluctuates between11-13 hours, many birds are managed withoutany light stimulation. In fact, under such hot weath-er, high light intensity conditions, excessivestimulation often results in prolapse and blowouts.In these situations if light stimulation is given, itshould follow rather than lead, the onset of eggproduction. It seems that for modern strains ofbirds, light stimulation at ‘maturity’ is not alwaysnecessary for adequate layer performance. In arecent trial, we have shown some advantages toconstant 14 h photoperiods for the entire life ofthe bird vs. an 8 h rearing photoperiod followedby a 14 h layer photoperiod (Table 3.36). Pulletsthat were grown on constant 14 h light and notgiven any extra day length at maturity producedfewer eggs mainly due to reduced peak pro-duction. However, this flatter peak was associ-ated with a significant increase in egg size anda significant improvement in shell quality (lower

eggshell deformation). The reason for improvedshell quality is not clear, although we have seenthis with other flocks that fail to show adequatesustained peaks – maybe giving up a few eggs atpeak is a means of improving shell quality. Theincreased egg size for birds on the constant 14h photoperiod is undoubtedly due to birds beingheavier at maturity, and then eating more feedthroughout the laying period.

When birds are light stimulated prior to firstegg, their age at light stimulation will have an effecton age at first egg. Our data suggest that after98d of age, for each 1 d delay in age at light stim-ulation, first egg will occur about 0.5 d later (Figure3.9). This means that light stimulating a pulletat 105 d rather than 125 d, will likely result inearlier maturity by about 10 days. At this time,it is important to re-emphasize the previousdiscussion concerning adequacy of body weightand body condition before considering earlierlight stimulation. Another program that can beused to stimulate growth is ‘step-down’ lighting(Figure 3.10).

In Figure 3.10, birds are given 23 hr light/d forthe first week and then day length is reduced byabout 1 h each week until 10 h per day isachieved, at which time it is held constant. Whenbirds are in open-sided houses, the minimum daylength achieved is dictated by the maximumnatural day length during this time. Birds can then

Photoperiod 336d egg Egg weight Shell deformation Rearing Laying production (g) (µg)

8h 14h 271a 58.4b 26.5a

14h 14h 256b 60.3a 25.4b

Table 3.36 Effect of rearing daylength on subsequent layer performance



Fig. 3.9 Age at light stimulation (8-14 hr) and sexual maturity.

Fig. 3.10 Step-down lighting.



be photostimulated at the normal time. The step-down program has the advantage of allowing thepullets to eat feed for considerably more time eachday during their early development. In hotweather conditions, this long day length meansthat birds are able to eat more feed during cool-er parts of the day. The system should not be con-fused with historical step-down lighting pro-grams that continued step-down until 18-20weeks; these older programs were designed to delaymaturity. For the program in Figure 3.10, matu-rity will not be affected as long as the step-downregime is stopped by 10 – 12 weeks of age, i.e.before the pullet becomes most sensitive tochanges in day length. The step-down lighting pro-gram is one of the simplest ways of increasing growthrate in pullets and is practical with both blackoutand open-sided buildings.

Keshavarz (1998) shows increased body weightof 15 week old pullets grown on a step-downlighting program of 23 to 8 h by 16 weeks (Table 3.37).In this study the step-down photoperiod was con-tinued through to 16 weeks, and this delayed sex-ual maturity resulting in a 1 g increase in egg size.

h) Feed restrictionFeed restriction may be necessary for controlling

the weight of brown egg pullets during cooler win -ter months. The goal of any restriction programis to ensure optimum weight-for-age at sexual matu-rity. Because many strains of brown egg birds are

now maturing very early and since their maturebody size has been decreased, the need forrestriction occurs less frequently. A major con-cern with restriction programs is maintenance offlock uniformity. With a mild restriction program,birds can be allowed to ‘run-out’ of feed one dayper week and usually this will do little harm touniformity. If it is necessary to impose a greaterdegree of feed restriction on a daily basis, thenit is important to ensure rapid and even feed dis-tribution, as subsequently discussed for broilerbreeders (Chapter 5). Feed restriction should berelaxed if birds are subjected to any stressessuch as beak trimming, vaccination, generaldisease challenges or substantial reduction in envi-ronmental temperature. An alternative man-agement procedure for overweight birds is to sched-ule an earlier light stimulation and move tolayer cages (see Figure 3.4).

Brown egg pullets do seem to consume lessenergy and so are smaller when given lower ener-gy diets. For example providing pullets grow-er-developer diets at 2750 vs. 3030 kcal ME/kgresulted in an 8% reduction in energy intake and4% reduction in body weight. These same dietsfed to Leghorn pullets resulted in just 4% reduc-tion in energy intake of the lower energy diet withvirtually no change in body weight. Reduced nutri-ent density should therefore be considered in con-junction with physical feed restriction, for con-trolled growth of brown egg pullets.

Table 3.37 Effect of continuous weekly step-down lighting on pullet development

Rearing Body wt 18 wk Feed intake Age first eggphotoperiod (15 wk) (g) uniformity (%) (0-18 wk) (kg) (d)

8 h 1070a 69 5.98 13023 to 8 h @ 16 wk1 1120b 78 6.20 140

11 hour decrease/wk Adapted from Keshavarz (1998)



Suggested Readings

Keshavarz, K. (1998). The effect of light regimen,floor space and energy and protein levels during thegrowing period on body weight and early egg size.Poult. Sci. 77:1266-1279.

Keshavarz, K. (2000). Re-evaluation of non-phytatephosphorus requirement of growing pullets withand without phytase. Poult. Sci. 79:1143-1153.

Leeson, S. and J.D. Summers, (1985). Response ofgrowing Leghorn pullets to long or increasing pho-toperiods. Poult. Sci. 64:1617-1622.

Leeson, S. and J.D. Summers, (1989). Performanceof Leghorn pullets and laying hens in relation tohatching egg size. Can. J. Anim. Sci. 69:449-458.

Leeson, S. and J.D. Summers, (1989). Response ofLeghorn pullets to protein and energy in the dietwhen reared in regular or hot-cyclic environments.Poult Sci. 68:546-557.

Leeson, S., (1986). Nutritional considerations ofpoultry during heat stress. World’s Poult. Sci.42:619-681.

Leeson, S., (1991). Growth and development ofLeghorn pullets subjected to abrupt changes in envi-ronmental temperature and dietary energy level.Poult. Sci. 70:1732-1738.

Leeson, S. and L.J. Caston, (1993). Does environmen-tal temperature influence body weight; shank lengthin Leghorn pullets? J. Appl. Poult. Res. 2:253-258.

Leeson, S., J.D. Summers and L.J. Caston, (1993).Growth response of immature brown egg strain pul-lets to varying nutrient density and lysine. Poult.Sci. 72:1349-1358.

Leeson, S., J.D. Summers and L.J. Caston, (1998).Performance of white and brown egg pullets fedvarying levels of diet protein with constant sulfuramino acids, lysine and tryptophan. J. Appl. Poult.Res. 7:287-301.

Leeson, S., J.D. Summers and L.J. Caston, (2000).Net energy to improve pullet growth with low pro-tein amino acid fortified diets. J. Appl. Poult. Res.9:384-392.

Lewis, P.D. and G.C. Perry, (1995). Effect of age atsexual maturity on body weight gain. Br. Poult. Sci.36:854-856.

Martin, P.A., G.D. Bradford and R.M. Gous, (1994).A formula method of determining the dietary aminoacid requirements of laying type pullets during theirgrowing period. Br. Poult. Sci. 35:709-724.

Patterson, P.H. and E.S. Lorenz, (1997). Nutrients inmanure from commercial White Leghorn pullets. J.Appl. Poult. Res. 6:247-252.

Summers, J.D. and S. Leeson, (1994). Laying henperformance as influenced by protein intake to six-teen weeks of age and body weight at point of lay.Poult. Sci. 73:495-501.

163FEEDING PROGRAMS FOR LAYING HENS4

4.1 Diet specifications and formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164

4.2 Feed and energy intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170

4.3 Problems with heat distress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177

a. Bird’s response to heat stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179

b. Maintaining energy balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182

c. Protein and amino acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184

d. Minerals and vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184

e. Electrolyte balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185

f. Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188

g. Effect of physical diet change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188

h. Summary of nutritional management during heat . . . . . . . . . . . . . . . . . .189

4.4 Phase Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190

4.5 Formulation changes and feed texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192

4.6 Nutrition and shell quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193

4.7 Controlling egg size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198

4.8 Diet and egg composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203

4.9 Diet involvement with some general management problems . . . . . . . . . . . . .214

4.10 Nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222

Page

CHAPTER

164 CHAPTER 4FEEDING PROGRAMS FOR LAYING HENS

SECTION 4.1Diet specifications and formulations

D iet specifications for laying hens areshown in Table 4.1, and are catego-rized according to age and feed intake.

There is no evidence to suggest that the energy levelof diets needs to be changed as the birds progressthrough a laying cycle. The layer’s peak energyneeds are most likely met at around 35 weeks ofage, when production and daily egg mass outputare maximized. However, the layer quite preciselyadjusts its intake according to needs for energy andso variable energy needs are accommodated bychange in feed intake.

Most Leghorn strains will now commence eggproduction with feed intakes as low as 80 – 85g/day, and it is difficult to formulate diets for sucha small appetite. For brown egg strains, initialfeed intake will be around 92 - 95 g/day and soformulation is more easily accommodated. Forall diets, maintaining the balance of all nutrientsto energy is the most important consideration dur-ing formulation.

In general terms, diet nutrient concentrationsdecrease over time, with the notable excep-tion of the need for calcium. Thus, diet proteinand amino acids expressed as a percent of the

diet or as a ratio to energy, decline as the birdprogresses through the laying cycle. In order tosustain shell quality, it is important to increasediet calcium level, and to concomitantly decreasediet phosphorus level, as the bird gets older. Theneed for less methionine is partially related to theneed for tempering late-cycle increase in egg size,since this is usually uneconomical regarding eggpricing and larger eggs have thinner shells.There is little evidence for change in needs forvitamins and trace minerals as birds get older, andso a single premix specification is shown inTable 4.1. For most of the B-vitamins, it is pos-sible to phase feed with up to 30% reduction bythe end of the laying cycle.

Examples of layer diets using corn, wheat, orsorghum as the main energy source and with orwithout meat meal, are shown in Tables 4.2 – 4.5.The diets are categorized according to age of bird.It is difficult to achieve desired energy level inPhase I diets (Table 4.2) without resorting to inclu-sion of significant quantities of fat. If fat supplyand quality is questionable, it may be advisableto reduce the energy level of the diet (and alsoall other nutrients in the same ratio), by up to 50– 70 kcal ME/kg.

4.1 Diet specifications and formulations

165CHAPTER 4FEEDING PROGRAMS FOR LAYING HENS


Approximate age 18-32 wks 32-45 wks 45-60 wks 60-70 wksFeed intake (g/bird/day) 90 95 95 100 100 105 100 110Crude Protein (%) 20.0 19.0 19.0 18.0 17.5 16.5 16.0 15.0Metabolizable Energy (kcal/kg) 2900 2900 2875 2875 2850 2850 2800 2800Calcium (%) 4.2 4.0 4.4 4.2 4.5 4.3 4.6 4.4Available Phosphorus (%) 0.50 0.48 0.43 0.4 0.38 0.36 0.33 0.31Sodium (%) 0.18 0.17 0.17 0.16 0.16 0.15 0.16 0.15Linoleic acid (%) 1.8 1.7 1.5 1.4 1.3 1.2 1.2 1.1Methionine (%) 0.45 0.43 0.41 0.39 0.39 0.37 0.34 0.32Methionine + Cystine (%) 0.75 0.71 0.70 0.67 0.67 0.64 0.6 0.57Lysine (%) 0.86 0.82 0.80 0.76 0.78 0.74 0.73 0.69Threonine (%) 0.69 0.66 0.64 0.61 0.60 0.57 0.55 0.52Tryptophan (%) 0.18 0.17 0.17 0.16 0.16 0.15 0.15 0.14Arginine (%) 0.88 0.84 0.82 0.78 0.77 0.73 0.74 0.70Valine (%) 0.77 0.73 0.72 0.68 0.67 0.64 0.63 0.60Leucine (%) 0.53 0.50 0.48 0.46 0.43 0.41 0.40 0.38Isoleucine (%) 0.68 0.65 0.63 0.60 0.58 0.55 0.53 0.50Histidine (%) 0.17 0.16 0.15 0.14 0.13 0.12 0.12 0.11Phenylalanine (%) 0.52 0.49 0.48 0.46 0.44 0.42 0.41 0.39

Vitamins (per kg of diet):Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 2Riboflavin (mg) 5Pyridoxine (mg) 3Pantothenic acid (mg) 10Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 10

Trace minerals (per kg of diet):Manganese (mg) 60Iron (mg) 30Copper (mg) 5Zinc (mg) 50Iodine (mg) 1Selenium (mg) 0.3

Table 4.1 Diet specifications for layers

1 2 3 4 5 6Corn 507 554Wheat 517 619Sorghum 440 373Wheat shorts 42 68 184Meat meal 70 70 70Soybean meal 327 245 261 171 311 214Fat 45 31 60 40 60 59DL-Methionine* 1.2 1.2 1.6 1.5 1.8 1.8Salt 3.6 2.6 3.0 2.0 3.6 2.6Limestone 99.5 92.3 100 94 100 93Dical Phosphate 15.7 2.9 14.4 1.5 14.6 1.6Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 20 20 20 20 20 20ME (kcal/kg) 2900 2900 2900 2900 2900 2900Calcium (%) 4.2 4.2 4.2 4.2 4.2 4.2Av Phosphorus (%) 0.5 0.5 0.5 0.5 0.5 0.5Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.45 0.46 0.45 0.45 0.45 0.45Meth + Cystine (%) 0.76 0.75 0.77 0.76 0.8 0.78Lysine (%) 1.14 1.15 1.12 1.05 1.17 1.16Threonine (%) 0.86 0.83 0.75 0.7 0.78 0.75Tryptophan (%) 0.28 0.26 0.30 0.28 0.28 0.26




Table 4.2 Examples of Phase 1 layer diets (18-32 wks)



1 2 3 4 5 6Corn 536 581Wheat 586 508Sorghum 419 382Wheat shorts 8 123 118 200Meat meal 70 60 65Soybean meal 301 220 233 156 279 192Fat 39 24.6 50 50 60 56DL-Methionine* 0.9 1.1 1.3 1.2 1.5 1.5Salt 3.3 2.3 2.7 1.8 3.4 2.5Limestone 106 100 107 99 107 100Dical Phosphate 12.8 11.0 11.1Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000




1 2 3 4 5 6Corn 584 626Wheat 648 571Sorghum 550 483Wheat shorts 113 35 143Meat meal 60 50 55Soybean meal 261 190 187 115 248 169Fat 29 14.8 40 40 40.5 40DL-Methionine* 1 1.2 1.3 1.5 1.5 1.5Salt 3 2 2.5 1.5 3.2 2.5Limestone 111 105 111 107 111 105Dical Phosphate 10 9.2 9.8Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 17.5 17.5 17.5 17.5 17.5 17.5ME (kcal/kg) 2850 2850 2850 2850 2850 2850Calcium (%) 4.5 4.5 4.5 4.5 4.5 4.5Av Phosphorus (%) 0.38 0.39 0.38 0.38 0.38 0.38Sodium (%) 0.16 0.16 0.16 0.16 0.16 0.16Methionine (%) 0.40 0.42 0.39 0.41 0.39 0.39Meth + Cystine (%) 0.67 0.67 0.67 0.67 0.70 0.68Lysine (%) 0.95 0.95 0.92 0.93 0.98 0.98Threonine (%) 0.76 0.73 0.63 0.60 0.68 0.64Tryptophan (%) 0.24 0.22 0.26 0.24 0.24 0.22







1 2 3 4 5 6Corn 638 619Wheat 570 527Sorghum 485 467Wheat shorts 51 126 190 156 200Meat meal 49 38 42Soybean meal 221 157 138 90 192 138Fat 13 9.7 40 40 40 37DL-Methionine* 0.8 1 1.1 1.2 1.2 1.4Salt 3 2.3 2.4 1.8 3 2.6Limestone 115 110 115 111 115 111Dical Phosphate 8.2 6.5 6.8Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000





SECTION 4.2Feed and energy intake

4.2 Feed and energy intake

F eeding programs for layers cannot bedeveloped without consideration for the rear-ing program as discussed in Chapter 3.

Unfortunately, many egg producers purchase point-of-lay pullets from independent pullet grow-ers, and here the goals of the two producers arenot always identical. Too often the egg produceris interested in purchasing mature pullets at thelowest possible cost per bird regardless of theircondition. For pullet growers to make a profitthey must produce birds at the lowest possiblecost. With feed representing some 60 to 70% ofthe cost to produce a pullet, the obvious way forthe pullet grower to reduce costs is to save onfeed cost. While they may be able to save a smallamount of feed by eliminating feed waste or byensuring that house temperatures are optimum,the only way to save a substantial amount of feedis to place the pullets on a growing program suchthat feed consumption is reduced and/or cheap-er diets are used. Because it is not possible toenhance the efficiency with which pullets con-vert feed into body weight gain, the net result isa smaller bird at time of transfer. If the birds havebeen on an increasing light pattern, they mightwell be mature, as judged from appearance, atthe onset of production. However, such pulletsmust still grow before they reach their opti-mum weight and condition as a laying hen.Consequently, the egg producer will have to feedthis pullet in an attempt to bring the body weightup to normal if a profitable laying flock is to beobtained. If egg producers attempt to save on feed,the result will be underweight birds at peak egg

production. This situation leads to smaller eggs,and often lower than normal peak or birds drop-ping relatively quickly in production shortlypast peak as discussed in the previous chapter.

It takes a certain amount of feed to producea laying hen with optimum body size. If this feedis not consumed in the growing period, it mustbe fed in the laying house. Of course, onewould have to be sure that the pullets are healthyand are not carrying an excess of body fat.However, the problem of excess body fat withtoday’s modern type, early maturing pullet, doesnot usually occur. Egg producers should also findout as much as possible about the pullets they arepurchasing, such as the type of feeding programthey have been on, the health status of the flock,and the type of waterers used in rearing. Withthis type of information, they should be in abetter position to ensure a profitable laying flock.

It is now common practice to describe feed-ing programs for layers according to the level offeed intake. It is well known that under normalenvironmental and management conditions,feed intake will vary with egg production and/orage of bird, and this must be taken into accountwhen formulating diets. While layers do adjustfeed intake according to diet energy level, thereis no evidence to suggest that such precision occurswith other nutrients.

The following daily intakes of nutrients are sug-gested under ideal management and environmentalconditions (Table 4.6).



Table 4.6 Daily nutrient needs for Leghorn birds.

Table 4.7 Feed intake of Leghorns as influenced by body weight, egg production, egg weight and environmental temperature1

Body weight Egg production Egg weight TemperatureBody wt Intake Egg production Intake Egg wt Intake ºC Intake

(g) (g/d) (%) (g/d) (g) (g/d) (g/d)1200 92.7 98 100.5 50 90.8 10 102.21250 94.9 94 98.8 55 94.0 15 102.11300 97.1 90 97.1 60 97.1 20 97.11350 99.3 86 95.4 65 100.3 25 92.11400 101.5 82 93.8 70 103.4 30 87.1

23g 1 g 2.4% 1 g 1.6 g 1 g 1ºC 1 g

1 Assumes 1300 g body weight, 90% egg production, 60 g egg weight and 20�C as the standard, with diet at 2850 kcal/kg

At any given time, it is necessary to adjust dietspecifications according to the actual feed intakeof the flock. Within a single strain it is possibleto see a ± 15 g variance in feed intake at any agerelated to stage of maturity, egg mass, bodysize and most importantly, environmental tem-perature.

It is possible to predict energy needs, and hencefeed intake, based on knowledge of the majorvariables. The equation most commonly usedis described below. Using this equation, Table4.7 was developed with variable inputs of bodyweight, egg production, egg weight and envi-ronmental temperature. Feed intake was calculatedassuming a diet energy level of 2850 kcal ME/kg.

Energy (kcal ME/bird/day) = [Body weight (kg)] [170 – 2.2 x ºC] + [2 x Egg mass/d (g)] + [5 x Daily weight gain (g)]

Age (wks)18 – 32 32 – 45 45 – 60 60 – 70

Protein (g) 20 18.5 17.5 16Metabolizable energy (kcal) 260 290 285 280Calcium (g) 4.0 4.2 4.4 4.6Av. Phosphorus (mg) 550 450 380 330Methionine (mg) 500 430 390 340TSAA (mg) 830 740 670 600Lysine (mg) 950 840 780 730



For these calculations, one factor at a time waschanged, and the standards for other parametersare highlighted across the middle of Table 4.7. Forexample, in the case of body weight, the effecton feed intake was calculated with 50 g incre-ments of weight from 1200 to 1400 g. For eachof these calculations for body weight, egg pro-duction was fixed at 90%, egg weight at 60 g andenvironmental temperature at 20˚C. Likewise,when egg production was the variable consideredall other factors remained constant. The summarydata appearing as the last row in Table 4.7 showthe relative change in each input parameter nec-essary to change feed intake by one gram/bird/day.Consequently, ± 23 g body weight, ± 2.4% eggproduction, ±1.6 g egg weight, and ± 1ºC all changefeed intake by ± 1 g/bird/day. Of these factors envi-ronmental temperature is usually the most vari-able on a day-to-day basis, and so, is likelyresponsible for most of the variation in feedintake seen in commercial flocks.

With variable feed intake, it is necessary toadjust the ratios of nutrients to energy to main-tain constant intakes of these nutrients. Whileit is impractical to consider reformulation basedon day-to-day fluctuation in environmental tem-perature, trends in feed intake associated with

high vs. low body weight etc. should be accom-modated in diet formulation.

A knowledge of feed intake, and the factorsthat influence it, are therefore essential for anyfeed management program. To a degree, the ener-gy level of the diet will influence feed intake,although one should not assume the precisionof this mechanism to be perfect. In general, birdsover consume energy with higher energy diets,and they will have difficulty maintaining normalenergy intake when diets of less than 2500 kcalME/kg are offered. In most instances, under- con-sumption rather than over-consumption is the prob-lem, and so use of higher energy diets during sit-uations such as heat stress will help to minimizeenergy insufficiency. Table 4.8 shows theLeghorn bird’s response to variable diet energy.

These Leghorn strain birds performed sur-prisingly well with the diluted diets, and showedan amazing ability to adjust feed intake as dietnutrient density changed, and down to 2600kcal ME/kg were able to maintain almost constantenergy intake. Only at 2450 kcal/kg, whichrepresents a 15% dilution of the original diet, werethere indications of failure to consume ade-quate amounts of energy (or other nutrients?).

Diet Feed intake (g/b/d) Feed (kg) Egg Energy energy _____________________ ____________ ___________________ intake

(kcal/kg)1 43 51 65 (19 – 67 wk) Number Mass (Mcal/365d)wks wks wks (kg)

2900 100b 103bc 103b 33.9b 290 17.9a 98.32750 100b 103bc 103b 34.3b 294 16.9b 94.72600 116a 113a 109ab 37.1a 304 17.9a 96.82450 112a 111a 115a 37.1a 302 17.3ab 91.2

1 All other nutrients in same ratio to energy across all diets Adapted from Leeson et al. (2001)

Table 4.8 Layer response to diet dilution (19 - 67 wks age)



These birds were maintained at 20 - 22˚C, andit is suspected that the layers may have had dif-ficulty maintaining nutrient intake with the dilut-ed diets if any heat distress conditions occurred.

The diet specifications listed in Table 4.1 showvalues for crude protein. If soybean meal andcorn, wheat or sorghum make up 60 – 70% ofthe diet, then protein per se gives an indicationof the likely adequacy of amino acid needs.Obviously formulation to total and digestible aminoacids is critical in more precisely meeting the bird’snutrient needs, yet there is still a need for othernitrogen containing nutrients that are variablydescribed as crude protein or non-essentialamino acids. Theoretically, a layer diet has to pro-vide only the ten essential amino acids andunder ideal conditions, these will be at require-ment levels. However, when diets are formulatedon this basis, production, and economic returnsare reduced, suggesting the need for a ‘minimal’level of crude protein. Under commercial con-ditions, production goals are rarely achieved whencrude protein levels much less than 15% are usedthrough the layer cycle regardless of the supplyof essential amino acids. Such effects imply a

requirement for nitrogen or non-essential aminoacids and/or that our assessment of essential aminoacid needs are incorrect. As crude protein levelof the diet is reduced, regardless of amino acidsupply, there is also increase in mortality andreduced feather score (Table 4.9). The feather-ing of white and especially brown egg birds isadversely affected by low protein diets (lower score).

There is little doubt that body weight atmaturity is a major factor influencing feed intakeof laying hens. Body weight differences seen atmaturity are maintained throughout lay almostregardless of nutrient profile of layer diets. It istherefore difficult to attain satisfactory nutrientintakes with small birds. Conversely, largerbirds will tend to eat more, and this may becomeproblematic in terms of the potential for obesi-ty and/or too large an egg towards end of lay. Phasefeeding of nutrients can overcome some ofthese problems, although a more simplisticlong-term solution is control over body weightat maturity. Under most economic conditions,‘heavier’ birds at maturity are ultimately most eco-nomical for table egg production in terms of eggrevenue relative to feed costs.

Table 4.9 Effect of crude protein on mortality and feather score

Feather score (Scale 0-20)

%CP %Cannibalism White Brown11.1 17.6 12.4 10.712.5 8.3 13.7 11.313.8 5.1 13.9 12.815.2 2.7 15.0 13.116.5 4.2 14.8 14.117.9 0.4 14.9 14.619.3 2.5 15.9 15.0Adapted from Ambrosen and Petersen (1997)



Feed management becomes even more crit-ical with earlier and higher sustained peak eggproduction from today’s strains of bird. Energyinsufficiency during pre-peak production can causeproblems during post-peak production. Eggproduction curves that show a 5 – 8% reductionafter peak are characteristic of birds with insuf-ficient appetite caused by too small a pullet atmaturity (Figure 3.1). The reduction in appetiteis of concern relative to the adequacy of ener-gy intake. Calculations of energy balance indi-cate a somewhat precarious balance aroundthe time of peak egg numbers, emphasizingthe need for stimulating feed intake and thepossibility of providing some labile energyreserves in the form of carcass energy (fat) stores.Tables 4.10 and 4.11 show such calculated val-ues for Leghorn and brown egg strains respec -

tively, and relate these to the required intake ofa standard diet.

The significance of energy intake as the lim-iting nutrient for egg production with modern strainsof layer is shown in Figure 4.1. There is a dra-matic response to energy intake from 184 – 312kcal/bird/day, in the form of egg output. Atvery high energy intakes, there is little apparentresponse to protein intake over the range of 13 – 21 g/bird/day. Only when energy intake islimiting is there any measurable increase inegg numbers in response to increased proteinintake. However, as will be detailed later (Figure 4.13), the converse applies in terms ofegg size, when the bird shows a dramaticresponse to protein intake, and little response toenergy intake.

Table 4.10 Energy balance of leghorn pullets during early egg production

Theoretical Daily Energy Requirement Required intake of Age (kcal ME per bird) 17% CP, 2850 ME

(wks) Maintenance Growth Eggs Total diet (g/d)16 133 40 177 6217 137 40 181 6418 142 40 186 6519 150 35 5 190 6720 154 35 10 199 7021 154 30 24 208 7322 154 30 44 228 8023 154 25 57 242 8524 154 25 78 257 9025 155 20 85 260 9126 155 18 87 262 9227 158 15 92 265 9328 158 15 95 268 9429 160 13 97 270 9530 161 12 100 273 96



Table 4.11 Energy balance of brown egg pullets during early egg production

Theoretical Daily Energy Requirement Required intake of Age (kcal ME per bird) 17% CP, 2850 ME

(wks) Maintenance Growth Eggs Total diet (g/d)16 148 50 2 200 7017 148 50 8 205 7218 134 50 30 214 7519 138 40 50 228 8020 142 40 60 242 8521 148 30 70 248 8722 152 30 80 262 9223 155 25 95 271 9524 160 25 96 274 9625 164 15 97 276 9726 166 15 98 279 9827 168 15 99 282 9928 173 12 100 285 10029 175 12 101 288 10130 176 12 102 290 102

Fig. 4.1 Egg production (18-66 weeks) in response to daily intakes of energy and protein.

An argument against being overly concernedabout uniformity, is that birds will adjust theirintake according to nutrient (energy) needs, andso early maturing birds will eat more, and late matur-ing birds less, during the early phases of produc-tion. However, if birds are given diets formulat-ed based on feed intake, this can lead to problems,the most serious of which is overfeeding of the larg-er early maturing bird. Another confoundingfactor is that as birds mature within a flock, the per-cent production realized on a daily basis does notreflect the number of birds laying at that time. Asshown in Figure 4.2, the proportion of layingbirds always exceeds the percent production cal-culated and this difference is most pronounced inearly production. For example, at about 40% pro-duction, there are, in fact, around 70% of the birdsmature and requiring proportionally more nutri-ents than suggested by egg production alone.



Many problems associated with marginal nutri-ent intake of young layers can most often be over-come by ensuring optimum body weight andappetite of young laying pullets. Unfortunately,mean weight of the flock at this age, is toooften considered independently of flock uniformity.Pullets may be of ‘mean’ body weight, yet be quitevariable in weight, and often outside the accept-ed range of 85% of the flock being within ± 10%of mean weight. The major problem with anon-uniform flock is variability in age at first egg,and so variability in feed intake. If diets are tai-lored to feed intake, then late maturing smallerbirds (with small appetites) will likely be under-fed. Conversely heavier, early maturing pulletswith increased appetites may be overfed at thistime. The consequence is often a delayed peak,and reduced overall egg production.

Fig. 4.2 Comparison of number of birds producing eggs and actual egg production


SECTION 4.3Problems with heat distress

4.3 Problems with heat distress

T he majority of the world’s laying hens arekept in areas where heat stress is likely tobe a major management factor at some

stage during the production cycle. The major prob-lem relates to birds not consuming enough feedat this time, although there are also some sub-tle changes in the bird’s metabolism that affectboth production and shell quality. While all typesof poultry thrive in warm environments duringthe first few weeks of life, normal growth anddevelopment of older birds is often adversely affect-ed. Obviously, the bird’s requirements for sup-plemental heat declines with age, because insu-lating feathers quickly develop and surfacearea, in relation to body size, is reduced. Heatstress is often used to describe bird status in hotenvironments, although it is obvious that morethan just environmental temperature per se isinvolved. Because birds must use evaporativecooling (as panting) in order to lose heat athigh temperatures, humidity of inhaled air

becomes critical. High temperature and humid-ity combined are much more stressful to birds thanis high temperature alone. Other environmen-tal factors such as air speed and air movement arealso important. It is also becoming clear that adap-tation to heat stress can markedly influenced birdresponse. For example, laying birds can tolerateconstant environmental temperatures of 35˚C andperform reasonably well. On the other hand, mostbirds are stressed at 35˚C when fluctuatingday/night temperatures are involved. In the fol-lowing discussion, it is assumed that fluctuatingconditions exist, since these are more commonand certainly more stressful to the bird.

Figure 4.3 shows the bird’s generalized responseto variable temperature and humidity. Regardlessof housing system, environmental conditions of >32˚C and > 50% RH are likely to cause some degreeof heat distress. Table 4.12 shows typical layerresponse to high environmental temperatures.

Table 4.12 Performance of brown egg layers at 18˚C vs. 30˚C

Feed intake Egg production Egg weight Shell (% of egg)(g/b/d) (%) (g) 40 wk 60 wk

18˚C 131 91.2 60.9 9.5 9.130˚C 108 83.6 57.2 9.0 8.6Adapted from Chen and Balnave (2001)



The main concern under hot weather con-ditions is the layer’s ability to consume feed. Aspoultry house temperature increases, then lessheat is required to maintain body temperatureand the birds consume less feed. In this situation,‘environmental’ energy is replacing feed energy

and is economical. However, the relationshipbetween body heat production and house tem-perature is not linear, since at a certain criticaltemperature, the bird’s energy demands areincreased in order to initiate body coolingmechanisms. The following factors should be con-

Fig. 4.3 Generalized bird response to temperature and humidity.

Fig. 4.4 Environmental temperature and body heat production.



sidered in attempting to accommodate the bird’sreaction to heat stress:

a) Bird’s response to heat stress –Figure 4.4 is a schematic representation of

a heat stress effect. Minimal body heat production(and hence the most efficient situation) is seenat around 23˚C. Below this temperature, (lowercritical temperature) birds generally have togenerate more body heat in order to keep warm.However, there is only a narrow range of tem-perature (19-27˚C) over which heat productionis minimal. Above 27˚C birds start to use moreenergy in an attempt to stay cool. For example,at 27˚C, birds will start to dilate certain blood ves-sels in order to get more blood to the comb, wat-tles, feet etc. in an attempt to increase coolingcapacity. More easily observed is the characteristicpanting and wing drooping that occurs at slight-ly higher temperatures. These activities at highenvironmental temperatures mean that the birdhas an increased, rather than decreased, demand

for energy. Unfortunately, the situation is not asclear cut as depicted in Figure 4.4 and this is like-ly the reason behind the variability seen inflock response to various environmental conditions.Rather than lower and upper critical temperaturebeing rigidly fixed under all conditions, heat pro-duction is likely to fluctuate in response to a num-ber of very practical on-farm conditions.

Variation in response can be caused by suchfactors as (a) increased feed intake; (b) degree offeathering or; (c) increased bird activity. Suchpotential variability in bird response should betaken into account when interpreting the quan-titative data discussed in Figures 4.5 and 4.6. Thewhole picture is further confused by the normalenergy intake pattern of the bird (Figure 4.5). Theupper line of Figure 4.5 represents energy intakefor a 1.5 kg white egg layer. As environmental tem-perature increases, energy intake declines. However,above 27 – 28˚C the decline becomes quite dramatic since the bird is changing its metabolic

Fig. 4.5 Environmental temperature and energy balance.



processes in response to the heat load, andactions such as panting, etc. adversely influencethe feeding mechanisms in the brain and also reducethe time available for feeding. The shaded areabetween the lines in Figure 4.5 represents the ener-gy available for production. At around 28˚C theenergy available for production is dramaticallyreduced and around 33˚C actually becomes neg-ative. If energy available for production is plot-ted against temperature, the energy potential foregg production is clearly evident (Figure 4.6).

A 60 g egg contains around 80 kcal gross ener-gy, and this requires around 100 kcal ME of dietaryinput, assuming 80% efficiency of utilization ofthis ingested energy. If the bird is at 95% pro-duction, then there is a need for 95 kcal ME/dto sustain peak egg output. There will also beneed for 15 – 25 kcal ME for daily growth of this

young pullet, for a total need of around 115 kcalME/d for productive purposes. At moderateenvironmental temperatures, such energy yieldis readily obtained from the feed, since with aver-age intakes of 270 – 275 kcal ME/bird/day,there is adequate energy for production andmaintenance. However, as feed intake declines,available energy will decline. Although main-tenance energy needs are less at higher tem-peratures, the non-linear relationship (Figure4.5) causes problems of energy sufficiency ataround 28˚C (Figure 4.6). Above this tempera-ture, if production and growth are to be sustained,the birds will have to use body energy reservesin order to balance energy demands. Thereare obvious limits to such fat reserves, especiallywith young pullets, and so it is unlikely that thepullet can sustain 95% egg production for toolong a period under these conditions.

Fig. 4.6 Environmental temperature and energy balance.



The bird has no option but to reduce egg out-put in order to sustain energy needs for main-tenance. Under actual farm conditions, thetemperatures at which critical changes occur (28˚Cand 33˚C in Figure 4.6) will vary, especiallywith acclimatization to temperature, but eventswill likely be initiated within ± 2˚C of the val-ues shown in Figure 4.6.

A major factor affecting the bird’s energy intakein response to environmental temperature isfeather cover, which represents insulating capac-ity for the bird. Coon and co-workers have

developed equations that take into accountdegree of feathering, although this assumes a lin-ear trend across all temperatures. Figure 4.7 usesthese equations to predict energy intake up toaround 25˚C, at which time it is assumed that adegree of heat distress will occur and this willbe most prevalent for the well-feathered bird. Theresponse after 26˚C assumes increased energyneed, as shown in Figure 4.5. The actual situ-ation may be more complex than this in tropi-cal regions where birds are held in open-sidedhouses and where there is the expectation of coolnightime temperatures.

Fig. 4.7 ME intake of layers with 60, 75 or 90% feather cover at 10-34˚C

Adapted from (Peguri and Coon, 1995)



b) Maintaining energy balance –The key to sustaining production in hot

climates is to maintain a positive energy balance.

i) Changing diet energy level - It is well knownthat birds consume less feed as the energy levelof the feed increases. This is because the birdattempts to maintain a given energy intake eachday. However, the mechanism is by no meansperfect and as energy level is increased, theactual decline in feed intake is often imper-fectly regulated, leading to ‘overconsumption’of energy. As environmental temperature increas-es, the mechanism seems even less perfect andso increasing diet energy level is often consid-ered in an attempt to stimulate energy intake. Payne(1967) showed this classical effect with brownegg layers fed 2860 to 3450 kcal ME/kg at 18˚Cor 30˚C (Table 4.13). At 18˚C there is fairlygood adjustment by the bird in that feed intakeis sequentially reduced as energy level increas-es and energy intake is maintained constant. Athigh temperatures, birds adjust feed intake lessperfectly and ‘overconsumption’ of energyoccurs. It is not suggested that these extremesof diet energy be used commercially, rather

that energy intake will be maximized with as higha diet energy level as is possible. In order toincrease diet energy level, the use of supplementalfat should be considered. Dietary fat has the advan-tage of increasing palatability and also reducingthe amount of heat increment that is producedduring its utilization for production.

ii) Physical stimulation of feeding activity –Various methods can be used to stimulate feed

intake. Feeding more times each day usuallyencourages feeding activity. Feeding at cooler timesof the day, if possible, is also a useful method ofincreasing the bird’s nutrient intake. If artificiallights are used, it may be useful, under extremeenvironmental conditions, to consider a so-calledmidnight feeding when temperature will hopefullybe lower and birds are more inclined to eat.When heat stress is extreme, making the dietmore palatable may be advantageous. Suchpractices as pouring vegetable oil, molasses, oreven water directly onto the feed in the troughswill encourage intake. Whenever high levels offat are used in a diet, or used as a top dressing asdescribed here, care must be taken to ensure thatrancidity does not occur. This can best be achiev-ed by insisting on the incorporation of quality

Table 4.13 Effect of diet energy level on metabolizable energy intake

18˚C 30˚CDiet energy Feed/day Energy/day Feed/day Energy/day

(kcal ME/kg) (g) (kcal) (g) (kcal)2860 127 363 107 3063060 118 360 104 3203250 112 364 102 3303450 106 365 101 350

Adapted from Payne (1967)



antioxidants in the feed and that feed not beallowed to ‘cake’ in tanks, augers or troughs.Freshness of feed becomes critical under theseconditions.

Diet texture can also be used to advantage.Crumbles or large particle size mash feed tend tostimulate intake while a sudden change fromlarge to small feed particles also has a transitoryeffect on stimulating intake. It is interesting to observethat a sudden change from small to large crumblesseems to have a negative effect on intake (Table 4.14).

Midnight feeding is often used when birds aresubjected to heat stress conditions. Light for 1– 2 hrs has at least a transitory effect on increas-ing feed intake (1 – 3 %) and often has a long-term effect. With moderately high tempera-tures it may only be necessary to provide lighting,while with extreme hot weather it is advisableto also run the feeder lines during this 1 hour timeperiod. An interesting observation with midnightfeeding is the bird’s dramatic increase in waterintake (see Figure 4.8). Layers will eat more feedin hot weather conditions, if the ‘effective tem-perature’ is reduced. This is sometimes achievedwith evaporative cooling depending upon inher-ent levels of humidity. A less costly, but very effec-tive system of stimulating intake, is to increaseair movement. Body temperature of the bird isclose to 41˚C, and the air within the 1-2 mm

boundary layer around the bird will be close tothis temperature. By increasing air speed, theboundary layer is disrupted, so aiding in cool-ing the bird. Table 4.15 shows the effect of airmovement on the cooling effect on the birdand the expected increase in feed intake.

iii) Body fat reserves – Adequacy of pulletrearing programs become most critical whenbirds are to be subjected to hot weather in thetime up to peak egg mass production. Asdetailed in Figure 4.6, the layer may well haveto rely on its body energy reserves as a supple-ment to its diminished energy intake from thefeed. Rearing programs designed to maximizegrowth have been discussed previously. Theheavier the bird at maturity, the larger the bodyweight throughout lay, and hence the largerthe potential energy reserve and also thegreater the inherent feed intake (Table 4.16)

It is not suggested that extremely fat pullets aredesirable, but it is obvious that birds of opti-mum weight with a reasonable fat reserve arebest suited to heat stress situations. Pulletsthat are subjected to heat stress and have less‘available’ energy than that required to sustainproduction, have no recourse but to reduceegg mass output in terms of egg weight and/oregg numbers, since maintenance energyneeds are always a priority.

Table 4.14 Effect of sudden change in feed particle size on feed intake 5-7d following this change

Crumb sizeRegular to small Regular to large

Regular (<2.4 mm) (> 2.4 mm)Feed (g/bird/day) 112b 124a 81c



c) Protein and amino acids – It is tempting to increase the crude protein

level of diets during heat stress conditions. Thishas been done on the basis of reduced feed intake,and hence protein levels have been adjustedupwards in an attempt to maintain intakes ofaround 19 g crude protein/bird/day. It is now real-ized that such adjustments may be harmful.When any nutrient is metabolized in the body,the processes are not 100% efficient and sosome heat is produced. Unfortunately, proteinis the most inefficiently utilized nutrient in thisregard and so, proportionately more heat isevolved during its metabolism compared tothat of fat and carbohydrates. The last thing thata heat stressed bird needs is additional waste heatbeing generated in the body. This extra heat pro-duction may well overload heat dissipationmechanisms (panting, blood circulation). We are

therefore faced with a difficult problem of attempt-ing to maintain ‘protein’ intake in situations ofreduced feed intake, when crude protein per semay be detrimental. The answer to the problemis not to increase crude protein, but rather to increasethe levels of essential amino acids. By feeding syn-thetic amino acids, we can therefore maintain theintake of these essential nutrients without theneed to catabolize excess crude protein (nitrogen).General recommendations are, therefore, toincrease the use of synthetic methionine andlysine and perhaps threonine to maintain dailyintakes of approximately 420, 820 and 660 mgrespectively for birds around peak egg production.

d) Minerals and vitamins – Calcium level should be adjusted according

to the anticipated reduction in feed intake, so thatbirds consume at least 4.2 g per day. Underextreme conditions, this may be difficult since,

Table 4.15 Cooling effect of air movement (wind chill) and expectedincrease in feed intake of layers maintained at 30ºC

Air movement Cooling effect Expected increase in (meters/second) (̊ C) feed intake (g/b/d)

0.5 1 Up to 1 g0.75 2 1 – 2 g1.0 3 2 - 3 g1.25 4 3 - 4 g1.50 5 4 – 5 g1.75 6 5 – 6 g

Table 4.16 Leghorn pullet size and energy intake

Body Weight (g) Daily energy consumption 18 wk 24 wk 18-25 wks (kcal)

1100 1400 2471200 1500 2541300 1600 2631400 1700 273



as previously indicated, high energy diets are alsodesirable and these are difficult to achieve withthe increased use of limestone or oyster shell. Table4.17 shows the diet specifications needed to main-tain intakes of Ca, P, and vitamin D3, all ofwhich are critical for eggshell quality.

Table 4.17 Diet nutrient levelsneeded to maintain constant intakeof these nutrients at varying levelsof feed intake

Feed intake Av P Ca Vit. D3(g/d) (%) (%) (IU/kg)

80 0.52 5.3 412590 0.47 4.7 3660100 0.42 4.2 3300110 0.38 3.8 3000

Because it is also necessary to increase theenergy level of the diet when feed intake islow, then it is counterproductive to add high lev-els of limestone and phosphates, which effectivelydilute the feed of all nutrients other than Ca andphosphorus. The problem of potential calciumdeficiency is most often met by top dressing feedwith oystershell or large particle limestone. Thedeficit of vitamin D3 is best met with use of D3supplements in the drinking water rather than for-mulation of a new premix.

There seems to be some benefit to adding sodi-um bicarbonate to the diet or drinking water.However, this must be done with care so as notto impose too high a load of sodium on the bird,and so salt levels may have to be altered. Thisshould be done with great caution, taking intoaccount sodium intake from the drinking water,which can be quite high during heat stress con-ditions. In most situations, there will be nonegative effects from replacing 30% of supple-mental salt with sodium bicarbonate on a kg forkg basis. There is also an indication of benefi-

cial effects of increasing the potassium levels inthe diet, although again, this must be accomplishedonly after careful calculation, since higher lev-els can be detrimental to electrolyte balance. Whilefew reports indicate any improvement in addingsupplemental B vitamins during heat stress,there are variable reports of the beneficial effectswith the fat soluble vitamins. Although notalways conclusive, increasing the levels of vita-mins A, D3 and E have all been shown to be advan-tageous under certain conditions. While vitaminC (ascorbic acid) is not usually considered in poul-try diets, there is evidence to support its useduring hot weather conditions. Under most cir-cumstances, birds are able to synthesize their needsof vitamin C but under heat stress, such productionmay be inadequate and/or impaired. Adding upto 250 mg vitamin C/kg diet has proven benefi-cial for layers in terms of maintaining productionwhen temperatures exceed 28ºC.

e) Electrolyte balance – As environmental temperature increases,

birds increase their respiration rate in an attemptto increase evaporative cooling. As birds pant,they tend to lose proportionally more CO2 andso changes in acid-base balance can quickly devel-op. With mild to severe alkalosis, blood pH maychange from 7.2 through 7.5 to 7.7 in extremesituations. This change in blood pH, together withloss of bicarbonate ions can influence eggshellquality and general bird health and metabolism.Under such heat stress conditions, it is the avail-ability of bicarbonate per se which seems to bethe major factor influencing eggshell synthesisand in turn, this is governed by acid-base bal-ance, kidney function and respiration rate.

Shell formation normally induces a renalacidosis related to the resorption of filteredbicarbonate. At the same time, shell secretioninduces a metabolic acidosis because the formation



of insoluble CaCO3 from HCO3 and Ca2+ involvesthe liberation of H- ions. Such H- release wouldinduce very acidic and physiologically destructiveconditions, and be necessarily balanced by the bicar-bonate buffer system in the fluid of the uterus. Whilea mild metabolic acidosis is therefore normalduring shell synthesis, a more severe situationleads to reduced shell production because ofintense competition for HCO3 as a buffer ratherthan for shell formation. A severe metabolic aci-dosis can be induced by feeding products such asNH4Cl, and this results in reduced shell strength.In this scenario, it is likely that NH4 rather than Cl-

is problematic because formation of urea in the liver(from NH4) needs to be buffered with HCO3ions, creating added competition for shell formation.Conversely, feeding sodium bicarbonate, especiallywhen Cl- levels are minimized, may well improveshell thickness. Under commercial conditions, theneed to produce base excess in order to buffer anydiet electrolytes must be avoided. Likewise it isimportant that birds not be subjected to severe res-piratory excess, as occurs at high temperatures,because this lowers blood bicarbonate levels andin extreme cases, causes a metabolic acidosis. Underpractical conditions, replacement of part (30-35%) of the supplemental dietary NaCl withNaHCO3 may be beneficial for shell production.

Acclimatization to heat stress is a con-founding factor because short-term (1-2 d) acuteconditions are more problematic to the bird. Forexample, pullets grown to 31 weeks under con-stant 35 vs 21ºC conditions exhibit little differ-ence in pattern of electrolytes. If birds areallowed to acclimatize to high environmental tem-peratures there is little correlation between plas-ma electrolytes and shell quality. Temporary acuteheat stress and cyclic temperature conditions areundoubtedly the most stressful to the bird.

Severe electrolyte imbalance can be preventedby considering the ratio of cation:anion in dietformulations. However, it must be accepted thatthe diet is only one factor influencing potentialimbalance, and so, general bird management andwelfare also become of prime importance.Electrolyte balance is usually a consideration ofNa+K-Cl in the diet, and under most dietary sit-uations, this seems a reasonable simplification.Electrolyte balance is usually expressed in termsof mEq of the various electrolytes, and for an indi-vidual electrolyte this is calculated as Mwt ÷ 1,000.This unit is used on the basis that most miner-als are present at a relatively low level in feeds.As an example calculation, the mEq for a diet con-taining 0.17% Na, 0.80% K and 0.22% Cl canbe calculated as follows:

Sodium Mwt = 23.0, Eq = 23g/kg, mEq = 23mg/kgDiet contains 0.17% Na = 1,700 mg/kg = 1700/23 mEq = 73.9 mEq

Potassium Mwt = 39.1, Eq = 39.1g/kg, mEq = 39.1mg/kgDiet contains 0.80% K = 8,000 mg/kg = 8,000 /39.1 mEq = 204.6 mEq

Chloride Mwt = 35.5, Eq = 35.5g/kg, mEq = 35.5mg/kgDiet contains 0.22% Cl = 2,200 mg/kg, = 2,200/35.5 mEq = 62.0 mEq

overall diet balance becomes Na + K – Cl = 73.9 + 204.6 – 62.0 = 216.5 mEq.



A balance of around 250 mEq/kg is usual, andso for this diet, there needs to be either anincrease in Na or K level of the diet, or adecrease in Cl level.

Under practical conditions, electrolyte bal-ance seems to be more problematic when chlo-ride levels are high. On the other hand, use ofNaHCO3 to replace NaCl, as is sometimes rec-ommended during heat stress, can lead to adeficiency of chloride. Changes in diet electrolytebalance most commonly occur when there is amajor change in ingredient usage and espe-cially when animal protein sources replace soy-bean meal and vice versa. Table 4.18 outlineselectrolyte balance of some major feed ingredients.

Within the cereals, Na+K-Cl for milo is low,while wheat is high relative to corn. Major dif-ferences occur in the protein-rich ingredients, andrelative to soy, all sources are low in electrolytebalance. As shown in Table 4.18, this situationdevelops due to the very high potassium contentof soybean meal. Careful consideration to elec-trolyte balance must therefore be given whenchanges are made in protein sources used in for-mulation. For example, the overall balance fora diet containing 60% milo and 25% soy is210 mEq/kg, while for a diet containing 75% milo

and 10% fish meal, the balance is only 75mEq/kg. The milo-fish diet would need to be sup-plemented with NaHCO3.

Assuming that heat stress cannot be temperedby normal management techniques, then elec-trolyte manipulation of the diet may be benefi-cial. However, the technique should be differ-ent for immature birds compared to egg layers.With layers, there is a need to maintain thebicarbonate buffer system as it influences eggshellquality. As such, diet or water treatment with sodi-um bicarbonate may be beneficial, again empha-sizing the necessity to meet minimum chloriderequirements. On the other hand, treatment ofrespiratory alkalosis in layers with acidifierssuch as NH4Cl, while relieving respiratory dis-tress, may well result in reduced shell quality. Forimmature pullets, treatment with electrolytesis often beneficial and there is less need forcaution related to bicarbonate buffering. Up to0.3% dietary NH4Cl may improve the growth rateof heat stressed birds, although it is not clear ifany effect is via electrolyte balance/blood pH orsimply via the indirect effect of stimulatingwater intake. Under commercial conditions,adding salt to the drinking water of young birdshas been reported to alleviate bird distress andto stimulate growth.

Table 4.18 Electrolyte content of feed ingredients

INGREDIENT Na K Cl Na+K-Cl (mEq)Corn 0.05 0.38 0.04 108Wheat 0.09 0.52 0.08 150Milo 0.04 0.34 0.08 82Soybean meal 0.05 2.61 0.05 675Canola meal 0.09 1.47 0.05 400Meat meal 0.55 1.23 0.90 300Fish meal 0.47 0.72 0.55 230Cottonseed meal 0.05 1.20 0.03 320



f) Water –A nutritional factor often overlooked during

heat stress is the metabolism of water. It is wellknown that birds in hot environments drinkmore water, yet this has not been capitalized uponto any degree. Table 4.19 shows the water bal-ance of layers held at 22˚C or 35˚C.

Table 4.19 Water balance of layersat 22ºC or 35ºC (ml/bird/day)

22˚C 35˚CWater intake 210 350Manure water 85 150Egg water 50 50Respiration water 75 150

Layers will drink at least 50% more water at35 vs. 22˚C. If such adaptation is not seen, thenit likely relates to birds not being able to consumesufficient quantities of water at times of peak need.Figure 4.8 shows the daily pattern of waterintake of layers when lights are on from 6:30 a.m.to 6:30 p.m. There is a doubling of water intakein the last 3 hours of the day, compared to all pre-vious times, and so the water system must be ableto accommodate this demand, especially inhot weather conditions.

Since water intake is often increased attimes when feed intake is decreased, it would belogical to try and provide limiting nutrients in thewater. However, this concept has met with

only limited success, possibly related to changein ‘taste’ of the water and/or the nutrients stim-ulating bacterial growth in the water lines.However there are always positive results seenwhen the drinking water is cooled. Feed intakecan be stimulated as much as 10% by coolingthe water 5 to 8˚C when environmental tem-perature is around 30 – 32˚C. Although this man-agement practice is relatively easy to achieve underexperimental conditions, it is a much morecomplex engineering problem with large com-mercial flocks.

g) Effect of physical diet change –Discussion to date has centered on the

potential of diet manipulation to alleviate heatstress. However, diet change per se may be detri-mental under certain conditions. It seems thatwhen the bird is confronted with an acute heatstress situation, diet change may impose anoth-er stress, which merely accentuates any meta-bolic imbalance. For example, it was recentlyreported that a diet change brought about byadding fat caused an immediate rise in body tem-perature for up to 4 d which can be disastrousto the bird and cause death. At the same time,the diet change had the desirable effect of stim-ulating energy intake. For this reason, it is sug-gested that under extreme heat stress condi-tions of 36 – 40˚C, that no diet change beimplemented, since it could lead to death fromheat prostration.

Fig. 4.8 Daily pattern of relative water intake. Lights on @ 6:30am for 12 hrs/d



@ 21 wks of age @ 33 wks of ageEgg Feed Shell Egg Feed Shell

Diet type prod. intake deformation prod. intake deformation(%) (g) (µm) (%) (g) (µm)

Pre-test7 d (18ºC) Control 82 86 21 92 101 24Stress Control 92 64a 22b 71 50a 35b

3 d (35ºC) High CP 90 36c 24a 56 20b 41ab

High Energy 94 40c 23ab 60 27b 46a

High Density 96 53b 24a 67 28b 37b

Post- Control 84a 76a 26c 77a 84a 30b

stress 4 d High CP 39c 24b 35ab 45b 61bc 41a

(18ºC) High Energy 56b 33b 41a 64a 57c 42a

High Density 69ab 76a 31bc 67a 73ab 29b

a-c means followed by different letters are significantly different

Table 4.20 Effect of diet change on layer performance during heat stress

Under these conditions, it would be usefulto be able to prejudge the rise in environmen-tal temperature and make the diet change ear-lier, when the bird is under ‘moderately’ stress-ful conditions (28 – 35˚C). However, even withshort-term heat stress situations, it may be inad-visable to change the diet (Table 4.20).

In these studies, birds were fed a control rationfor 7 d at an environmental temperature of18˚C. A heat stress of 35˚C was suddenlyimposed, and birds offered the same control diet,or diets high in energy, protein or all nutrients(termed high density). Feed intake was depressedalmost immediately in response to heat stress,although changes in egg production and shell qual-ity were not seen until after the 3 d stress peri-od. However, during this post-stress period, birdsshowed a dramatic loss in egg numbers and shellquality. There was no instance of diet change alle-viating the effects of heat stress, and in most sit-uations, production deteriorated. Under such con-ditions of short-term heat stress, it is suggested

that sudden diet change merely imposed anadditional stress and was not beneficial to the bird.

h) Summary of nutritional management during heat

1. Never place underweight pullets in the laying house.They will always remain small with low feedintake and have little body fat reserve to sustainenergy balance through the period of peak eggmass production.

2. Increase the energy level of the diet with a min-imum of 2850 kcal ME/kg, ideally by incorporationof fats or oils. Limit the level of crude fiber.

3. Reduce crude protein (17% CP maximum) whilemaintaining daily intakes of methionine (420mg), lysine (820 mg) and threonine (660 mg).

4. Increase mineral-vitamin premix in accordance withanticipated change in feed intake. Maintaindaily intakes of calcium (4.2 g) and available phos-phorus (400 mg).


SECTION 4.4Phase Feeding

5. Where shell quality is a problem, considerthe incorporation of sodium bicarbonate. Atthis time, monitor total sodium intake, andensure adequate chloride levels in the diet.

6. Use supplemental vitamin C at 250 mg /kg.

7. Increase the number of feedings per day and try to feed at cooler times of the day.

4.4 Phase Feeding

P hase feeding refers essentially to reduc-tions in the protein and amino acid levelof the diet as the bird progresses through

a laying cycle. The concept of phase feeding isbased on the fact that as birds get older, their feedintake increases, while egg mass output decreas-

Fig. 4.9 Bird age: egg production, egg weight and egg mass.

8. Keep drinking water as cool as possible.

9. Use crumbled feed or large particle mash feedif available.

10. Do not make any diet change when suddenshort-term (3 – 5 d) heat stress occurs.

es. For this reason, it should be economical toreduce the nutrient concentration of the diet. Atthis time, it is pertinent to consider a conventionalegg production curve of a layer, and superimposeboth egg weight and daily egg mass output(Figure 4.9).


SECTION 4.4Phase Feeding

If nutrient density is to be reduced, this shouldnot occur immediately after peak egg numbers,but rather after peak egg mass has been achieved.The two reasons for reducing the level of dietaryprotein and amino acids during the latter stagesof egg production are first, to reduce feed costsand second, to reduce egg size. The advantagesof the first point are readily apparent if protein costsare high, but the advantages of the second pointare not so easily defined and will vary depend-ing upon the egg pricing. When a producer is beingpaid a premium for extra large and jumbo eggs,there is no advantage to using a phase feeding pro-gram unless eggshell quality is a problem.

It is difficult to give specific recommendationsregarding any decrease in dietary protein oramino acid level that can be made to temper eggsize without also decreasing the level of production.The appropriate reduction in protein level willdepend on the season of the year (effect of tem-perature on feed consumption, age and productionof the bird, and energy level of the diet). Hence,it is necessary that every flock be considered onan individual basis before a decision is made toreduce the level of dietary protein. As a guide,it is recommended that protein intake be reducedfrom 19 to 18 g/day after the birds have droppedto 90% production, and to 15-16 g/day after theyhave dropped to 80% production. With an

average feed intake of 95 g/day, this would beequivalent to diets containing 20, 19 and 16%protein. It must be stressed that these values shouldbe used only as a guide, and after all other fac-tors have been properly considered. If a reduc-tion in the level of protein is made and eggproduction drops, then the decrease in nutrientintake has been too severe and it should beimmediately increased. If, on the other hand, pro-duction is held constant and egg size is notreduced, then the decrease in protein or aminoacid intake has not been severe enough and itcan be reduced still further. The amino acid tobe considered in this exercise is methionine, sincethis is the amino acid that has the greatest effecton egg size. As for the situation with protein, toolarge a single step reduction in methionine willlikely lead to loss in egg production and possi-bly an increase in feed intake. A one-timereduction in diet methionine of 20% has beenreported to reduce egg size by 3% with con-commitant loss in egg production of 8%.

Phase feeding of phosphorus has also been rec-ommended as a method of halting the decline inshell quality invariably seen with older birds.Using this technique, available phosphorus lev-els may be reduced from approximately 0.42 –0.46% at peak production to slightly less than 0.3%at end of lay. Table 4.21 shows an example of

Table 4.21 Phase feeding of major nutrients after peak egg mass, assumingconstant daily feed intake at 100 g

Bird characteristics Diet levels (%)Age (wks) Egg production Crude Methionine Calcium Av.

(%) protein phosphorus<35 93 19.0 0.41 4.2 0.4445 90 18.0 0.38 4.3 0.4155 85 17.0 0.36 4.4 0.3670 80 16.0 0.34 4.5 0.32


SECTION 4.5Formulation changes and feed textures

phase feeding of protein, methionine and phos-phorus, related to controlling egg size, opti-mizing shell quality and minimizing feed costs.

A major criticism of phase feeding is that birdsdo not actually lay ‘percentages’ of an egg. Forexample, if a flock of birds is producing at 85%production does this mean that 100% of the flockis laying at 85% or is 85% of the flock laying at100% production. If a bird lays an egg on a spe-cific day, it can be argued that its production is100% for that day, and so its nutrient requirementsare the same regardless of the age of bird.Alternatively, it can be argued that many of thenutrients in an egg, and especially the yolk,accumulate over a number of days, and so this

concept of 100% production, regardless of age,is misleading.

Advocates of phase feeding indicate thatbirds can be successfully managed by reducingprotein/amino acid contents of the diet – otherssuggest that nutrient specifications are too highto start with initially, and that phase feedingmerely accomplishes normalization of diet in rela-tion to requirement. The bottom line is that envi-ronmental and management conditions varyfrom flock to flock, and certainly from season toseason within a flock. For this reason, the basisof phase feeding must be an accurate assessmentof the nutrient intake relative to requirement forproduction, growth and maintenance.

W ith diets formulated to least costingredient input, it is often necessaryto change ingredient concentrations,

and depending upon economic circumstances,the computer invariably ‘asks’ for major changesat certain times. In these situations, nutritionistsare often reluctant to make major ingredient sub-stitutions in consecutive diets, on the basis thatsuch change may adversely affect feed intake andhence product. In a recent study, birds were feda range of diets over a 12-month cycle, with thesituation of least cost where major changes in ingre-dient use occurred in most months. Control birdswere fed least cost formulated diets, although inthis situation major ingredient changes frommonth to month were not allowed, rather thesechanges occurred more gradually as occurscommercially. Birds responded reasonably to thesechanges and no major adverse effects wereseen. However, a slight improvement in egg pro-duction and egg size with a conventional leastcost system, where diet changes were temperedto prevent drastic swings in diet composition, some-

what negated the savings in feed costs seenwith absolute least cost. The economic situationin terms of egg return minus feed cost was in favorof conventional least cost, mainly due to a dou-bling of the mortality rate with the major swingsin diet composition. It seems that while theabsolute least cost diets are initially attractive inreducing feed cost, they offer little overall eco-nomic advantage and generally pose an additionaleconomic risk.

The texture of diets for laying hens is perhapssubject to more variability than for any other classof poultry. In some countries, very fine mash-es are used, whereas crumbles are used in otherareas. There is little doubt that any type of feedtexture can be made to work physically, althoughbird response is not always the same. Ourresearch data suggests that regardless of nutrientprofile, layers prefer large particles of feed.When layers were offered a crumbled diet, theyshow a marked preference for the largest size par-ticles available. Smaller particles of feed only

4.5 Formulation changes and feed texture


SECTION 4.6Nutrition and shell quality

start to disappear later within a 24 h period, whenall the large particles have been eaten. In thisstudy, there was no disappearance of very fineparticles <0.6 mm, although this result may beconfounded with the break down of large parti-cles. Feed intake increased when birds were sud-denly presented with feed of small particle size,and intake temporarily declined when birdswere offered only large size particles. A criticismof mash diets is that they tend to separate out whenused in long runs of feed trough, and especial-ly where continous chain feeders are used. Froma survey of commercial flocks in Ontario, we foundcomparable physical separation of feed withboth mash and crumbles (Table 4.22).

In this study, feed samples were taken direct-ly from the feed tank and then at points pro-gressively further from the initial point of distributionwithin the feed trough. Particle and nutrient sep-aration were seen at all farms (Table 4.22).With crumbled feed, particle size was dramat-ically reduced as feed traveled along the trough,although this was not associated with any majorchange in nutrient profile. Higher calcium lev-els per se in the trough, rather than the tank, relatesto feed samples in the trough including all feedin front of the bird that included fine particlesbeneath the feeder chain. Particle separation wasalso seen with the mash feeds, although this wasonly during the first 18 m run of the feed trough.

Table 4.22 Particle segregation and calcium analysis of feed collected fromfarms using either mash or crumbles (%)

Type of feed Particle At feed Distance along feed trough (m)size (mm) tank

+18 +36 +72 +108Crumbles >2.36 46.0 29.8 25.3 20.6 16.0

>1.18 28.8 26.5 25.5 24.7 23.7>0.85 6.9 9.4 10.1 10.9 11.1>0.71 3.4 5.5 6.1 6.7 7.1>0.60 3.2 5.6 6.2 6.7 7.1<0.60 11.7 23.2 26.8 30.3 33.8

%Calcium 3.5 4.3 4.5 4.7 4.5Mash >2.36 17.3 10.0 8.3 8.5 10.5

>1.18 22.7 21.1 20.0 19.6 21.0>0.85 11.9 13.4 13.2 14.5 15.1>0.71 7.2 8.9 9.0 9.2 9.0>0.60 7.4 8.6 9.0 9.3 8.2<0.60 33.5 38.0 40.5 38.9 36.2

%Calcium 4.0 4.9 5.3 5.6 5.0

4.6 Nutrition and shell quality

N utrition can have a major impact oneggshell quality, and is often the firstparameter considered when problems

arise. After peak egg production, the layer pro-

duces a fairly consistent quantity of shell mate-rial for each egg, regardless of its size. As the egggets larger, therefore, the shell necessarily getsthinner, and this becomes more prone to breakage.



Even with ideal conditions,4–5% of eggs leavingthe farm will be graded as ‘cracks’, and togetherwith cracked and broken eggs on-farm, means that7–8% of eggshells break for various reasons.The composition of the shell is very consistent sincethe major constituent is calcium carbonate.When considering eggshell quality, the nutri-tional factors most often investigated are dietlevels of calcium, phosphorus, and vitamin D3.Since larger eggs have thinner shells, then levelsof protein, methionine, and TSAA may also comeunder scrutiny.

A shell contains around 2 g of calcium theorigin of which is the feed, with a portion of thiscycling through the medullary bone. The mostactive period for shell formation usually coincideswith the dark phase of the photoperiod, and sobirds are not eating at this time (Figure 4.10). Inthe first 6 hours of the 24 h ovulatory cycle, thereis virtually no shell deposition. This is the time

of albumen and shell membrane secretion, andthe time of redeposition of medullary bone.From 6 – 12 hr about 400 mg calcium aredeposited, while the most active period is the 12– 18 hr period when around 800 mg shell cal-cium accumulates. This is followed by a slow-er deposition of about 500 mg in the last 6 hr,for a total of around 1.7 g shell calcium, depend-ing upon egg size.

During the evening, when shell calcificationis greatest, a portion of the required calcium willcome from the medullary bone reserves. The totalmedullary calcium reserves are probably less than1 g. This reserve normally contributes no more than0.1 g to a shell containing 2g calcium, yet areessential for the almost daily shell formation processof the modern layer. The medullary bone is com-posed of calcium phosphate, and so the quantityof calcium liberated for shell synthesis, is asso-ciated with a similar release of phosphorus.

Fig. 4.10 Shell mineral deposition over a 24h ovulation cycle



Since there is little immediate need for thisphosphorus, it is excreted and there is need forboth calcium and phosphorus to replenish thismedullary reserve during periods between suc-cessive ovulations. Figure 4.11 shows the cal-cium and phosphorus balance of a bird ataround 35 weeks of age.

Figure 4.11 shows zero net accretion of cal-cium and phosphorus in medullary bone. It islikely that the quantity of medullary calcium andphosphorus reserves are maximum when the birdis around 30 weeks of age, and a slight negativebalance over time contributes to reduced shellquality in older birds.

There is often discussion about the physicalform and source of calcium supplied to layers.Calcium is usually supplied as limestone, oras oystershell which is much more expensive.Oystershell and large particle limestone areexpected to be less soluble than is fine particlelimestone, and so remain in the gizzard forlonger and will hopefully be there in the periodof darkness when the bird is not eating. Table 4.23

Table 4.23 Limestone types and solubility

Description Particle Relative1

size (mm) solubilityFine < 0.2 100Medium 0.2 – 0.5 85Coarse 0.6 – 1.2 70Extra coarse 1.3 – 2.0 55Large (hen size) 2.0 – 5.0 30Oystershell 2.0 – 8.0 301 Reduced solubility results in longer retention within the digestive tract

gives an example of descriptions used for lime-stone and associated relative solubility.

Twelve hours after feeding, there will likelybe twice as much calcium in the gizzard fromlarge vs. fine particle limestone. Oystershell isexpected to have solubility characteristics sim-ilar to those of large particle limestone. The largeparticles are more important for older birds andseem to help maintain the quantity and activi-ty of medullary bone. The only problem with largeparticle limestone is its abrasive characteristic withmechanical equipment.

Fig. 4.11 Schematic of daily calcium balance in a laying hen.



Using particulate limestone or oystershell doesallow the bird a degree of nutrient selection. Thepeak in calcium requirements coincides with shellcalcification, and this starts each day in thelate afternoon. If given a choice situation, lay-ers will voluntarily consume more calcium at thistime of day. In fact, a specific appetite for cal-cium is the likely reason for the late afternoonpeak in feed intake seen when layers do not havethe opportunity at nutrient/ingredient selection.

If birds do not receive adequate quantities ofcalcium there will be almost immediate loss inshell integrity. If the deficit is large, ovulation oftenceases and so there is no excessive bone resorp-tion. With marginal deficiencies of calcium, ovu-lation often continues, and so the birds relymore heavily on bone resorption. Total medullarybone calcium reserves are limited and so afterproduction of 3 – 4 eggs on a marginally calci-

um deficient diet, cortical bone may be erodedwith associated loss in locomotion. As calciumcontent of the diet decreases, there is a transient(1 – 2 d) increase in feed intake, followed by adecline associated with reduced protein and ener-gy needs for egg synthesis. Calcium deficiencyis exacerbated by high levels of dietary chloride(0.4 – 0.5%). In such dietary situations, there isgreater benefit to feeding sodium bicarbonate.If birds are fed a calcium deficient diet, eggproduction and eggshell calcium return to nor-mal in 6 to 8 days after the hens receive a dietadequate in calcium. After three weeks, the legbones will be completely recalcified. The find-ing that the adrenal gland is enlarged in calci-um deficiency indicates that this is a stress in theclassical sense.

Calcium is the nutrient most often consideredwhen shell quality problems occur,although

Fig. 4.12 Decline in shell weight for hens fed a diet devoid of Vitamin D3 supplementation.



deficiencies of vitamin D3 and phosphorus canalso result in weaker shells. Vitamin D3 isrequired for normal calcium absorption, and ifinadequate levels are fed, induced calciumdeficiency quickly occurs. Results from ourlaboratory suggest that diets devoid of synthet-ic vitamin D3 are quickly diagnosed, because thereis a dramatic loss in shell weight (Figure 4.12).

A more serious situation occurs when amarginal, rather than absolute deficiency ofvitamin D3 occurs. For example, birds fed a dietwith 500 IU D3/kg showed only an 8% declinein shell quality, yet this persisted for the entirelaying cycle and would be difficult to detect interms of cracked and reject eggs etc. A major prob-lem with such a marginal deficiency of vitaminD3 is that this nutrient is very difficult to assayin complete feeds. It is only at concentrationsnormally found in vitamin premixes, that mean-ingful assays can be carried out, and so if vita-min D3 problems are suspected, access to thevitamin premix is usually essential. In additionto uncomplicated deficiencies of vitamin D3, prob-lems can arise due to the effect of certain myco-toxins. Compounds such as zearalenone, thatare produced by Fusarium molds, have beenshown to effectively tie up vitamin D3, resultingin poor egg shell quality. Under these circum-stances dosing birds with 300 IU D3 per day, forthree consecutive days, with water soluble D3may be advantageous.

Vitamin D3 is effectively ‘activated’ byprocesses occurring first in the liver and then inthe kidney. This first activation in the liveryields 25(OH)D3 while the second product is theresult of further hydroxylation to yield1,25(OH)2D3. This latter compound is a verypotent activator of calcium metabolism, althoughis not likely to be available as a feed ingredient.The first hydroxylation product, 25(OH)D3, is how-ever, now available to the feed industry, and seems

to promote increased calcium retention in lay-ers (Table 4.24).

Table 4.24 Effect of Hy-D®25(OH)D3on daily calcium rentention

Hy-D® Calcium(µg/kg) retained (mg)

0 41010 45020 50040 53060 540

Adapted from Coelho (2001)

Minimizing phosphorus levels is also advan-tageous in maintaining shell quality, especially underheat stress conditions. Because phosphorus is avery expensive nutrient, high inclusion levelsare not usually encountered, yet limiting these with-in the range of 0.3% to 0.4%, depending upon flockconditions, seems ideal in terms of shell quality.Periodically, unaccountable reductions in shell qual-ity occur and it is possible that some of these maybe related to nutrition. As an example, vanadi-um contamination of phosphates causes anunusual shell structure, and certain weed seedssuch as those of the lathyrus species, cause majordisruptions of the shell gland.

Up to 10% reduction in eggshell thicknesshas been reported for layers fed saline drinkingwater, and a doubling in incidence of total shelldefects seen with water containing 250 mgsalt/liter. If a laying hen consumes 100 g of feedand 200 ml of water per day, then water at 250mg salt/liter provides only 50 mg salt comparedto intake from the feed of around 400 mg salt.The salt intake from saline water therefore,seems minimal in relation to total intake, but nev-ertheless, shell quality problems are reported tooccur under these conditions. It appears that saline


SECTION 4.7Controlling egg size

water results in limiting the supply of bicar-bonate ions to the shell gland, and that this is medi-ated via reduced activity of carbonic anhydraseenzyme in the mucosa of the shell gland.However, it is still unclear why saline waterhas this effect, in the presence of overwhelmingly

more salt as provided by the feed. There seemsto be no effective method of correcting this lossof shell quality in established flocks, although fornew flocks the adverse effect can be minimizedby adding 1 g vitamin C/liter drinking water.

T he main factor dictating the size of an eggis the size of yolk released from theovary and this in turn is greatly influenced

by body weight of the laying hen. The weight ofthe hen at maturity is therefore the major factorinfluencing egg size, and so it is expected thata large bird will produce more large grade eggsand vice-versa for a small bird. Assuming a givenweight of bird, then nutrition can have some influ-ence on egg size. Within a flock, birds that eatthe most feed tend to produce the largest egg. Forcommercial flocks, where eggs are priced accord-ing to specific weight classes (grade) there is theneed to maximize egg size as soon as possible.However, once 80% of eggs are falling into thelargest, most economic weight category there isoften need to temper further increases in eggweight, so as to sustain good eggshell quality. Thisearly increase in egg size and late tempering ofegg size can be influenced by nutrition to someextent. For the rapidly developing egg breakoutmarket, weight of individual eggs assumes lessimportance than overall egg mass output. Apartfrom manipulating feed intake, egg size cansometimes be manipulated by adjusting dietarylevels of energy and/or fat and/or linoleic acid,or by adjustment to levels of protein and/ormethionine and/or TSSA. Assuming that diet nutri-ents are tied to energy level, and that the bird canmaintain its energy intake, then energy per se has

little effect on egg size. The effects of protein andenergy on egg size are shown in Figure 4.13 whichdepicts the bird’s response to a range of nutrientintakes. Unlike the situation with egg produc-tion (Figure 4.1) there is an obvious relationshipbetween increased egg size and increased pro-tein intake. At low protein intakes (less than 14– 15 g/d) there is an indication of reduced eggsize when energy intake is increased.

The response in egg weight to diet protein ismost likely related to intakes of methionine orTSAA (Table 4.25). Roland et al. (1988) showeda consistent linear trend for increase in eggweight of young birds as the level of TSAA wasincreased from 0.65 to 0.81%. Analysis of thisdata indicates that egg size of young layersincreases by 0.7 g for each 0.05% increase in dietTSAA. Table 4.26 shows a summary of 6 exper-iments reported by Waldroup et al. where arange of methionine levels were tested, at 0.2%cystine, for various ages of bird. As methioninelevel of the diet is increased, there is an almostlinear increase in egg size.

As the bird progresses through a productioncycle, the egg weight response to methioninechanges slightly. In the first period, between 25– 32 weeks, using 0.38 vs. 0.23% methionineresults in a 5.6% increase in egg size (Table 4.26).

4.7 Controlling egg size



Comparable calculations for the other age peri-ods show 7.3% improvement from 38 – 44weeks, and 6.7% and 6.0% at 51 – 58 and 64– 71 weeks respectively. The egg weight responseto methionine therefore, closely follows the nor-mal daily egg mass output of the laying hen.

Dietary levels of methionine or TSAA’s are mosteasily adjusted by use of synthetic methionine.There has recently been a resurgence in discussionregarding the efficacy of DL-methionine vs.methionine hydroxy analogue, and in particu-lar Alimet®, as they influence layer perform-ance and in particular egg weight. When unbi-ased studies are conducted, and the levels ofmethionine are comparable to industry standards,then DL-methionine is comparable to Alimet®

on an equimolar basis. In terms of egg weight,Harms and Russell (1994) show similar respons-es to the two products (Table 4.27).

There has been a suggestion that L-methio-nine may, in fact, be superior to any othersource. This product is not usually produced com-mercially, because routine manufacture ofmethionine produces a mixture of D- and L-methio-nine. This is the only amino acid where there isapparently 100% efficacy of the D-isomer.However, most research data indiates no differencein potency of L- vs DL-methionine sources.

Methionine acts as a methyl donor, and so theefficacy of methionine vs. choline is often discussed.While choline can spare some methionine in adiet, it is obvious that there are severe limitationsto this process, and this becomes most obviouswhen egg size, rather than simply egg production,is a major consideration. Data from Parsonsand Leeper (Table 4.28) clearly shows the advan-tage of using methionine over choline in termsof egg size, and that this effect becomes most crit-ical as diet crude protein level is reduced.

Fig. 4.13 Egg weight (18-66 weeks) in response to daily intakes of energy and protein.



Table 4.25 Effect of TSAA on egg weight from young laying hens (g)

Table 4.26 Effect of methionine on egg weight – mean of 6 experiments

Table 4.27 Effect of methionine source on layer performance 1

Bird age Total sulphur amino acids (%)(wks) 0.65 0.69 0.72 0.76 0.81

25 49.3 49.1 50.2 50.2 51.629 53.8 53.5 53.9 54.4 54.733 55.3 55.1 56.0 56.0 56.3

Adapted from Roland et al. (1998)

Bird age (wks) % Diet methionine with 0.2% cystine0.23 0.26 0.29 0.32 0.35 0.38

25 - 32 49.8 51.0 51.9 52.1 52.0 52.638 – 44 53.2 55.0 56.4 56.3 56.3 57.151 - 58 56.2 57.9 59.6 59.2 59.2 60.064 - 71 56.8 59.4 59.5 59.5 59.5 60.2

Adapted from Waldroup et al. (1995)

Diet methionine (%) Egg weight (g)Exp #1 Exp #2

DL Alimet® DL Alimet®0.228 (basal) 54.5 54.5 51.5 51.50.256 56.2 55.3 53.2 52.70.254 56.8 56.8 55.1 56.20.311 57.6 57.2 55.9 55.70.366 - 378 58.0 57.5 57.0 56.8

1Mean 80% egg production Harms and Russell (1994)

Table 4.28 Egg size with methionine vs. choline (23 – 35 wks)

Diet Supplement Egg production Egg weight protein (%) (g)

None 82.8 53.216% 0.1% methionine 84.0 56.6

0.1% choline 82.4 54.0None 72.8 52.5

14% 0.1% methionine 84.5 54.90.1% choline 78.9 51.9

Adapted from Parsons and Leeper (1984)



Bird age Linoleic acid (% of diet)(wks) 0.79 1.03 2.23 2.73

20 – 24 60.5 61.3 61.4 61.425 – 28 60.8 61.7 62.0 62.029 – 32 62.8 63.7 63.1 63.4

Adapted from Grobas et al. (1999)

Table 4.29 Effect of linoleic acid on egg weight (g)

Table 4.30 Effect of reducing dietary protein level on egg size of 60wk-oldlayers (Av. for 2, 28-day periods)

Dietary Egg Av. feed Egg wt. (g) Daily egg Av. protein protein level production intake per mass (g) intake per

(%) (%) day (g) day (g)17 78.8 114 64.8 51.0 19.415 77.5 109 64.3 49.7 16.413 78.3 107 62.2 49.1 13.911 72.7 108 61.7 45.1 11.99 54.3 99 58.2 36.1 8.9

All diets 2800 kcal ME/kg

The other nutrient most often consideredwhen attempting to maximize early egg size islinoleic acid. In most situations, 1% dietary linole-ic acid meets the bird’s needs, although formaximizing egg size, levels as high as 2% are oftenused. It is difficult to separate the effect oflinoleic acid versus that of energy, since sup-plemental fat is usually used in such studies.Assuming that the bird is consuming adequateamounts of energy, then the response to extradietary linoleic acid is minimal (Table 4.29). Inthis study there was no increase in egg sizewith levels of linoleic acid greater than 1%,which is the quantity normally found in a cornbased diet.

As layers get older, then depending on strainof bird, it is often economical to try and tempersubsequent increases in egg size, in order to helpmaintain shell quality. It seems more difficult totemper egg size than to increase egg size. For

older birds, body weight is still the major factorinfluencing egg size, and so it is difficult tocontrol egg size if birds are overweight. Reducingthe level of linoleic acid has no effect on egg size,and so the only options are for reducing crudeprotein and/or methionine levels in the diet.Our studies indicate that protein levels around13% and less are necessary to bring about a mean-ingful reduction in egg size (Table 4.30). However,with protein levels much less than this, loss inegg numbers often occurs.

Methionine levels can also be adjusted in anattempt to control late cycle egg size. Results ofPeterson show some control of egg size withreduced methionine levels (Table 4.31). However,these results are often difficult to achieve undercommercial conditions because reduction indiet methionine levels often leads to loss inegg numbers and body weight. Phase feedingof amino acids must therefore be monitored



very closely, since the bird is very sensitive to ‘defi-ciencies’ of methionine. Uzu et al., (1993)using brown egg birds show the sensitivity ofchanges in feed intake (Figure 4.14) when birdswere alternated monthly between adequate(0.33% methionine; 0.6% TSAA) and deficientdiets (0.23% methionine; 0.5% TSAA). Layerswere very sensitive to levels of methionineand increased their feed intake apparently in anattempt to maintain methionine intake. Interestinglythis same precise pattern of feed intake wasseen when diets were changed weekly. Thesedata confirm that it is important not to reduce

methionine levels too much or too quickly,since any economic saving can be offset byincrease in feed intake. Waldroup et al. (1995)suggest that for older birds the methionine andTSAA requirements of layers are greater for eggnumbers than for optimizing egg weight (Table4.32). These data reinforce the concept that phasefeeding of methionine to control egg size mayhave a detrimental effect on egg numbers.During peak egg mass output (38 – 45 weeks) themethionine requirement for egg size is greaterthan for egg numbers, while the latter require-ment peaks at 51- 58 weeks of age.

Table 4.31 Methionine and late cycle egg size (g)

Daily methionine Exp. 1 Exp. 2 Exp. 3intake (mg/d) (38-62 wk) (38 – 70 wk) (78 – 102 wk)

300 60.1a 63.7a 66.3a

285 60.3a 63.1b 65.5b

270 59.1ab 62.0c 64.0c

255 58.5b 62.0c 63.9c

Average egg prod (%) 86 80 75

Adapted from Peterson et al. (1983)

Fig. 4.14 Feed intake of brownegg layers hens fed adequate on deficient levels of methionine. (g/b/d)

Adapted from Uzu et al. (1993)


SECTION 4.8Diet and egg composition

This data suggests that we should be very care-ful in reducing methionine levels much before60 weeks of age.

As stated at the outset of this section, maturebody weight is the main determinant of egg size,and this applies particularly to late-cycle per-

4.8 Diet and egg composition

formance. The best way to control late cycle eggsize is through manipulation of body weight at timeof initial light stimulation. Larger birds at matu-rity will produce much larger late cycle eggs andvice versa. There is an obvious balance necessarybetween trying to reduce late cycle egg size with-out unduly reducing egg size in young birds.

Table 4.32 Estimated methionine and methionine + cystine requirements(mg/day) for egg number, weight and mass.

Table 4.33 Egg components and major nutrients (60 g egg)

Bird age (wks) Egg # Egg weight Egg massMethionine 25 – 32 364b 356b 369b

38 – 45 362b 380a 373b

51- 58 384a 364a 402a

64 - 71 374ab 357b 378b

Methionine + 25 – 32 608b 610ab 617b

Cystine 38 – 45 619b 636a 627b

51 – 58 680a 621ab 691a

64 - 71 690a 601b 676a

Adapted from Waldroup et al. (1995)

Yolk Albumen Shell

Wet weight (g) 19.0 35.0 6.0

Dry weight (g) 10.0 4.2 5.9

Protein1 (%) 17.0 11.0 3.0(g) 3.2 3.9 0.2

Fat (%) 32.0 - -(g) 6.0 - -

Carbohydrate (%) 1.0 1.0 -(g) 0.2 0.4 -

Minerals (%) 1.0 0.6 95.0(g) 0.2 0.2 5.7

1 As is basis

T ables 4.33 – 4.35 show egg compositionand nutrient content together with an

indication of the contribution of these nutri-ents to human nutrition.



Table 4.34 Vitamin and mineral composition of contents from a 60 g egg

VitaminsA (I.U.) 300D3 (I.U.) 30E (I.U.) 2K (mg) .02B1 (mg) .06B2 (mg) .18B6 (mg) .20B12 (mg) .001

Pantothenic acid (mg) 1.2Folacin (mg) .008Niacin (mg) .06Choline (mg) 350Biotin (mg) .01

Minerals (mg)Calcium 30

Phosphorus 130Sodium 75Chloride 100

Potassium 80Magnesium 7Manganese 2

Iron 1Copper 2Zinc 1

Iodine .02Selenium .01



Table 4.35 Contribution of eggs toHuman DRI for selected nutrients

NutrientTwo eggs supply the

following of an adult’sdaily requirement (%)

Protein 20Energy 8Calcium 10Phosphorus 20Iron 20Vitamin A 25Vitamin D3 20Thiamin 10Riboflavin 30Niacin 15

i) Yolk color - In most markets it is important tocontrol and maintain the color of the yolk. Theyellow/orange color of the yolk is controlled by

the bird’s intake of xanthophyll pigments and inparticular lutein, zeaxanthin and various syntheticpigments such as canthaxanthin and apoc-arotenoic esters. As the level of dietary xanthophyllsincreases, there is increase in yolk color asassessed on the Roche Scale of 1 to 15. Figure4.15 shows the general relationship between xan-thophyll content of the feed and egg yolk on theRoche Color Score.

The desired yolk color will vary in differentmarkets, although a color score of 8 – 9 is com-mon in many areas. A high degree of pigmen-tation is a score of 11 – 12 while for some spe-cialty pasta markets, there may be need toachieve 14 – 15. The common feed ingredientshigh in xanthophylls, are corn and corn glutenmeal as well as dehydrated alfalfa. Table 4.36shows the expected color score contributed bythe various levels of each of these ingredients.

Fig. 4.15 Roche color scale and dietary xanthophylls



Table 4.36 Ingredients and yolkcolor

Ingredient Inclusion Yolk color level (%) (Roche scale)

0 220 6

Corn 40 860 9

Corn 2 6gluten 6 9meal 8 14

2 4Alfalfa 6 7meal 8 9

Carotenes themselves have little pigment-ing value for poultry, although the various hydrox-ylated carotenes are excellent pigments and thebird preferentially stores these in yolk, body fat,and its shanks. The red/orange colors can be pro-duced by adding synthetics such as canthaxan-thin, although usually this degree of coloring isunacceptable to most consumers. These pigmentscan be used in limited quantities as long as thediet has a base level of xanthophylls – otherwisethe yolk color tends towards an objectionable red,rather than acceptable orange color. These redpigments also produce undesirable color in noo-dles made from egg yolk, and so care must be takenin selection of pigmenting agents in eggs destinedfor industrial uses. In most markets, it is commonto add 7 – 8 g of supplemental xanthophylls pertonne of feed. Levels below 5 g/tonne usually resultin too pale a yolk.

There are a number of dietary and man-agement factors which can reduce the effectivedeposition of xanthophylls in the yolk. Ingredientswhich are potential oxidizing agents, such as min-erals and certain fatty acids, have been shown

to reduce pigmentation. High levels of vitaminA, as sometimes used during water medicationfor various stress situations, have been shown tocause temporary loss in yolk pigmentation.High environmental temperature, coccidiosis andaflatoxin contamination of feed are also impli-cated in production of pale colored yolks.Natural pigments in cereals tend to declinewith prolonged storage, with up to 50% loss report-ed at elevated temperatures. Without blendingof corn therefore, a slight natural loss in pigmentsis expected to cause subtle loss in yolk colorthroughout the year. Yolk color seems to beenhanced when high levels of vitamin E areused, and when the diet contains antioxidants.

In addition to pigmenting the yolk for mar-keting needs, there is growing evidence thatlutein and zeaxanthin may be important nutri-ents for humans. These pigments concentrate inthe macular region of the eye, and are thoughtto help prevent macular degeneration, whichtogether with cataracts, are the leading causesof blindness in developed countries. The mac-ula is found on the back wall of the eye and isresponsible for sharp central vision. The irreversibleand untreatable degeneration of the maculaleads to loss of central vision and eventually totalblindness. Some 20% of North Americans overthe age of 65 have some degree of maculardegeneration. It seems that diets rich in luteinand zeaxanthin increase the level of these pig-ments in the macula and acting as antioxidantsand/or filters to damaging blue light, protectthis sensitive area of the inner eye surface.Current intakes of lutein and xeaxanthin in mostcountries are less than 1 mg/d which is much lessthan the 5 – 6 mg/d now suggested for preventionof macular degeneration and also occurrence ofcataracts. It seems possible to further increase the xanthophyll content of the layers diet, to produce eggs enriched in this important nutrient.



ii. Egg yolk fatty acids – The fatty acid contentof the yolk is greatly influenced by the fattyacid profile of the bird’s diet. Since there is nowconcern about our consumption of saturated fattyacids, it seems beneficial to manipulate theratio of unsaturates:saturates in the yolk. This isachieved by including proportionally moreunsaturated fatty acids in the bird’s diet.Additionally there is the opportunity for feedingthe bird specific polyunsaturates that are now rec-ommended for improved human health. Thesefatty acids are termed omega-3 fatty acids, asopposed to omega-6 fatty acids which are the mostcommon unsaturates in ingredients such ascorn oil and soybean oil. The omega-3 fatty acidsof greatest interest are linolenic acid, (18:3n3)eicosapentaenoic acid (20:5n3) and docosa-hexaenoic acid (22:6n3), and these are knownto reduce the risk of chronic heart disease.

Individuals suffering from CHD seem tohave lower levels of linolenic acid in their adi-pose tissue. Linolenic acid is a precursor ofprostaglandin E, which is reported to be a coro-nary vasodilator, an inhibitor of free fatty acidrelease (as occurs during acute CHD) and is oneof the most potent inhibitors of platelet aggregation.Unfortunately, the diet of most humans is not wellfortified with linolenic acid, which is most com-monly found in plant tissues. However, thechicken has the somewhat unique ability todivert large quantities of linolenic acid into theegg when its diet contains high levels of this nutri-ent. This situation is most easily achieved by includ-ing 8 – 10% flaxseed in the bird’s diet. There seemsto be a linear relationship between flax inclusionlevel and egg linolenic acid content. Figure 4.16was compiled from 6 different research studiesinvolving linolenic acid enrichment of eggs.

Fig. 4.16 Relationship between dietary flaxseed and egg omega-3 content.



Table 4.37 Effect of 2% dietary menhaden oil on egg organoleptics(Subjective score 0-10)

Category Control Menhaden oil2% 2%Deodorized

Aftertaste 6.3a 7.5ab 8.2b

Off-Flavor 3.9a 6.5b 6.9b

Adapted from Gonzalez and Leeson (2000)

In most markets such designer eggs need tohave a guarantee of 300 mg omega-3 fattyacids, and so this necessitates around 10% flaxin the birds diet (Figure 4.16). Perhaps themost important fatty acid for prevention of CHDin humans is docosahexaenoic acid (DHA).Flax does not contain very much DHA and eggDHA level seems to quickly plateau at 70 – 80mg with 5% flaxseed (Figure 4.17).

A more useful and concentrated source of DHAis fish oils. With menhaden oil, it is possible to

increase egg DHA up to 200 mg with inclusionof 2% in the bird’s diet (Figure 4.18). Unlike thesituation with using flaxseed, the inclusion of fishoil in the bird’s diet will result in a change in tasteof the egg. In a recent study, we fed layers 2%menhaden oil or 2% deodorized menhadenoil to study the effect on DHA enrichment.When these eggs were assessed in taste panels,there was a distinct negative effect regarding ‘aftertaste’ and off-flavors. Deodorizing the oil priorto use in the layer diet had no beneficial effecton egg taste (Table 4.37).

Fig. 4.17 Effect of dietary flaxseed on egg DHA



Fig. 4.18 Effect of dietary menhaden on egg DHA content.

Fig. 4.19 Effect of dietary menhaden oil on egg weight of layers at 2,6 and 9 months of production.

(Gonzalez and Leeson, 2000)



Regardless of bird age, the inclusion of men-haden oil also reduced egg size by up to 0.35 gper 1% fish oil inclusion in the diet (Figure4.19). The reduction in egg weight may berelated to the decrease in circulating triglycerides,which is common in birds fed fish oils, so lim-iting lipids for yolk synthesis.

Table 4.38 summaries the enrichment ofeggs with omega-3 fatty acids and DHA inresponse to using flaxseed and fish oil.

Table 4.38 Egg enrichment of fattyacids

Fatty acid Ingredient EnrichmentTotal omega-3 1% Flaxseed 40 mgDHA 1% Fish oil 50 mgDHA 1% Flaxseed 8 mgCLA 1% CLA 50 mg

For total omega-3’s in response to flax andDHA with fish oil, there is a linear response with-in the range of ingredient levels likely to beused in a diet. There is a distinct plateau withDHA in response to flaxseed, where regardlessof flaxseed levels, egg enrichment does not getmuch beyond 70 mg /egg.

Conjugated linoleic acid (CLA) is a posi-tional isomer of linoleic acid that is claimed tohave potent anticarcinogenic properties. Thereare a few natural ingredients rich in CLA, and sostudies to date have used CLA itself as a feed ingre-dient. Each 1% inclusion of dietary CLA seemsto result in 50 mg deposition of CLA in the egg.

iii) Egg cholesterol – Eggs naturally contain a highlevel of cholesterol because of its role in sustainingthe developing embryo. Cholesterol has manyand varied functions in the embryo including itsrole as a structural component of cell membranes,

and as a precursor for sex and adrenal hor-mones, vitamin D, and the bile acids. Young chicksdo not have the enzymes necessary for choles-terol synthesis, which emphasizes the importanceof cholesterol being deposited in the egg. An eggcontains about 180 mg cholesterol and it seemsvery difficult to reduce this without adversely affect-ing other production parameters.

Factors that influence egg cholesterol con-tent include the hen’s body weight and herintake of energy and fat. Diet fat per se does notseem to be a factor, although in most instanceshigh fat diets imply that high-energy diets are used.Restricting the energy intake of laying hensresults in less cholesterol being deposited inthe egg, although this is usually associated witha reduction in egg production. The influence ofdietary energy and body weight of the hen on eggcholesterol is mediated through their effects onyolk size and egg size. Reducing energy intakein order to achieve a measurable reduction in eggcholesterol concentration has the disadvantageof adversely affecting both egg production andegg weight.

Dietary fiber influences cholesterol metab-olism by a possible combination of differentprocesses. These include lowered cholesterolabsorption and resorption, binding with bilesalts in the intestinal tract, shortening the intes-tinal transit time, and increasing fecal sterolexcretion. Alfalfa is one of the most effectivesources of fiber with minimal detrimental effectson egg size, egg production, and feed efficien-cy. Alfalfa seems to efficiently bind bile acids.

Reduction in egg cholesterol achieved by suchdietary manipulations is, however only mar-ginal, with little evidence to suggest a com-mercially important change.



There is an indication that very high levelsof dietary copper can reduce egg cholesterol con-tent. High levels of copper decrease the productionof liver glutathione, which in turn regulatescholesterol synthesis through stimulation ofmethyl glutaryl Co-A. Using up to 250 ppm dietarycopper has been reported to reduce egg cholesterolby up to 25% (Table 4.39). In this particular study,egg production was unaffected, although inmore long-term trials, reduced egg output has beenrecorded. Of concern today is the bioaccumulationof copper in the manure, since the vast major-ity of the dietary copper is not retained (Table 4.39).

One reason for the insensitivity of egg cho-lesterol to diet manipulation is the basic bio-chemistry of the lipoproteins within eggs. Eggcholesterol is determined by the cholesterolcontent of individual yolk lipoprotein moieties,rather than by the bird’s plasma cholesterolconcentration. Given that most cholesterol inlipoproteins is associated with the surface lay-ers, reduction in egg cholesterol content can there-fore occur only when the lipoprotein particle sizeis increased. Such a scenario will reduce the con-tribution of surface cholesterol molecules rela-tive to total fat. Unfortunately, an increase inlipoprotein particle size will tend to reduce theefficiency of the critical transport of bigger sized‘molecules’ through the follicle wall.

iv) Egg vitamins - Many food items are nowenriched with vitamins and consumers considerthese as healthy products. The egg contains bothfat and water soluble vitamins and there is poten-tial for enrichment. Currently, most omega-3enriched eggs also contain additional vitamin E,ostensibly as a natural antioxidant. It is likely thatthe fat soluble vitamins will be the easiest groupto manipulate. The influence of dietary vitaminintake on vitamin enrichment of the egg is quitevariable among vitamins. Riboflavin level in theyolk and albumen responds rapidly to manipu-lating the dietary level of this vitamin. Similarly,the egg content of vitamin B12 is almost exact-ly proportional to diet content over one to fourtimes normal inclusion levels. There does notseem to be a ceiling on vitamin B12 transfer tothe eggs although a plateau is quickly reachedwith riboflavin enrichment. There are somenatural changes in egg vitamin levels related toage of bird. Riboflavin, pyridoxine and vitaminB12 levels of eggs decline while biotin levelincreases with increasing age of hens. Thedecline in egg content of some vitamins withincreasing age is related to a higher rate of pro-duction, since egg output is not completelycompensated for by increasing dietary intake ofthese vitamins. Thiamin content of eggs from WhiteLeghorn hens was reported to be about 50% greaterthan that of eggs laid by Rhode Island Reds orBarred Plymouth Rocks fed the same diet.

Table 4.39 Effect of dietary copper on egg cholesterol and copper accumulation in yolk and manure

Diet Cu Egg cholesterol (mg) Yolk Manure copperppm 4 wk 8 wk copper (µg) (ppm DM)

6 163a 176a 9.4 36130 121b 123b 11.9 540255 114b 116b 13.9 937

Adapted from Pesti and Bakalli (1998)



Naber (1993) in a review of factors influ-encing egg vitamin content concluded that feedvitamin content has the greatest and most wide-spread influence on egg vitamin content. Usingdata from studies that reported diet vitamin leveland feed intake on the one hand, and egg output,i.e. egg weight and production on the other,Naber calculated the efficiency of vitamin trans-fer into eggs as a function of intake (Table 4.40).The transfer efficiency of vitamin A was veryhigh (up to 80%), but this dropped markedlywhen the dietary level was raised to four timesrequirement. This is an indication of the possi-bility of egg enrichment with vitamin A, eventhough this trend declines at high levels of dietvitamin enrichment. The transfer of dietaryvitamin B12 into eggs was as efficient as forriboflavin, pantothenic acid and biotin, e.g.about 50% with dietary levels at one to two timesrequirement. Unlike riboflavin, however, this levelof transfer efficiency continued in the case of vita-min B12 even at very high dietary levels of up to40 times requirement. Clearly, substantialenrichment of eggs with vitamin B12 is possible.

All of the research work conducted to datehas studied the potential of enriching singlevitamins in isolation. In a recent study, weattempted to enrich all vitamins. Considering theexpected transfer efficiency (Table 4.40) a vitamin premix was formulated that contained2 – 10 times the regular level of inclusion. Afterfeeding layers for 60 d, eggs were assayed for allvitamins (Table 4.41).

The results were somewhat discouraging inthat only for vitamin B12 and vitamin K were weable to achieve adequate enrichment to supply100% of DRI. The enrichment for other vitaminswas quite variable, where, for example, with pan-

tothenate there was little response, while for vita-mins D3 and E there was some 3-fold increasein egg concentration. It is possible that at the high-er levels of vitamins used, there is some antag-onism and/or preferential loading of absorp-tion mechanisms.

Table 4.40 Classification of vita-mins by relative transfer efficiencyfrom diet to egg

Transfer efficiency Vitamin

Very High (60 – 80%) Vitamin AHigh (40 – 50%) Riboflavin

Pantothenic acidBiotinVitamin B12

Medium (15 – 25%) Vitamin D3Vitamin E

Low (5 – 10%) Vitamin KThiaminFolacin

Adapted from Naber (1993)

v. Yolk mottling - Egg yolk mottling continuesto be a problem that appears sporadically in anumber of flocks. Although the condition hasbeen known for some time, there appears to beno definite evidence as to its cause or of waysto alleviate it. Diet has been implicated, but thereis no real evidence that nutrition is a factorwith the majority of mottling problems thatappear. However, it is known that certain feedadditives such as nicarbazin can cause a mot-tling condition if they are inadvertently added toa laying diet. Most cases of yolk mottling are report-ed in the spring of the year and most often ‘dis-appear’ during the summer or fall. However,



Table 4.41 Vitamin content of eggs from hens fed regular or enriched levelsof vitamins

Table 4.42 Yolk mottling as influenced by temperature

Vitamin Units Regular egg Enriched egg DRI1 % DRIBiotin µg/kg 16 18 30 60Folic acid µg/kg 8.7 10 400 3Niacin mg/kg 0.04 0.08 16 1Pantothenate mg/kg 0.76 0.77 5 15Vit A IU/kg 17.7 22.5 270 8Vit B1 mg/kg 0.048 0.06 1.2 5Vit B2 mg/kg 0.21 0.25 1.3 19Vit B6 mg/kg 0.027 0.03 1.3 2Vit B12 µg/kg 0.872 3.37 2.4 140Vit D3 µg/kg 0.39 1.1 5 22Vit E mg/kg 1.3 3.78 15 25Vit K mg/kg 0.12 0.13 0.12 108

1 Daily recommended intake for adult

Haugh Yolk color Severity ofunits index mottling (%)

Fresh eggs 85.4 11.3 7.1Eggs held 1 week at 12.5˚C 70.8 10.9 45.6Eggs held 2 weeks at 12.5˚C 66.7 10.9 44.0Eggs held 1 week at room temperature - - 47.6Eggs held 2 days at 31.7˚C - - 60.0

whether the season of the year or the type of lay-ing house management is a factor has not beenproven. Table 4.42 shows the result of a studyin which eggs held for various lengths of time andunder different environmental conditions, werechecked for severity of yolk mottling. It is evi-dent that the majority of mottling appears dur-ing storage. Storing, even at ideal temperaturefor one week, can result in a marked increase inthe condition. It has been suggested that the mod-ern strains of birds are more prone to yolk mot-tling than are traditional strains although researchdata does not confirm this assertion.

The vitelline membrane surrounding theyolk is much weaker when yolks are mottled. Withsevere mottling it is very difficult to manually sep-arate the yolk without breaking the membrane.It is not known if the change in vitelline mem-brane integrity is a cause or effect of mottled yolks.In terms of nutrition, nicarbazin or high gossy-pol cottonseed are most usually implicated.

vi Albumen quality – The main factor influencingalbumen quality is storage time. Over time, espe-cially at temperatures > 10˚C, there will be a break-down of thick albumen, and so loss in egg quality.


SECTION 4.9Diet implications with some general management problems

Over the last few years there has been increas-ing concern about the quality of the thin rather thanthick albumen in fresh eggs. Most measures ofalbumen quality, such as Haugh unit, only meas-ure characteristics of the thick albumen, and soapparently ‘Grade A’ eggs can have problems withthe thin albumen. In certain birds, we see the areaof thin albumen to be as much as 120 sq. cm., com-pared to 60 – 70 sq. cm. for a ‘normal’ egg.These spreading albumens are especially problematicin the fast-food industry where eggs are pre-pared on flat-surface grills. We have tested var-ious levels of protein and amino acids, and fed birdsdiets of vastly different acid-base balance, and seenno effect on this phenomenon. We have select-ed birds producing normal vs. spreading albumenand their offspring show similar characteristics. Thecurrent thin albumen problem therefore seems tobe an inherited characteristic.

Magnesium plays a role in stabilization of thickalbumen, and so there have been studies aimed

at improving albumen quality by feeding layershigh levels of this mineral. In one study, feed-ing 4 – 8,000 ppm Mg on top of a basal level of1500 ppm did help maintain thick albumenafter egg storage for 20 d at 20˚C. In control eggs,there was almost 70% liquification of thickalbumen, while in magnesium enriched birds therewas only 25% conversion of thick to thin albu-men. Unfortunately, high levels of dietary mag-nesium cause loss in shell quality and so this hasto be considered if magnesium salts are used inlayer diets.

There have been inconsistent reports ofimprovement in albumen quality in response to10 ppm dietary chromium. On the other hand10 ppm vanadium results in dramatic loss in albu-men quality. Such levels of vanadium can be con-tributed by contaminated sources of phosphates.Interestingly, the negative effect of vanadium isreported to be corrected by use of 10 ppmchromium in the diet.

4.9 Diet involvement with some general management problems

i) Hysteria -

A lthough not widespread in commer-cial flocks, hysteria can be a very seri-ous nuisance and economic cost factor

if encountered in a flock. Hysteria is easy to dis-tinguish from an ordinary flighty flock, as the birdsseem to lose all normal social behaviour and senseof direction and will mill and fly in every direc-tion making unusual crying and squawkingsounds. Birds often go into a molt, and then eggproduction declines. The condition of hysteriais more difficult to distinguish from flightiness inbirds that are cage-reared rather than floor-reared. However, if one studies the flock for aperiod of time, differences can be seen.

The exact cause of hysteria is unknown,and attempts to artificially induce it in flocks havefailed. Many people believe it is related tonutritional or environmental factors, or to acombination of both. Hysteria is more oftenencountered in birds 12 to 18 weeks of age;although it is sometimes also seen in olderbirds. Overcrowding is thought to be a factor intriggering the condition. Many drugs, feed sup-plements and management practices have beentried in an attempt to cure the condition with lit-tle or no success. Some people believe that itis a behavioral problem with the hens reactingto any noise or stimulus to which they are notaccustomed. Why some flocks react different-ly to others is not known; however, it is well known



that small differences in various stressors resultin markedly different responses in flocks. Anumber of diet modifications have been tried inan attempt to alleviate hysteria. These includehigh levels of methionine (2 kg/tonne), niacin (200g/tonne supplement) or tryptophan (up to 5kg/tonne supplement). The latter is thought tohave a sedative-like effect by influencing brainneuro- transmitters. However, the responsehas been variable, and hysteria seems to returnonce tryptophan is withdrawn from the diet. Inaddition, until the price of tryptophan is reducedthe treatment is prohibitively expensive. Thereis anecdotal evidence that adding meat meal orfish meal to a diet resolves the situation in birdsfed all-vegetable diets.

ii) Prolapse - In the past, prolapse mortality of2 to 3% per month over several months after hous-ing pullets was not uncommon. Such losses wereusually the result of a number of factors work-ing together rather than any single problem.In most cases, the prolapse was due to pickingrather than any physical stress resulting in ‘clas-sical prolapse’. Some of the problems that canlead to pickouts or blowouts are as follows:

- lights too bright (or sunlight streaming into open-sided buildings)

- temperature too high (poor ventilation)

- improper beak trimming

- pullets carrying excess of body fat

- poor feathering at time of housing

- too early a light stimulation

- too high protein/amino acid level in the diet causing early large egg size in relation to body and frame size

The condition is usually more severe with larg-er cage size groups and is a factor of floor spaceper bird rather than bird density. Frequently theincidence of picking has been shown to be

higher in multiple bird cages where there is inexcess of 460 sq. cm. of space per bird. Whenbirds are more confined, they do not seem to beas aggressive. One of the most effective ways ofavoiding a problem is to reduce light intensity.Where rheostats are available, these should beadjusted to a sufficiently low level that pickingor cannibalism is kept to a minimum. With bet-ter control and understanding of light programstoday, prolapse and associated problems aremore likely to occur later in the productioncycle. Mortality of 0.1% per month due toprolapse is now considered problematic.

While this type of problem is aggravatedby high light intensity as well as high stockingdensity and poor beak trimming, it is felt that oneof the main factors triggering the condition is lowbody weight. Even if pullets mature at bodyweights recommended by the breeder, many ofthem are up to 100 g lighter than standard at peakproduction. This, we suspect, is because the pul-let is maturing with a minimum of body reserves.The bird also has a low feed consumption as ithas been conditioned on a feed intake near tomaintenance just prior to commencement of layand so hasn’t been encouraged to develop a largeappetite. The pullet is laying at 92-96% and thusutilizes her body reserves (fat) in order to main-tain egg mass production. This smaller body weightbird is often more nervous and so more proneto picking. Under these conditions, the nutritionalmanagement program of pullets outlined earli-er in this chapter should be followed.

Prolapse can sometimes be made worse byfeeding high protein/amino acid diets to smallweight pullets in an attempt to increase early eggsize. Coupled with an aggressive step-up light-ing program this often leads to more double yolkeggs and so greater incidence of prolapse andblowouts. Such pullets are often below standardweight at 12 – 14 weeks, and so any catch up



growth is largely as fat, which also accentuatesthe problem. Being underweight at 12 – 14 weeksusually means that they have reduced shank length,and because the long bones stop growing at thistime, short shanks are often used as a diagnos-tic tool with prolapse problems in 22 – 34 weekold pullets.

iii) Fatty Liver Syndrome - The liver is themain site of fat synthesis in the bird, and so a ‘fatty’liver is quite normal. In fact, a liver devoid offat is an indication of a non-laying bird. However,in some birds, excess fat accumulates in the liverand this fat can oxidize causing lethal hemorrhages.Excess fat accumulation can only be causedby a surfeit of energy relative to needs for pro-duction and maintenance. Low protein, high-energy diets, and those in which there is an aminoacid imbalance or deficiency can be majorcontributors to a fatty liver condition in layers.It is known that diets low in lipotrophic factorssuch as choline, methionine, and vitamin B12 canresult in fatty infiltration of the liver. However,these nutrients are seldom directly involved inmost of the fatty liver problems reported from thefield. Excessive feed intake and more specificallyhigh energy intake is the ultimate cause of thecondition. It is well known that laying hens willover-consume energy, especially with higherenergy diets and this is particularly true of highproducing hens. Pullets reared on a feeding pro-gram that tends to develop a large appetite orencourages ‘over-eating’ (high fiber diets orskip-a-day feeding), are often more suscepti-ble to the condition when subsequently offereda high energy diet on a free-choice basis duringlay. There is some information to suggest that dailyfluctuations in temperature, perhaps affectedby the season of the year, will stimulate hens toover-consume feed. Hence, it is important toattempt some type of feed or energy restrictionprogram if feed intake appears to be excessive.

When fatty liver is a problem, adding a mix-ture of so-called ‘lipotrophic factors’ to the dietis often recommended. A typical addition mayinvolve 60 mg CuSO4; 500 mg choline; 3 µg vita-min B12 and 500 mg methionine per kg of diet.It should be emphasized that in many cases, theaddition of these nutrients will not cure theproblem. Increasing the level of dietary proteinby 1 to 2% seems to be one of the most effec-tive ways of alleviating the condition. However,such treatments do not work in all cases. Anothertreatment that may prove effective is to increasethe supplemental fat content of the diet. This appar-ently contradictory move is designed to offer thebirds a greater proportion of energy as fat ratherthan carbohydrate. The idea behind this dietmanipulation is that by reducing carbohydrateload there is less stress on the liver to synthesizenew fat required for egg yolk production. By sup-plying more fat in the diet, the liver merely hasto rearrange the fatty acid profile within fats, ratherthan synthesize new fat directly. For this treat-ment to be effective, the energy level of thediet should not be increased, the recommendationmerely being substitution of carbohydrate withfat. This concept may be the reasoning forapparent effectiveness of some other treatmentsfor fatty liver syndrome. For example, substitutionof barley or wheat for corn has been suggestedand this usually entails greater use of supplementalfat with these lower energy ingredients. Similarly,substitution of soybean meal with canola orsunflower meals usually means using more sup-plemental fat if energy level of the diet is to bemaintained.

More recent evidence suggests that mortal-ity is caused by eventual hemorrhaging of the liverand that this is accentuated or caused by oxida-tive rancidity of the accumulated fat. On this basis,we have seen a response to adding variousantioxidants, such as ethoxyquin and vitamin E.



Adding ethoxyquin at 150 mg/kg diet and extravitamin E at 50 – 60 IU/kg has been shown toreduce the incidence of hemorrhage mortality.

Experience has shown that it is difficult toincrease production in a flock once the conditionis established. Thus, it is important that a prop-er program be followed to prevent the develop-ment of fatty livers. In some cases, the cause ofthe trouble can be traced back to pullets cominginto the laying house carrying an excess of bodyfat. If these birds are then fed a diet in which thebalance of protein and energy is slightly subop-timal for a particular strain of bird, a buildup offat in the liver may occur. In addition, the feed-ing of crumbles or pellets in the laying house mayaggravate this condition since the hen may over-consume energy. The results of an experiment study-ing effects of the level of dietary protein on per-cent liver fat are shown in Table 4.43.

These older birds were all laying at a reasonablelevel and no Fatty Liver Syndrome problemswere reported. As can be noted, all birds hadlivers high in fat. This is perfectly normal for agood laying bird and thus should not be confusedwith the Fatty Liver Syndrome where liver hem-orrhage is the condition that usually kills the hen.

Recent information suggests that a conditionsimilar to the so-called Fatty Liver Syndrome may

be caused by certain types of molds or mold tox-ins. Although no definite relationship has beenestablished to date between molds and fattylivers, care should be taken to ensure that moldsare not a factor contributing to poor flock per-formance. Periodically canola meal has beenimplicated with the Fatty Liver Syndrome. Whilethere were earlier reports with some of the highglucosinolate rapeseed meals triggering such acondition, there is no evidence to suggest thatcanola varieties are a factor in the fatty liver con-dition. Hemorrhage due to feeding rapeseed isusually not associated with excess fat infiltrationof the liver.

iv) Cage Layer Fatigue - As its name implies, CageLayer Fatigue (CLF) is a syndrome most commonlyassociated with laying hens held in cages, andso its first description in the mid 1950’s coincideswith the introduction of commercial cage sys-tems. Apart from the cage environment, CLF alsoseems to need a high egg output to trigger thecondition, and for this reason it has traditionallybeen most obvious in White Leghorns. Ataround the time of peak egg output, birdsbecome lame, and are reluctant to stand in thecage. Because of the competitive nature of thecage environment, affected birds usually moveto the back area of the cage, and death can occurdue to dehydration/starvation because of their reluc-tance to drink or eat.

Table 4.43 Influence of dietary protein on liver fat

Dietary protein level Egg production Feed Liver fat (%) (HDB) (%) (g/d) (dry weight basis) (%)

13 76.4 108 49.315 77.0 107 40.217 78.0 107 38.2



The condition is rarely seen in litter floor man-aged birds and this leads to the assumptionthat exercise may be a factor. In fact, removingCLF birds from the cage during the early stageof lameness and placing them on the floor usu-ally results in complete recovery. However,this practice is usually not possible in largecommercial operations. In the 1960 – 70’s, upto 10% mortality was common, although nowthe incidence is considered problematic if 0.5%of the flock is affected. There is no good evidenceto suggest an association of CLF to general bonebreakage in older layers, although the two con-ditions are often described as part of the samegeneral syndrome.

If birds are identified early, they appear alertand are still producing eggs. The bones seem frag-ile and there may be broken bones. Dead birdsmay be dehydrated or emaciated, simply due tothe failure of these birds to eat or drink. The ribsmay show some beading although the mostobvious abnormality is a reduction in the den-sity of the medullary bone trabeculae. Paralysisis often due to fractures of the fourth and fifth tho-racic vertebrae causing compression and degen-eration of the spinal cord. If birds are examinedimmediately after the paralysis is first observed,there is often a partly shelled egg in the oviduct,and the ovary contains a rich hierarchy of yolks.

If birds are examined some time after the onsetof paralysis, then the ovary is often regressed, dueto reduced nutrient intake.

CLF is obviously due to an inadequate sup-ply of calcium available for shell calcification,and the bird’s plundering of unconventionalareas of its skeleton for such calcium. Becausecalcium metabolism is affected by the avail-ability of other nutrients, the status of phos-phorus and vitamin D3 in the diet and theiravailability are also important. Birds fed diets defi-cient in calcium, phosphorus or vitamin D3will show Cage Layer Fatigue assuming there isa high egg output.

Calcium level in the prelay period is often con-sidered in preventative measures for CLF. Feedinglow calcium (1%) grower diets for too long a peri-od or even 2% calcium prelay diets up to 5% eggproduction often leads to greater incidence of abnor-mal bone development. It has been suggested thatthe resurgence in cases of CLF in some commercialflocks may be a result of too early a sexual matu-rity due to the genetic selection for this trait cou-pled with early light stimulation. Feeding a layerdiet containing 3.5% Ca vs a grower diet at 1%Ca as early as 14 weeks of age has proven ben-eficial in terms of an increase in the ash andcalcium content of the tibiotarsus (Table 4.44).

Table 4.44 Diet calcium and bone characteristics of young layers in responseto prelay diet calcium

Time of change to Tibiotarsus3.5% Ca (wk) Ash (%) Ca (mg/g)

20 53.5c 182b

18 55.7b 187b

17 59.3a 202a

16 58.9a 199a

15 58.9a 197a

Adapted from Keshavarz (1989)



Feeding a high calcium diet far in advanceof maturity seems unnecessary, and in fact, maybe detrimental in terms of kidney urolithiasis.Change from a low to a high calcium dietshould coincide with the observation of secondarysexual characteristics, and especially combdevelopment, which usually precedes first ovipo-sition by 14 – 16 d.

We recently observed CLF in a group ofindividually caged Leghorns. The birds were 45weeks of age and all fed the same diet. Withina 10 d period, 5% of the birds had CLF, and feedanalyses showed adequate levels of calciumand phosphorus. The only common factor wasan exceptionally high egg output for these affect-ed birds. All these birds averaged 96% productionfrom 25 – 45 weeks of age, and all had individualclutch lengths of 100 eggs. One bird had a clutchlength of 140 eggs (i.e. 100% production). Theirsisters in adjacent cages fed the same diet andwithout CLF, had maximum clutch lengths of 42eggs in this period, and average productioncloser to 90%. These data suggest that in cer-tain situations CLF is correlated with excep-tionally high egg output.

There have been surprisingly few reportson the effect of vitamin D3 on CLF in young birds.It is assumed that D3 deficiency will impaircalcium utilization, although there are no reportsof testing graded levels of this nutrient as a pos-sible preventative treatment. The other major nutri-ent concerned with skeletal integrity is phosphorus,and as expected, phosphorus deficiency can accen-tuate effects of CLF. While P is not directlyrequired for shell formation, it is essential for thereplenishment of Ca, as CaPO4, in medullary boneduring periods of active bone calcification.Without adequate phosphorus in the diet, thereis a failure to replenish the medullary Ca reserves,and this situation can accelerate or precipitatethe onset of CLF and other skeletal problems. Low

phosphorus intake is sometimes caused by thetrend towards lower levels of diet phosphorus cou-pled with very low feed intake of pullets throughearly egg production. For strains susceptible toCLF, then at least 0.5% available phosphorus isrecommended in the first layer diet to be fed upto 28 – 30 weeks of age.

v) Bone breakage in older hens - CLF mayrelate to bone breakage in older hens, althougha definitive relationship has never been verified.It is suspected that like the situation of CLFwith young birds, bone breakage in older birdsresults as a consequence of inadequate calcifi-cation of the skeleton over time, again relatedto a high egg output coupled with the restrict-ed activity within the cage environment. Few livebirds have broken bones in the cage, the majorproblem occurring when these birds are removedfrom their cages and transported for processing.Apart from the obvious welfare implications, bro-ken bones prove problematic during the mechan-ical deboning of the muscles.

Adding more calcium to the diet of older lay-ers does not seem to improve bone strength,although this can lead to excessive eggshellpimpling. Adding both calcium and phospho-rus to the diet has given beneficial results in someinstances, although results are quite variable. Inyoung birds at least, adding 300 ppm fluorine tothe water has improved bone strength, althoughthere are no reports of such treatment with endof lay birds. Moving birds from a cage to litterfloor environment seems to be the only treatmentthat consistently improves bone strength. Thisfactor indicates that exercise per se is an impor-tant factor in bone strength of caged birds, butdoes not really provide a practical solution to theproblem at this time.

It is not currently known how to improve thebone integrity of older high producing hens



without adversely affecting other traits of economicsignificance. For example, it has been shown thatbone breaking strength in older birds can beincreased by feeding high levels of vitamin D3.Unfortunately, this treatment also results in anexcessive pimpling of the eggshells (as occurs withextra calcium) and these extra calcium depositson the shell surface readily break off causing leak-age of the egg contents. It may be possible toimprove the skeletal integrity of older birds bycausing cessation of ovulation for some time priorto slaughter. Presumably, the associated reduc-tion in the drain of body calcium reserves wouldallow re-establishment of skeletal integrity.Currently such a feeding strategy is uneco-nomical, although consideration for bird welfaremay provide the impetus for research in this area.

vi) Molting programs - Molting has come underscrutiny over the last few years, and in some coun-tries, it is not allowed based on welfare issues.Undoubtedly, the most efficient way to moltbirds, in terms of time and optimum second cycleproduction, is with light, water and feed with-drawal. It is the extensive period of feed with-drawal that raises welfare concerns even thoughmortality during this period is exceptionallylow. With one molting, it is possible to prolongthe production cycle to 90 weeks (52 + 40weeks), while with two moltings the cycle canbe 45 + 40 + 35 weeks. The productive life ofthe bird can therefore be doubled. When birdsresume their second or third laying cycle,eggshell quality is almost comparable to that of

20-week-old birds, while even the first eggsproduced will be large grade. Shell quality dete-riorates more quickly in second and third cyclesand this situation dictates the shorter cycles. Theaim of a molting program is not necessarily to inducefeather loss, but rather to shut down the reproductivesystem for a period of time. Generally the longerthe pause in lay, the better the post-molt production.Egg pricing usually dictates the length of themolting period. If egg prices are high then a shortmolt period may be advantageous, whereas a longermolt period may ultimately be more economicalwhen egg prices are low.

Examples of molt induced by feed with-drawal are shown in Table 4.45. With the typeof programs shown in Table 4.45, one canexpect birds to molt and to decline to near zeropercent egg production. The lowest egg productionwill likely occur about 5 – 7 d after initiation ofthe program, and maximum feather loss will occura week later than this. Programs should beadjusted depending upon individual flock cir-cumstances. For example, under very hotweather conditions it would be inadvisable to with-draw water for extended periods of time. Witha feed withdrawal program, body weight of thebird is one of the most important factors. Ideally,the body weight at the end of the first moltshould be the same as the initial mature weightwhen the bird was 18 – 19 weeks of age. Thiseffectively means that the molting program has to induce a weight loss equivalent to the weight gain achieved in the first cycle of lay.



In reality this is difficult to achieve and a +100g weight for second vs first cycle ‘mature’ weightis more realistic. Mortality is usually exceptionallylow during the period of feed withdrawal, andin fact less than in the 4 – 8 week period priorto the molt. If mortality exceeds 0.1% perweek, then it is cause for concern and perhapsa need for reintroducing feed. The actual peri-od of feed withdrawal should be no more than7 d, and ideally less than this if the desiredweight loss is achieved.

The reduction in day length is a major stim-ulus to shutting down the ovary. While this is eas-ily achieved in blackout houses, special condi-tions must be used with open-sided buildings. Inorder for the bird to be subjected to a significantstep-down in daylength, then 5 – 7 d prior to thestart of the molt, birds should be given 23 – 24

hr light each day. This means that with 16 hr nat-ural light per day, removing the artificial light inducesa significant reduction in day length which willhelp to reduce estrogen production.

Alternatives to feed withdrawal for moltingare now being considered due to welfare issues.These alternative systems involve either high lev-els of minerals in conjunction with ad-lib feed-ing or the use of low nutrient dense diets/ingre-dients that are naturally less palatable.Considerable work has been conducted using highlevels of dietary zinc, where up to 20,000 ppmcauses a pause in lay, often without a classicalmolt, followed by resumption of productionand fairly good second cycle production. Virtuallyall of this dietary zinc will appear in the manure,and so today there are environmental concernsregarding its disposal. Birds can also be molt-

Table 4.45 Molting with feed withdrawal

White egg Brown egg1. Light

0 – 1 d None None

1 – 40 d 8 hr or natural1 8 hr or natural1

41d+ Step-up Step-up2. Water

0 – 1 d None None1 d+ Ad-lib Ad-lib

3. Feed0 – 7 d None None7 – 10 d 20 g cereal/d 25 g cereal/d

10 – 20 d 45 g cereal/d 50 g cereal/d20 – 35 d Pullet developer Pullet developer35 d+ Layer II Layer II

4. Body weight (kg)1st cycle maturity 1.25 1.40End 1st cycle 1.60 1.75End 1st molt 1.35 1.50End of 2nd cycle 1.70 1.85

1 provide 23 – 24 hr light/d for 5 d prior to start of molt


SECTION 4.10Nutrient management

ed by feeding diets deficient in sodium or chlo-ride, although results tend to be quite variable withthis system.

Using low nutrient density diets and ingredientsseems to hold some promise for inducing apause in lay. Dale and co-workers at Georgia haveused diets with 50% cottonseed meal fed ad-lib,and recorded weight loss comparable to a feed

withdrawal program. Birds fed this special dietlost 20% body weight within 10 d and egg pro-duction ceased after 5 d. Offering a diet containing90% grape pomace also seems to work well incausing a dramatic decline in egg production.Adding thyroxine to the diet is also a potentstimulus to shutting down the ovary, although eggsproduced by such birds contain elevated levelsof thyroxine and so could not be marketed.

4.10 Nutrient management

P oultry manure is a valuble source ofnitrogen, phosphorus and potassium forcrop production. However, with the

scale of layer farms today, the issue is the quan-tity of these nutrients produced within a smallgeographic location. The composition of manureis directly influenced by layer feed composition,and so higher levels of nitrogen in feed forexample are expected to result in more nitrogenin the manure. One approach to reducing theproblem of manure nutrient loading on farmland,is to reduce the concentration of these nutrientsby altering feed formulation. Since this essentiallyentails reduction in feed nitrogen and phospho-rus there are obviously lower limits for feed for-mulation such that production is not adversely affect-ed. As a generalization, about 25% of feednitrogen and 75% of feed phosphorus ends up inthe manure. Also, layers will produce about asmuch manure (on a wet basis) as the feed eatenover a given period of time. The actual weight ofmanure is obviously greatly influenced by mois-ture loss both in the layer house and during stor-age. Table 4.46 shows average compositon of freshcage layer manure.

The major issue today is loading of manurewith nitrogen and phosphorus. Of these two nutri-ents, the level of nitrogen assayed in manure is

the most variable since housing system andtype of manure storage can have a dramatic effecton nitrogen loss as ammonia (Table 4.47).

Table 4.46 Composition of freshcage layer manure

Moisture (%) 70.0Gross energy (kcal/kg) 250Crude Protein (%) 8.0True Protein (%) 3.0Nitrogen (%) 1.2Uric acid (%) 1.7

Ash (%) 8.0Calcium (%) 2.2Phosphorus (%) 0.6P205 (%) 1.3K20 (%) 0.6Sodium (%) 0.1

Fat (%) 0.5NSP (%) 10.0Crude Fiber (%) 4.2

Arginine (%) 0.12Leucine (%) 0.18Lysine (%) 0.11TSAA (%) 0.10Threonine (%) 0.12Tryptophan (%) 0.10



Table 4.47 Nitrogen loss as ammo-nia for 10,000 layers per year (kg)

Total nitrogen excretion into manure 7200Average house NH3 loss -660Average storage NH3 loss -120Average land NH3 loss -1140

Total nitrogen loss as ammonia -1920Total nitrogen available for crops 5280

Variable losses:a) Housing system:

Liquid deep pit 680High-rise solid 290Belt, force drying 290Deep litter 1470

b) Storage system:Belt drying 410Lagoon 3870

c) Application system:Dry 710Slurry 1740

Adapted from Van Horne et al. (1998)

of essential amino acids. At some point in thereduction of crude protein, we seem to losegrowth rate or egg production/egg size which sug-gests that either we have reached the point at whichnon-essential amino acids become important, orthat we have inadequately described the bird’samino acid needs or that the synthetic amino acidsare not being used with expected efficiency.Of these factors, the need to more adequatelydescribe amino acid needs under these specif-ic formulation procedures is probably mostimportant. However, we can readily reduce crudeprotein supply by 15 – 20% if the use of syntheticamino acids is economical or if there is a costassociated with the disposal of manure nutrients.The expected reduction in nitrogen output relativeto diet crude protein in shown in Figure 4.20. Aspreviously described, we cannot use extremely lowprotein levels without reduction in performance.For example, in the study in Figure 4.20, reduc-ing CP from 17 to 13% resulted in a 2 g loss in eggsize. Currently we can probably reduce proteinlevels to 14 – 15% for older layers. However, a5% reduction in crude protein from 19% to 14%means a reduction in nitrogen output of about 2tonnes per year for 10,000 layers.

Manure phosphorus levels are more easilypredicted, since there is no subsequent lossonce the manure is produced. As expected,manure phosphorus level is largely a factor of dietphosphorus level. Because phosphorus is anexpensive nutrient, it tends not to be overfor-mulated, however, there is usually some poten-tial to reduce levels. Most of the manure phos-phorus is undigested phytate phosphorus fromthe major feed ingredients such as corn and soy-bean meal. The phytate level in corn and soy-bean is variable and so this results in somevariance in phosphorus in the manure. Table 4.48shows the range of phosphorus in corn andsoybean samples from Ontario, Canada.

Most of the nitrogen excreted by the bird relatesto undigested material and those amino acids thatare imbalanced with respect to immediate needsfor tissue or egg synthesis. Nitrogen excretioncan, therefore, be dramatically reduced by sup-plying a balance of amino acids that moreexactly meets the bird’s needs with minimum ofexcess, and also by providing these amino acidsin a readily digested form. With methionine, lysine,and threonine now available at competitiveprices, it is possible to formulate practical dietsthat provide a minimum excess of amino acidsand non-protein nitrogen. Unfortunately, we seemunable to take this approach to its logical con-clusion and formulate diets with very low lev-els of crude protein that contain regular levels



Table 4.48 Phosphorus content of corn and soybean meal1

Average Lowest 15% Highest 15%Corn:Samples tested 198 30 30

Average P (%) 0.31 0.26 0.36Minimum P (%) 0.24 0.34Maximum P (%) 0.28 0.40

Soybean meal:Samples tested 106 16 16Average P (%) 0.70 0.53 0.88Minimum P (%) 0.43 0.80Maximum P (%) 0.59 1.00

1 adjusted from analysis of soybeans assuming 20% fat content Adapted from Leach (2002)

Fig. 4.20 Nitrogen intake and excretion of layers in relation to diet protein level.



Table 4.49 Hectares of corn land required for manure disposal from 10,000 layers/yr

Diet CP (%) Hectares Diet P (%) Hectares20 47 0.55 4519 45 0.50 4018 44 0.45 3617 41 0.40 3216 40 0.35 2815 37 0.30 2314 35 0.25 19

A corn-soy diet containing ingredients fromthe highest 15% vs lowest 15% grouping ofphosphorus content is expected to increasemanure phosphorus content by 20 – 25%.

Phytase enzyme now allows for significantreduction in diet phosphorus levels (25 – 30%)and this relates to a corresponding reduction inmanure phosphorus levels. For more details onphytase, see Section 2.3 g.

Although there are lower limits to protein andphosphorus levels in layer diets, phase feedingprograms involving the sequential reductions inN and P content of layer feed over time will havea meaningful effect on manure nutrient loading.

Table 4.49 shows the land base required for 10,000layers per year assuming that the land is used togrow corn and fertilizer rate is 140 kg N/hectareand 40 kg P/hectare. As CP level of the dietdecreases from 20 to 14%, the land base requiredto adequately use the manure is reduced by 25%.With phosphorus there is potential reduction of50% in land based relative to diet P levels usedin formulation.

In the future, we may have to re-evaluate thelevels of trace minerals fed to layers, sincemanure concentration of zinc and copper maycome under closer scrutiny regarding soil accu-mulation.


Suggested Readings

Atteh, J.O. and S. Leeson (1985). Response of layinghens to dietary saturated and unsaturated fatty acidsin the presence of varying dietary calcium levels.Poult. Sci. 64:520-528.

Bean, L.D. and S. Leeson, (2002). Metabolizableenergy of layer diets containing regular or heat-treat-ed flaxseed. J. Appl. Poult. Res. 11:424-429.

Bean, L.D. and S. Leeson, (2003). Long-term effectsof feeding flaxseed on the performance and egg fattyacid composition of brown and white hens. Poult.Sci. 82:388-394.

Calderon, V.M. and L.S. Jensen, (1990). The require-ment for sulfur amino acid by laying hens as influ-enced by protein concentration. Poult. Sci. 69:934-944.

Caston, L.J., E.J. Squires and S. Leeson, (1994). Henperformance, egg quality and the sensory evaluationof eggs from SCWL hens fed dietary flax. Can. J.Anim. Sci. 74:347-353.

Chah, C.C., (1972). A study of the hen’s nutrientintake as it relates to egg formation. M.Sc. Thesis,University of Guelph.

Chen, J. and D. Balnave, (2001). The influence ofdrinking water containing sodium chloride on per-formance and eggshell quality of a modern, coloredlayer strain. Poult. Sci. 80:91-94.

Clunies, M. and S. Leeson, (1995). Effect of dietarycalcium level on plasma proteins and calcium fluxoccurring during a 24h ovulatory cycle. Can. J.Anim. Sci. 75:539-544.

Faria, D.E., R.H. Harms, and G.B. Russell, (2002).Threonine requirement of commercial laying hensfed a corn-soybean meal diet. Poult Sci. 81:809-814.

Gonzalez, R. and S. Leeson, (2001). Alternatives forenrichment of eggs and chicken meat with omega-3fatty acids. Can. J. Anim. Sci. 81:295-305.

Gonzalez R. and S. Leeson, (2000). Effect of feedinghens regular or deodorized menhaden oil on pro-duction parameters, yolk fatty acid profile and sen-sory quality of eggs. Poult. Sci. 79:1597-1602.

Harms, R.H. and G.B. Russell, (1994). A compari-son of the bioavailability of DL-methionine andMHA for the commercial laying hen. J. Appl. Poult.Res. 3:1-6.

Harms, R.H. and G.B. Russell, (2000). Evaluation ofthe isoleucine requirement of the commercial layerin a corn-soybean meal diet. Poult. Sci. 79:1154-1157.

Hoffman-La Roche, (1998). Egg yolk pigmentationwith carophyll. 3rd Ed. Publ. F. Hoffmann-La Rocheand Co. Ltd. Publ. 1218. Basle, Switzerland.

Ishibashi, T., Y. Ogawa, T. Itoh, S. Fujimura, K.Koide, and R. Watanabe, (1998). Threonine require-ments of laying hens. Poult. Sci. 77:998-1002.

Keshavarz, K., (1989). A balance between osteo-porosis and nephritis. Egg industry. July p 22-25.

Keshavarz, K., (2003). The effect of different levelsof nonphytate phosphorus with and without phy-tase on the performance of four strains of layinghens. Poult. Sci. 82:71-91.

Leach S.D., (2002). Evaluation of and alternativemethods for determination of phytate in Ontariocorn and soybean samples. MSc Thesis, Universityof Guelph.

Leeson, S. and J.D. Summers, (1983). Performanceof laying hens allowed self-selection of variousnutrients. Nutr. Rep. Int. 27:837-844.

Leeson, S. and L.J. Caston, (1997). A problem withcharacteristics of the thin albumen in laying hens.Poult. Sci. 76:1332-1336.

Leeson, S., (1993). Potential of modifying poultryproducts. J. Appl. Poult. Res. 2:380-385.

Leeson, S., R.J. Julian and J.D. Summers, (1986).Influence of prelay and early-lay dietary calciumconcentration on performance and bone integrity ofLeghorn pullets. Can. J. Anim. Sci. 66:1087-1096.

Naber, E.C., (1993). Modifying vitamin compositionof eggs: A review. J. Appl. Poult. Res. 2:385-393.

Newman, S. and S. Leeson, (1997). Skeletal integri-ty in layers at the completion of egg production.World’s Poult. Sci. J. 53:265-277.


Peganova, S. and K. Eder, (2003). Interactions of var-ious supplies of isoleucine, valine, leucine and tryp-tophan on the performance of laying hens. Poult.Sci. 82:100-105.

Rennie, J.S., R.H. Fleming, H.A. McCormack, C.C.McCorquodale and C.C. Whitehead, (1997). Studieson effects of nutritional factors on bone structure andosteoporosis in laying hens. Br. Poult. Sci. 38 (4):417-424.

Roland, D.A., (1995). The egg producers guide tooptimum calcium and phosphorus nutrition. Publ.Mallinckrodt Feed Ing.

Sell, J.L., S.E. Scheideler and B.E. Rahn, (1987).Influence of different phosphorus phase-feedingprograms and dietary calcium level on performanceand body phosphorus of laying hens. Poult. Sci.66:1524-1530.

Waldroup, P.W. and H.M. Hellwig, (1995).Methionine and total sulfur amino acid require-ments influenced by stage of production. J. Appl.Poult. Res. 3:1-6.

Zhang, B. and C.N. Coon, (1994). Nutrient model-ing for laying hens. J. Appl. Poult. Res. 3:416-431.

FEEDING PROGRAMS FOR BROILER CHICKENS

229

55.1 Diet specifications and feed formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

5.2 Feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

a. General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

b. Prestarters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

c. Low nutrient dense diets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

d. Growth restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

e. Heavy broilers/roasters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

f. Feed withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

5.3 Assessing growth and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

a. Broiler growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

b. Feed efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

5.4 Nutrition and environmental temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

a. Bird response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

b. Potential nutritional intervention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

5.5 Nutrition and lighting programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

5.6 Nutrition and gut health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

5.7 Metabolic disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

a. Ascites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

b. Sudden death syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277

c. Skeletal disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277

d. Spiking mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

5.8 Carcass composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

5.9 Skin integrity and feather abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

a. Feather development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

b. Skin tearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

c. Oily bird syndrome (OBS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

5.10 Environmental nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

Page

CHAPTER

230 CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENS

SECTION 5.1Diet specifications and feed formulations

G enetic selection for growth rate con-tinues to result in some 30-50 g yearlyincrease in 42-49 d body weight. There

has also been an obvious improvement in feedefficiency and reduction in the incidence ofmetabolic disorders over the last 5 years, and sothese changes have dictated some changes in feedformulation and feed scheduling. The modernbroiler chicken is however, able to respondadequately to diets formulated over a vast rangeof nutrient densities. If there is no concern regard-ing classical measures of feed efficiency, then thehighest nutrient dense diets are not always themost economical.

To a large extent, the ability of the broiler togrow well with a range of diet densities relatesto its voracious appetite, and the fact that feedintake seems to be governed by both physical sati-ety as well as by cues related to specific nutri-ents. For example, varying the energy level ofa broiler diet today has much less of an effect onfeed intake, as expected on the basis of appetitebeing governed by energy requirement. This appar-ently subtle change in bird appetite has led toincreased variability in diet type and diet allo-cation used by commercial broiler growers.However, as will be discussed later, attemptingto ‘cheapen’ broiler diets through the use of lowerprotein/amino acid levels, while not havingmajor effects on gross performance, leads to sub-tle changes in carcass composition. Feed pro-grams may, therefore, vary depending upon thegoals of the producer versus the processor.

Another major change in broiler nutrition thathas occurred over the last 5 years is the realizationthat maximizing nutrient intake is not always the

most economical situation, at least for certain timesin the grow-out period. A time of so-called‘undernutrition’, which slows down early growthrate appears to result in reduction in the incidenceof metabolic disorders such as Sudden DeathSyndrome and the various skeletal abnormali-ties. A period of slower initial growth, followedby ‘compensatory’ growth is almost alwaysassociated with improved feed efficiency, becauseless feed is directed towards maintenance. Asincreasing numbers of broilers are grown inhot climates, an understanding of the bird’sresponse to temperature, humidity and pho-toperiod is becoming more important.

Diet specifications are shown in Tables 5.1,5.2 and 5.3. Table 5.1 shows relatively high nutri-ent dense diets, while Table 5.2 indicates an alter-nate program for low nutrient dense diets. Thechoice of such feeding programs is often dictatedby strain of broiler, environmental temperatureand the relative cost of major nutrients such asenergy and protein. Within these feeding pro-grams a common vitamin-mineral premix isused, albeit at different levels, according tobird age. Because birds will eat more of the lowvs. high nutrient dense diets, there is potentialto reduce the premix nutrient levels by up to 10%for Table 5.2 vs. Table 5.1. When broilers are grownto very heavy weights (63 d+) then there is anadvantage to using lower nutrient dense diets (Table5.3). Tables 5.4 – 5.7 show examples of high nutri-ent dense diets appropriate for the specificationsshown in Table 5.1. There are six variations ofdiets for the starter, grower, finisher and withdrawalperiods. The diets differ in the major cereal usednamely corn, sorghum or wheat, and with or with-out meat meal as another option.

5.1 Diet specifications and feed formulation

231CHAPTER 5FEEDING PROGRAMS FOR BROILER CHICKENS


Approximate age 0-18d 19-30d 31-41d 42d+Starter Grower Finisher Withdrawal

Crude Protein (%) 22 20 18 16Metabolizable Energy (kcal/kg) 3050 3100 3150 3200Calcium (%) 0.95 0.92 0.89 0.85Available Phosphorus (%) 0.45 0.41 0.38 0.36Sodium (%) 0.22 0.21 0.2 0.2Methionine (%) 0.5 0.44 0.38 0.36Methionine + Cystine (%) 0.95 0.88 0.75 0.72Lysine (%) 1.3 1.15 1.0 0.95Threonine (%) 0.72 0.62 0.55 0.5Tryptophan (%) 0.22 0.2 0.18 0.16Arginine (%) 1.4 1.25 1.1 1.0Valine (%) 0.85 0.66 0.56 0.5Leucine (%) 1.4 1.1 0.9 0.8Isoleucine (%) 0.75 0.65 0.55 0.45Histidine (%) 0.4 0.32 0.28 0.24Phenylalanine (%) 0.75 0.68 0.6 0.5

Vitamins (per kg of diet) 100% 80% 70% 50%Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12

Trace minerals (per kg of diet) 100% 80% 70% 50%Manganese (mg) 70Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3

Table 5.1 High nutrient density diet specifications for broilers



Approximate age 0-18d 19-30d 31-41d 42d+Starter Grower Finisher Withdrawal

Crude Protein (%) 21 19 17 15Metabolizable Energy (kcal/kg) 2850 2900 2950 3000Calcium (%) 0.95 0.9 0.85 0.8Available Phosphorus (%) 0.45 0.41 0.36 0.34Sodium (%) 0.22 0.21 0.19 0.18Methionine (%) 0.45 0.4 0.35 0.32Methionine + Cystine (%) 0.9 0.81 0.72 0.7Lysine (%) 1.2 1.08 0.95 0.92Threonine (%) 0.68 0.6 0.5 0.45Tryptophan (%) 0.21 0.19 0.17 0.14Arginine (%) 1.3 1.15 1.0 0.95Valine (%) 0.78 0.64 0.52 0.48Leucine (%) 1.2 0.9 0.8 0.75Isoleucine (%) 0.68 0.6 0.5 0.42Histidine (%) 0.37 0.28 0.25 0.21Phenylalanine (%) 0.7 0.65 0.55 0.46

Vitamins (per kg of diet) 100% 70% 60% 40%Vitamin A (I.U) 8000Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12

Trace minerals (per kg of diet) 100% 70% 60% 40%Manganese (mg) 70Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3

Table 5.2 Low nutrient density diet specifications for broilers



Approximate age 0-15d 16-30d 31-45d 46-56d 57d+Starter Grower #1 Grower #2 Finisher #1 Finisher #2

Crude Protein (%) 20 19 18 16 15Metabolizable Energy (kcal/kg) 2850 2900 2950 3000 3000Calcium (%) 0.95 0.9 0.85 0.8 0.75Available Phosphorus (%) 0.45 0.41 0.36 0.34 0.3Sodium (%) 0.22 0.21 0.19 0.18 0.18Methionine (%) 0.42 0.38 0.33 0.30 0.28Methionine+cystine (%) 0.85 0.76 0.68 0.66 0.64Lysine (%) 1.13 1.02 0.95 0.92 0.90Threonine (%) 0.64 0.56 0.47 0.42 0.39Tryptophan (%) 0.20 0.18 0.16 0.13 0.11Arginine (%) 1.22 1.08 0.94 0.89 0.85Valine (%) 0.73 0.60 0.49 0.45 0.42Leucine (%) 1.13 0.85 0.75 0.71 0.67Isoleucine (%) 0.64 0.56 0.47 0.39 0.35Histidine (%) 0.35 0.26 0.24 0.20 0.18Phenylalanine (%) 0.66 0.61 0.52 0.43 0.39

Vitamins (per kg of diet) 100% 80% 70% 60% 40%Vitamin A (I.U) 8000

Vitamin D3 (I.U) 3500Vitamin E (I.U) 50Vitamin K (I.U) 3Thiamin (mg) 4Riboflavin (mg) 5Pyridoxine (mg) 4Pantothenic acid (mg) 14Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 400Vitamin B12 (µg) 12

Trace minerals (per kg of diet) 100% 80% 70% 60% 40%Manganese (mg) 70

Iron (mg) 20Copper (mg) 8Zinc (mg) 70Iodine (mg) 0.5Selenium (mg) 0.3

Table 5.3 Diet specifications for very heavy broilers



1 2 3 4 5 6Corn 533 559Wheat 568 597Sorghum 523 542Wheat shorts 60 60 70 72 68 69Meat meal 40 50 42Soybean meal 342 295 334 281 283 230Fat 28.7 21.0 37.0 33.5 45.3 38.0DL-Methionine* 2.5 2.6 2.6 2.8 2.8 2.9L-Lysine 0.8 0.9 0.4 0.3 1.1 1.1Salt 4.4 3.9 4.6 3.9 3.9 3.3Limestone 15.8 12.0 16.0 11.2 16.2 12.5Dical Phosphate 11.8 4.6 11.4 2.3 10.7 3.2Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000


Table 5.4 Examples of high nutrient dense broiler starter diets




1 2 3 4 5 6Corn 613 646Wheat 630 665Sorghum 573 600Wheat shorts 31 30 60 64 64 65Meat meal 50 52 53Soybean meal 295 237 289 230 223 160Fat 26 16.4 44 34 49 37.3DL-Methionine* 2.4 2.5 2.5 2.7 2.7 2.9L-Lysine 0.8 0.8 0.3 0.2 1.1 1.1Salt 4.2 3.5 4.2 3.7 3.6 2.8Limestone 16 11.3 16 11.5 16.4 11.9Dical Phosphate 10.6 1.5 10 0.9 9.2Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000 1000 1000


Table 5. 5 Examples of high nutrient dense broiler grower diets




1 2 3 4 5 6Corn 693 726Wheat 714 779Sorghum 643 676Wheat shorts 50 50 50 23Meat meal 50 50 50Soybean meal 250 192 236 178 161 100Fat 23.7 13.1 38.5 27.9 43 29.8DL-Methionine* 1.7 1.8 1.8 2.0 2.0 2.2L-Lysine 0.8 0.8 0.3 0.2 1.2 1.2Salt 3.9 3.3 4 3.4 3.2 2.5Limestone 16 11.3 16.3 11.5 16.5 11.3Dical Phosphate 9.9 0.7 9.1 8.1Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000 1000 1000


Table 5.6 Examples of high nutrient dense broiler finisher diets




1 2 3 4 5 6Corn 745 783Wheat 772 812Sorghum 695 728Wheat shorts 50 50 50 60Meat meal 60 50 50Soybean meal 196 127 181 123 100 27Fat 25 12.6 40.4 30 45 34DL-Methionine* 2.0 2.2 2.2 2.3 2.4 2.6L-Lysine 2.2 2.2 1.7 1.6 2.7 2.7Salt 3.9 3.1 4 3.4 3.1 2.3Limestone 15.4 8.9 15.7 10.7 16 8.4Dical Phosphate 9.5 9.0 7.8Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000 1000 1000


Table 5.7 Examples of high nutrient dense broiler withdrawal diets



SECTION 5.2Feeding programs

5.2 Feeding programsa) General considerations

W hile nutrient requirement values anddiet formulations are fairly standardworldwide, there is considerable

variation in how such diets are scheduled with-in a feed program. Feed program is affected bystrain of bird, as well as sex and market age ormarket weight. Other variables are environmentaltemperature, local disease challenge and whetherthe bird is sold live, as an intact eviscerated car-cass, or is destined for further processing.Management factors such as stocking density, feedand water delivery equipment and presence ornot of anticoccidials and growth promoters,also influence feed scheduling.

The underlying factors to such inputs forfeed scheduling, often relate to their influenceon feed intake. Predicting daily or weekly feedintake is therefore of great importance in devel-oping feed programs. Table 5.8 outlines expect-ed feed intake for male and female broilers to 63and 56 d respectively. In the first 20 d of growth,male and female broilers eat almost identical quan-tities of feed, and growth is therefore compara-ble. After this time, the increased growth of themale is a consequence of increased feed intake.Ten years ago, age in days x 4 gave an estimateof daily feed intake. Today, this estimate no longerholds true, since growth rate and feed intake haveincreased. For a male broiler chicken, daily feedintake of starter, grower, finisher and withdrawalcan be estimated by multiplying bird age indays by 4, 5, 4 and 3.5 respectively.

The major factor influencing choice of feedscheduling is market age and weight. As a gen-

eralization, the earlier that a bird is marketed, themore prolonged the use of starter and grower feeds.For heavier birds, the high nutrient dense starterand grower feeds are used for shorter periods oftime. Feed schedules for male and female broil-ers are shown in Tables 5.9 and 5.10 respectivelywhile Table 5.11 outlines data for mixed-sex birds.

Feed scheduling tends to be on the basis offeed quantity or according to bird age, andboth of these options are shown in Tables 5.9-5.11. The withdrawal diet is used for 5-10 ddepending on market age although it must beemphasized that scheduling of this diet is dic-tated by the minimum withdrawal time of spe-cific antibiotics, growth promoters and/or antic-occidials, etc.

The need for strain-specific diets is oftenquestioned. Tables 5.12-5.14 outline the nutrientrequirements of the three major commercialstrains currently used worldwide. Since it is pro-hibitively expensive for breeding companies to con-duct research on defining needs of all nutrients fortheir strains at all ages, then their requirement val-ues are often based on information collectedfrom customers worldwide. The publishedrequirement values (Tables 5.12 – 5.14) are there-fore considered to be the most appropriate for theindividual strains under most commercial grow-ing conditions. With this in mind, there are no majordifferences in nutrient requirements for any spe-cific strain. In reality, the nutrient needs andfeeding program for a 42 d vs. 60 d Ross male aregoing to be much more different than are require-ments of a 42 d Ross vs. 42 d Cobb bird.



Age Male Female Age Male Female(d) Daily Cum.* Daily Cum. (d) Daily Cum. Daily Cum.1 13 13 13 13 33 159 2726 136 25552 15 28 15 28 34 163 2889 140 26953 18 46 18 46 35 167 3056 143 28384 21 67 21 67 36 170 3226 147 29815 24 91 23 90 37 172 3398 150 31316 25 116 25 115 38 174 3572 152 32837 27 143 26 141 39 176 3748 153 34368 32 175 32 173 40 178 3926 154 35909 37 212 37 210 41 180 4106 154 3744

10 42 254 41 251 42 182 4288 154 389811 47 301 46 297 43 184 4472 155 405312 53 354 52 349 44 185 4657 156 420913 59 413 58 407 45 186 4843 156 436514 66 479 65 472 46 187 5021 157 452215 74 553 70 542 47 188 5209 158 468016 80 633 76 618 48 189 5398 159 483917 85 718 81 694 49 190 5588 160 499918 90 808 86 785 50 191 5779 161 516019 95 903 91 876 51 192 5971 161 532120 100 1003 96 972 52 193 6164 162 548321 105 1108 102 1074 53 194 6358 163 564622 110 1218 106 1180 54 195 6553 164 581023 115 1333 110 1290 55 196 6749 165 597524 120 1453 114 1404 56 197 6946 165 614025 125 1578 117 1521 57 198 714426 129 1707 120 1641 58 199 734327 133 1840 123 1764 59 200 754328 137 1977 126 1890 60 201 774429 141 2118 130 2020 61 202 794630 145 2263 132 2152 62 203 814931 149 2412 133 2285 63 204 835332 155 2567 134 2419

Table 5.8 Feed intake of male and female broilers (g/bird)

* Cumulative



Feed

all

ocat

ion

(kg/

bird

)A

ge

Bod

y F:

GSt

arte

rG

row

erFi

nish

erW

ithd

raw

alTo

tal

Feed

(d)

Wt.

(g)

(kg)

(age

)(k

g)(a

ge)

(kg)

(age

)(k

g)(a

ge)

(kg)

4224

351.

740.

750-

17 d

2.45

18-3

6 d

1.00

37-4

2 d

4.24

4325

101.

760.

700-

17 d

2.72

18-3

7 d

1.00

38-4

3 d

4.42

4425

851.

780.

650-

16 d

2.95

17-3

8 d

1.00

39-4

4 d

4.60

4526

601.

800.

650-

16 d

2.13

17-3

3 d

1.00

34-3

9 d

1.00

40-4

5 d

4.79

4627

351.

820.

600-

16 d

1.88

17-3

1 d

1.50

32-4

0 d

1.00

41-4

6 d

4.98

4728

101.

840.

600-

16 d

1.62

17-3

0 d

1.90

31-4

1 d

1.05

41-4

7 d

5.17

4828

851.

860.

600-

16 d

1.41

17-2

8 d

2.30

29-4

2 d

1.05

43-4

8 d

5.37

4929

601.

880.

580-

15 d

1.32

16-2

8 d

2.56

29-4

3 d

1.10

44-4

9 d

5.56

5030

301.

900.

560-

15 d

1.55

16-2

9 d

2.55

30-4

4 d

1.10

45-5

0 d

5.76

5131

001.

920.

540-

15 d

1.70

16-3

0 d

2.61

31-4

5 d

1.10

46-5

1 d

5.95

5231

701.

940.

520-

15 d

1.80

16-3

0 d

2.73

31-4

6 d

1.10

47-5

2 d

6.15

5332

401.

960.

500-

14 d

1.90

15-3

1 d

2.80

32-4

7 d

1.15

48-5

3 d

6.35

5433

101.

980.

480-

14 d

1.95

15-3

1 d

2.97

32-4

8 d

1.15

49-5

4 d

6.55

5533

802.

000.

460-

14 d

2.00

15-3

1 d

3.15

32-4

9 d

1.15

50-5

5 d

6.76

5634

502.

020.

440-

13 d

2.10

14-3

2 d

3.28

33-5

0 d

1.15

51-5

6 d

6.97

5735

202.

030.

420-

13 d

2.20

14-3

2 d

3.32

33-5

1 d

1.20

52-5

7 d

7.15

5835

902.

040.

400-

13 d

2.30

14-3

3 d

3.44

34-5

2 d

1.20

53-5

8 d

7.32

5936

602.

060.

400-

13 d

2.40

14-3

4 d

3.54

35-5

3 d

1.20

54-5

9 d

7.54

6037

302.

080.

400-

13 d

2.50

14-3

4 d

3.64

35-5

4 d

1.20

55-6

0 d

7.76

6138

002.

090.

400-

13 d

2.60

14-3

5 d

3.65

36-5

5 d

1.30

56-6

1 d

7.94

6238

702.

110.

400-

13 d

2.70

14-3

5 d

3.75

36-5

5 d

1.30

56-6

2 d

8.14

6339

402.

120.

400-

13 d

2.80

14-3

5 d

3.85

36-5

5 d

1.30

56-6

3 d

8.35

Table 5.9 Feed schedule for male broilers



Table 5.10 Feed schedule for female broilers

Feed

all

ocat

ion

(kg/

bird

)A

geB

ody

F:G

Star

ter

Gro

wer

Fini

sher

Wit

hdra

wal

Tota

l Fe

ed(d

)W

t. (

g)(k

g)(a

ge)

(kg)

(age

)(k

g)(a

ge)

(kg)

(age

)(k

g)

3516

421.

730.

50-

14 d

1.66

15-3

0 d

0.68

31-3

5 d

2.84

3617

041.

750.

50-

14 d

1.79

15-3

1 d

0.70

32-3

6 d

2.98

3717

651.

770.

50-

14 d

1.89

15-3

2 d

0.73

33-3

7 d

3.12

3818

271.

790.

50-

14 d

2.02

15-3

3 d

0.75

34-3

8 d

3.27

3918

881.

820.

480-

13 d

2.20

14-3

4 d

0.78

35-3

9 d

3.44

4019

491.

840.

480-

13 d

2.31

14-3

5 d

0.80

36-4

0 d

3.59

4120

121.

860.

450-

13 d

2.47

14-3

6 d

0.82

37-4

1 d

3.74

4220

751.

880.

450-

13 d

2.61

14-3

7 d

0.84

38-4

2 d

3.90

4321

351.

900.

450-

13 d

2.75

14-3

8 d

0.86

39-4

3 d

4.06

4421

941.

920.

430-

13 d

2.88

14-3

8 d

0.90

39-4

4 d

4.21

4522

521.

940.

430-

13 d

2.48

14-3

6 d

0.50

37-3

9 d

0.95

40-4

5 d

4.37

4623

081.

960.

430-

13 d

2.44

14-3

5 d

0.70

36-4

0 d

0.95

41-4

6 d

4.52

4723

631.

980.

410-

13 d

2.37

14-3

5 d

0.90

36-4

1 d

1.00

42-4

7 d

4.68

4824

172.

000.

410-

13 d

2.32

14-3

4 d

1.10

35-4

2 d

1.00

43-4

8 d

4.83

4924

702.

020.

410-

13 d

2.28

14-3

4 d

1.30

35-4

3 d

1.00

44-4

9 d

4.99

5025

222.

040.

410-

12 d

2.23

13-3

4 d

1.50

35-4

4 d

1.00

45-5

0 d

5.14

5125

732.

060.

400-

12 d

2.15

13-3

3 d

1.70

34-4

4 d

1.00

45-5

1 d

5.30

5226

232.

080.

400-

12 d

2.11

13-3

3 d

1.90

34-4

5 d

1.05

46-5

2 d

5.46

5326

722.

100.

400-

12 d

2.06

13-3

2 d

2.10

33-4

6 d

1.00

47-5

3 d

5.61

5427

202.

130.

400-

11 d

2.04

12-3

2 d

2.27

33-4

7 d

1.05

48-5

4 d

5.81

5527

702.

160.

300-

11 d

2.02

12-3

1 d

2.56

32-4

8 d

1.10

49-5

5 d

5.98

5628

202.

180.

300-

11 d

2.00

12-3

1 d

2.74

32-4

9 d

1.10

50-5

6 d

6.14



Feed

all

ocat

ion

(kg/

bird

)A

ge

Bod

yF:

GSt

arte

rG

row

erFi

nish

erW

ithd

raw

alTo

tal

(d)

Wt.

(g)

(kg)

(age

)(k

g)(a

ge)

(kg)

(age

)(k

g)(a

ge)

Feed

(kg)

4222

551.

810.

600-

16 d

2.53

17-3

6 d

0.92

37-4

2 d

4.08

4323

231.

830.

580-

15 d

2.74

16-3

7 d

0.93

38-4

8 d

4.25

4423

601.

850.

540-

15 d

2.92

16-3

8 d

0.95

39-4

4 d

4.37

4524

561.

870.

540-

13 d

2.31

16-3

4 d

0.75

35-3

9 d

0.98

40-4

5 d

4.59

4625

211.

890.

520-

15 d

2.16

16-3

3 d

1.10

35-4

0 d

0.98

41-4

6 d

4.76

4725

861.

910.

510-

15 d

2.00

16-3

2 d

1.40

33-4

1 d

1.03

42-4

7 d

4.94

4826

511.

930.

510-

15 d

1.87

16-3

1 d

1.70

32-4

2 d

1.03

43-4

8 d

5.12

4927

151.

950.

500-

14 d

1.80

15-3

1 d

1.93

32-4

3 d

1.05

44-4

9 d

5.29

5027

761.

970.

490-

14 d

1.89

15-3

1 d

2.03

32-4

4 d

1.05

45-5

0 d

5.47

5128

361.

990.

470-

14 d

1.93

15-3

1 d

2.16

32-4

5 d

1.08

46-5

1 d

5.64

5228

962.

010.

460-

14 d

1.96

15-3

2 d

2.32

33-4

6 d

1.08

47-5

2 d

5.82

5329

562.

030.

450-

13 d

1.98

14-3

2 d

2.45

33-4

7 d

1.10

48-5

3 d

6.00

5430

152.

060.

440-

13 d

2.00

14-3

2 d

2.62

33-4

8 d

1.13

49-5

4 d

6.21

5530

752.

080.

380-

12 d

2.01

13-3

1 d

2.86

32-4

9 d

1.13

50-5

5 d

6.40

5631

352.

100.

350-

12 d

2.06

13-3

2 d

3.01

33-5

0 d

1.13

51-5

6 d

6.58

Table 5.11 Feed schedule for mixed-sex broilers



Starter GrowerHubbard Ross Cobb Hubbard Ross Cobb

ME (kcal/kg) 3000 3040 3023 3080 3140 3166CP (%) 22.0 22.0 21.5 20.0 20.0 19.5Ca (%) 0.95 1.0 0.90 0.90 0.90 0.88Av P (%) 0.44 0.50 0.45 0.40 0.45 0.42Na (%) 0.19 0.21 0.20 0.19 0.21 0.17

Methionine (%) 0.50 0.53 0.56 0.45 0.46 0.53Meth + Cys (%) 0.90 0.97 0.98 0.83 0.85 0.96Lysine (%) 1.25 1.35 1.33 1.15 1.18 1.25Threonine (%) 0.81 0.87 0.85 0.75 0.70 0.80

Finisher WithdrawalHubbard Ross Cobb Hubbard Ross Cobb

ME (kcal/kg) 3150 3200 3202 3160 3220 3202CP (%) 19.0 18.0 18.0 18.0 17.0 17.0Ca (%) 0.87 0.85 0.84 0.82 0.76 0.78Av P (%) 0.37 0.42 0.40 0.34 0.37 0.35Na (%) 0.19 0.21 0.16 0.19 0.21 0.16

Methionine (%) 0.42 0.43 0.48 0.39 0.42 0.44Meth + Cys (%) 0.80 0.80 0.88 0.75 0.79 0.88Lysine (%) 1.05 1.09 1.10 0.93 1.03 1.04Threonine (%) 0.72 0.72 0.73 0.69 0.70 0.70

Table 5.12 Diet specifications for 2.5 kg broilers

Table 5.13 Diet specifications for 2.5 kg broilers



Hubbard Ross CobbVitamin A (I.U) 7000 8270 12000Vitamin D3 (I.U) 3500 3030 4000Vitamin E (I.U) 40 50 30Vitamin K3 (I.U) 2.2 2.2 4.0Thiamin (mg) 4.0 2.4 4.0Riboflavin (mg) 6.0 7.7 9.0Pantothenate acid (mg) 11.0 12.7Niacin (mg) 45 51.8Pyridoxine (mg) 3.3 2.4 4.0Choline (mg) 750 - 400Folic acid (mg) 1.0 1.1 1.5Biotin (µg) 100 110 150Vitamin B12 (µg) 12 15.4 20

Manganese (mg) 66 120 120Zinc (mg) 50 110 100Iron (mg) 80 20 40Copper (mg) 9.0 16 20Iodine (mg) 1.0 1.25 1.0Selenium (mg) 0.30 0.30 0.30

Table 5.14 Vitamin-Mineral Premixes (starter or general)

b) PrestartersIt is generally recognized that the neonate chick

does not produce an adult complex of digestiveenzymes, and so digestibility is somewhatimpaired. This situation is further complicatedby the change in nutrient substrate of lipid andprotein in the embryo to quite complex carbo-hydrates, proteins and lipids in conventional starterdiets. So even though chicks grow quite rapid-ly in the first few days of life, there is the idea thatthis could be further enhanced by use of aprestarter. Prestarters therefore, either pre-con-dition the chick such that it can digest complexsubstrates and/or provide more (or more high-ly digestible) substrates until the chick’s enzymeproduction has ‘matured’.

The role of the unabsorbed yolk sac in earlylife nutrition is open to debate. On an evolutionaryscale the yolk sac likely provides a source of ener-gy, water and perhaps, most importantly, IgAmaternal antibodies for the young bird. Most altri-cial birds have virtually no yolk sac, while pre-cocial birds have considerable yolk reserves athatch. The yolk sac in chicks weighs around 8-10 g depending on the size of the original eggyolk. It is often stated that the residual yolk willbe used more quickly if the chick is without feedand water. It seems that yolk utilization is unaf-fected by presence or not of feed with a lineardecline in yolk weight up to 3 d post-hatch. Byday 3, regardless of feed supply, yolk size is onlyaround 2-3 g. During this time there is an



increase in enzyme supply within the intestin-al lumen. Specific activity of individual enzymesactually declines over the first week of life,although this is compensated for by rapidincrease in secretory cell numbers. Early cell dam-age, especially in the duodenum will greatly impair digestion.

While corn-soybean meal diets are regard-ed as ideal for poultry, there is evidence thatdigestibility is sub-optimal for the young chick.Parsons and co-workers show reduced AMEn andamino acid digestion in chicks less than 7-10 dof age (Figure 5.1).

Figure 5.1 Age effect on AMEn and lysinedigestion of a corn-soy diet (Batal andParsons, 2002)

With some 10% reduction in nutrient diges-tion compared to expected values, it is obviousthat our conventional starter diets are not idealfor young chicks.

The idea in formulating prestarter diets is tocorrect any such deficiency, and so hopefullyincrease early growth rate and/or improve uni-formity of such early growth. Two types ofprestarter diets are used for broiler chickens. Thefirst option is to use greater than normal levelsof nutrients while the alternate approach is to usemore highly digestible ingredients. Accordingto Figure 5.1, if we increase nutrient supply by10-15%, it should be possible to correct any defi-ciency in digestibility, and so realize expectedAMEn and amino acid utilization. A potentialproblem with this approach is the acceptance thatnutrients will not be optimally digested andthat such undigested nutrients will fuel micro-bial overgrowth.

An alternate approach is to use more high-ly digestible ingredients, with little change in levelof nutrients. Such prestarter diets are going tobe very expensive, since alternative ingredi-ents are invariably more expensive than arecorn and soybean meal. Table 5.15 showsingredients that could be considered in formu-lating specialized prestarter diets.

Using these ingredients, it is possible toachieve 190-200 g body weight at 7 d, comparedto 150-160 g with conventional corn-soybeandiets. This improved early growth rate contin-ues during most of the subsequent grow-outperiod (Table 5.16).

In this study, male broilers were 34% heav-ier than standard, when a highly digestibleprestarter was fed for the first 4 d. Because ofthe ingredients used in formulation, this prestarterwas twice as expensive as the conventionalcorn-soy starter diet. As shown in Table 5.16, theadvantage of using the prestarter diminisheswith age, although birds were still significantlyheavier at 42 d. Interestingly, the highly digestibleprestarter had no effect on uniformity of body



Max. % inclusion

Cereals Rice 40Corn 30Glucose (cerelose) 5Oat groats 5

Proteins Fish meal 5Fish protein concentrate 5Blood plasma 10Casein 8Soybean meal 20Alfalfa 4

Fats Vegetable oil 4

Additives Wheat enzymeMannanoligosaccharideProbioticLactic acid

Table 5.15 Potential ingredients for highly digestible prestarter diets

Table 5.16 Effect of using a highly digestible prestarter to 4 d of age, ongrowth of male broilers

Age (days)4d 7 d 21 d 33d 42d

Prestarter (0-4 d) 117 190 820 1900 2670Conventional 87 150 700 1700 2450Difference 34% 21% 17% 12% 9%

(Swidersky 2002, unpublished data)

weight at any time during the trial. In this andother studies, we have seen no advantage to usingso called ‘mini-pellets’ vs. using good quality fine crumbles.

c) Low nutrient dense dietsBy offering low protein, low energy diets (Table

5.2) it is hoped to reduce feed costs. However,

it is obvious that the birds will necessarily con-sume more of these diets and that birds may alsotake longer to reach market weight. These twofactors result in reduced feed efficiency.Surprisingly, broiler chickens seem to perform quitereasonably with low nutrient dense diets, and in certain situations these may prove to be themost economical program. If diets of low



energy level are fed, the broiler will eat more feed(Table 5.17).

In this study, only the energy level waschanged and the broiler adjusted reasonably wellin an attempt to maintain constant energy intake.Diet energy from 3300 – 2700 kcal ME/kg hadno significant effect on body weight, and this sug-gests the bird is still eating for its energy need.Obviously these data on growth rate are con-founded with the intake of all nutrients other thanenergy. For example, birds offered the dietwith 2700 kcal ME/kg increased their protein intakein an attempt to meet energy needs. Usingthese same diets, but controlling feed intake ata constant level for all birds (Table 5.18) showsthat energy intake per se is a critical factor in affect-ing growth rate.

With low energy diets, therefore, we can expectslightly reduced growth rate because ‘normal’

energy intake is rarely achieved and this fact isthe basis for programs aimed at reducing earlygrowth rate. However, live body weight is oftennot the ‘end-point’ of consideration for broilerproduction, since carcass weight and carcass com-position are often important. From the point ofview of the processor or integrator, these cheap-er diets may be less attractive. Carcass weightand meat yield are often reduced, and this is asso-ciated with increased deposition of carcass fat,especially in the abdominal region. Low proteindiets are therefore less attractive when one con-siders feed cost/kg edible carcass or feed cost/kgedible meat. This consideration of carcass com-position leads to development of diets that max-imize lean meat yield.

Another concept for feeding broilers is truelow nutrient dense diets, where all nutrient con-centrations are reduced (in practice energy andprotein/amino acids are most often the only

Table 5.17 Performance of broilers fed diets of variable energy content

Body weight (g) Feed intake (g/bird)Diet ME

25 d 49 d 0 – 25 d 25 – 49 d 0 – 49 d(kcal/kg)

3300 1025 2812 1468 3003 44713100 1039 2780 1481 3620 51012900 977 2740 1497 3709 52062700 989 2752 1658 3927 5586



Body weight (g) Feed intake: body weight gain

Diet ME 25 d 49 d 0 – 49 d(kcal/kg)3300 825a 2558ab 1.84c

3100 818a 2599a 1.82c

2900 790b 2439b 1.94b

2700 764b 2303c 2.05a

Table 5.18 Performance of broilers given fixed quantities of feed

Table 5.19 Response of male broiler to low nutrient dense finisher diets (35 – 49 d)

Diet nutrients Body wt. (g) Feed intake (g) Carcass wt. (g) Breast wt. (g)

ME CP 42 d 49 d 35 – 49 d 49 d 49 d(kcal/kg) (%)

3210 18.0 2420 2948 2583 2184 418

2890 16.2 2367 2921 2763 2107 404

2570 14.4 2320 2879 2904 2063 400

2250 12.6 2263 2913 3272 2088 402

1925 10.8 2170 2913 3673 2073 390

1605 9.0 2218 2892 4295 2038 378

nutrients changed in such a program). Examplesof such diets are shown in Table 5.2. With thistype of feeding program, one can expect slow-er growth and inferior feed efficiency, althoughthis should not be associated with increased fatdeposition. Depending upon local economic con-ditions and the price of corn and fat, this type ofprogram can be economical.

The older the broiler chicken, the greater itsability to adapt to very low nutrient dense diets.When broilers are offered very low nutrientdense diets in the finisher period, they adapt quitewell and growth rate is little affected (Table5.19). In the 42-49 d period broilers adjustedalmost perfectly to the low nutrient dense diets,and growth rate was maintained by adjustment

to feed intake. With the lowest nutrient densediet for example, which is at 50% of the controllevel of nutrients, broilers exactly doubled theirfeed intake. The reduction in carcass and breastweight is likely a reflection of reduced intake dur-ing the 35-42 d period of adjustment. It is notlikely that 50% diet dilution is economical, yetthe data in Table 5.19 indicates that the broileris not eating to physical capacity, and givensufficient time for adjustment, can at least dou-ble its feed intake. In the 42-49 d period, broil-ers fed the diet of lowest nutrient density con-sumed over 300 g feed each day.

d) Growth restrictionBroilers are usually given unlimited

access to high nutrient dense diets, or have



limited access during brief periods of darkness.It is generally assumed that the faster the growthrate, the better the utilization of feed, sincemaintenance nutrient needs are minimized

Figures 5.2 and 5.3 indicate the increase ingenetic potential of the male broiler over the last30 years. It is obvious that there has beenmajor emphasis placed on early growth rate, sincethe modern broiler is now at least 300% heav-

ier at 7 d compared to hatch weight, while 20years ago. This value was closest to 200%.

However, fast initial growth rate can lead to man-agement problems, such as increased incidence ofmetabolic disorders. Also, if early growth rate canbe tempered without loss in weight-for-age at 42 –56 d, then there should be potential for improvedfeed efficiency due to reduced maintenance needs.This concept is often termed compensatory gain.

Figure 5.2 Male Broiler Growth over the last 30 Years

Figure 5.3 Percentage weekly increase in growth of male broilers.



If growth rate is to be reduced, then basedon needs to optimize feed usage, nutrient restric-tion must occur early in the grow out period (Table5.20). As the bird gets older, a greater propor-tion of nutrients are used for maintenance andless is used for growth. Therefore, reducingnutrient intake in, say the first 7 d, will have lit-tle effect on feed efficiency, because so little feedis going towards maintenance (Table 5.20). At8 weeks of age, a feed restriction programwould be more costly, because with say a 20%restriction there would likely be no growth,because 80% of nutrients must go towardsmaintenance. Early feed restriction programs there-fore make sense from an energetic efficiency pointof view, and are the most advantageous in pro-grams aimed at reducing the incidence of meta-bolic disorders.

Table 5.20. Proportion of energy forgrowth vs. maintenance

benefits of improved feed efficiency are notrealized. This situation often happens when theperiod of undernutrition is too prolonged, or thedegree of undernutrition is too severe. A peri-od of undernutrition can be achieved by phys-ical feed restriction, diet dilution or by limitingaccess time to feed as occurs with some light-ing programs (see section 5.5).

In early studies, we fed broiler chickensconventional starter diets to 4 days of age andthen the same diet diluted with up to 55% ricehulls from 6 – 11 days. After this time, theconventional starter was reintroduced, followedby regular grower and finisher diets. Table 5.21indicates the amazing ability of the broilerchicken to compensate for this drastic reductionin nutrient intake from 6 – 11 days of age.

When broilers are fed limited quantities offeed through to market age, there is a pre-dictable reduction in growth rate (Table 5.22).

When there is continuous feed restriction, feedefficiency is compromised, since there is nopotential for compensatory growth. When feedrestriction is applied only during early growth,then there is potential for compensatory growth(Table 5.23).

(%) DistributionWeek Maintenance Growth

1 20 802 30 703 40 604 50 505 60 406 70 307 75 258 80 20

If birds grow more slowly in the first few weeksand achieve normal market weight for age,then the difference in the growth curves shouldbe proportional to the reduction in mainte-nance energy needs. Figure 5.4 shows an exam-ple of compensatory growth in female broilers,achieved by feed restriction from 4 – 10 d of age.

If regular market weight-for-age is notachieved due to early life undernutrition, then

Figure 5.4 Compensatory growth curveexhibited by female broilers.



Table 5.21 Effect of diet dilution with rice hulls from 6 – 11 days of age, oncompensatory growth of male broiler chickens

Treatment Body weight (g) Feed:gain ME/kg gain21 d 35 d 42 d 49 d 21 – 35 d 0 – 49 d 0 – 49 d

Control 733 1790 2390 2890 1.84 2.01 6.2150% dilution 6-11 d 677 1790 2380 2950 1.70 1.93 5.90

Table 5.22 Effect of 5 – 15% feed restriction from 1 – 42 d on broiler growth

Feeding system Body wt. (g) F:G Mortality (%) Carcass wt. (g)Ad lib 2401a 1.68 5.6b 1849a

5% restriction 2201b 1.76 4.5ab 1716b

10% restriction 2063bc 1.75 3.2ab 1625bc

15% restriction 1997c 1.78 1.1b 1518c

Adapted from Zubair and Leeson (1994)

Adapted from Urdaneta and Leeson (2002)

Table 5.23 Effect of feeding at 90% of ad-lib intake for various times, ongrowth and mortality of male broilers

Body wt. (g) F:G Mortality (%)35 d 49 d (0 – 49 d) Total SDS Ascites

Ad-lib 1744 2967 1.75 11.7 8.3 1.75 – 10 d1 1696 2931 1.71 8.3 4.9 1.7

5 – 15 d 1725 2934 1.69 8.3 3.3 1.75 – 20 d 1727 2959 1.70 8.3 4.9 1.75 – 25 d 1734 2947 1.69 8.3 4.9 1.75 – 30 d 1676 2875 1.69 5.1 1.6 0

190% of ad-lib

With 10% feed restriction from 5 up to 25 daysof age, there was minimal effect on growth rate,although feed efficiency was improved. Thisimprovement in feed utilization is a conse-quence of reduced mortality and reduced main-tenance need due to slower initial growth.When feed restriction occurs in the mid-periodof growth (14 – 28 d) there is little effect on mor-tality and growth compensation is rarely achieved.

The results of early feed restriction or under-nutrition on carcass composition are quite vari-

able. The early work of Plavnik and co-workerssuggested that feeding to maintenance energyneeds from 4 – 11 d of age resulted in a markedreduction in carcass fatness and especially yieldof the abdominal fat pad. The reasoning behindreduced fatness was limited early growth ofadipose cells. We have not been able to con-sistently duplicate these results. However, in moststudies, even when body weight compensationis achieved, there are often subtle reductions incarcass yield and especially breast meat yield.



A consistent result of early undernutrition isreduction in the incidence of metabolic disor-ders and especially SDS. Although such conditionsare less problematic than 5 –10 years ago theyoften still represent the major cause of mortal-ity and condemnations, and any reduction in mor-tality is of economic importance. It seems asthough early undernutrition can be economicalas long as final weight-for-age is not compromised.

A practical problem with diet dilution or feedrestriction, is deciding on levels of anticoccidi-als and other feed additives. With diet dilution,birds will eat much more feed. If for example,feed intake is doubled due to a 50% dilution,should the level of anticoccidial be reducedby 50%? With 50% feed restriction on theother hand, does there need to be an increasein concentration of these additives? This generalarea needs careful consideration, and results maywell vary with the chemical compounds underconsideration due to potential toxicity at criti-cal levels.

Where broilers are necessarily grown athigh altitude or when birds are exposed to envi-ronmental temperatures of <15˚C, mortalitydue to ascites is inevitable. Although the breed-ing companies have selected against this condition,mortality of up to 10% is still common in malebroilers grown under these adverse conditions.In these situations, mild feed restriction through-out rearing is often economical, where the 2 –3 d longer growing period is offset by much lowermortality. Table 5.24 gives examples of mild and

severe restriction programs for male broilers. Feedrestriction can start as early as 3 – 4 d. Table 5.24shows cumulative feed intake expected in the firstweek together with subsequent intakes each 2d. The cumulative intake data takes into accountthe intake on the odd days not shown.

e) Heavy broilers/roastersIn relation to its mature weight, the broiler

chicken is marketed at a relatively young age. At49 – 56 d, growth rate of the male bird is still lin-ear, even though maximum growth rate occursat 5 – 6 weeks of age. Modern strains of malebroilers are still able to increase their bodyweight by 450-500 g each week through to 11or 12 weeks of age. The breast yield of these olderbirds is maintained, and so very heavy broilersor roasters find ready niche markets. The majorchallenge in growing these heavy birds is pre-venting high levels of mortality. In a recentstudy in which broilers were offered ad-lib feedto a mature weight of around 8 kg, 70% mortalityoccurred in the male birds.

Perhaps the most important consideration ingrowing heavy broilers is development of spe-cialized feed programs that are not merely ‘con-tinuations’ of conventional 0 - 49 d broiler pro-grams. Table 5.3 provides examples of diets forheavy broilers grown to 60 – 70 d of age. Thereseems to be no need for high nutrient dense dietsat any time during growout, and even single stagelow-nutrient dense diets give reasonable results(Table 5.25).



Age

(d)

Stan

dard

Pro

gram

(g/

b)Se

vere

Res

tric

tion

(g/

b)M

ild

Res

tric

tion

(g/

b)D

aily

Cum

ulat

ive

Dai

lyC

umul

ativ

eD

aily

Cum

ulat

ive

834

184

3117

132

174

1049

274

4425

246

258

1258

387

4935

155

365

1472

524

6146

766

491

1681

680

6960

075

636

1891

857

7775

085

801

2010

010

5385

917

9698

822

109

1266

9811

0810

511

9324

118

1497

106

1316

115

1416

2612

417

4311

215

3812

216

5828

132

2003

123

1776

130

1913

3013

922

7712

920

3013

921

8732

147

2566

137

2299

147

2476

3415

428

7114

625

8615

427

8136

159

3188

151

2887

159

3098

3816

335

1215

531

9516

334

2240

167

3844

159

3510

167

3754

4217

141

8416

238

3317

140

9444

173

4529

164

4161

173

4439

4617

648

8016

744

9417

647

90

4818

052

3717

648

4418

051

47

Table 5.24 Examples of mild and severe feed restriction programs aimed atreducing incidence of metabolic disorders



Die

t C

P:M

E (

%:k

cal/

kg)

Bod

y w

t F:

GM

orta

lity

P

rote

in

Ene

rgy

Rel

ativ

e fe

ed

(g)

(%)

effi

cien

cyef

fici

ency

cost

0-21

d21

– 4

9 d

49 –

70

d70

d0

– 70

d0

– 70

dkg

/kg

gain

Mca

l/kg

gai

n(p

er k

g ga

in)

20:3

100

18:3

100

16:3

200

4193

a2.

26b

19.2

0.39

c7.

1ab

100

20:3

100

18:2

900

16:2

800

4088

ab2.

55a

16.7

0.44

b7.

3ab

101

20:3

100

18:2

900

18:2

900

4077

ab2.

48a

16.7

0.45

ab7.

2ab

9720

:310

020

:310

020

:310

040

46ab

2.40

ab12

.50.

48a

7.4a

105

18:2

900

18:2

900

18:2

900

4260

a2.

45ab

13.3

0.39

c6.

9b85

16:2

800

16:2

800

16:2

800

3753

b2.

45ab

10.8

0.39

c6.

9b85

Table 5.25 Growth of male broilers to 70 d when fed diets of varying nutrient density

Lees

on e

t al

. 200

0



Only with the single diet of 16% CP at 2800kcal ME/kg fed from 0 – 70 d was there reducedgrowth rate. In this study a single diet of 18% CPand 2800 kcal ME/kg appeared to be the most eco-nomical. Carcass yield and breast meat yield werenot different for all but the 16% CP diet. As shownin Table 5.25, mortality declined as nutrientdensity declined, yet even with just 16% CPand 2800 kcal ME/kg there was over 10% mor-tality to 70 d. Regardless of diet nutrient densi-ty, we have been unable to reduce mortalitybelow 10% without recourse to using mashdiets. It seems as though regardless of nutrientdensity, the broiler is able to increase its intakeof pelleted feed, and this undoubtedly con-tributes to high mortality. In order to reduce mor-tality this voracious appetite has to be controlled,and this can be achieved quite easily by offeringmash, rather than pelleted diets (Table 5.26).

grow-out. At the same time mortality wasreduced from 20% to 4%, and so feed efficien-cy was actually superior with the mash diet. Withlow nutrient dense diets growth rate is more great-ly affected by using mash diets, where 70 dmales are some 5 – 6 d behind schedule.Although there are logistical problems when usingmash diets in mechanized feeders and microbialcontrol may be more difficult, adapting feed texture seems to have great potential in growingvery heavy male broilers.

f) Feed withdrawalThe current major concern about feed with-

drawal relates to microbial contamination dur-ing processing. Regardless of withdrawal time,the gut will retain some digesta, and this can con-taminate birds during transportation as well asthe scald water during processing. Also if the intes-tines are broken during evisceration there ispotential for contamination.

Withdrawing feed 6 – 8 hr prior to catchingseems to be optimum in terms of the bird clear-ing the upper digestive tract and so reducing thechance of contamination and for ease of processinggizzards. The bird will lose weight during feed with-drawal, and this will average about 10 g/hrdepending on age and liveweight. A significantportion of this loss will be excreta evacuation bythe birds. The loss in eviscerated carcass weightis closer to 2 g/hr, with equal losses to breast andleg/thigh meat. Feed withdrawal does not seemto have major effects on blood or liver glucose orglycogen levels, and this may be the reason for therebeing fewer post-mortem changes such as PSE asoccurs with pigs and sometimes turkeys.

In addition to the concern about gut fill at pro-cessing, there is now interest in the pathogen loadof the digestive tract. The ceca have a veryhigh bacterial load and some of these will be

Table 5.26 Performance of malebroilers to 70 d when fed mash vs.pellet diets

Feeding high nutrient dense mash vs. pelleteddiets reduced growth rate by about 300 g to 70d, which represents just 2 – 3 d prolonged

Body Wt. F:G3 Mortality 70 d (g) (%)

High density1

Mash 3850 2.31 4.2Pellets 4166 2.44 20.0

Low density2

Mash 3571 2.45 5.8Pellets 4111 2.50 12.5

1 20% CP:3100 Kcal/kg ME, starter (0-21 d); 18% CP:3100 Kcal/kg ME, grower (21-49 d); 16% CP:3200 Kcal/kg ME, finisher (49-70 d).

2 18% CP:2900 Kcal/kg ME (0-70 d)3 Adjusted for mortality

Adapted from Leeson et al. 2000



pathogens of concern regarding food safety. Ina recent study, broilers were held on the litter orin crates for 24 hr without feed and surprising-ly there was little change in pH of the cecal con-tents or the bacterial populations. In fact, therewere few lactic acid producing bacteria, whichis a situation that allows pathogens to flourish.

Excessively long periods of feed withdrawalseem to actually increase the pathogen load inthe upper digestive tract. With 12 hr+ of feed with-drawal, there are often high counts ofCampylobacter in the upper digestive tract, andagain this is associated with a reduction in the pres-ence of lactic acid producing organisms. Withprolonged feed withdrawal, broilers are more like-ly to eat litter and this seems to be the source ofthe pathogens. Because problems are oftencorrelated with reduced populations of Lactobacillitype organisms, there is interest in offering birdslactic acid in the water during feed withdrawal.Water with 0.5% lactic acid has been shown toreduce the incidence of Salmonella andCampylobacter in the upper digestive tract by atleast 80%.

A more serious concern arises if birds are acci-dentally without feed for 12 hr+ in the 2 - 3 d priorto feed withdrawal. Broilers again are seen toeat litter, drink excessive amounts of water andso produce very wet manure. Both sexes havebeen observed to lose up to 100 g body weightafter 18 hr of no feed being available. Coupledwith a potential growth of 70 – 80g in this peri-od, means that birds are at least 170 g behind

expected standard weight. There is some com-pensation when feed is reintroduced, with birdseating up to 300 g in the first 24 hr following refeed-ing. Depending upon time of feed outage rel-ative to eventual withdrawal, means the bird canhave excessive quantities of digesta throughoutthe intestine.

The other aspect of late cycle broiler nutri-tion is potential for reducing nutrient levels,and particularly the inclusion of trace minerals,vitamins and various feed additives. Broilers seemmost responsive to total withdrawal of vita-mins, than to removal of trace minerals (Table 5.27).

Table 5.27 Broiler growth and F:Gfrom 42 – 49 d in response to vitaminand trace mineral supplementation

Vitamins Minerals Growth(g) F:G

+ + 564 2.41+ - 562 2.40- + 537 2.58- - 481 2.85

Adapted from Maiarka et al. 2002

Feed efficiency and growth are both com-promised by total withdrawal of vitamins from thefeed, and this effect is accentuated when trace min-erals are also removed. There is also concern withhigher mortality when vitamins and minerals arewithdrawn under heat stress conditions (Table 5.28).

Table 5.28 Removal of vitamins and trace minerals fromheat-stressed (24-35˚C) broilers

Vitamins Minerals 35-49 d wt gain (g) F:G Mortality (%)+ + 1280a 2.66a 9.6- - 1240b 2.86b 13.2

Adapted from Teeter (1994)


SECTION 5.3Assessing growth and efficiency

There are inconsistent reports on the effectsof removing anticoccidials and growth promot-ers during the last 5 – 10 d. This situation prob-ably relates to health status of individual flocks,and level of biosecurity etc. Since many ionophore

anticoccidials seem to influence proliferation ofnecrotic enteritis, then if growth promoters are notused in a feeding program, removal of ionophoresfor an extended period can compromise birdhealth and performance.

5.3 Assessing growth and efficiency

a) Broiler growth

W ith yearly increases in genetic poten-tial, standards for growth rate becomequickly dated. Over the past 20

years, there has been at least an annual increaseof 25g in body weight at 42 d of age, and in cer-tain periods we have seen gains of 30 – 50 g eachyear. This growth rate is fueled by feed intake. Withincreasing growth rate, there has been everincreasing efficiency of gain. It seems unlikely thatthe bird has increased its ability to digest protein,amino acids and energy from commonly used ingre-dients, and so, change in efficiency is simply a con-sequence of reduced maintenance need. Whilethere has to be a biological limit to growth rate,it is likely that management concerns will bethe issue that imposes a lower limit on market age.For example, there is now concern on the ‘matu-rity’ of the skeleton of female broilers destined forthe 1.75 kg market, where market age could be30 d or less within the next 5 – 7 years.

Factors influencing feed intake have the sin-gle largest effect on growth rate. Birds eat morein cooler environments and vice-versa, althoughthis situation is confounded with humidity,acclimatization and stocking density. As a gen-

eralization, maintenance energy requirementincreases by about 3% for each 1˚C decline inenvironmental temperature below 30˚C. Ifmaintenance represents 60% of total energyneeds, then feed intake is expected to change byabout 2% for each 1˚C change in temperature.Under commercial conditions stocking densityis going to be one of the major variables affect-ing growth and feed intake (Table 5.29).

With a higher stocking density, birds eat lessfeed, presumably due to greater competition at thefixed number of feeders. However this slightlyreduced growth is often accepted since there isgreater liveweight production from the broiler house.

It is generally assumed that broilers hatched fromlarger eggs will grow more quickly than those hatchedfrom small eggs. As broiler breeders get older, theyproduce larger eggs and so broiler growth is oftencorrelated with breeder age. In a recent study, wehatched broilers from breeders at 28, 38, 48 and58 weeks of age, and grew them under standardconditions within the same broiler facility.Interestingly, the growth of female broilers was mosthighly correlated with breeder age (Table 5.30).

Table 5.29 Influence of stocking density on broiler performance

Density (birds/m2) 49 d B.wt. (g) Feed intake (g) kg/m2

10.5 2337b 4973b 23.4a

13.5 2261a 4803a 28.9b

Adapted from Puron et al. (1997)



There was a significant linear trend over timeand from these data we can predict that bothliveweight and carcass weight will be influencedby differences in egg weight that result as a con-sequence of increased breeder age (Table 5.31).

Larger eggs usually have larger yolks, and itis often suggested that yolk size is the factorinfluencing growth as shown in Tables 5.30 and5.31. However, experimental removal of yolk mate-rial from an incubating egg has little effect on chicksize at hatch. Removal of albumen does howevercause reduction in chick size, and so perhaps itis the albumen content of large eggs that influenceschick size and subsequent broiler growth.However, a confounding effect is that yolk size doesinfluence the size of the residual yolk at hatch, andthis may have some effect on early growth ifchick placement is delayed.

While growth rate is of prime economicimportance, uniformity of growth is becoming ofincreasing concern. With mechanized feeding sys-tems, small birds have difficulty reaching feed andwater as they are raised to best suit the flockmean growth rate. The current lack of uniformityhowever, seems to start as early as the first weekof age. Even in well-managed flocks, there is skeweddistribution of that body weight, with a prepon-derance of smaller chicks (Figure 5.5).

Table 5.30 Broiler growth characteristics as affected by breeder age

Breeder age (wks)28 38 48 58

Male broiler:49 d live wt. (g) 3186 3249 3221 32730 – 49 d F:G 1.88 1.80 1.86 1.9649 d carcass wt. (g) 2498 2562 2610 -Deboned breast wt. (g) 587 605 607 -

Female broiler:49 d live wt. (g) 2595 2633 2667 27120 – 49 d F:G 2.11 1.95 2.01 2.0049 d carcass wt. (g) 1972 2028 2118 -Deboned breast wt. (g) 462 468 492 -

Table 5.31. Change in broiler live weight and carcass weight per1 g increase in breeder egg weight

Live weight Carcass weightMale broiler (49 d) + 5 g/g egg wt. +11 g/g egg wt.Female broiler (49 d) + 8 g/g egg wt. +14 g/g egg wt.

Fig. 5.5 Distribution of chick weight in awell managed broiler flock.



When specific health problems occur, suchas ‘feed passage’ or ‘stunting-runting syndrome’then the weight distribution is heavily biasedtowards small chicks (Figure 5.6).

There is a suggestion that yield of yolk andalbumen is not highly correlated with egg size.

b) Feed efficiencyA measure of the efficiency of feed utiliza-

tion is obviously of economic importance.Classical feed efficiency is calculated as feed intake÷ body weight, while the converse measure ofbody weight ÷ feed intake is often used inEurope. Feed is used by the bird for two basicreasons, namely for growth and for mainte-nance. In young birds most feed is used for growth(80%) and little is used for maintenance (20%)and so efficiency is very good. Over time effi-ciency deteriorates because the broiler has an ever-increasing body mass to maintain. Table 5.32shows expected changes in classical feed efficiencyrelated to age of bird.

These data suggest that at around 1.75 kg bodyweight, feed conversion will increase by 0.01 unitsfor each day of growth or that conversion willincrease by 0.013 units for each 100 g increasein market weight. As the bird gets heavier,these units of change increase (Table 5.32).

Over the years we have seen a steady declinein classical feed conversion from around 2.2 inthe early 1960’s to 1.75 today under certain sit-uations. This continually improving situation isdue to improved genetic potential, and the factthat more feed is directed towards growth (andless for maintenance) as days to market decline.

Body weight is a consequence of feed intake,and so feed intake tends to be the main variablein assessing feed efficiency. Historically broilerswere grown to 45 ± 3 days and fed diets with ener-gy levels that were standardized across the indus-try. Under these conditions, the measure of clas-sical feed efficiency is useful, and should relatedirectly to economics of production. Today, the

Fig. 5.6 Distribution of chick weight in afloor unit with obvious health problems.

In most flocks today there is a skewed dis-tribution of 7 d body weight with the unevennesscontributed by 12 – 15% of small chicks. Thistype of uneven distribution occurs even with hatch-es of eggs from individual breeder flocks. Thisearly loss in uniformity influences subsequent flockcharacteristics.

Each 1 g change in 7 d body weight alters18 d body weight by 3 g (i.e. a chick that is 30g underweight at 7 d will be 90 g underweightat 18 d. By 49 d the correlation is 1 g @ 7 d 5 g @ 49 d.

It is well known that chick size is influ-enced by size of the hatching egg. A range of eggweights are set, but usually the extremely smalland very large eggs are discarded. The currentvariance therefore occurs within the range of set-table eggs. The effects seen in Figures 5.5 and5.6 are made worse when broiler flocks arederived from a number of different age breed-er flocks. However the problem is not fullyresolved when eggs are graded prior to setting.



Weight Change in F:G per Daily change incategory 100 g body wt. F:G

1.75 kg 0.013 0.0102.50 kg 0.015 0.0143.50 kg 0.017 0.016

Table 5.32 Adjustments to feed efficiency based on body weight or age

Table 5.33 Performance and economic considerations of feeding broilersdiets of varying nutrient density

Mean diet energy1 Relative feed 45 d male body wt Feed:Gain Relative feed(kcal/kg) cost (kg) cost/bird

3000 100 2.7 2.10 1003100 105 2.7 2.00 993200 114 2.7 1.90 1023300 123 2.7 1.80 105

1 all other nutrients tied to energy

industry grows birds over a vast range of ages/mar-ket weights, and there is now considerable vari-ation in diet nutrient density. The fact that a clas-sical feed efficiency of 1.9 is achieved with a certainflock, has to be qualified in terms of sex ofbird, market age and diet nutrient density. Thelowest numerical feed efficiency may thereforenot be the most economical (Table 5.33).

As nutrient density increases, feed conversionpredictably declines. However, body weight isunaffected. Since high nutrient dense diets costmore, the feed cost per bird will only be reducedif birds eat correspondingly less feed. In thisexample, the most economic situation ariseswith mean energy level at 3100 kcal/kg, even thoughclassical feed efficiency is not optimized. Socalled ‘broiler growth models’ today should be ableto identify the most profitable diet, given feed price,broiler prices, expected performance, etc. The dietis ultimately least-costed in the traditional way, butthis prior selection is often referred to as ‘maxi-mum profit formulation”. A more useful meas-

ure of feed utilization is efficiency of energy use.When efficiency is based on energy, the energylevel of the diet is irrelevant, and so this major vari-able is resolved. Table 5.34 indicates expectedenergy efficiency in male and female broilers.

Table 5.34 Energy efficiency inbroilers

Energy intake Mcal/kg gain

Market age (d) Male Female 35 - 5.3542 5.39 5.8349 5.84 6.2856 6.30 6.8063 6.63 -

Assesssment of efficiency can be taken furtherthan the level of individual bird production to accom-modate such factors as feed cost, carcass yield andstocking density. In the future we may evenhave to consider manure management in ourassessment of production criteria (Table 5.35)


SECTION 5.4Nutrition and environmental temperature

Criteria Measurement Comments

Energy efficiency Energy intake: weight gain Energy is the most expensive nutrient, and so this value is important. To some extent, values are independent of feed intake.

Feed cost Feed cost: weight gain Takes into account the fact that the most expensive diet is not always the most profitable.

Carcass yield Energy intake: carcass wt. Takes into account the fact that birds of similar Energy intake: breast meat weight may not always yield the same amount Feed cost: carcass wt. of edible carcass.Feed cost:breast meat

Bird placement Feed cost/kg bird/sq. meter Optimizes the use of the building e.g.: higher floor space/yr nutrient dense diets give faster growth rate, Economic return/sq. meter therefore more crops per year.floor space/yr

Environment Nitrogen excretion/bird Future considerations for environmentalPhosphorus excretion/bird stewardship.

Table 5.35 Future considerations in assessment of efficiency of feed usage inbroiler production

5.4 Nutrition and environmental temperaturea) Bird response

M ost broiler farms will be subjected toheat stress conditions for at least partof the year. The terms heat stress or

heat distress are used to describe the conditionsthat affect broilers in hot climates. Becausebirds must use evaporative cooling (panting) tolose heat at high temperatures, humidity of theair also becomes critical. Consequently, a com-bination of high temperature and humidity is muchmore stressful to birds than are situations ofhigh temperature coupled with low humidity.Other environmental factors, such as air speedand air movement, also become important. Itis also becoming clear that adaptation to heat stresscan markedly influence broiler growth. Forexample, broilers can tolerate constant envi-ronmental temperatures of 38˚C (100˚F) and

perform reasonably well. On the other hand, mostbroilers are stressed at 38˚C (100˚F) when fluc-tuating day/night temperatures exist. In the fol-lowing discussion, it is assumed that fluctuatingconditions occur, because these are more com-mon and certainly more stressful to the bird.

A market weight broiler produces about 5 –10 kcals energy each hour. This heat, which isgenerated by normal processes in the body,must be lost to the environment by convec-tion, conduction and/or evaporation. The broil-er will conduct heat from its body to whateverit touches, assuming that these objects (litter, etc)are at a lower temperature than is body temperature(41˚C). The broiler will also convect heat awayfrom its body, through circulating air, again



assuming that the air temperature is less than bodytemperature. The balance of heat production andheat loss is such that body temperature is main-tained at around 41˚C.

Interestingly, under thermoneutral condi-tions, body temperature has little influence onperformance. However, as body temperature getsmuch above 41.5˚C for broilers under heat dis-tress, then there is good correlation between risein body temperature and decrease in perform-ance. Much above 42˚C mortality is inevitable.

In order to dissipate more and more heat, evap-orative cooling has to be increased. Water bal-ance and evaporative water loss of the broiler undernon-heat stress conditions changes over time.In the first week of life, about 35% of total waterintake is excreted through evaporative losses.By seven weeks of age, this amount increases to70%. This increased emphasis on evaporative waterloss with age is one of the reasons why the olderbird has more problems in balancing its heatload during heat stress, because evaporative sys-tems are so heavily relied upon under normal con-ditions. The bird does not have sweat glands, andso at high temperatures, evaporative cooling is theonly effective means of greatly increasing heat loss.As the bird pants under heat stress conditions, watervapour is lost in the exhaled air with each breath.Some heat is lost in raising the temperature ofexhaled water vapour, from ambient (drinking watertemperature) to that of body temperature. However,this heat loss is insignificant in relation to the heatloss needed to evaporate water. About 0.5 kcals

of energy are lost for each gram of water evapo-rated during breathing. A market weight broilerproducing 200 kcals heat energy per day needsalmost 400 grams water loss by evaporation.This is an extreme case, because other heat dis-sipation mechanisms are also active and the birdalso loses some water via the urine. However, thissimple calculation does emphasize the need forincreased water intake during excessive heatstress. Unfortunately, the situation is made worseby the fact that cooling mechanisms, such aspanting, generate significant quantities of body heat.In fact, it has been calculated that panting intro-duces an extra 20 – 25% heat load on the bird.

The major heat load in the body arises fromthe digestion and metabolism of food. A simpleway of avoiding heat stress, therefore, is toremove feed. Under less stressful conditions, weare interested in maintaining growth rate closeto genetic potential, and this means feeding atclose to normal physical intake. However, dif-ferent nutrients produce different quantities ofheat during metabolism. For example, themetabolism of fat is most efficient, and metab-olism of protein is least efficient in this respect.Unfortunately, the metabolism of all nutrient isfar from being 100% efficient, and so even fordietary fats, there will be some heat evolved dur-ing normal metabolism.

This means that diet formulation can be usedto advantage in trying to minimize heat load.Unfortunately, the major heat load is going to bea consequence of feed intake per se (Table 5.36).



Feed/day0 g 50 g 100 g 150 g

24˚C environment:Heat production 192 204 212 236Sensible loss 160 168 180 192Evaporative loss 44 40 44 48

Balance -12 -4 -12 -4

35˚C environment:Heat production 196 220 240 248Sensible loss 88 112 96 132Evaporative loss 72 88 92 96

Balance 36 20 52 20

Table 5.36 Energy balance of a 2 kg broiler (kcal/bird)

Adapted from Wiernusz and Teeter, (1993)

Table 5.37 Male broiler feed intake at 15-30˚C

Male broiler (g feed/bird/day)

Age (d) 15˚C 20˚C 25˚C 30˚C14 78 72 65 5921 120 110 100 9028 168 154 140 12635 204 187 170 15342 240 220 200 18049 264 242 220 194

At 24˚C, the broiler is in near perfect balance,with heat production being similar to heat dis-sipation. At 35˚C, the broiler is in severe pos-itive energy balance, where heat dissipation can-not match the heat load generated by feedmetabolism. In this situation, the broiler has toquickly correct the balance, and the easiestsolution is to reduce heat load by voluntary reduc-tion in feed intake. Such changes in feed intakewill occur very quickly, certainly within hours,because the birds must maintain the balance atclose to zero. Table 5.37 shows the expectedfeed intake of male broilers housed at varyingenvironmental temperatures.

Broilers will acclimate to warm conditionsand can perform reasonably well at constant tem-peratures as high as 36˚C. However, if broilersare normally held at 25˚C a sudden change intemperature to 36˚C may prove fatal, and willcertainly influence growth rate. There is someresearch to suggest that intentionally subjectingyoung broiler chicks to high temperaturesenables them to better withstand subsequent heatstress conditions when they are older. Such accli-mated birds seem to show less of an increase intheir core body temperature when later (up to 4– 6 weeks) exposed to high temperatures. Heatacclimatized birds do seem to drink more



water and eat more feed under heat stress conditions. Therefore, because acclimatizedbirds are prepared to eat more feed, this inducesa greater heat load, so this can counterbalancethe effect of prior acclimatization. For prioracclimatization to be useful therefore, it seemsnecessary to combine this with some degree offeed restriction if maximum benefits are to be

achieved. It is likely that the confounding effectof ‘increased’ feed intake by acclimatized birdsis responsible for variation in results of trials andfield studies of early life heat stress acclimatization.

The general growth response of male broil-ers of 500-2500 g body weight to a range of envi-ronmental temperatures is eloquently shownby the data of May et al. (1998).

500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500Beginning weight, g Adapted from May et al, 1998

100

95

90

85

80

75

70

65

60

Gai

n/da

y, g

23C25C27C29C31C

Fig. 5.7 Effect of environmental temperature on daily growth of male broilers.



b) Potential nutritional intervention

Nutritional intervention to limit the effects ofheat stress include change in levels of nutrients,change in ingredient composition, time of feed-ing and in extreme situations, removal of feed.

In terms of nutrients and ingredients, thelevel of crude protein should be minimizedand the level of supplemental fat increased to prac-tical maximums. It is usually not economical touse constraints for crude protein that increase over-all diet cost by more than 5 – 8%. In general,economical reductions in crude protein level arein the order of 2 – 3% (e.g. 22 20% CP). Amajor problem related to metabolism of proteinsis the heat increment related to transamination(rearrangement), deamination (breakdown), andexcretion of nitrogen as uric acid in the urine.It follows therefore, that amino acid balance with-in a diet is as important as the total level of crudeprotein. With 4% excess CP in a diet (due to usingpoorer quality ingredients, while trying to achievethe level of limiting amino acids), the bird’sheat output is increased by 8 – 10%. Protein qual-ity, therefore, becomes critical in these diets.

Because energy intake is often the limitingfactor to growth during heat stress, it is tempt-ing to recommend high-energy diets that con-tain high levels of supplemental fats. Unfortunately,the broiler is still eating to its energy requirement,so simply increasing the energy concentrationof a diet does not ensure a major increase in ener-gy intake. Broilers will tend to eat more ener-gy with higher energy diets, so it can be usefulto consider such a formulation change althoughin itself this change will not correct growthdepression.

Acid:base (electrolyte) balance in the broil-er is altered at high temperatures because of the

associated effect of increased carbon dioxide lossdue to panting. There has been considerableresearch in this area, investigating the potentialof maintaining normal anion:cation balanceduring heat-stress. However, the general con-sensus at this time is that acid:base balanceper se is not a major factor influencing eithergrowth rate or survival of broilers in heat stressconditions. This is not to say that adding elec-trolytes to the feed or water is ineffective, rather,their mode of action may be other than by alter-ing or maintaining acid:base balance.

It seems as though the benefit of addingelectrolytes to the feed or water is simply to increasethe bird’s water intake which in turn fuels evap-orative cooling. Various studies have been con-ducted in which broilers have been given min-eral supplements in the water, producing arange of anion-cation balance. For example, both(NH4)2SO4 and NaHCO3 are effective water sup-plements used in trying to combat heat stress, yettheir ion balances are very different. The ben-eficial effects of these supplements seem moreclosely correlated with their effects on water intake.

Adding a mineral salt, such as KCl increas-es water intake and evaporative heat loss ofthe bird. A common treatment and/or preven-tative measure during heat stress, is to add NaClat 0.5% to the birds’ drinking water. For broil-ers eating 100 g of feed containing 0.2% Na (0.5%salt) each day, means that birds consume 30%of their daily Na from feed and 70% of Nafrom treated water. The level of water supple-mentation should therefore, represent a signif-icant increase in the birds’ Na (or K) intake.Maintaining or stimulating water intake seemsto be a key factor in maintaining growth rate ofolder broilers subjected to hot environments. Inthis regard, the use of drinker equipment is a fac-tor (Table 5.38)



Birds were always heaviest when using the opentrough drinkers, and nipple height also influ-enced growth. At 30˚C, the difference in growthfor birds using open trough vs. nipples is greatly accentuated. The actual reason behind better growthwith open trough drinkers is not fully resolved. Itis likely that birds drink more water, but they alsomay immerse their wattles in open trough drinkersand this aids evaporative cooling. However,nipple drinkers are often preferred, since litter con-dition is easier to manage. Nipple height is alsocritical for optimum water intake. As a rule-of-thumb nipple height should be at 10 cm at dayof age, and then increase by 5 cm per week.

In situations when broiler mortality is the mainconcern, the best recourse is to remove feed, soas to reduce heat load on the bird. The time of

peak mortality due to heat stress is usually in lateafternoon, which does not always coincide withthe hottest time of the day. The late afternoon peri-od does, however, coincide with the time of peakheat of digestion and metabolism for birds eat-ing substantial quantities of feed in the early-midmorning period. Consequently, it is often rec-ommended to withdraw feed prior to antici-pated time of peak environmental temperature,to minimize the heat load of the bird.

A common management scenario is toremove feed at 10 a.m. and re-feed at 5 p.m. Sucha system assumes having some supplemental lightsso that they can eat at cooler times of the day.Table 5.39 summarizes recommendations for feedformulation and feeding management for heatstressed broilers.

Table 5.38 Broiler growth at 25˚C vs 30˚C using open trough or nippledrinkers (g/bird)

Water system 25˚C 30˚C28 d 49 d 28 d 49 d

Open trough 1424a 3275a 1349d 2632d

Low nipple 1411b 3199b 1336e 2395e

Medium nipple 1400b 3164b 1333e 2300f

High nipple 1385c 2995c 1303f 2104g

Adapted from Lott et al. (2001)


SECTION 5.5Nutrition and lighting programs

Strategy Activity

Feed formulation 1. Reduce crude protein by 2 – 3%.2. Maintain levels of Meth + Cys, Lysine and Threonine.3. Increase diet energy by direct substitution of 2% fat for 2% of major cereal.4. Add 250 mg Vitamin C/kg diet.5. Use only highly digestible ingredients.6. Select appropriate anticoccidials.

Feed management 1. Withdraw feed 10 a.m. – 5 p.m.2. Ensure adequate feeder space and drinkers.3. Manage nipple height according to bird age.4. Add 0.5% salt to the drinking water.5. Keep drinking water as cool as possible.

Bird management 1. Increase air flow at bird level.2. Maintain litter quality.3. Use lower stocking density.4. Do not disturb birds at time of peak heat distress

Table 5.39 Strategies for reducing the impact of heat stress

L ighting programs are now used routine-ly in growing broilers, and in someEuropean countries it is mandatory to give

broilers a period of darkness. An extendedperiod of darkness each day seems to reduce theincidence of SDS and leg problems, and inwinter months may help to control ascites in heav-ier males. The major advantage to these lightprograms is a period of rest and/or tempering ofgrowth rate, which both seem to improve livability.There may also be some subtle effects of lightthat influence the bird’s metabolism. In addi-tion to influencing sex hormone output inmature birds, light also affects the pineal glandat the base of the brain, and this is responsiblefor production of another hormone, namelymelatonin. Melatonin is produced during longperiods of darkness, and is the hormone respon-sible for shutting down the reproductive system

in wild birds during the fall. Broilers subjectedto long periods of darkness will produce moremelatonin, and this is thought to be involved insome way with the beneficial effects of such lightprograms. Adding synthetic melatonin to the dietof broilers does cause a calming effect, but doesnot seem to have any influence on mortality. Themain feature of a lighting program for an imma-ture bird such as the broiler is simply that duringdarkness, birds are more reluctant to eat, and sothis controls growth rate.

If one visits 20 different broiler farms, it is pos-sible to see 20 different lighting programs.However, all have the common feature of impos-ing a long period of darkness that lasts for at least8 hours. Differences occur in the ages at whichthe light restriction is initiated and the pattern ofreturning to a longer daylength.

5.5. Nutrition and lighting programs



Broilers are reluctant to eat in the dark, andso the major ‘activity’ during darkness is simplysitting. However, some birds will attempt to eatand drink at this time and this disturbance cancause scratching and downgrading of the carcass.Such problems, which lead to infection, will bemore prevalent with high stocking densities,and when longer (> 8 hr) periods of darkness areused after 22 – 25 days of age. The shorter theperiod of light the greater the reduction in feedintake, and so the greater the control overgrowth. If birds are kept on constant short daysto 49 d (i.e. no compensatory step-up) thengrowth rate will be reduced. On average, for each1 hour of darkness, broiler growth will bereduced by 20 g. Therfore, keeping birds on con-stant 12 hr vs. constant 24 hr from 1 – 49 d, willreduce growth by about 240 g. However, thereduced growth will be accompanied by reducedmortality. In practice, it is more common to step-up the hours of light after 2 – 3 weeks, and thisallows for growth compensation.

There is little doubt that short-day lighting pro-grams are most beneficial for male broilers.They are particularly successful for males grownto heavier weights and less useful (and perhapsdetrimental) to lightweight females. Table 5.40shows typical research results for 49 d malebroilers.

While broilers will be smaller during theperiod of extended darkness, they are able to com-pensate by 49 d. Mortality is reduced, and espe-cially the incidence of leg disorders. Although oftennot statistically significant, there is usually aslight reduction in breast meat yield for broilerson reduced daylength as shown in Table 5.40.

As previously mentioned, there are manydifferent light programs, and selection depends onsex of bird, diet nutrient density, pellet quality, mar-ket weight and whether or not blackout or open-sided housing is used. In addition, the extendedperiod of darkness may be less severe or shortenedsomewhat in the summer vs. winter, since hot weath-er also reduces growth rate, and the two combinedcan cause delay in grow-out. Table 5.41 summarizesthe factors influencing choice of light program. Table5.42 shows examples of lighting programs takingthese factors (Table 5.41) into account.

Light intensity can also influence bird activ-ity and feed intake. The higher the intensity,usually the greater the bird activity and so this canlead to more maintenance costs, and poorerfeed efficiency. Higher body weights and betterfeed efficiency have been recorded at 5 vs. 150lux. Light intensity after brooding should be at 2– 5 lux, which is the minimal intensity for the stock-person to adequately inspect birds and equipment.

Table 5.40 Effect of step-down, step-up lighting for male broilers

Treatment 49 d B. wt. F:G Mortality Leg problems Breast yield (kg) (%) (%) (%)

23L:1D 2.86 1.85 8.5 20.0 24.8Step-down:Step-up 2.82 1.86 3.0 9.5 24.2

Adapted from Renden et al. (1996)



Parameter Consideration for light:dark schedule

1. Strain of bird Earlier fast growth means need for earlier introduction of reduced daylength.

2. Diet nutrient density With higher nutrient density there is more benefit to a longer and more extended period of darkness.

3. Pellet quality The better the pellet quality, the greater the need for light control.4. Market weight For older, heavier birds, delay step-up schedule.5. Open sided vs. blackout housing Open-sided housing dictates the maximum period of darkness.

With blackout housing there is absolute control over duration and intensity of light period.

6. Season Less severe programs in hot weather because growth-rate is already reduced.

Table 5.41 Factors influencing choice of light program

Table 5.42 Examples of light programs for birds grown to 42 or 56 d in eithersummer or winter, in open or blackout houses (hours light/day)

Age (d) Black out Open-sidedSummer Winter Summer Winter

42 d 56 d 42 d 56 d 42 d 56 d 42 d 56 d0 – 5 23 23 23 23 23 23 23 235 – 8 14 12 12 10 Natural Natural Natural Natural8 - 12 14 12 12 10 Natural Natural Natural Natural12 – 16 14 12 14 12 14 Natural Natural Natural16 – 20 16 14 14 12 16 14 14 Natural20 – 24 16 14 16 14 16 14 14 1424 – 28 18 16 16 14 18 16 16 1428 – 32 18 16 18 16 18 16 16 1632 – 36 18 16 18 16 18 16 16 1636 – 40 18 18 18 16 18 18 18 1640 – 44 18 18 18 18 18 18 18 1644 – 48 - 18 - 18 - 18 18 1848 – 52 - 18 - 18 - 18 - 1852 - 56 - 18 - 18 - 18 - 18


SECTION 5.6Nutrition and gut health

There is little information available on theeffect of color (wavelength) of light on broilers. Itseems as though wavelengths above 550 nm (pur-ple-orange-red colors) cause reduced growth rate.On the other hand, shorter wavelengths, at the blue-green end of the spectrum produce increasedgrowth rate. These effects are quite subtle (5% max-imum) yet it is conceivable that light color couldbe used to either slow down or speed up growthrate at specific times during grow-out. Currentlybulbs that produce light at a specific wavelengthe.g. red or green, are very expensive.

Intermittent lighting is another option formanaging broilers, although unlike the step-down step-up programs described previously, thissystem is intended to stimulate growth rate.

Short cycles of light and dark are repeatedthroughout the day, the most common being eightcycles of 1 hr light:2 hrs darkness. The idea behindthe program is that birds will eat during thelight period and then sit down during the 2 hrdark cycle and be ready to eat again whenlights return. Obviously adequate feeder spaceis essential with the program and it is onlyviable with black-out housing (Table 5.43).

With intermittent lighting, it is assumed thatenergy efficiency will be improved, since birdsare inactive for 66% of the day. In the studydetailed in Table 5.43, there was greater overallheat production for birds on the 1L:2D pro-gram, and so increased growth was simply a fac-tor of increased feed intake.

5.6 Nutrition and gut health

Bacterial and parasitic infections of thegastro-intestinal tract are an ever presentthreat to broilers grown on litter floors. The

microbial status of the tract is kept in balance byuse of anticoccidials in conjunction with so-called growth promoters. The mode of action ofgrowth promoters has never really been fullyexplained, yet when they are excluded from thediet, bacterial overgrowth can occur. The role ofgut health in broiler performance has suddenlybecome topical because of current or pending leg-islation concerning use of antibiotics in poultrydiets. With the current pressure on antibiotic usein animal diets, it seems less likely that new

products will be developed, and so one sce-nario is that at most, only currently registered prod-ucts will be available.

We are greatly hampered in the study ofgut health by not knowing, with any great pre-cision, the normal microflora present in healthybirds. It has been suggested that, at best, con-ventional culture techniques are isolating 50%of the species of bacteria present in the gut. Newertechniques involving DNA fingerprinting ofmicrobes may give us a better understanding ofthe complexity of the microflora, and in partic-ular, how they change in response to various diet

Table 5.43 Male broiler growth with intermittent vs. continuous lighting

Body weight (g)Lighting 21 d 42 d 56 d 0 – 56 d F:G

Continuous 717 2393 3459 2.071 hr L: 2 hr D 696 2616 3637 2.03

NS * ** NS

Adapted from Ohtani and Leeson (2000)



treatments. On the other hand, we are awareof the major pathogens, and as a starting pointin maintaining gut health, it is more promisingin the short-term to concentrate on their control.

The chick hatches with a gut virtually devoidof microbes, and so early colonizers tend to pre-dominate quite quickly. The enzyme system andabsorptive capacity of the newly hatched chickis also quite immature. As previously describedin section 5.2b, selection of ingredients eaten bythe chick in the first few days of life will undoubt-edly influence microbial growth and perhapsmicrobial species. Any undigested nutrientswill be available to fuel microbial growth in thelower intestine and ceca – if these happen toinclude pathogens, then the chick will be dis-advantaged. The ‘normal’ gut microflora devel-ops quite quickly, and so microbial numbers andspecies present on the hatching tray, in thehatchery, during delivery, and the first few daysat the farm will likely dictate early colonization.While ‘dirty-shelled’ eggs may hatch quite well,they do provide a major source of microbial col-onization for the hatchling.

The Nurmi concept of manipulating gutmicrobes relies on early introduction of non-path-ogenic microbes. Ideally, these microbes will helpprevent subsequent pathogenic colonizations.Today, there is not an ideal culture for such a com-petitive exclusion product, which is again afactor of our not knowing the profile of a healthymicroflora. In the past, undefined cultures havebeen used with reasonable success, but now reg-ulatory agencies are insisting on dosing birds onlywith accurately defined cultures. It seems thatif competitive exclusion (CE) is to be successful,cultures must be administered as soon as pos-sible, and time of placement at the farm may betoo late. However CE is undoubtedly going tobe one of the management tools routinely usedin broiler production.

Rapid early development of the intestinalepithelium is also another prerequisite for nor-mal digestion. The villi and microvilli growrapidly in the first few days, and any delay in thisprocess is going to reduce nutrient uptake.Presence of pathogens, mycotoxins and ani-mal and plant toxins will all delay microvilli devel-opment. Selection of highly digestible ingredi-ents, devoid of natural toxins where possible, istherefore important for rapid early gut development.As the epithelium develops within the microvil-li, where mucus is secreted and this acts as animportant barrier against pathogenic coloniza-tion and also auto digestion from the bird’sown digestive enzymes. Some bacteria areable to colonize because they are able to break-down this protective mucus layer. Heliobacterpylori, the bacteria that causes gastric ulcers inhumans, secretes urease enzyme that destroysthe protective mucus coating, thereby making thestomach wall susceptible to degradation byhydrochloric acid and pepsin. It would beinteresting to study the gut microflora of birds fedhigh urease soybean meal.

In addition to capturing digested nutrients, theepithelium of the gut also secretes large quanti-ties of water that aid in digestion. For eachgram of feed ingested, up to 2 ml of water maybe infused into the gut lumen, and this will sub-sequently be resorbed in the lower intestine. Ifthe epithelium is damaged by pathogens or tox-ins, then it can become a net secretor of water,and this contributes to diarrhea type conditions.Some strains of E. coli can also secrete toxins thatdisrupt water balance and contribute to diarrhea.Rancid fats also contribute to diarrhea by caus-ing sub-lethal injury to the microvilli epithelium

Without the use of antibiotic growth promoters,the incidence of necrotic enteritis and coc-cidiosis are often the main production con-cerns. It now seems obvious that one of the major



modes of action of growth promoters is controlover necrotic enteritis caused by Clostridium per-fringens. The association between coccidiosisand necrotic enteritis may be as simple as coc-cidial oocysts damaging the gut epithelium andso allowing for greater adhesion of clostridial bac-teria. There is no doubt that judicious use ofionophore anticoccidials or coccidial vaccinesare important in the control of necrotic enteritis.

There has been a significant increase in theincidence of necrotic enteritis (NE) in Europe fol-lowing removal of growth promoting antibi-otics. Unfortunately, broiler diets in Europeare often based on wheat as the major cereal andit is well documented that clostridia multiply andcolonize more quickly when the diet containsmuch more than 20% wheat. An interesting obser-vation in Europe is that clostridia are now col-onizing the upper digestive tract as well as the

normal site of adhesion in the small intestine.Coupled with increased incidence of NE, socalled ‘dysbacteriosis’ is now common inEuropean broiler operations, and representsabnormal microbial overgrowth in the absenceof antibiotic growth promoters. This latter con-dition does not seem to be related to diet com-position or ingredient selection. Necrotic enteri-tis is also more common if the diet contains pectinscontributed, for example, by ingredients such asrye. While rye is not a common component ofbroiler diets, such findings indicate that diges-ta viscosity, and associated maldigestion, areideal for bacterial proliferation. There is a suggestionthat clostridial growth is greatly reduced in dietscontaining wheat that is processed through aroller mill, rather than a conventional hammer mill.Table 5.44 summarizes suggestions for trying tominimize the incidence of necrotic enteritis in birdsfed diets devoid of antibiotic growth promoters.

Table 5.44 Actions to reduce the incidence of necrotic enteritis in broilers

Action Effect1. Minimize feed changes Change in ingredient/nutrient composition is

associated with change in gut microflora

2. Use highly digestible ingredients Undigested nutrients fuel bacterial overgrowth

3. Minimize the use of wheat (< 20% Increased digesta viscosity leads to greater clostridialideally) activity. Enzyme addition important

4. Process wheat through a roller mill Change in digesta viscosity?

5. Use only quality fats and oils Rancid fats injure the microvilli

6. Ensure low level of urease/trypsin Urease can destroy protective mucus barrierinhibitor in soybean meal

7. Use ingredients with minimal levels of Toxins can destroy epithelial cells in the microvillimycotoxins, especially up to 28 d of age

8. Use appropriate ionophore anticoccidials Coccidiosis predisposes clostridial growthor coccidial vaccines


SECTION 5.7Metabolic disorders

Another approach to maintaining gut healthis microbial reduction in feed and water. Thereis no doubt that high temperature pelleting (�80˚C)can inactivate pathogens such as salmonella.However, ‘sterile’ feed is an ideal medium for sub-sequent bacterial colonization (since there is nocompetition for growth) and so a practical prob-lem is to prevent subsequent recontaminationbetween the time feed leaves the mill and is deliv-ered to the feed trough. Organic acids, such aspropionic acid, can help prevent such reconta-mination, and where allowed by regulatoryagencies, formaldehyde is especially effectiveagainst colonization by salmonella.

Drinking water is another potential routeof bacterial infection. Many farms utilize somesystem of water sanitation, such as chlorine at3 – 4 ppm. While such sanitizers hopefullyensure a clean water supply at the nipple, theyhave no effect on gut health. Of more recent inter-est is the use of organic acids, such as lactic acid,as both a sanitizer and to manipulate gut pH.Adjusting water pH from regular levels of 7.2 –7.5, down to pH 5 with products such as lacticacid are claimed to reduce pathogen load in young

broilers. In a recent study, we observed improvedgrowth with using drinking water at pH 5 vs. pH7.5. Interestingly, at pH 4, produced by simplyusing more organic acid, we observed fila-mentous yeast growth in the water lines, and thisimpacted water intake by clogging nippledrinkers. Yeast are always present in poultry facil-ities and thrive in acid environments.

The other alternate dietary intervention forpreventing bacterial overgrowth is use of manan-oligosaccharides. Many pathogens such as E. coliattach to the gut epithelium by small appendagescalled fimbriae. These fimbriae actually attachby binding to mannose sugar receptors. If man-nose sugars are included in the diet, they also attachto these binding sites and effectively blockattachment by many strains of E. coli andSalmonella. Commercial products such asBioMos®, which is derived from the outer cellwall of Saccharomyces yeast, is often used as part of an alternative strategy to antibiotics.Such products seem most efficacious whenused on a step-down program, such as 2 kg, 1kg and 0.5 kg per tonne in starter, grower and finisher diets.

5.7 Metabolic disorders

T here has been a steady decline in theincidence of classical metabolic disor-ders as a consequence of genetic selection

for liveability. Metabolic disorders such as ascites,Sudden Death Syndrome (SDS) and leg disorderscollectively still account for the majority of mor-tality and morbidity in healthy flocks, although thetotal incidence is now closer to 2 – 3 % vs. 4 – 5% just 10 years ago. In male broilers, SDSwill usually be the major cause of mortality start-ing as early as 10 – 14 d of age. At high eleva-

tions, and/or in cool climates ascites can still beproblematic and often necessitates tempering ofgrowth rate as a control measure.

a) AscitesAscites is characterized by the accumulation

of fluid in the abdomen, and hence the basis forthe common name of ‘water-belly’. Fluid in theabdomen is, in fact, plasma that has seepedfrom the liver, and this occurs as the end resultof a cascade of events ultimately triggered by oxy-



gen inadequacy within the bird. For various rea-sons, the need to provide more oxygen to the tis-sues leads to increased heart stroke volume,and ultimately to hypertrophy of the right ven-tricle. Such heart hypertrophy, coupled with mal-function of the heart valve, leads to increased pres-sure in the venous supply to the heart and sopressure builds up in the liver, and there isoften a characteristic fluid leakage.

Because of the relationship with oxygendemand, ascites is affected and/or precipitatedby such factors as growth rate, altitude (hypox-ia) and environmental temperature. Of these fac-tors, hypoxia was the initial trigger some yearsago, since the condition was first seen as amajor problem in birds held at high altitude, wheremortality in male broilers of 20 – 30% was notuncommon. Today, ascites is seen in fast grow-ing lines of male broilers fed high nutrient densediets at most altitudes and where the environmentis cool/cold at least for part of each day. Mortalityseen with ascites is dictated by the number of ‘stres-sors’ involved and hence the efficacy of thecardio-pulmonary system to oxygenate tissues.

Although growth rate per se is the major fac-tor contributing to oxygen demand, the com-position of growth is also influential, because oxy-gen need varies for metabolism of fats vs.proteins. Oxygen need for nitrogen and proteinmetabolism is high in relation to that for fat,although it must be remembered that the chick-en carcass actually contains little protein ornitrogen. The carcass does contain a great dealof muscle, but 80% of this is water. On the otherhand, adipose tissue contains about 90% fat, andso its contribution to oxygen demand is pro-portionally quite high. Excess fatness in birds willtherefore lead to significantly increased oxygenneeds for metabolism. At high altitude, these effectsare magnified due to low oxygen tension inthe air. Interestingly, broilers grow more slow-

ly at high altitude, and comparable slowergrowth (4 – 5%) at sea level would virtually elim-inate the incidence of ascites. Regions of highaltitude invariably have cool night time tem-peratures (< 15˚C) and no one has really quan-titated the effects due to altitude per se vs. coolnight temperatures.

Keeping birds ‘warm’ is perhaps the singlemost practical way of reducing the incidence ofascites. As environmental temperature changes,there is a change in the bird’s oxygen requirement.If one considers the thermoneutral zone fol-lowing the brooding to be 24 – 26˚C, then tem-peratures outside this range cause an increasein metabolic rate, and so increased need for oxy-gen. Low environmental temperatures are mostproblematic, since they are accompanied by anincrease in feed intake with little reduction ingrowth rate. While there is an increased oxygendemand at high temperatures due to panting etc.,this is usually accompanied by a reduced growthrate, and so overall there is reduced oxygendemand. Under commercial farm conditions,cold environmental conditions are probablythe major contributing factor to ascites. Forexample, at 10 vs. 26˚C, the oxygen demand bythe bird is almost doubled. This dramaticincrease in oxygen need, coupled with the needto metabolize increased quantities of feed,invariably leads to ascites.

Manipulation of diet composition and/orfeed allocation system can have a major effecton the incidence of ascites. In most instances,such changes to the feeding program influenceascites via their effect on growth rate. However,there is also a concern about the levels of nutri-ents that influence electrolyte and water balance,the most notable being sodium. Feeding high lev-els of salt to broilers (> 0.5%) does lead toincreased fluid retention, although ascites invari-ably occurs with diets containing a vast range of



salt, sodium and chloride concentrations. Apartfrom obvious nutrient deficiencies, or excessesas in the situation with sodium, the majorinvolvement of the feeding program as it affectsascites revolves around nutrient density andfeed restriction. Ascites is more common whenhigh energy diets are used, especially whenthese are pelleted. Dale and co-workers grewbirds on high energy diets designed to promoterapid growth and likely to induce ascites. Therewas no correlation between 14 d body weightand propensity of ascites, although birds fed 3000

3100 kcal ME/kg rather than 2850 2950kcal ME/kg had twice the incidence of ascites.

When diets of varying nutrient density are used,there is a clear relationship of energy level andincidence of ascites (Table 5.45).

Because feeding program, nutrient density andgrowth rate are all intimately involved in affect-ing the severity of ascites, then there is invariablydiscussion on the possible advantages of feedrestriction. The goal of such programs is toreduce the incidence of ascites without adverse-ly affecting economics of production. It isexpected that nutrient restriction programs willreduce final weight-for-age to some degree,

and obviously there is a balance between thedegree of feed restriction and commerciallyacceptable growth characteristics. Using feedrestriction or restricted access time to feed,ascites can be virtually eliminated in male broil-ers (Table 5.46).

Although low energy diets have little appar-ent effect on growth rate, there is often reductionin ascites. Using high energy diets with accessat 8 h/d is perhaps the most practical way of con-trolling ascites in problem situations. As shownin Table 5.46, elimination of ascites is at thecost of a 200 g or 2 d delay in growth rate. A 2– 3 d delay in market age sounds quite a reasonabletrade-off for a major reduction in ascites. However,careful economic analysis must be carried out todetermine the real cost of such decisions. A oneday delay in market age can be accepted if mor-tality is reduced by at least 2.5%.

Another factor to consider in diet formula-tion is the balance and the quality of the protein.Excess nitrogen must be removed from the body,and this is an oxygen demanding process. Thereis a potential to reduce the oxygen demandthrough minimizing crude protein supply whilemaintaining essential amino acid levels in a

Table 5.45 Effect of diet nutrient density and composition on incidence ofascites at 49 d

Diet ME Crude protein Added Fat Ascites mort. (kcal/kg) (%) (%) (%)

2950 23 0 8.82950 23 4 8.73100 24 4 15.82950 21 0 9.02950 21 4 8.53100 22 4 12.0

Adapted from Dale and Villacres (1986)



Diet treatment Weight gain Mortality (%)(g) Total Ascites

High energy (3000 3300) 2616a 12.8 3.8Low energy (2900 3100) 2607a 11.3 1.4High energy (8 h/d) 2422b 8.7 0.6High energy (90% ad lib) 2452b 9.0 0.2

Table 5.46 Incidence of ascites in male broilers fed restricted quantities offeed or limited access time to feed

Adapted from Camacho-Fernandez et al. (2002)

diet. If we consider two diets providing the samelevel of available amino acids, but with 20 vs.24% crude protein, then there will be a need forbirds to deaminate an extra 4% CP in the high-protein diet. If birds consume 130 g feed/d, thismeans an extra 5 g/d of protein for catabolism.Such protein catabolism will likely result inuric acid and fat synthesis, and these are calculatedto need 2 and 1 litres of oxygen per day respec-tively. Therefore, catabolism of an extra 5 g crudeprotein each day means a 3 litre increase in oxy-gen demand, which represents about an 8%increase relative to the bird’s total requirements.There is an obvious incentive to minimize crudeprotein per se, because its catabolism merelyimposes another stress on the oxygen demandof the bird. There has been recent interest in themetabolism of two specific amino acids with poten-tial to influence incidence of ascites. Arginineis a precursor of nitric oxide, which acts as a potentvasodilator. Feeding more arginine shouldtherefore lessen the effects of increased pressurewithin the cardiovascular system. Feeding an extra10 kg arginine/tonne does, in fact, cause a dra-matic reduction in pulmonary arterial pressure.Unfortunately synthetic arginine is prohibitive-ly expensive and no natural ingredients are suf-ficiently enriched to supply such high levels inthe diet. Groundnut and cottonseed meal are per-

haps the richest sources of arginine, at around4%. Taurine is an amino acid rarely consideredin poultry nutrition. It is required by cats wheredeficiency causes heart defects somewhat sim-ilar to those seen with ascites. However, addingtaurine to broiler diets has no effect on growthrate or cardio-pulmoary physiology, and with meatmeal in the diet ‘deficiency’ is unlikely to occur.

If ascites mortality is sufficiently high, the following diet changes may be considered:

• Low energy feeds throughout the entire lifecycle e.g.:

Starter (2850 kcal ME/kg)Grower (2950 kcal ME/kg)Finisher (3100 kcal ME/kg)

• Use mash rather than pelleted feeds. Do not use too fine a mash diet, since thisencourages feed wastage and causes dustiness at broiler level.

• Consider skip-a-day feeding from 7 – 20 d of age. Longer periods of restricted feedingmay be necessary where ascites levels arevery high. Water management becomesmore critical with this system.



• Consider limit-time feeding, such that birdshave access to feed for 8 – 10 hours eachday. Extra care is needed in water manage-ment so as to prevent wet litter.

• Use no more than 21% crude protein instarter diets, 19% in grower and 17% in finisher/withdrawal.

b) Sudden Death SyndromeSudden Death Syndrome (SDS) has been

recognized for over 35 years. Also referred toas Acute Death Syndrome or ‘flip-over’, SDS ismost common in males and especially whengrowth rate is maximized. Mortality may startas early as 10 – 14 d, but most often peaks ataround 3 – 4 weeks of age, with affected birdsinvariably being found dead on their back.Mortality may reach as high as 1 – 1.5% inmixed sex flocks, and in male flocks the conditionis often the major single cause of mortality,with death rates as high as 2% being quitecommon. The economic loss is therefore sub-stantial. Confirmation of SDS by necropsy isdifficult as no specific lesions are present. Birdsare generally well-fleshed with partially filled cropand gizzard. There seems little doubt that anynutritional or management factors that influ-ence growth rate will have a correspondingeffect on SDS. Sudden Death Syndrome can vir-tually be eliminated with diets of low nutrient den-sity although these may not always be eco-nomical in terms of general bird performance.Research data suggests that diets based on pureglucose as an energy source result in muchhigher incidence of SDS compared to birds fedstarch or fat-based diets. It seems likely that someanomaly in electrolyte balance is involved in SDSand that there is a genetic predisposition to thisin terms of heart arrhythmia. In part, this is dueto the fact that metabolic changes occur rapid-

ly after death, and hence blood profiles taken fromSDS birds will likely vary depending upon sam-pling time following mortality. SDS can bereduced or eliminated by nutritional or man-agement practices that reduce growth rate.Obviously, such decisions will have to be basedon local economic considerations. At this time,there is no indication of a single causative fac-tor, and diet manipulation other than that relat-ed to reduced growth rate, is usually ineffective.

c) Skeletal disordersMost broiler flocks will have a proportion of

birds with atypical gait, although growth rate maybe unaffected. There is now greater incidenceof birds with twisted toes, yet again this is in birdsthat achieve standard weight-for-age. Most legproblems likely have a genetic basis, althoughseverity of problems can be influenced by nutri-tional programs. The most common skeletal abnor-malities seen in broilers are tibial dyschon-droplasia (TD) and rickets. The fact that legproblems are more prevalent in broilers (andturkeys) than in egg-type birds, has led to the spec-ulation of growth rate and/or body weight ascausative factors. On this basis, one is faced withnumerous reports of general nutritional factorsinfluencing leg problems. For example, it has beensuggested that energy restriction in the first fewweeks halves the number of leg problems in broil-ers, while reduced protein intake results infewer leg abnormalities. Similarly, restricting accessto feeder space also seems to result in fewer legdefects. However, most recent evidence suggeststhat body weight per se is not a major predisposingfactor to leg problems. From experiments involv-ing harnessing weights to the backs of broiler chick-ens and poults it is concluded that severity of legabnormality is independent of body weight andthat regular skeletal development is adequate tosupport loads far greater than normal body



weight. There seems to be some disparitybetween the effects on skeletal development of(1) limiting the incidence by reducing the planeof nutrition and (2) failing to aggravate the prob-lem by artificially increasing body weight. Thisapparent dichotomy suggests that it is the rate ofgrowth rather than body weight per se that is apredisposing factor.

In addition to the confounding effect ofgenetics on skeletal development, there is alsosome effect of steroid hormones. Castratedturkeys have a higher incidence of leg abnormalitiesthan do intact toms or those treated with testos-terone. It is suggested that androgens act to fusethe epiphyses and shafts of long bones. Theremay well be major sex differences in the hormonalcontrol of skeletal development related to the bal-ance of androgens:estrogens. However, theeffect of androgens:estrogens per se on skeletaldevelopment in the relatively juvenile broiler oftoday is perhaps questionable due to the fact thatlittle sex differentiation in tibiotarsal length is seenuntil after 5 weeks of age.

It is often suggested that use of low proteindiets reduces the incidence of leg disordersalthough this is likely a consequence of reducedgrowth rate. Diets high in protein can interferewith folic acid metabolism and in so doing,increase the incidence of leg problems. However,in recent studies involving folic acid deficient diets,we were unable to show an effect with 22 vs. 30%crude protein diets. In studying factors influencingskeletal development in broiler breeders andLeghorns, we have shown that while early skele-tal development was little influenced by mineraland vitamin fortification, shank and keel lengthscould be increased by feeding diets of higher pro-tein content (22 vs. 16% CP). It is also conceivablethat the ratio of amino acids:non-protein nitro-gen may be of importance in the developmentof bone organic matrix. Evidence for this con-

cept comes from experiments involving syn-thetic amino acids and purified diets. The bird’snitrogen requirement for optimum organicmatrix development is often greater than the appar-ent requirement for growth. The wry neck con-dition sometimes seen in broiler breeders, andespecially males, may also be related to disruptedamino acid metabolism. While not directly a skele-tal abnormality, the condition seems to be relat-ed to the metabolism of tryptophan or niacin.During incubation, wry neck arises in the embryobecause of greater muscle pull on one side of theneck, which together with pressure from theamnion, causes the ‘apparent’ skeletal deformity.

Certain feed ingredients have been associatedwith leg disorders. Much of the early work in thisarea centered on brewer’s yeast and its ability toreduce leg disorders. With current interest in pro-biotics and other yeast-based additives, thisidea may receive renewed attention. There areisolated reports of certain samples of soybean mealcontributing to TD in broilers although this maysimply be a factor of acid:base balance of the diet.

It is realized that feedstuffs contaminated withcertain mycotoxins can induce or aggravateskeletal problems. Grains contaminated withFusarium roseum have been shown to cause TD.Aflatoxin and ochratoxin both decrease bonestrength, and this may be related to vitamin D3metabolism. Under such field conditions birdssometimes respond to water soluble D3 admin-istered via the drinking water, regardless of thelevel and source of D3 in the diet. Attempts atreducing leg problems by minimizing microbialcontamination of the litter have met with avarying degree of success. Adding sorbic acidto the diet, or treating litter with potassium sor-bate improves leg condition only in isolatedtrials. A number of fungicides used in grain treat-ment can also themselves lead to leg problems.The presence of tetramethylthiuram significantly



increases the incidence of TD, while tetram-ethylthiuram disulphide causes the ‘classical’ con-dition of irregular penetration of blood vesselsinto the cartilage, which is a precursor to TD.

High chloride levels induce TD, although sincethere are no major shifts in plasma ions with TD,it is concluded that the problem is not simply relat-ed to defective calcification. The occurrence ofcrooked legs seems to be greater when chicks arefed diets with a narrow range of cations:anionsand the incidence of TD and bowed legs appearsto increase with increase in anion content of thediet. There may be a relationship between ionbalance and vitamin D3 metabolism. Increasingthe chloride content of the diet from 10 to 40mEq/100 g was reported to markedly enhancecartilage abnormalities when the cation (Na+, K+)content of the diet was low. Thus, with excessCl-, chicks become acidotic, although the con-dition can be corrected with dietary sodiumand potassium carbonates, suggesting that ifthe diet is high in Cl-, then it must be balancedwith equimolar concentrations of Na+ + K+ in theform of readily metabolizable anions. Workersfrom France have indicated that liver homogenatesfrom acidotic chicks lose 50% of their capaci-ty to synthesize 1,25-cholecalciferol which is theactive D3 metabolite. This possibly infers arelationship between acid:base balance TD,and vitamin D3 metabolism.

In certain situations, a deficiency of D3 willmimic both Ca and P deficiency situations.While Ca deficient chicks are usually hypocal-cemic and hyper-phosphatemic, D3 deficiencyinvariable results in hypocalcemia and hypo-phos-phatemia. In the D3 deficient chick a greater rel-ative P deficiency is caused by parathyroid hor-mone. In situations of D3 repletion, the skeletonseems to respond much more slowly than doesthe intestine, since the immediate effect of re-feed-ing D3 is better ‘absorption’ of the diet Ca.

There is also evidence to suggest that D3 isinvolved with collagen synthesis, where thematuration of collagen crosslinks seems D3dose related. While 1-25 (OH)2D3 is unlikelyto be available to the feed industry, nutritionistsnow have the option of using , 25(OH)2 commonlyreferred to as Hy-D®. Since the synthesis of,25(OH)2 normally occurs in the liver, then prod-ucts such as Hy-D® are going to be most ben-eficial when liver function is impaired for what-ever reason.

While deficiencies of most vitamins have beenassociated with leg problems, pyridoxine has per-haps received the most attention. There is over-whelming evidence to suggest that low levels leadto skeletal abnormalities and/or that supple-mentation reduces the incidence. It has beenhypothesized that pyridoxine may exert its ben-eficial effect via involvement with zinc home-ostasis and in particular the formation of picol-inic acid which is involved in intestinal zincabsorption. There is an apparent synergismbetween zinc, B6 and tryptophan involved in theprevention of leg weakness. The situation withpyridoxine is further complicated through the effectof diet protein as previously described withfolic acid. Common to many other diet situations,pyridoxine deficiency manifests itself through epi-physeal lesions consisting of uneven invasion ofirregular blood vessels into the maturing growthplate. Presumably the higher level of diet pro-tein increases the metabolic requirement forpyridoxine through such processes as transam-ination and/or deamination. While deficienciesof many vitamins can therefore, precipitate legproblems in broilers, there is also evidence to sug-gest that certain vitamin excesses may be detri-mental. Very high levels of vitamin A in the dietincrease the incidence of rickets, while impairedbone formation has been observed with excessdietary vitamin E. It must be pointed out how-ever, that all these reported effects of vitamin excess



on bone metabolism relate to dietary levelsgrossly in excess (5 – 10 times) of normal feed-ing levels and hence would only be practical-ly encountered under unusual circumstances.

As with vitamins, deficiencies, or excessesof a vast range of minerals, can also influencebone development. The effect of abnormal lev-els and/or ratios of calcium:phosphorus arewell documented. Confusion sometimes existswith respect to diagnosis of calcium or phosphorusdeficiencies, and accurate on-farm diagnosisof phosphorus deficiency vs. calcium excess isdifficult, and immediate recommendations of dietchange can be misleading prior to complete dietanalysis. Identical lesions for the two conditionsare seen suggesting that excess calcium forms insol-uble Ca3(PO4)2 in the intestine, thereby induc-ing phosphorus deficiency. Table 5.47 shows nor-mal levels of minerals in bone ash, and sovalues which are much different to these are acause for concern.

Table 5.47 Normal mineral contentof bone ash

collagen secretion and this can be restored byadministration of Fe2+ or Fe2+ with Mn2+, butnot by Mn2+ alone. The agent seems to block thesynthesis of hydroxylysine and within this mech-anism there seems to be a step requiring Fe2+.Copper metabolism has always been suspect instudies of leg problems, since there are certainsimilarities between the cartilage of copperdeficient birds and those with TD. However,attempts to correct TD with supplements of Cuhave invariable proved disappointing.Solubilization studies indicated that dystrophiccartilage (TD) is not deficient in cross-linked col-lagen, a situation often seen with classical cop-per deficiency.

Skeletal disorders are sometimes seen inthe first few days after hatching and so it is pos-sible that metabolic disorders are initiated dur-ing incubation. Skeletal mineralization starts ataround the eighth day of incubation, and atthis time the yolk serves as a source of calcium.Shell calcium is not utilized until about the12th day of incubation, although during thecourse of embryonic development, the embryowill take up some 120 mg Ca from the shell.Culturing developing embryos in a mediumdeficient in calcium quickly results in grossskeletal abnormalities. There have been noreports linking breeder eggshell quality withbone formation in broiler offspring. Similarly, therehave been relatively few reports of the effect ofbreeder nutrition and management on skeletaldevelopment of the embryo. There seems littledoubt that more common leg problems, such astibial dyschondroplasia (TD) are inherited tosome degree and hence pedigree has a poten-tially confounding effect on studies of leg abnor-malities. TD is related to a major sex linkedgene, the recessive of which is associated witha higher incidence of TD. This situation suggestsa large maternal component, and therefore, femalelines would greatly influence the expression.

Calcium 37%Phosphorus 18%Magnesium 0.6%

Zinc 200 – 250 ppmCopper 20 ppm

Manganese 3 – 5 ppmIron 400 – 500 ppm

The effect of manganese deficiency on the inci-dence of perosis is obviously well documentedalthough some evidence suggests that interac-tion with iron may be a complicating factor.Administration of hydralazine, a manganesesequestering agent, causes leg defects very sim-ilar to those seen in classical manganese deficiency,and in fact, successful Mn treatment has beenrecorded in these situations. Hydralazine blocks


SECTION 5.8Carcass composition

d) Spiking mortalitySpiking mortality affects young broiler chicks

between the ages of 7 and 21 days, and is char-acterized by severe hypoglycemia. All affectedbirds exhibit extremely low blood glucose lev-els, which account for many of the observed signsof spiking mortality, including huddling andtrembling, blindness, loud chirping, litter eating,ataxia and rickets. Mortality rates of around 1%are observed daily for three to five days. Chicksthat survive, experience long-term stunting andgrowth reduction. There are now field observationsof an increasing occurrence of spiking mortal-ity in broilers fed ‘all vegetable diets’. Amongmany suspected etiological agents of spiking mor-tality are viral infections, mycotoxins and feedanti-nutrients together with poor managementpractices, although mycotoxins and anti-nutri-ents have been dismissed as primary causativeagents. The short time frame and low mortali-ty rate experienced with spiking mortality mightwell be the result of a hormonal or metabolic dis-order affecting young chicks during the periodof rapid growth.

Field reports suggest that diets containing ‘all-vegetable’ feed ingredients produce a muchhigher incidence of spiking mortality. The linole-ic acid concentration of these diets in particu-

lar has been directly related to the severity of thesyndrome when it occurs. Calf-milk replacer inthe drinking water is suggested for treatment. Thisproduct is high in casein which itself is a rich sourceof the amino acid serine. Blood glucose levelsin birds are influenced by glucagon more so thanby insulin, and serine is a precursor of glucagonsynthesis. It is possible that ‘all-vegetable’ dietsare ‘deficient’ in serine, and that this predisposesthe bird to hypoglycemia. In a recent study, weobserved reduced blood glucose in broilers fedvegetable diets, and that this could be correct-ed with milk powder, casein or serine (Table 5.48).

Table 5.48 Blood glucose level in 18d broilers fed various supplementsto all vegetable diets

Diet Glucose(mg/dl)

Corn-soy-meat 270ab

All vegetable 243b

All vegetable + serine 275a

All vegetable + casein 273a

All vegetable + milk powder 275a

Adapted from A. Leeson et al.(2002 unpublished observations)

D uring processing, cut-up and debon-ing, knowledge of expected yield isimportant in efficient scheduling of pro-

duction. Carcass composition is affected by livebird weight, sex of bird and to some extent the nutri-ent content of the diets used and the feedingprogram. Modern strains of broiler have been devel-oped for increased breast meat yield, and so

obviously, this component has increased as aproportion of the carcass. At comparable weights,male and female birds have similar yields of car-cass portions, and often the female will yieldthe most breast meat. However, since the femalebroiler tends to deposit more fat beyond about 2kg liveweight, the yield of edible meat may be lessthan for the male if both are fed the same diet.

5.8 Carcass composition



Energy and crude protein are the nutrients thathave the greatest influence on carcass compo-sition. Diets high in energy produce a fatter car-cass while high protein diets result in a leanerbird. The situation is a little more complexthan this, since it is actually the balance of pro-tein to energy that is important. If the bird con-sumes excess energy in relation to protein, a fat-ter bird develops, whereas a leaner bird can beproduced by feeding larger quantities of proteinin relation to energy. Unfortunately, simplechanges such as these are not economical,since the required degree of leanness in thecarcass often only results from uneconomical-ly high levels of protein.

When discussing the effect of diet protein orenergy level on carcass composition, it is veryimportant to appreciate the units of measurement.Often there is discussion about the effects of dieton percentage changes in composition, and insome situations the percentage of a compo-

nent in the carcass changes simply becausethere has been a corresponding change in the levelof another component. In fact, the grams of pro-tein or meat on a carcass are little influenced bynutrition. Assuming there is no amino acid defi-ciency, then actual protein (meat) yield is dictatedby genetics. Feeding more protein or morelysine for example than is required for opti-mum growth is going to have very minimaleffect on protein deposition. So-called ‘leaner’carcasses are therefore a consequence of therebeing less fat deposited. The fat content of a car-cass is greatly influenced by nutrition. Themore energy consumed by the bird, the greaterthe potential for fat deposition. Over the normalrange of diet energy and protein levels used inindustry, proportions of fat and protein can varyby about 3 – 4% due to nutrient intake. A 3%increase in carcass fat will be associated with 3%decrease in carcass protein, and vice-versa.Figure 5.8 details the component yield expect-ed from a 2.5 kg live weight broiler.

Figure 5.8 Carcass components



The proportional yields are essentially afactor of body weight, and so there will beslight changes in major components for lighteror heavier birds (Tables 5.49, 5.50). The chem-

ical composition of the carcass will also changeover time; with increase in the proportion of fatand decrease in proportion of protein over time(Figure 5.9).

Figure 5.9 Chemical composition of the eviscerated carcass of male broilers

Table 5.49 Carcass weight and portions from male broilers (% carcass weight)

Live wt. Carcass Abdominal Wings Drums Thighs Bone-in De-boned(g) wt. (g) fat pad breast breast

1224 818 2.5 10.2 14.8 17.6 29.4 18.51754 1237 2.6 10.4 13.3 17.0 30.1 19.82223 1596 3.0 9.7 13.1 16.5 31.2 20.12666 1982 3.3 9.6 13.6 16.3 31.4 20.53274 2500 3.5 9.4 13.5 16.0 32.5 21.63674 2731 4.2 9.3 16.1 16.0 36.0 23.6

Table 5.50 Carcass weight and portions from female broilers (% carcass weight)

Live wt. Carcass Abdominal Wings Drums Thighs Bone-in De-boned (g) wt. (g) fat pad breast breast1088 720 2.8 10.8 14.4 17.5 29.5 20.41582 1160 3.2 10.5 13.8 16.6 29.7 19.51910 1376 3.4 10.2 13.6 16.5 31.5 21.52382 1753 4.3 9.8 13.2 16.4 32.5 21.72730 1996 4.3 9.6 13.0 16.4 34.2 22.6



Table 5.51 Effect of feeding tallow, sunflower oil and flax oil from 28 – 48 don fatty acid content of female broilers (% of total fat)

There is increasing interest in the manipulationof carcass fat composition related to humannutrition. As with eggs, the fatty acid profile ofthe diet has a direct influence on the fatty acidcontent of the carcass (Table 5.51).

The level of supplemental fat used in this studywas higher than for commercial application,yet there is an obvious correlation between sat-uration of dietary fat and that deposited in thebody. In terms of producing niche products forhealth conscious consumers, accumulation of totalomega 3 fatty acids, and that of componentlinolenic acid, EPA and DHA are of interest. Theselong chain omega-3 unsaturates are most eco-nomically included in the feed as flax and fishoils (Table 5.52).

Adding flax to the diet results in enrich-ment of linolenic acid, while fish oil results inaccumulation of EPA and DHA that also contributeto the omega-3’s. The accumulation of specif-ic fatty acids in the carcass seems to be a factorof dietary oil level and also feeding time. In thisstudy, the supplements were fed only for the last7 or 14 d of growth. It is obviously not essen-tial to feed products such as flax or fish oil for

the entire grow-out period, since significantenhancement occurs from feeding just from 42– 49 d. The data shown in Table 5.52 relate tothe intact eviscerated carcass. It seems asthough the individual fatty acids accumulate atdifferent rates in different regions of the carcass,and so marketing strategy may have to be mod-ified if portions or deboned meat are producedfrom these carcasses (Table 5.53).

Thigh meat yields more omega-3 fatty acidsthan does a comparable quantity of breast meat,which is a factor of the amount of intramuscu-lar fat in these portions. However, the greatesteffect on fatty acid profile of individual portions,is presence or not of skin (Table 5.53).

Unlike the situation with eggs, production of‘designer’ broiler meats enriched in variousfatty acids can be complicated by problems ofoff-flavor. With only 0.75% of fish oil in the diet,panelist are reported to be able to detect more‘off-flavors’ and rank these meats accordingly. Themarketing of omega-3 broiler meat will requiresome entrepreneurial skill in overcoming thesechallenges.

Body fat 10% Tallow 10% Sunflower oil 10% Flax oil

C14:0 2.48 0.28 0.31C16:0 23.10 10.70 10.9C18:0 8.28 4.12 4.52C18:1 41.74 19.09 18.97C18:2 13.60 61.90 17.8C18:3n3 1.39 0.99 43.0

Adapted from Crespo and Esteve-Garcia (2002)


SECTION 5.9Skin integrity and feather abnormalities

Flax Fish oil Time Fatty acid (% of fat)(%) (%) (d) Linolenic EPA DHA Total omega-3

- - 1.3 0 0 1.310 7 3.4 0 0.1 3.610 14 5.3 0.1 0.1 5.7- 0.75 7 1.3 0.2 0.1 1.8- 0.75 14 1.3 0.4 0.3 2.1

10 0.75 7 3.3 0.3 0.2 3.910 0.75 14 6.0 0.5 0.3 7.1- 1.5 7 1.4 0.4 0.3 2.2- 1.5 14 1.4 0.8 0.5 2.9

10 1.5 7 3.6 0.4 0.3 4.510 1.5 14 5.9 0.8 0.5 7.7

Table 5.52 Effect of feeding flaxseed or fish oil for the last 7 or last 14 d oncarcass fat composition in 49 d male broilers


Table 5.53 Total omega-3 content of breast and thigh meat in birds fed flaxor fish oil (mg/100g cooked meat)

Flax Fish oil Time (d) Meat & Skin Meat% % Breast Thigh Breast Thigh10 - 14 673 995 143 206- 0.75 14 380 393 182 98

10 0.75 7 484 708 118 16310 0.75 14 858 1309 188 312


F eathers are continuously being shed andregenerated by the bird, and even duringthe juvenile growth of the broiler, it under-

goes 2 – 3 molts. Feathers arise from feather fol-licles that are arranged in distinct tracts on the skin.The follicle number is determined by about 14 dof incubation. The fact that the body is not uni-formly covered by follicles means that certain areasof the skin would naturally be featherless. Theseareas will only receive a protective covering as

feathers in adjacent areas grow, and overlap tocover the entire body. The younger the bird, thegreater the area of apparently featherless skin. Asthe feathers grow, they conform to the shape ofthe bird’s body and may lock together. Abnormalfeather growth is often noticed when feathers arenot contoured close to the body, and birds appear‘rough’ or with ‘helicopter wing’ etc. Table 5.54shows the composition of feathers from marketweight broilers.

5.9 Skin integrity and feather abnormalitiesa) Feather development



Table 5.54 Composition of feathersfrom 45 d broilers

Figure 5.10 shows feather yield of sexedbroilers, while Figure 5.11 indicates standardsfor length of primaries and back feathers.

Feathers are composed mainly of keratinprotein that is formed in the epidermis of the fol-licle. Virtually all growth occurs in the follicle,and so abnormalities seen 2 – 5 cm from the fol-licle will have occurred days or even weekspreviously. The keratin structure is very rich incystine, with each molecule containing around8 half-cystine residues, and this is why methio-nine/TSAA levels are important for good feath-er structure. Marginal levels of methionine + cys-tine will cause abnormal feather growth and/orreduced feathering, although deficiencies ofother amino acids will also cause featheringproblems. With general amino acid inadequa-cy, the primary feathers have a characteristic spoon-like appearance that is caused by retention of anabnormally long sheath that covers the first50% of the feather shaft. Deficiencies of manyessential amino acids also cause abnormal curl-ing of feathers away from the body. Interestingly,these same characteristics are seen with deficienciesof some of the B vitamins.

Birds fed T-2 toxin (4 ppm) develop only sparsefeathering, and the feathers that do develop, tendto protrude from the bird at odd angles, leadingto some areas of the skin begin exposed. WithT-2 toxin, most feathers are affected, unlike thesituation with nutrient deficiencies that most char-acteristically first affect the primary feathers.

Feather growth is also affected by thyroid func-tion, and thyroid antagonists will delay normalfeather growth. Poor feathering is sometimes seenat farms changing from corn to milo-baseddiets. While a number of diet situations may beinvolved in such a change, it is interesting to notethat milo is very low in iodine content comparedto other cereals.

%Crude protein 90

Total amino acids 60Methionine 0.7

Cystine 5.5Arginine 7.1

Lysine 2.4Threonine 4.2

Valine 6.5Magnesium 0.2

Sodium 0.8Iron 0.06

Copper 12 ppmZinc 10 ppm

Selenium 0.7 ppm

Figure 5.10 Feather yield of sexed broilers.

Figure 5.11 Growth of wing and backfeathers in male and female broilers.

Adapted from McDougald and Keshavavz (1984)



Unfortunately, in most field cases of poor feath-ering, there is no apparent dietary deficiency asdetermined by routine analyses or considerationof formulation consistency/changes. Oftenproblems are isolated to particular flocks with-in a site where all flocks receive the same feed.These factors support the concept of poor feath-ering being caused by infectious agents (likelyin the feather follicle itself) or factor(s) causinggeneral malabsorption of nutrients. Because feath-ers are very fast growing, especially in the first7 – 14 d of age their development is very sensitiveto general availability of circulating nutrients.

b) Skin tearingAbout 5% of downgrades at processing are

due to skin tears. Most tears occur post-mortem,and so are related to scald water temperature andpick time. High temperatures with shorter picktimes cause less tears than lower scald tem-perature with prolonged pick time. However,regardless of processing conditions, a proportionof carcasses have torn skin. Skin strength is greaterin males vs. females, and for both sexes, itincreases with age. Most problems are thereforeencountered with carcasses from younger femalebirds. There is a genetic component, because dif-ferent strains show differences in skin tearing, andin one study it was shown that skin from slow feath-ering strains was less elastic than that from fastfeathering birds.

Skin strength is highly correlated with its col-lagen content, and so skin with greater collagencontent is less prone to tearing. Any nutrition-al factor that influences skin collagen content willtherefore indirectly affect susceptibility to tear-ing. The amino acid proline is a component ofhydroxyproline which itself is responsible for thestability and rigidity of collagen. Zinc, copperand vitamin C all play a role in collagen synthesisand so deficiencies of any one of these nutrients

results in less skin collagen production. However,gross deficiencies of these nutrients also causepoor growth rate, a characteristic that is notusually seen in situations of excessive skin tear-ing. Unfortunately, there seems to be little ben-efit to increasing the dietary levels of thesenutrients, or even increasing the level of prolinein the diet.

A specific dietary situation involves theanticoccidial, halofuginone. When this productis fed at normal recommended levels, there is sig-nificant loss in skin thickness and skin strength,especially in female birds. In one study, usinghalofuginone (at 3 ppm of the diet) resulted ina 50% reduction in skin collagen content and 50% increase in the incidence of skin tears.Halofuginone seems to affect skin strength in femalebirds, more than it does with males, and becausethe female has an inherently weaker skin, this leadsto the greater incidence of tearing. It has beenshown that halofuginone interferes with theconversion of proline to hydroxyproline in theskin cells, and that this adverse effect cannot becorrected by adding more proline to the diet.

When skin tearing is a problem, assuming thatprocessing conditions have been scrutinized, theonly potential nutritional factors involved arehalofuginone and level of zinc, copper andvitamin C. Skin tearing is more problematic inhot weather. This situation leads to recom-mendations of supplemental vitamin C, althoughbirds under these conditions almost alwayscarry more subcutaneous fat. Feeding higher lev-els of crude protein has also been shown toincrease skin strength although the reason for thisis not clear. More crude protein may provide moreof the non-essential amino acid glycine whichaccounts for about 30% of the amino acids in col-lagen, or alternatively more protein per se maysimply reduce carcass fatness.



c) Oily bird syndrome (OBS)As its name implies, birds with OBS have skin

that is oily or greasy to the touch. OBS isobserved most frequently in older broilers andespecially those fed high-energy diets in thewarmer summer months. The problem alsoseems to relate to specific processing plants, wherethe occurrence is greater with the increased‘stress’ applied during processing, and espe-cially plucking. Interestingly, the condition is rarelyseen in hand-plucked birds. The condition is alsoassociated with increased water retention inthe carcass, especially in regions of the car-cass where skin ‘elasticity’ had been affected. Thesepockets of water are most often seen in femalebirds. The problem is most noticeable in pock-ets of the skin that separate in the back region.Because the skin seems more prone to tearing,these pockets rupture and the surrounding skinbecomes noticeable oily.

A general finding in situations of OBS is achange in the skin ultrastructure, such thateither the layers of skin separate to allow the pock-ets of oil and/or chilled water to accumulate, orthe skin tears more easily. Apparently, fat satu-ration is not a factor in OBS, rather there issome change in the integrity of the various lay-ers of the skin because the skin from affected car-casses is easily separated and removed from theunderlying musculature. The five collagenouslayers beneath the epidermis seem less compactthan normal, and the deepest layers containthe most fat cells.

While there is no real change in total skin thick-ness with OBS, its breaking strength seems to bereduced. Although males usually have thinnerskin than do females, it is usually stronger pos-

sibly due to there being less subcutaneous fat.Males also exhibit more insoluble skin collagen,and so this may be important in reducing prob-lems of solubilization and water uptake as oftenoccurs with OBS carcasses in chill water tanks.

The main collagen layer in birds with OBSis 30% weaker at normal body temperatureand up to 50% weaker at temperatures used dur-ing processing. The problem may relate toimpaired collagen crosslinking. In mammals, andin the formation of eggshell membranes, lysyl oxi-dase is thought to be the only enzyme involvedin crosslink maturation of collagen and elastin,converting lysine and hydroxylysine into alde-hydes. Lysyl oxidase is a copper metalloenzymethat requires pyridoxal phosphate as a co-factor,and copper deficiency is known to impair nor-mal collagen crosslink structure. However, it doesnot seem as though copper deficiency is the sim-ple solution to this problem.

OBS occurs only in broilers grown in warm cli-mates, and experimentally the syndrome canonly be duplicated by using warm growing con-ditions. At higher temperatures, birds carry moresubcutaneous carcass fat, and so this may be thetrigger mechanism. Because of the oily nature ofthe carcass, various diet ingredients and nutrientlevels have come under investigation. Fat levelsand sources in the diet have come under close scruti-ny, although there does not seem to be a simplerelationship. Higher levels of fat and/or energy inrelation to the level of protein in the diet have causedmore problems, although research results areinconsistent. Even though the bird’s skin has anoily appearance, levels of unsaturated fatty acidsdo not correlate with OBS, and in fact, moreproblems are seen in birds fed tallow.



If OBS occurs, then the only immediatepractical solution is to modify the processing con-ditions, and in particular, scald temperatureand pick time. Because the exact cause ofimpaired collagen crosslinking has not beenidentified, then other changes to the diet and/or

environment are of questionable value. Whilefat levels in the diet do not seem to be a factor,there is an indication of more problems occur-ring with saturated fats such as tallow. The dietshould contain adequate levels of copper and notcontain excessive levels of zinc or vitamin A.

5.10 Environmental nutrient management

M anure composition is now a factor indiet formulation. With the concen-tration of broiler production in many

world locations, disposal of manure is now a con-straint to production. The actual concern todayis disposal of manure in a manner commensu-rate with environmental regulations. Most broil-er farms are situated on a minimal land base andso, meeting environmental regulations nowmeans transporting manure some distance fromthe farm. Where such transportation costs areprohibitive, then incineration is an option.

The current major concern with litter disposal,is its content of nitrogen and phosphorus. Thereis also awareness of content of other minerals such

as zinc and copper and this is leading to re-eval-uation of dietary needs for these trace minerals.

Broiler litter is relatively bulky and of low nutri-ent concentration compared to cage layer manure.The litter composition is dictated by the amountadded to the broiler facility prior to brooding, andsince there is little change in this quantity overtime, this amount is predictable at time of clean-out. The most common litter materials usedtoday are wood shavings, straw and rice hulls. Allof these litter materials contain negligible quan-tities of nitrogen and phosphorus.

Table 5.55 outlines a series of calculationsbased on 10,000 broiler chickens eating 45,000kg of feed.



Dry litter material 2,000 kg

Feed intake 45,000 kg @ 90% DM @ 70% metabolizability

12,000 kg dry matter excreted @ 60% DM

20,000 kg ‘as is’ excreta22,000 kg ‘as is’ litter

Wood shavings/straw/rice hulls = 17% of DM of litterExcreta = 83% of DM of litter

Wood shavings, etc. = 6% of ‘as is’ litterExcreta = 94% of ‘as is’ litter

Litter = 4% N, 3% P2O5, 2% K2O on ‘as is’ basis

20,000 kg @ 4% N = 800 kg N@ 3% P2O5 = 600 kg P2O5@ 2% K2O = 400 kg K2O

Table 5.55 Calculations of manure production and composition per 10,000broilers

Feed intake and metabolizability of feed aregoing to be fairly consistent across the broiler indus-try for a given weight of bird. Consequently, thedry matter excretion of the flock will be quite pre-dictable. The major variable will be the drymatter content of the final litter, and this will direct-ly influence ‘as is’ concentration of nutrients. Themoisture content of litter will be a factor ofwater intake, water holding capacity of the exc-reta, ventilation rate and humidity of outsideair. In the example shown in Table 5.55, a valueof 60% DM was used in the calculation. Thismeans the litter has a water content of 40%. Theabove variables can combine to produce litter at25-55% moisture in extreme conditions.

One of the main reasons for ventilation is toremove moisture from the building. If outside air

is at high humidity, and close to saturation at ahigh temperature, there will be minimal moisturepick-up. If birds have loose and sticky manure,as occurs with some disease challenges or feedpassage, the water holding capacity of excretaincreases, and regardless of ventilation rate andhumidity, the excreta releases little moisture,and again, this contributes to wetter litter. Dietformulation will also influence water intake,and so litter moisture content. High levels of pro-tein, sodium and potassium are most often the rea-sons for increased water intake.

The nitrogen and phosphorus content ofbroiler feed has a direct effect on the content ofthese nutrients in manure. There is little varia-tion in nitrogen content of broiler diets fedworldwide, and relatively little scope for further



reduction. Each 1% reduction in dietary crude pro-tein influences litter nitrogen by only about 0.2%.Considering the size of the broiler industry today,a 0.2% reduction in manure nitrogen content is ofglobal significance, yet at the farm level, thischange is of little economic importance. As the pro-tein content of diets is reduced, there is often lossin broiler performance, even though levels ofmethionine + cystine, lysine, tryptophan and eventhreonine are maintained by use of syntheticamino acids. Because protein and amino acids arerelatively well digested by broilers, then there is min-imal scope for reducing litter nitrogen content bydiet formulation. There is more scope for reduc-ing the phosphorus content of broiler litter throughsimple reduction in total phosphorus content of thediet. Depending on bird age only 30 – 60% of dietphosphorus is digested, and so the vast majority ofingested phosphorus is excreted in the manure. Thereis also more variance in diet phosphorus than fordiet nitrogen, so again there is greater potential forstandardization. The situation with phosphorus isalso helped by the availability of phytase enzymes.Most phytase enzymes will liberate the equivalentof 0.1% available phosphorus and so diet formu-lation can be adjusted accordingly. There is adirect relationship between dietary available phos-phorus and excreta phosphorus (Figure 5.12).

There are obviously lower limits to phos-phorus content of diets, and the requirement forskeletal integrity is often higher than needs for gen-eral performance. The lower limits to diet phos-phorus levels are therefore often dictated by car-cass processing conditions. There is little doubtthat diet phosphorus needs decline over timeand that very heavy broilers have minimal require-ments. For broilers much older than 60 d, itseems as though conventional ingredients, evenof plant origin, can provide adequate phospho-rus for 10 – 14 d.

When calculating manure phosphorus appli-cation rates, and the potential for run-off intostreams etc, the situation is clouded by the con-cept of soluble vs. insoluble P in manure. Theuse of phytase does not seem to increase the pro-portion of soluble phosphorus in manure.Soluble phosphorus will presumably be availableto plants, while truly insoluble phosphorus willbe unavailable. Manure phosphorus that issoluble in citric acid is often considered as a meas-ure of the phosphorus available to plants. Ifphosphorus is soluble there is concern thatmore will be lost as run-off into streams.However, the alternate argument is that truly insol-uble phosphorus will not leach into soil, and sowill always be subject to physical run-off depend-ing on topography of the land. This issue seemsto be a factor of soil chemistry, topography,season of manure application to land, and leveland intensity of rainfall. With all of these vari-ables, it is obvious that unanimous conclusionsabout the importance of phosphorus solubilityin manure are not likely in the near term.

Of increasing concern is the level of trace min-erals in broiler litter, again as it influences soilaccumulation and water leaching. In someregions of the southern U.S.A. it is no longer pos-sible to use broiler litter as fertilizer on land usedto grow cotton since the accumulated zinc con-

Figure 5.12 Manure Phosphorus output per20,000 2.5 kg broilers



tent of soil greatly reduces plant growth. Of poten-tial concern is the accumulation of zinc and cop-per in soil. Table 5.56 describes average min-eral content of poultry litter.

The zinc and copper levels in manure aredirectly related to diet inclusion levels. Mineralpremixes usually contain around 80 ppm zincand 10 ppm copper. The bioavailability of traceminerals in the major feed ingredients is large-ly unknown, and in most situations their con-tribution is ignored. The major ingredients dohowever, contain significant quantities of mosttrace minerals (Table 5.57).

If copper was 100% bioavailable in corn andsoybean meal, then there would be little advan-tage to using supplements. The limited data avail-able on trace mineral availability from work20 – 40 years old, indicates values of 40 - 70%.The use of phytase further complicates the issue,since some of the minerals present in natural ingre-dients (Table 5.57) will be present within the phy-tate molecule. When phytase is used, presum-

ably there is greater bioavailability of mineralssuch as zinc from corn and soybean meal.There may be up to a 10% increased bioavail-ability of zinc as a result of using phytase. It seemsas though it is theoretically possible to greatlyreduce trace mineral supplements in broilerdiets, thereby reducing their accumulation inmanure.

Trace mineral proteinates, although much moreexpensive than oxides or sulfates, are of more pre-dictable bioavailability. In using very low lev-els of trace minerals under experimental conditions,we have recently used such mineral proteinatesbecause of their high and consistent bioavailability.In this study, birds were fed a conventionalmineral premix using oxides and sulfates. Thesupplements were arbitrarily assigned a digestibil-ity value of 70%, and then this level of ‘digestibleminerals’ provided as mineral proteinates.Mineral levels were further reduced by using only80% 20% of these already reduced con-centrations (Table 5.58).

Table 5.56 Trace mineral content of broiler litter

Table 5.57 Trace mineral content of selected feed ingredients (ppm)

Mineral (ppm)Zn Cu Fe Mn Mg Al Ca Na

Dry matter 300 500 3000 400 6000 2000 3000 4000As is (40% DM) 120 200 1200 160 2400 800 1200 1600

Zinc Manganese Iron CopperCorn 12 10 107 11Soybean meal 37 19 184 15Meat meal 97 7 285 12Wheat shorts 76 104 203 16



Treatment 0-42 d Mineral output (kg/yr)Wt gain (g) F:G Zn Mn Fe Cu

Inorganics1 2217 1.75 470 273 535 19Bioplex2 2351 1.70 318 217 523 17Bioplex 80% 2239 1.73 294 185 491 18Bioplex 60% 2285 1.72 309 172 494 16Bioplex 40% 2185 1.74 299 156 487 16Bioplex 20% 2291 1.69 292 130 446 15

Table 5.58 Broiler performance and calculated mineral output in manurefrom a farm growing 5 crops of 100,000 male broilers annually

1 Zn, 100 ppm; Mn, 90 ppm; Fe, 30 ppm; Cu, 5 ppm2 Zn, 70 ppm; Mn, 63 ppm; Fe, 18 ppm; Cu, 3 ppm

Using the 20% inclusion of the mineralproteinate, supplements were Zn, 14 ppm; Mn,13 ppm; Fe, 3.6 ppm and Cu, 0.6 ppm. Even atthese low levels, broiler performance was unaf-fected. Based on a 3 d total collection periodof manure at 18 d and at 39 d, it was possibleto predict manure mineral output extrapolatedfor the 42 d grow-out period (Table 5.58). Therewas a 37% reduction in zinc output and 21%

reduction in copper output in manure. If thereis future legislation concerning trace mineral con-tent of manure, much as now exists for N andP in many countries, then it should be possibleto reduce levels by nutritional intervention. Ifsuch legislation occurs, it will be interesting tosee what happens to the current common prac-tice of using high levels of copper as an anti-bacterial agent.


Suggested Readings

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Arce, J., M. Berger and C. Coello (1992). Control ofascites syndrome by feed restriction techniques. J. Appl. Poult. Res. 1:1-5.

Baker, D.H., A.B. Batal, T.M. Parr, N.R. Augspurgerand C.M. Parsons (2002). Ideal ratio (relative tolysine) of tryptophan, threonine, isoleucine andvaline for chicks during the second and third weeksposthatch. Poult. Sci. 81(4):485-494.

Bartov, I. (1987). Effect of early nutrition on fatten-ing and growth of broiler chicks at 7 weeks of age.Br. Poult. Sci. 28:507-518.

Bigot, K., S. Mignon-Grasteau, M. Picard, and S. Tesseraud (2003). Effects of delayed feed intakeon body, intestine, and muscle development inneonate broilers. Poult. Sci. 82(5):781-788.

Cabel, M.C. and P.W. Waldroup (1990). Effect of dif-ferent nutrient restriction programs early in life onbroiler performance and abdominal fat content.Poult. Sci. 69:652-660.

Corzo, A., E.T. Moran Jr., and D. Hoehler (2002).Lysine need of heavy broiler males applying theideal protein concept. Poult. Sci. 81(12):1863-1868.

Dale, N. and A. Villacres (1986). Nutrition influ-ences ascites in broilers. World Poult. Misset. Aprilpp 40.

Dale, N. and A. Villacres (1988). Relationship oftwo-week body weight to the incidence of ascites inbroilers. Avian Dis. 32:556-560.

Ducuypere, E., J. Buyse and N. Buys (2000). Ascitesin broiler chickens: exogenous and endogenousstructural and functional causal factors. World’sPoult. Sci. 56 (4):367-377.

Dozier, W.A. III, R.J. Lien, J.B. Hess, S.F. Bilgili,R.W. Gordon, C.P. Laster and S.L. Vieira (2002)Effects of early skip-a-day feed removal on broilerlive performance and carcass yield. J. Appl. Poult.Res. 11(3):297-303.

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Emmert, J.L. and D.H. Baker (1997). Use of the idealprotein concept for precision formulation of amino acidlevels in broiler diets. J. Appl. Poult. Res. 6:462-470.

Emmert, J.L., H.M. Edwards III and D. H. Baker(2000.) Protein and body weight accretion of chickson diets with widely varying contents of soybeanmeal supplemented or unsupplemented with its lim-iting amino acids. Br. Poult. Sci. 41:204-213.

Fancher, B.I. and L.S. Jensen (1989). Dietary proteinlevel and essential amino acid content. Influenceupon female broiler performance during the growerperiod. Poult. Sci. 68:897-908.

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Granot, I., I. Bartov, I. Plavnik, E. Wax, S. Hurwitzand M. Pines (1991a). Increased skin tearing inbroilers and reduced collagen synthesis in skin invivo and in vitro in response to coccidiostat halofug-inone. Poult. Sci. 70:1559-1563.

Hinton, A., Jr., R.J. Buhr and K.D. Ingram (2000)Physical, chemical and microbiological changes inthe crop of broiler chickens subjected to incrementalfeed withdrawal. Poult. Sci. 79:212-218.

Howlider, M.A.R. and S.P. Rose (1988). Effect ofgrowth rate on the meat yields of broilers. Br. Poult.Sci. 29:873.

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Kerr, B.J., M.T. Kidd, G.W. McWard, and C.L.Quarles (1999). Interactive effects of lysine and thre-onine on live performance and breast yield in malebroilers. J. Appl. Poult. Res. 8:391-399.

Kerr, B.J., M.T. Kidd, K.M. Halpin, G.W. McWardand C.L. Quarles (1999). Lysine level increases liveperformance and breast yield in male broilers. J. Appl. Poult. Res. 8:381-390.

Kidd, M.T., B.J. Kerr, K.M. Halpin, G.W. McWard,and C.L. Quarles (1998). Lysine levels in starter andgrower-finisher diets affect broiler performance andcarcass traits. Appl. Poult. Res. 7:351-358.

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Leeson, S. (1993). Potential of modifying poultryproducts. J. Appl. Poult. Res. 2:380-385.

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Sklan, D. (2003). Fat and carbohydrate use inposthatch chicks. Poult. Sci. 82(1):117-122.

Sklan, D. and I. Plavnik (2002). Interactions betweendietary crude protein and essential amino acid intakeon performance in broilers. Br. Poult. Sci. 43(3):442-449.

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Taylor, N.L., J.K. Northcutt and D.L. Fletcher (2002).Effect of a short-term feed outage on broiler per-formance, live shrink, and processing yields. Poult.Sci. 81(8):1236-1242.

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Xu, Z.R., C.H. Hu, M.S. Xia, X.A. Zhan and M.Q.Wang (2003). Effects of dietary fructooligosaccha-ride on digestive enzyme activities, intestinalmicroflora and morphology of male broilers. Poult.Sci. 82:1030-1036

Yan, F., J.H. Kersey, C.A. Fritts and P.W. Waldroup(2003). Phosphorus requirements of broiler chicks sixto nine weeks of age as influenced by phytase sup-plementation. Poult. Sci. 82(2):24-300.

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297

T he continuing increase in geneticpotential of the broiler chicken posesever-greater challenges for feeding

and managing breeders. Growth and repro-ductive characteristics are negatively correlated,and because of the relative economic signif-icance of broiler performance within integratedoperations, broiler performance is necessar-ily of primary importance. As appetite andweight for age increase in commercial broil-ers, so nutrient restriction of young breedersmust start at earlier ages and/or be of increas-ing severity at older ages. The modern breed-er hen at 22 weeks of age must be compara-ble in weight to her offspring at 6 weeks of age.It is, therefore, not too surprising that appetitecontrol of parent flocks is becoming more chal-lenging. Like most other classes of poultry, theabsolute requirements of broiler breeders areinfluenced by both feeding level and diet

nutrient specifications. However, this dual effectmeans that nutrient intake can be controlledmuch more closely, and so represents greatpotential for matching intake to requirement.High-yield breeders are often slightly later matur-ing (7 – 10 d) than are conventional broilerbreeders and have a longer feed clean-uptime. In general, managers should not reacttoo quickly in changing the feed allocation ordiet as they normally would to circumstancesarising with conventional breeders. High-yieldroosters also pose some interesting new feedmanagement problems, related to their aggres-sive behaviour. Tables 6.1 and 6.2 show dietspecifications for growing and adult breeders,while Table 6.3 provides examples of corn baseddiets. Tables 6.4, 6.5 and 6.6 indicate nutri-ent specifications for adult birds as detailedby the primary breeding companies.

Page

FEEDING PROGRAMS FORBROILER BREEDERS

6CHAPTER

6.1 Diet specifications and feed formulations

6.1 Diet specifications and feed formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

6.2 Breeder pullet feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

6.3 Prebreeder nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

6.4 Breeder hen feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

6.5 Factors influencing feed and nutrient intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

6.6 Breeder male feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

6.7 Feed efficiency by breeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

6.8 Nutrition and hatchability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

6.9 Caged breeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

298 CHAPTER 6FEEDING PROGRAMS FOR BROILER BREEDERS


Table 6.1 Diet specifications for broiler breeder pullets

Starter Grower Developer PrebreederAge (wks) 0 – 4 4 – 12 12 – 22 20 - 22Crude Protein (%) 18.5 17.0 16.0 16.0Metabolizable Energy (kcal/kg) 2850 2850 2850 2850Calcium (%) 0.95 0.92 0.89 2.25Available Phosphorus (%) 0.45 0.40 0.38 0.42Sodium (%) 0.20 0.19 0.17 0.17

Methionine (%) 0.42 0.35 0.32 0.37Methionine + Cystine (%) 0.80 0.72 0.65 0.64Lysine (%) 1.00 0.90 0.80 0.77Threonine (%) 0.72 0.67 0.60 0.58Tryptophan (%) 0.20 0.18 0.16 0.15Arginine (%) 1.15 1.00 0.86 0.80Valine (%) 0.75 0.70 0.65 0.60Leucine (%) 0.90 0.85 0.92 0.88Isoleucine (%) 0.70 0.60 0.51 0.48Histidine (%) 0.20 0.18 0.29 0.26Phenylalanine (%) 0.65 0.60 0.53 0.49

Vitamins (per kg of diet)Vitamin A (I.U.) 8000Vitamin D3 (I.U.) 3000Vitamin E (I.U.) 50Vitamin K (I.U.) 3Thiamin (mg) 2Riboflavin (mg) 10Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (ug) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 15

Trace minerals (per kg of diet)Manganese (mg) 60Iron (mg) 30Copper (mg) 6Zinc (mg) 60Iodine (mg) 0.5Selenium (mg) 0.3

299CHAPTER 6FEEDING PROGRAMS FOR BROILER BREEDERS


Phase 1 Phase 2 Phase 3 MaleAge (wks) 22 – 34 34 – 54 54 – 64 22 - 64

Crude Protein (%) 16.0 15.0 14.0 12.0Metabolizable Energy (kcal/kg) 2850 2850 2850 2750Calcium (%) 3.00 3.20 3.40 0.75Available Phosphorus (%) 0.41 0.38 0.34 0.30Sodium (%) 0.18 0.18 0.18 0.18

Methionine (%) 0.36 0.32 0.30 0.28Methionine + Cystine (%) 0.65 0.62 0.59 0.55Lysine (%) 0.80 0.74 0.68 0.55Threonine (%) 0.62 0.61 0.57 0.51Tryptophan (%) 0.18 0.16 0.14 0.13Arginine (%) 0.90 0.82 0.74 0.65Valine (%) 0.60 0.55 0.50 0.46Leucine (%) 0.80 0.74 0.70 0.64Isoleucine (%) 0.62 0.58 0.52 0.45Histidine (%) 0.18 0.17 0.16 0.12Phenylalanine (%) 0.55 0.50 0.45 0.40

Vitamins (per kg of diet)Vitamin A (I.U.) 8000Vitamin D3 (I.U.) 3000Vitamin E (I.U.) 75Vitamin K (I.U.) 3Thiamin (mg) 2Riboflavin (mg) 10Pyridoxine (mg) 4Pantothenic acid (mg) 12Folic acid (mg) 0.75Biotin (ug) 100Niacin (mg) 40Choline (mg) 500Vitamin B12 (µg) 15


Table 6.2 Diet specifications for adult broiler breeders



Table 6.3 Example of breeder diets (kg)

Starter Grower Developer Prebreeder Breeder 1 MaleCorn 487 538 539 600 666 455Wheat shorts 264 250 280 154 45 367Wheat bran 100Soybean meal 213 178 148 178 201 52DL-Methionine* 2.3 1.9 1.6 1.3 1.3 1.7L-Lysine 0.8 0.9 0.6 0.2Salt 3.8 3.5 3 3.1 3.4 3.3Limestone 16.6 17.2 18 51 70.5 17Dical Phosphate 11.5 9.5 8.8 11.6 11.8 2.8Vit-Min Premix** 1 1 1 1 1 1

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 18.5 17.0 16.0 16.0 16.0 13.4ME (kcal/kg) 2850 2893 2895 2850 2850 2750Calcium (%) 0.95 0.93 0.93 2.25 3.00 0.75Av Phosphorus (%) 0.45 0.40 0.38 0.42 0.41 0.30Sodium (%) 0.20 0.19 0.17 0.17 0.18 0.18Methionine (%) 0.53 0.47 0.42 0.41 0.41 0.38Meth + Cystine (%) 0.80 0.72 0.65 0.64 0.65 0.55Lysine (%) 1.00 0.90 0.80 0.78 0.80 0.55Threonine (%) 0.75 0.70 0.65 0.67 0.69 0.52Tryptophan (%) 0.25 0.23 0.21 0.22 0.22 0.19

* or equivalent MHA** with choline



Hubbard Cobb Ross

Metabolizable energy (kcal/kg) 2865 2860 2860Crude protein (%) 15.5 16.0 16.0Calcium (%) 3.2 2.9 3.0Av. Phosphorus (%) 0.40 0.45 0.40Sodium (%) 0.17 0.17 0.16Linoleic acid (%) 1.25 1.5 1.25

Methionine (%) 0.35 0.35 0.35Meth + cystine (%) 0.58 0.64 0.61Lysine (%) 0.71 0.78 0.83Tryptophan (%) 0.17 0.17 0.21

Vitamin A (TIU/kg) 8.8 11.0 5.45Vitamin D3 (TIU/kg) 3.3 1.75 1.6Vitamin E (IU/kg) 44 40 45Vitamin K3 (mg/kg) 3.3 5.0 2.0Thiamin (mg/kg) 4.4 2.5 3.0Riboflavin (mg/kg) 8.8 10.0 5.5Pantothenate (mg/kg) 15.5 20.0 7.0Niacin (mg/kg) 53 45 18Pyridoxine (mg/kg) 3.3 5.0 2.0Choline (mg/kg) 660 186 450Folic acid (mg/kg) 1.0 1.25 0.90Biotin (mg/kg) 0.22 0.20 0.20Vitamin B12 (µg/kg) 11 20 20

Manganese (mg/kg) 80 90 30Zinc (mg/kg) 80 75 40Iron (mg/kg) 66 20 30Copper (mg/kg) 9 3.6 4Iodine (mg/kg) 1.1 1.5 0.46Selenium (mg/kg) 0.30 0.13 0.10

Table 6.4 Nutrient specifications for breeder diets1

(Management Guide Data)

1Phase I, if more than one diet recommended



Table 6.5 Breeder diet specifications for amino acids expressed per unit ofprotein or per unit of energy

Hubbard Cobb RossMethionine

(g/kg CP) 22.5 22.2 21.3(g/Mcal) 1.26 1.20 1.19

Meth + Cys(g/kg CP) 37.4 40.0 36.3(g/Mcal) 2.02 2.20 2.03

Lysine(g/kg CP) 45.8 48.8 50.0(g/Mcal) 2.47 2.68 2.80

Tryptophan(g/kg CP) 10.9 10.6 11.3(g/Mcal) 0.59 0.58 0.63

Hubbard Cobb Ross

Energy (kcal) 458 469 478Crude protein (g) 24.8 25.8 26.7Calcium (g) 5.1 4.7 5.0Av. Phosphorus (mg) 640 724 668Methionine (mg) 560 563 567Meth + cys (mg) 928 1030 967Lysine (mg) 1136 1256 1336Feed intake (g) 160 161 161Body Weight (g) 3100 3130 3150

Table 6.6 Daily intake of selected nutrients for breeders at 28 weeks of age1

1Calculated from Management Guide Data


SECTION 6.2Breeder pullet feeding programs

Pullets RoostersAge B. wt. Feed intake1 Uniformity B. wt. Feed intake1 Uniformity

(wks) (g) (g/d) (%) (g) (g/d) (%)1 120 25 75 125 27 702 230 27 75 280 30 703 330 29 75 440 32 704 420 31 80 610 34 755 510 34 80 720 36 756 610 36 80 840 39 757 680 40 80 930 42 758 760 43 80 1040 46 809 860 46 80 1180 50 8010 960 49 80 1300 53 8011 1050 53 80 1420 55 8012 1150 58 80 1550 58 8013 1250 62 80 1700 63 8014 1350 66 85 1880 66 8215 1450 68 85 2060 70 8216 1550 71 85 2200 76 8217 1670 76 85 2320 81 8518 1790 82 85 2450 90 8519 1900 88 90 2600 95 8520 2040 94 90 2830 100 8521 2200 98 90 2970 105 8522 2320 102 90 3100 110 85

Table 6.7 Standards for pullet and rooster growth and development

1Mean diet ME 2900 kcal/kg

6.2 Breeder pullet feeding programs

P ullets and roosters must be managed soas to achieve the desired uniform weightat time of photostimulation, which is

usually around 22 – 24 weeks of age. Growthand uniformity are influenced by feeding programand to a lesser extent, feed formulation. Withinreason, it is possible to achieve the desiredweight for age when using diets with a vastrange of nutrient specification. Nutrient intakeis largely controlled by the degree of feed restric-tion. For example, it is theoretically possible to

grow pullets on diets with energy levels rang-ing from 2600-3100 kcal ME/kg. In practice,diet energy level is usually within the range of2750-2950 kcal ME/kg, although for diets nec-essarily formulated outside of this range, ener-gy intake can be controlled by adjusting feedintake. It is usually more difficult to maintainuniformity with high-energy diets, since this nec-essarily implies much smaller quantities offeed being distributed at any one time. Generalstandards for growth and feed intake are shownin Table 6.7.



Each commercial strain is going to havecharacteristic patterns of growth and these canbe used to dictate feeding program. These strainswill have an ‘optimum’ mature weight which isaround 2.2 kg for pullets and 3.1 kg for roostersat 22 weeks of age. Interestingly as broiler growthpotential has increased continuously over the last20-30 years, the mature weight of breeders haschanged very little. With the potential to influ-ence nutrient intake with both diet modificationand degree of feed restriction, it is obvious thattarget weights can be achieved by various routes,and these will influence rearing (feed) costs.Over the years, both qualitative and quantitativenutrient restriction programs have been studied.

a) Qualitative feed restrictionTheoretically, it should be possible to con-

trol growth of juvenile breeders by providing eitherlow nutrient dense diets and/or formulatingdiets with marginal deficiencies of certain nutri-ents. It is impossible to achieve the desired growthrate of birds simply by feeding low nutrientdense diets. The bird’s voracious appetite meansthat it can growth quite well on diets as low as2300 - 2400 kcal ME/kg, on an ad-lib basis, andso diets of less than 2000 kcal ME/kg are prob-ably required to limit growth. Such diets are veryexpensive per unit of energy, are expensive to trans-port, and result in very wet litter.

Diets that are borderline deficient in proteinand amino acids will limit growth. In mostinstances, such programs have failed since not

all birds in a flock have identical nutrient require-ments. For example, reducing the methioninecontent of the diet by 25% may well lead to areduction in mean flock weight. Unfortunately,those birds with a high inherent methioninerequirement will be very light in weight, whilethose birds with an inherently low methioninerequirement will be little affected by the diet andgrow at a normal rate. Therefore, while meanflock weight can often be manipulated withqualitative feed restriction, uniformity of flockweight is usually very poor, often reaching 30 –40% compared to 80% under ideal conditions(% of birds ± 15% of flock mean weight). Forexample, our studies with salt deficient diets indi-cated that mean flock weight could be quite accu-rately controlled by regulating the level of saltadded to a corn-soybean meal based diet.Unfortunately, flock uniformity at 20 weekswas very low, and consequently many birdswere over- or under-weight in the breeder houseand both egg production and fertility wereimpaired. Similar attempts at qualitative feedrestriction have been made with manipulationof fatty acid and amino acid levels in the diet.

b) Quantitative feed restrictionSome type of physical feed restriction is

universally used to control breeder growth. Thetraditional system has been skip-a-day where, asits name implies, birds are fed only on alternatedays. An example skip-a-day program is shownin Table 6.8.



Age Pullets (g) Roosters (g)(wks)

1 Ad-lib Ad-lib2 Controlled 25/d Controlled 30/d3 Controlled 30/d Controlled 40/d4 70 805 80 906 90 1007 100 1108 105 1159 110 12010 115 12511 120 13012 125 13513 130 14014 135 14515 140 15016 145 15517 155 16018 165 17019 175 18020 185 190

Table 6.8 Skip-a-day feed restriction program for pullets and roosters (diet at2900 kcal/kg)

The skip-a-day feed intake will obviouslydepend upon nutrient density and environ-mental conditions, yet these values can be usedas guidelines. The concept of feeding to bodyweight and the regulation of body weight will bediscussed more fully in a subsequent section. Table6.8 indicates a restricted feeding program for bothpullets and cockerels to be initiated at 4 weeksof age. Prior to this, ‘controlled’ feeding shouldbe practiced so as to acclimatize birds to a lim-ited feed intake. Controlled feeding should beadjusted to ensure that birds are cleaning up theirfeed on a daily basis within 4 – 6 hours. Becausedifferent strains of birds have different growth char-acteristics, then initiation of controlled andrestricted feeding must be flexible in order to con-trol body weight. For strains with inherently fast

early growth rate, restricted feeding on a dailybasis may be necessary as early as 7 – 10 d of age.For other strains, ad-lib feeding to 3 – 4 weeks ispossible since they have a slow initial growth rate.

With skip-a-day, birds are given these quan-tities of feed only every other day. The conceptbehind this program is that with every other dayfeeding, birds are offered a considerable quan-tity of feed and this is easier to distribute so thateven the smallest most timid bird can get achance to eat. The usual alternative to skip-a-day feeding is feeding restricted quantities everyday. For example, at 11 weeks of age, pullets couldbe fed 60 g each day. The problem with everyday feeding is that feed is eaten very quickly andso all birds within a flock may not get ade-



quate feed. With such small quantities of feed,and using slow-speed feed chains or augerdelivery, it is not unheard of for birds to ‘keep-up’ with feed delivery close to the feed hoppers,and reduce effective feeder space. With every-day feeding, birds may well consume their dailyallocation within 30 minutes, and so adequatefeeder space is essential with this type of program.However, there is a trend towards every day feed-ing since it is more efficient and with goodmanagement and supervision, good uniformitycan be achieved. Improved efficiency results frombirds utilizing feed directly each day, ratherthan there being the inherent inefficiency ofskip-a-day fed birds having to utilize storedenergy for maintenance on the off-feed day.Most daily feed allowances are derived by halv-ing corresponding skip-a-day programs. Forexample in Table 6.8, the skip-a-day allowancefor a 9 week pullet is 110 g. If pullets are given55 g daily, they will gain more weight since theyuse this feed more efficiently. In practice, skip-a-day allowances have to be divided by about2.2 (rather than 2) in order to achieve the samegrowth rate. Table 6.9 shows growth rate of pul-lets and roosters fed skip-a-day or exactly 50%of this allowance on a daily basis. Birds fed dailyat 50% of the skip-a-day allowance are consis-tently 8 – 10% heavier.

Whatever system of feed restriction is used,the goals are to obtain uniform and even growthrate through to maturity. Ideally the pullets androosters will be close to target weight by 16 – 17weeks of age, since attempts at major increases(or decreases) in growth after this time oftencompromise body composition, maturity andsubsequent reproductive performance.

Some flocks will invariably get heavier thanthe desired standard and their growth rate hasto be tempered more than normal. It is tempt-ing to drastically reduce the feed intake of suchflocks, so as to quickly correct the excess growth.Such action is usually accompanied by loss inuniformity. Overweight flocks must be broughtback to standard more slowly, perhaps over 6 -8 weeks depending on age. Underweight flocksare more easy to manage, since it is easy to givemore feed. However, it is again necessary to cor-rect the flock by a gradual increase in feedallowance, such that desired body weight isrealized within 3 – 4 weeks. Table 6.10 showsexamples of records from actual breeder flockseach of about 40,000 pullets, that were over orunderweight at either 6 or 13 weeks of age. Weightreadjustment, achieved by altering feed allowance,occurred slowly to maintain uniformity withinthese flocks.

Table 6.9 Effect of providing equal quantities of feed by skip-a-day or everyday feeding on growth of pullets and roosters

Pullet weight1 (g) 19 wk Rooster weight2(g)Age (wks) Skip-a-day Every day Diet treatment Skip-a-day Every day

8 530b 790a 2850 ME, 15% CP 2410 253011 950b 1010a 2850 ME, 20% CP 2320 251014 1190b 1290a 2000 ME, 15% CP 1960 215017 1540b 1630a 2000 ME, 20% CP 1920 204020 1890b 1980a

1Adapted from Bennett and Leeson (1989); 2Adapted from Vaughters et al. (1987)



Age

(w

ks)

12

34

56

78

910

1112

1314

1516

1718

1920

Stan

dard

wt.

(kg)

.12

.23

.33

.42

.51

.61

.68

.76

.86

.96

1.05

1.15

1.25

1.35

1.45

1.55

1.67

1.79

1.90

2.04

Floc

k #1

Ove

rwei

ght

at 6

wks

.75

.81

.88

.97

1.06

1.15

1.24

1.34

1.43

1.52

1.61

1.73

1.84

1.95

2.09

Floc

k #2

Und

erw

eigh

t at

6 w

ks.5

0.5

8.6

9.8

0.9

11.

021.

151.

251.

351.

451.

551.

671.

791.

902.

04

Floc

k #3

Ove

rwei

ght

at 1

3 w

ks1.

401.

491.

581.

671.

791.

902.

012.

14

Floc

k #4

Und

erw

eigh

t at 1

3 w

ks1.

101.

221.

351.

481.

621.

751.

902.

04

Tab

le 6

.10

Bod

y w

eigh

t go

als

for

pu

llet

s th

at b

ecom

e ov

erw

eigh

t or

un

der

wei

ght

at 6

or

13 w

ks

of a

ge

Day

Syst

em1

23

45

67

89

10Sk

ip-a

-day

160

016

00

160

016

00

160

02

– 1

120

120

012

012

00

120

120

012

03

- 1

106

106

106

010

610

610

60

106

106

6 -

193

9393

9393

930

9393

93

Tab

le 6

.11

Exa

mp

les

of a

lter

nat

e fe

ed p

rogr

ams

to p

reve

nt

chok

ing

in

15 –

18

wee

k o

ld b

reed

er p

ull

ets

(g f

eed

/bir

d/d

ay e

qu

ival

ent

to 8

0 g/

bir

d/d

ay)



Choking and death can sometimes occur withbreeders at 14 – 18 weeks when fed skip-a-day.Assuming that there is adequate feeder space, thenthis program can only be resolved by changingthe program so as to give smaller quantities offeed at any one time. Example programs are shownin Table 6.11, where the standard is ‘equivalency’of 80 g/bird/day. Changing to one of these pro-grams also helps in the transition from skip-a-dayto daily feeding as adults.

Whatever system is used, there needs to beflexibility related to status of the flock as affect-ed by various management decisions. Certainvaccinations and the physical movement ofbirds can cause a 1– 2 day delay in growth rate.These periods of known stress should be coun-teracted by extra feeding. For example, if skip-a-day fed birds are scheduled to be moved onday 6 as shown in Table 6.11 (non feed day), thenbirds should be given feed this day regardless ofthe preplanned schedule.

Coccidiosis is an ever present problem whenrearing breeder pullets on litter. Because antic-occidials are not usually allowed in adult breed-er diets, the bird must develop immunity duringrearing. Such immunity does not develop withanticoccidials commonly used for commercialbroilers, and in particular the ionophores. Thismeans that if ionophores are used during rear-ing of breeder pullets, they will most likely pre-vent clinical coccidiosis, but these birds may devel-op clinical symptoms as soon as they aretransferred to the breeder house. If an anticoc-cidial is used during rearing, then productssuch as amprolium are more advantageous.Compounds like amprolium usually preventacute clinical symptoms, while at the sametime, allowing some build-up of immunity. Incertain countries, depending upon feed regulations,amprolium can be used throughout the life-

cycle of the bird. An alternate approach, and onethat requires superior management skills, is touse non-medicated feed during rearing, and totreat birds as soon as clinical symptoms occur.Since treatment must be immediate, only water-dispensable products, such as amprolium, are rec-ommended. It is now more common to vacci-nate chicks with attenuated live vaccines. Chicksare sprayed at the hatchery and immunity shoulddevelop during early rearing.

c) Specific programs for roostersRoosters can be grown with the hens or

grown separately, but in both situations they willalmost exclusively be fed starter and growerdiets designed for the female birds. This posesno major problem, because there are no largedifferences in nutrient requirements of the sexesup to the time of maturity. Where males andfemales are grown together, the onset of restric-tion programs and general feed allocation sys-tems are usually dictated by progress in hen weightand condition. Male growth and conditioncannot be controlled as well under these situa-tions, and this has to be an accepted consequenceof this management decision.

Growing roosters separately provides thebest opportunity to dictate and control theirdevelopment. As with commercial broilers,the male breeders will respond more to high pro-tein starter diets or to more prolonged feedingof these diets. The opposite situation alsoapplies, in that male breeder chicks will bemore adversely affected by low protein or lowamino acid starter diets. For example, under idealconditions, a well-balanced 16% CP diet can beused as a starter for female chicks and thisresults in slower early growth rate with theadded advantage of delay in introducing restrict-ed feeding. Male chicks can also be grown on



such diets, although it is not usually recom-mended, because there will be poorer earlyfeathering and perhaps more uneven growth rate.These problems resolve themselves over time, butas a general rule it is better to start male breed-er chicks on at least a 17 – 18% CP diet. The malebreeder chick is also more sensitive to the effectsof low protein diets that contain anticoccidials,such as monensin. Again, poor feathering willresult if starter diets contain much less than18% CP. Poor early feathering has no longlasting effect on subsequent breeder performance,although the chicks obviously look differentand they may suffer more from early cold stress.

As for the hens, it is usual to start feed restric-tion of rooster chicks at around 3 weeks of age.Starting at 3 weeks of age, groups of 10 chicks canbe weighed together to give an idea of body weightand controlled feeding started. Starting at 4weeks of age, sample birds should be weighedindividually, just as occurs with the hens, and meanweight and uniformity plotted to give a visual imageof flock progress. Ideally, feed allocation will beincreased on a weekly basis, although this shouldbe dictated by the weekly body weight meas-urements. Changes in environmental tempera-ture or unprogrammed changes in diet energy (dueto ingredient variability, etc.) will affect nutrientneeds, feed intake and/or growth rate. Usuallythe body weight and uniformity of the birds rep-resents their true feed needs at that time and sothere needs to be flexibility in feed allocation toaccount for these variables.

Skip-a-day feeding is usually the preferred sys-tem up to time of transfer to the breeder house.However in some situations, choking can occurwith males after 14 – 16 weeks of age, and thisis caused by rapid and excessive feed intake onfeeding days. Such choking causes 0.5% mor-tality per day in extreme situations, but cansometimes be resolved by ensuring that water is

available for at least 1 hour prior to feeding. Wherethis technique fails to correct the problem, it maybe necessary to change to a 5:2 or even a 6:1 feed-ing program as previously described for females.These programs provide the same amount of feedon a weekly basis, but this is given as smaller quan-tities, more often. There seems to be less gorgingwhen birds eat smaller quantities of feed more often.A potential problem with changing to 5:2 or 6:1feeding programs is loss of uniformity, because dailyfeeding time will be very short. If males aregrown separately from females, then this unifor-mity problem can sometimes be resolved bychanging to a lower nutrient density diet, and giv-ing proportionally more feed so as to maintain nor-mal nutrient intake (however under these condi-tions, daily feed intake will still be less than withskip-a-day feeding). Whatever feeding system isused, it is essential to provide adequate feeder spacesuch that all birds can eat at one time.

d) Water managementSome type of water restriction program is also

important for juvenile breeders. With feedrestriction, birds can consume their feed in 30minutes to 2 hours depending upon the systemand age of bird. Given the opportunity, these birdswill consume excessive quantities of water sim-ply out of boredom or to satisfy physical hunger.Certainly birds given free access to water seemto have wetter litter, and there is no doubt thata water restriction program is necessary in orderto maintain good litter quality and help preventbuild-up of intestinal parasites and maintainfoot pad condition. Various water restriction pro-grams are used and there are no universal guide-lines that should be adhered to. Pullets devel-op normally when given as little as half hour accessto water each day, although longer periods thanthis are usually recommended. It seems advis-able to give birds one half to 1 hour access to waterprior to feed delivery, especially with skip-a-day



feeding. The reason for this is prevention of sud-den-death type syndrome that occurs with asmall proportion of birds that invariably have gross-ly distended crops full of dry feed. The exact causeof death is unknown although it is possible thatthe sudden intake of a large volume of dry feedacts as a ‘sponge’ to normal body fluids and soupsets the bird’s water/electrolyte balance.Giving birds access to water prior to feed deliv-ery often seems to resolve this problem. Table6.12 provides general recommendations forwater access. These values should be considered

as guidelines only, and during periods of heat stressor during disease conditions and around the timeof moving etc., time allocations should beincreased. With skip-a-day feeding, it is usualto more severely limit water access on off-feeddays based on the assumption that birds tend todrink most water on this day (due to boredomor need to meet physical intake satiety) since theyare without feed. However, our studies suggestthat breeder pullets drink most water on feed days,and seem generally uninterested in water on off-feed days (Table 6.13).

Table 6.12 Suggested water access time for juvenile breeders

Feed Day Off-feed Dayam pm am pm

Skip-a-day feeding 2-3 hr, starting 1 hr prior to feeding 1 hr 1 hr 1 hrEvery day feeding 2 hr, starting 1 hr prior to feeding 1 hr - -

Table 6.13 Total water usage of 13-week old skip-a-day or daily fed birdswith free or restricted access to water (ml/bird/day)

Adapted from Bennett (1989)

Skip-a-day fed birds Daily fed birdsWater Water Free access Free access

restricted each restricted on to water to waterday feed days

Feed day 192 196 273 205Off-feed day 122 122 37 217Mean intake 157 161 155 211Water:feed 2.38 2.44 2.35 3.20


SECTION 6.3Prebreeder nutrition

When birds are daily fed, there is a fairly con-sistent pattern of water intake. With skip-a-day feeding and free access to water, pullets sur-prisingly consume very little water on an off-feedday – for these birds, the largest water intake occurson the feed day. If this data can be substantiat-ed under field conditions, it suggests that the majoremphasis on water restriction of skip-a-day fedbirds should occur on the feed day rather thanthe off-feed day. These results are perhaps nottoo surprising in view of the well established rela-tionship between the intakes of water and feed.It also appears as though daily feeding stimulatesoverall water usage and increases the water:feedratio. As previously discussed, the major factorinfluencing water needs, is environmental tem-perature. At higher temperatures, birds need morewater to enhance evaporative cooling. Waterrestriction programs must therefore be flexibleas environmental temperatures change (Table 6.14).

in order to establish the bird’s calcium reservesnecessary for rapid and sudden onset of eggshellproduction. The same situation can be appliedto heavy breeders today, because with flocks ofuniform body weight and with good light man-agement, synchronization of maturity leads to rapidincrease in egg numbers up to peak production.However, most often prebreeder diets are usedin an attempt to ‘condition’ or correct growth and/orbody composition problems that have arisen dur-ing the 14 – 18 week growing period. In thesesituations managers are perhaps ill-informedof the expectations that result from merelychanging diet specifications at this time.

Although there is no specific prebreeder‘period’, most breeder managers consider the 21– 24 week period to be the major transition

Age (wks) 20ºC 35ºC4 70 1456 105 1758 115 19210 130 22012 145 24014 160 27016 175 29018 190 32020 205 345

Table 6.14 Daily water consump-tion of pullets on skip-a-day feed-ing (litres/1000 pullets)

T here is considerable variation in applicationand use of prebreeder diets. While mostprimary breeding companies show spec-

ifications for prebreeder diets, there are signif-icant numbers of birds that are changed direct-ly from grower diet to breeder diet. Choice ofprebreeder diet and its application must be tai-lored to individual farm circumstances.

Using a prebreeder diet assumes that the bird’snutrient needs are different at 21 – 24 weeks ofage, which is the most common time for feed-ing such diets. However, apart from consider-ations for calcium metabolism, it can be arguedthat any change in the bird’s requirements canbe accommodated by adjusting the level offeed intake. With commercial egg layers, ‘pre-lay’ diets usually involve a change in calcium level,

6.3 Prebreeder nutrition



time for sexual development of the bird. Duringthis time (3 weeks) the pullet is expected toincrease in weight by about 450 g. This issomewhat more than the growth expectation ofaround 400 g for the previous 4 weeks (17 – 21weeks) but comparable to the 450 g for the 4 weeksfrom 24-28 weeks of age. It is expected that asignificant proportion of this growth will be asovary and oviduct, which are developing inresponse to light stimulation. However, there islittle evidence to suggest that high nutrientdense diets and/or feed allocation have anymeaningful effect on ovary or oviduct development.Studies suggest that the protein requirement ofthe breeder at this critical time is only around 10g/bird/day, which is much less than is providedby most prebreeder diets. There is some evidenceto suggest that excess protein fed during the lategrowing/prebreeder period causes an increasein plasma uric acid levels and especially 2 – 3hours after feeding. Plasma uric acid levels insuch birds are similar to those of birds showingarticular gout, and so there is concern about excessprotein contributing to the potential for legproblems in these young breeders.

A practical complication of this sexual devel-opment, is that it invariably coincides withmoving the pullets from grower to breeder facil-ities. During transportation over long distancesor during heat stress, etc., birds can lose up to100 g of body weight at this critical time. If weightloss does occur during transportation, then pul-lets should be given an extra feeding. For exam-ple, pullets should be moved on an ‘off-feed’ day,but they should nevertheless be fed that day inthe breeder house after all birds are housed. Weightloss cannot be allowed at this critical time, andso the question to be answered is – do pre-breeder diets help in this physical move, aswell as prime the bird for sexual maturity?

Development of the ovary and oviduct requiresboth protein/amino acids and energy (fat accre-tion). Nutrients of interest, therefore, are proteinand energy, together with an increase in calciumfor early deposition of medullary bone. It has neverbeen clearly established that such nutrients needto come from a specially fortified diet versus sim-ply increasing the feed allowance of the grow-er diet or breeder diet that is introduced prior tomaturity. Following are factors to consider in feed-ing the bird in the prebreeder transition period,and the need or not for specialized diets.

a) Calcium metabolismPrebreeder diets can be used to pre-condi-

tion the pullet for impending eggshell produc-tion. The very first egg represents a 1.5 – 2.0 gloss in calcium from the body, the source of whichis both feed and medullary bone reserve. Breederhens today are capable of a sustained longclutch length which is necessary to achievepotential peak production at 85 – 87%. Calciummetabolism is, therefore, very important for thebreeder. With Leghorn hens the consequenceof inadequate early calcium balance is cagelayer fatigue. Breeders do not show such signs,because they naturally have more exercise, andalso have a readily available alternate source ofdiet calcium in the form of their flockmates’ eggs.Hens have an innate ability to seek diet calciumin any source and so improperly fed breeders willeat litter and eggshells in an attempt to bal-ance their diet. However, inadequate calciumin the diet does lead to disruption of ovula-tion, and so these birds stop laying until their mea-ger calcium reserves are replenished. In abreeder flock, it is the larger bodied, earlymaturing pullets that are disadvantaged in thismanner. Commercially, three different approach-es are used in prebreeder calcium nutrition.



Firstly, is the use of grower diets that containjust 0.9 - 1.0% calcium being fed up to 5% eggproduction. This is the system that was used manyyears ago. At 5% egg production, 100% of theflock is not producing at 5% egg production –rather closer to 5% of the early maturing heav-ier pullets are producing at almost 100% pro-duction. Pullets can produce just 2 – 3 eggs witha diet containing 1% calcium. After this time theywill eat litter and/or eggs as previously described,or more commonly, they simply shut down theovary. With this approach, the flock may in factbe at 10 – 15% production before the breederdiet is introduced, since no farm system allowsfor instantaneous change in feed supply becausefeed tanks are hopefully never completely empty.While delayed introduction of the breeder dietmay therefore disadvantage early maturing birds,there is one specific situation where this approachseems beneficial. Certain strains, sometimes exhib-it high mortality, reaching 1% weekly from 25– 30 weeks of age. The condition is referred toas calcium tetany or SDS and seems to reflect theconsequences of hypocalcemia, being somewhatsimilar to milk fever in dairy cows. It is most com-mon in non-uniform flocks when either breed-er or moderately high calcium prebreeder dietsare fed for 4 – 6 weeks prior to maturity. The con-dition can usually be prevented by using a lowcalcium (max 1%) grower diet to 1% egg pro-duction. When calcium tetany occurs, theseverity can be minimized by feeding large par-ticle limestone at 3 g/b/d for three consecutivedays, ideally in the late afternoon.

The second alternative for calcium feedingat this time involves the classical prebreeder dietcontaining around 1.5% calcium, which is real-ly a compromise situation. It allows for greatermedullary bone reserves to develop, without hav-ing to resort to the 3.0% calcium as used in a

breeder diet. However 1.5% calcium is still inad-equate for sustained eggshell production – withthis diet the breeder can produce 4 – 6 eggs beforethe ovulation pattern is affected. If a prebreed-er diet is used therefore, and a moderate calci-um level is part of this program, then the diet mustbe replaced by the breeder diet no later than at5% production.

The third option is perhaps the most simplesolution, and involves changing from grower tobreeder at first egg (10 days before 1% pro-duction). Having the breeder diet in placebefore maturity, ensures that even the earliest matur-ing birds have adequate calcium for sustainedearly egg production. Proponents of prebreed-er diets suggest that breeder diets introduced earlyprovide too much calcium and that this contributesto kidney disorders, because the extra ingestedcalcium must be excreted in the urine. There isan indication that feeding adult breeder diets for10 – 12 weeks prior to maturity can adverselyaffect kidney function, especially if birds are alsochallenged with infectious bronchitis. Howeverfeeding ‘extra’ calcium for two to three weeksprior to maturity has no such effect. It is also inter-esting to realize that most roosters today are fedhigh calcium breeder diets, which provide 4 –6 times their calcium needs, yet kidney dysfunctionis quite rare in these birds. Early introduction ofthe breeder diet is not recommended whenfarms have a history of high mortality due to cal-cium tetany.

b) Considerations of bodyweight and stature

Body weight and body condition of the birdaround the time of maturity, are perhaps the mostimportant criteria that will ultimately influencebreeder performance. These parameters should



not be considered in isolation, although at thistime we do not have a good method of readilyassessing body condition. Each strain of bird hasa characteristic mature body weight that must bereached or surpassed for adequate egg pro-duction and egg mass output. In general, pre-breeder diets should not be used in an attemptto manipulate mature body size. The reason forthis is that with most flocks it is too late at thisstage of rearing (21 – 24 weeks) to meaningful-ly influence body weight. However, if birds areunderweight when placed in the breeder house,then there is perhaps a need to manipulate bodyweight prior to maturity. Under controlled envi-ronmental conditions, this can sometimes beachieved by delaying photostimulation. If pre-breeder diets are used in an attempt to correctrearing mismanagement it seems as though thebird is most responsive to energy. This fact fitsin with the effect of estrogen on fat metabolism,and the significance of fat for liver and ovary devel-opment at this time. While higher nutrient den-sity prebreeder diets may be useful in manipu-lating body weight, it must be remembered thatany late growth spurt (if it occurs) will not be accom-panied by any meaningful change in skeletalgrowth. This means that in extreme cases, wherebirds are very small in weight and stature at 18– 20 weeks of age, the end result of using highnutrient dense prebreeder diets may well bedevelopment of pullets with correct body weight,but of small stature. These short shank length breed-ers seem more prone to prolapse/pick-out, andso this is another example of the limitations in theuse of high density prebreeder diets.

Use of high nutrient dense prebreeder dietsto manipulate late growth of broiler breederpullets does, however, seem somewhat redun-dant. The reason for this is that with restricted feed-

ing programs, it is more logical to increase feedallowance than to add the complexity of intro-ducing another diet. The only potential problemwith this approach is that in extreme cases, feedintake is increased to a level that is in excess ofthe initial allowance of the breeder diet at startof lay. This can be a potential problem becausebreeders should not be subjected to a step downin feed allocation prior to peak production.

c) Considerations of body composition

While body composition at maturity maywell be as important as body weight at this age,it is obviously a parameter that is difficult to meas-ure. There is little doubt that energy is likely thelimiting nutrient for egg production, and that at peakproduction, feed may not be the sole source of suchenergy. Labile fat reserves at this time are, there-fore, essential to augment feed sources. These labilefat reserves become critical during situations of heatstress or general hot weather conditions. Once thebird starts to produce eggs, then its ability todeposit fat reserves is greatly limited. If labile fatreserves are to be of significance, then they mustbe deposited prior to maturity. There is obvious-ly a fine balance between ensuring adequatelabile fat depots vs. inducing obesity and associ-ated loss of egg production.

d) Considerations for subsequentegg weight and hatchability

Egg size is influenced by the size of theyolk that enters the oviduct. In large part yolksize is influenced by body weight of the bird, andso factors described previously for body weightcan also be applied to concerns with egg size.There is a general need for as large an early egg


SECTION 6.4Breeder hen feeding programs

size as possible. Increased levels of linoleic acidin prebreeder diets may be of some use, althoughlevels in excess of the regular 1% found in mostdiets produce only marginal effects on earlyegg size. From a nutritional standpoint, egg sizecan best be manipulated with diet protein andespecially methionine concentration. It is log-ical, therefore, to consider increasing the methio-nine levels in prebreeder diets. For these diets,DL-methionine and Alimet® are comparableand both promote maximum early egg size.Early egg size can also be increased by more rapidincrease in feed allocation. However suchpractice is often associated with more doubleyolked eggs and erratic ovulation resulting in yolksfalling into the body cavity.

Eggs from young breeders have lower thanideal hatchability and to some extent this relatesto egg composition. The reason for this early hatchproblem is not fully resolved, but most likely relatesin some way to maturity and development ofembryonic membranes and their effect on trans-

fer of nutrients from the yolk to the embryo. Theremay also be a problem of inadequate transfer ofvitamins into the egg although simply increas-ing vitamin levels in prebreeder diets does notseem to resolve this problem. For a number ofcritical B vitamins, their concentration in successiveeggs does not plateau until after 7 – 10 eggs havebeen laid. The effect of prebreeder nutrition onthese factors warrants further study, but at this timethese problems cannot be resolved by simply over-fortifying prebreeder diets with vitamins, certainfatty acids or amino acids.

Prebreeder diets can successfully be used aspart of a feeding program aimed at maximizingproduction potential in young breeders. Howeverany desired increase in nutrient intake prior tomaturity can most easily be achieved by simplyincreasing the feed allowance of either groweror adult breeder diet at this time. If prebreed-er diets are used, then 21 – 24 weeks seems themost ideal time, assuming 1% production willoccur at around 24 weeks of age.

6.4 Breeder hen feeding programs

A dult breeders must be continued onsome type of restricted feeding pro-gram. After 22 weeks of age, regardless

of rearing program, all birds should be fed on adaily basis. General goals for male and femalebreeders are shown in Table 6.15.

Data from flocks around the world, housedunder various conditions and fed varying typesof diet indicate that better performance is invari-ably achieved when body weight gain is optimumthrough the late rearing-prebreeder early-breed-er transition period. The key nutrient under

these conditions is most likely energy, becauseas with the Leghorn pullet, the broiler breederis in a somewhat delicate balance regardingenergy input and energy expenditure. There isconsiderable variation in suggested energyrequirements for the breeder at this time ofearly egg production. In fact, reported values varyfrom 400 – 500 kcal/bird/day.

In attempting to rationalize this obviousrange of recommendations, energy require-ments were calculated for a commercial strainof broiler breeder (Table 6.16). In these calcul-



Body weight Feed intake1 Egg Hatchability Cumulative(g) (g/b/d) Production

Age % % Hatching Saleable (wks) eggs chicks

22 2320 3100 110 120 - - - -24 2550 3270 125 123 5 - - -26 2800 3500 135 125 35 80 2 1.628 3100 3650 145 128 75 84 10 8.430 3250 3820 150 130 85 88 20 17.232 3300 4000 150 130 85 90 32 28.034 3350 4100 150 132 84 92 42 37.236 3400 4200 148 132 82 92 55 49.240 3450 4250 146 132 78 90 75 67.244 3500 4300 144 134 74 88 95 84.848 3550 4350 142 134 70 86 115 102.052 3600 4400 140 134 66 85 130 114.856 3650 4450 139 136 62 84 145 125.560 3700 4500 138 136 58 82 160 137.864 3750 4550 137 136 55 80 174 144.0

Table 6.15 Guidelines for mature breeders

1Diet ME 2850 kcal/kg

Table 6.16 Comparison of calculated energy requirement and feedallowance for the breeder pullets. (Units are kcal ME equivalents)

Age Body wt. Total maintenance Growth Eggs Total daily Highest feed(wks) (kg) (kcal) (kcal) (kcal) energy req. allowance (kcal)

(kcal)20 2.07 235 85 - 320 25021 2.17 245 85 - 330 31522 2.27 255 105 - 360 33023 2.39 260 105 - 365 35024 2.67 290 110 10 410 38025 2.80 300 90 20 410 42026 2.91 305 75 40 420 44027 3.00 310 50 60 420 47028 3.06 315 30 80 425 480



ations, values for maintenance energy require-ments were extrapolated from our work with breed-ers. A subsequent factor of 0.82 was used in con-version to ME. An arbitrary 35% activityallowance was included, while growth wasassumed to require 5.8 kcal ME/g (50:50, fat:mus-cle). As shown in Table 6.16 there is concern overthe calculated energy requirement in relation tofeed allowance, even at the highest feedinglevel recommended by the management guide.These results suggest that the breeder is in a veryprecarious situation with regard to energy bal-ance at the critical time of sexual maturity.

This problem of energy availability may wellbe confounded by the nutritionist’s overesti-mation of that portion of diet energy availableto the broiler breeder. Most energy levels of dietsand/or ingredients, when assayed, are derived usingLeghorn type birds. Work at Guelph indicatesthat broiler breeders are less able to metabolizediet energy, than are Leghorn birds (Table 6.17).Regardless of diet specifications, it would appearthat broiler breeders metabolize about 2.5%less energy from feeds than do Leghorns. Thisrelates to some 70 kcal/kg for most breeder

diets. Deficiencies of energy around the time ofpeak egg production will likely reduce egg pro-duction at this time, or as often happens incommercial situations, production will declinesome 2 – 3 weeks after peak, when a characteristic‘dip’ in production is seen. It is concluded thatoptimum breeder performance will occur whenthe bird is in positive energy balance, and suf-ficient energy is available for production.

With energy intakes of 325, 385, or 450kcal ME/bird/day, Spratt (1987) observed thefollowing partitioning of diet energy intake dur-ing a 24 – 40 week laying period (Table 6.18).

It is interesting to observe that even with rel-atively low energy intakes birds still produce areasonable number of eggs and still accruebody mass. In fact, proportional partitioning of‘retained’ energy into growth or eggs was littleaffected by energy intake. It is tempting tospeculate that energy intake is the controlling fac-tor of egg production of breeders. If this is cor-rect, then it is suggested that the followingmodel applies for the response of the breeder toenergy intake (Figure 6.1).

Fig. 6.1 Schematic representation of adult breeder’s response to diet energy intake.



Table 6.18 Energy partitioning of broiler breeders (24 – 40 wks)

Daily energy intake (kcal/bird)High Medium Low

Input as: Feed (kcal) 60,000 51,000 42,000Output as: Body fat (kcal) 21,300 14,700 12,100

Body protein (kcal) 0 1,900 2,400Eggs (kcal) 11,000 10,000 8,000

% ME into growth 36 32 33% ME into eggs 18 20 19

Table 6.17 Diet ME determined with Leghorn and broiler breeder pullets

Diet ME (kcal/kg)Diet type Leghorn Broiler breeder �

20% CP, 2756 ME 2805 2736 -2.5%14% CP, 2756 ME 2847 2806 -1.5%16% CP, 2878 ME 2976 2906 -2.4%15% CP, 2574 ME 2685 2622 -2.4%

Spratt and Leeson, 1987

In this scenario, egg production is maximizedat a point where some body protein and body fatdeposition occurs, i.e. as previously suggested, itis essential that the breeder hen continues togain weight throughout the laying cycle. Figure6.1 indicates a fine balance between optimum eggoutput and development of obesity. As will be dis-cussed later, this balance can best be achieved bymonitoring feed allocation according to egg pro-duction, egg size, body weight and feed clean-uptime. If these calculations of energy metabolismare correct, then it is obvious that energy intakeand energy balance are critical to breeders thatare expected to consistently peak at 82 – 85% eggproduction. This concept reinforces the statement

made earlier regarding optimum body weightand optimum body condition of birds at start oflay. The fact that birds seem to do better when theyare slightly heavy at maturity is likely a factor ofsuch increased body mass acting as a source ofadditional energy in order to meet the bird’srequirements at this time. It is undoubtedly truethat any flock that does not gain some weight eachweek through peak production will give inferioregg production and hatchability.

Because energy intake is the major factor con-trolling egg production, then it is critical that feedintake be adjusted according to energy densityof the diet (Table 6.19).



Daily energy Diet ME (kcal/kg)need (kcal) 2600 2700 2800 2900 3000

300 115 111 107 103 100320 123 119 114 110 107340 130 126 121 117 113360 138 133 129 124 120380 146 141 136 131 127400 153 148 143 138 133420 162 156 150 145 140440 169 163 157 152 147460 177 170 164 159 153480 185 178 171 166 160500 192 185 179 172 166520 200 193 186 179 172

Table 6.19 Adjusting feed intake according to diet energy level at 22ºC,g/bird/day

Fig. 6.2 Egg Production of Broiler Breeder Hens From 25 to 60 Weeks of Age. (From Lopez and Leeson, 1993)

Fig. 6.3 Body Weight of Broiler Breeder HensFrom 18 to 60 Weeks of Age. (From Lopez and Leeson, 1993)


SECTION 6.5Factors influencing feed and nutrient intake

Protein and amino acid needs of the breed-er hen have not been clearly established. In gen-eral, most breeder flocks will be over-fed ratherthan under-fed crude protein because it is difficultto justify much more than 23 – 25 g protein perday. With a feed intake of 150 g daily, thismeans a protein need of only 15%. We have car-ried out studies involving very low protein dietswhere levels of methionine + cystine and lysinewere kept constant (Figure 6.2). Diets wereformulated at 0.82% lysine and 0.59% methio-nine + cystine in 10, 12, 14 or 16% CP diets. Alldiets contained the same level of energy and allother nutrients, and quantities fed daily were assuggested by the primary breeder. All roosterswere separate fed a 12% CP male diet. Breedersfed 10% CP performed remarkably well, andalthough they did not have the highest peak, theirbetter persistency meant no difference in over-all egg production (Figure 6.2).

One of the most surprising results from thestudy, was better fertility with the lower proteindiets. For example, overall fertility to 64 weeksfor birds fed 10 vs. 16% CP was 95.4 vs. 90.6%.The reason for better fertility is thought to be duesimply to the fact that these birds gained less weight(Figure 6.3), because there is a negative corre-lation between obesity and fertility.

These data suggests that protein/amino acidintake of the breeder hen is related to weight gain,and that excessive weight gain occurring after peakegg production is not merely a factor of energybalance. The results from this study were there-fore somewhat unexpected, because birds fed thelowest level of protein produced the most chicks.Although we are not advocating 10% CP dietsfor breeder hens, these data shows that wecould consider lower, rather than higher levelsof protein, assuming that adequate amino acidbalance is maintained.

a) Egg production

A n egg contains around 100 kcal of grossenergy, and so it takes some 120 kcalME/d for egg synthesis. The yolk devel-

ops over a number of days, and so it is importantto initiate feed increases prior to realizing actu-al production numbers. This concept is oftenreferred to as lead feeding, and implies that thepredetermined peak feed allowance will actuallyoccur at some time prior to peak egg numbers.The suggestion is that peak feed be given atanywhere from 30 – 60% egg production. If flocksare very uniform in weight, it is possible to peakfeed at 30 – 40%. However, with poorer uniformity(<80% @ ± 15%) then peak allowance should notbe given until 60% egg production, or even

later. Lead feeding programs are also influ-enced by management skills. Where there is goodmanagement with precise and even feed distri-bution, then peak feed can occur earlier.

The feed allowance for hens up to 26–28 weeksmay need to be slightly higher than theoreticalneeds, since it is common for males to feedfrom the hen feeding lines. After 28 weeks, thehead size of the males usually excludes them fromthe female feeder lines, and so after this time, feedallocation tends to be more precise.

High and sustained peak egg productioncan only be achieved with uniform breederflocks fed to meet their nutritional requirements.

6.5 Factors influencing feed and nutrient intake



With 85 – 88% peaks now possible, it is obvi-ous that we have to carefully plan and executea feeding program tailored to meet the breeder’snutrient needs. Underfeeding results in peakslasting only 3 – 4 weeks, and these are usuallyassociated with the classical sign of loss orstall-out in body weight for 1 – 2 weeks. On theother hand overfeeding, especially with energy,will result in excessive weight gain, and whilepeak production may be little affected, there willbe precipitous loss in egg production through 34– 64 weeks of age. The basis of feed allocationat this critical time is obviously to allow genet-ic potential for increases in both egg numbers andegg size, and also to allow for modest weekly gainsin body weight. Managers should consider‘challenge feeding’ as part of their feed man-agement system at this critical time.

Challenge feeding involves giving the hensextra feed on 2 or 3 days each week, based onneed, without changing the base feed quantityscheduled for the flock. For example, a flock mayreceive 150 g/bird/day at peak, with an additional‘challenge’ of 5 g/bird/day given three dayseach week. The challenge feed is therefore,equivalent to 3 x 5 g ÷ 7d = 2 g/bird/day. In real-ity birds receive the equivalent of 150 g + 2 g =152 g/bird/day. The immediate question is whybother with this more complicated system,rather than just give the flock a base feedallowance of 152 g/bird/day? The advantages ofchallenge feeding, rather than simply increasingthe base allocation are:

• on days of challenge feeding, feeding timewill increase, and this helps to improve over-all flock uniformity.

• it is easier to make adjustments to nutrientintake based on day-to-day change inneeds as may occur with changes in envi-ronmental temperature.

• birds become accustomed to change in feedallocation, which will be important oncefeed withdrawal is practiced after peak.

• ease of tailoring nutrient needs to indi-vidual flocks. For example, a base feed allo-cation of 150 g /bird/day may be stan-dardized across all flocks, with individualflock needs at peak being tailored withthe quantity and/or frequency of chal-lenge, depending on actual production, envi-ronmental temperature, etc.

The actual quantity and timing of challengefeeds must be flexible if they are to be used effi-ciently. In practice, the challenge should not rep-resent more than 5% of total feed intake, and mostoften the quantity will be 1 – 3%. On the otherhand, the quantity of the challenge should be largeenough to meaningfully contribute to the factorslisted previously. For this reason, there needs tobe a balance between the quantity of feedgiven, and the frequency of this feeding. For exam-ple, a daily challenge of 2 g/bird/day will be muchless effective than 5 g/bird/day given 3 times eachweek. In both instances birds are receiving14-15 g/week as a challenge, but in the later exam-ple the challenge quantity is more meaningfuland we are more likely to see a bird response interms of egg output.

Challenge feeding should start when birds areat 60 – 70% production, and should be dis-continued when egg production falls below80%. For most flocks, therefore, we can expectto practice challenge feeding from about 29through 40 weeks of age. The idea of challengefeeding is to more closely tailor feed allocationto breeder hen needs, and so there should be nostandardized system. Managers must be givenflexibility to alter challenge feeding based on fluc-tuating needs. In most instances, the challenge



will be used to lead birds into a sustained peak.Because the concept of challenge feeding is tomore closely tailor feed allocation to needs,then it is usual practice to alter the quantityand/or duration of challenge as birds progressthrough peak egg production. Maximum chal-lenge feeding should coincide with peak egg out-put, with lesser quantities given prior to, and afteractual peak. On this basis we recommendchallenge feeding to be reduced (but not dis-continued) once birds are 2% below peak eggproduction. Following are three examples of chal-lenge feeding tailored to three different flock sit-uations (Tables 6.20 – 6.22).

In Table 6.20, because birds are uniform inboth weight and maturity and a good quality dietis used, and there is no major temperature stress,the challenge is quite mild. For this flock, a heav-ier challenge may result in excess weight gain.This type of mild challenge is most frequently usedwhere feed quality is ideal, and there is minimaldisease and mycotoxin exposure.

In Table 6.21, there needs to be more challengefeed, because nighttime temperature is quite lowand there is a problem with maturity related to poorer uniformity. On average, this flock maygain a little more weight than example birds in

Table 6.20 Breeders fed a high nutrient dense feed with good ingredient qualitycontrol. Expected high-low temperatures of 31ºC – 24ºC. Good flock uniformi-ty at 20 weeks of age and previous flocks show consistent peaks of 85 – 87%

Table 6.21 Breeders fed a high nutrient dense feed with good ingredient qual-ity control. Expected high-low temperatures of 28ºC – 14ºC. Poor to averageflock uniformity and previous flocks show variable peaks at 81 – 87%

Egg production Base feed Challenge feed35% 150 g None60% 150 g 5 g/d, 2x/wk80% 150 g 8 g/d, 2x/wk

-2% from peak 150 g 5 g/d, 2x wk79% 150 g None

<79% Reduce None


-2% from peak 155 g 6 g/d, 3x/wk79% 155 g None

<79% Reduce None



Table 6.22 Low nutrient dense feed used with poor ingredient quality control,and so feed composition may be variable. Expected high-low temperatures,28ºC – 20ºC. Average to good flock uniformity at 20 weeks of age, and pastflocks show variable peaks at 80 – 86%


-2% from peak 165 g 8 g/d, 3x/wk79% 165 g None

<79% Reduce None

Table 6.20 and this will have to be accommo-dated with a more vigorous post-peak feedwithdrawal program.

In Table 6.22, base feed allowance is increasedbecause a low nutrient dense feed is used andchallenge is fairly aggressive again due to con-cern over feed quality and poor uniformity. Inthe examples shown in Tables 6.20 – 6.22, it isassumed that managers will continue to main-tain breeder body weight through peak, andmake necessary adjustments to the challenge ifover- or under-weight conditions are seen.

Challenge feeding can also be used post-peakif there are precipitous declines in egg produc-tion related to minor disease challenge or man-agement or environmental stress. Under theseconditions, challenges of 6 g/bird/day for two con-secutive days are recommended. If no immediateresponse is seen in egg production, then the chal-lenge should be discontinued. If egg productionreturns to normal, then the challenge should grad-ually be reduced over the next 2 – 3 days.

Challenge feeding allows tailoring of feed allo-cation to suit individual flock needs. Managersshould be flexible in actual allocations, althoughmaximum challenge feed allocation needs to coin-

cide with peak egg production. Breeder hens willrespond to a carefully planned challenge program,with sustained peak production and better post-peak persistency. On the other hand, the chal-lenge should not usually represent more than 5%of total feed intake, because excessive chal-lenge will invariably result in obesity and relat-ed loss in post-peak performance. In general, whenbirds are subjected to such stresses as variablefeed quality, mycotoxin challenge and/or fluc-tuating or extreme environmental temperature,then a high base feed allowance, coupled withaggressive feed challenge, is recommended.On the other hand, lower feed inputs are pos-sible where consistent quality high-energy feedsare used, and where there is good environ-mental control.

Once birds have peaked in egg production,it is necessary to reduce feed intake. There is oftenconfusion and concern as to how much and howquickly feed should be removed, and this issomewhat surprising, since the same basic rulesused pre-peak also apply at this time. Thismeans that birds should be fed according to eggproduction, body weight and clean-up time.After peak production, feed clean-up time oftenstarts to increase, and this is an indication of birds



being overfed. The main problem we are tryingto prevent at this time is obesity. If feed is notwithdrawn after peak, then because egg productionis declining, proportionally more feed will be usedfor growth. After peak therefore, body weightbecomes perhaps the most important parame-ter used in manipulating feed allocation. It is stillimportant for birds to gain some weight, sinceloss of weight is indicative of too severe a reduc-tion in feed allowance.

Feed allocation and withdrawal for breederhens has to be based on needs. The hen needsnutrients for four major reasons, namely forgrowth, egg production, maintaining normalbody functions and for daily activity. Each of theseneeds varies with the age of hen and environmentaltemperature, and also each need varies with respectto the type of nutrients utilized. Growth, egg pro-duction and maintenance all require proteinand energy, while activity is only really demand-ing on energy needs. Actual estimates for thesenutrient needs are shown in Table 6.23.

The maintenance need is perhaps surprisinglyby far the largest single factor affecting energyrequirements of the breeder. Secondly, it isegg production and lastly, growth and activity.In terms of protein needs, egg production and main-tenance are the only two meaningful factors.However, as the bird gets older, the actual nutri-ent needs and the distribution of these needschange (Table 6.23). At 55, rather than 32weeks of age, therefore, the bird needs lessenergy and protein for eggs, because egg pro-duction has declined (even though egg size hasincreased) but she needs more of these nutrientsfor maintenance because over the 23 weekperiod the bird has grown and so needs more feedto maintain herself. At 55 weeks, if all goes well,we have significantly reduced growth rate, andso both protein and energy needs for growth are

greatly reduced. The reduction in nutrient needsfor lower egg production and less growth out-weighs the needs for more maintenance, and thebottom line is overall reduction in daily need ofthe hen for both energy (460 vs 510 kcal) andprotein (19 vs 21 g).

Reduced nutrient needs can be achievedby either simply reducing feed intake or main-taining feed intake constant but changing the ener-gy and protein levels of the diet. In practice, reduc-ing feed intake after peak production is by far theeasiest and most foolproof method of reducingthe bird’s nutrient intake. Changing to a lower-energy, lower-protein diet means a change of for-mulation, which itself can be stressful to the bird.On multi-age farms, it is also more hazardous tohave multiple diets being delivered to the farmwhich can get placed in the wrong feed tank.

The consequences of not reducing nutrientintake of the breeder hen after peak should befairly obvious. The bird will not lay more eggsor become more active as a result of supplyingmore protein or energy than is required.Oversupply of these nutrients goes directly toincreased growth which itself quickly causesincreased maintenance requirement. This extragrowth will be as fat, and muscle (protein)growth. Obesity quickly leads to reduced eggproduction, diverting even more nutrients intogrowth (fat). This vicious circle is often respon-sible for the very sudden drop in egg productionseen with flocks that are overfed after peak eggproduction.

The final questions of course, are how muchand how often do we reduce feed allocation afterpeak production? Regardless of how high a peakproduction is actually realized, we should notstart to reduce feed while birds are at �80% pro-duction. The main reason for this is that peak egg



numbers do not usually coincide with peak nutri-ent needs for eggs because egg size is increas-ing through this period. In most flocks, peak nutri-ent needs for eggs (production X egg weight) willhave been reached by the time birds havedeclined to 79 – 80% production, at about 39– 40 weeks of age. At this stage of production,we can start to gradually reduce feed intake, andin general, the quantity of feed to be removedwill depend on peak feed allowance. If birds werepeaked on 165 g/bird/day then we likely needto remove more feed than for a flock peaked on150 g/bird/day. Also, if temperature/seasonalchanges are anticipated, then this should befactored into feed allocation. Impending warmerweather means we can take more feed away, whileif cooler temperatures are anticipated, we mayneed to take very little feed away (becausemaintenance needs will naturally increase).Assuming that we have peaked a flock at 155g/bird/day, and anticipate no major change in envi-ronmental temperature, then a feed reduction pro-gram, as shown in Table 6.24 is suggested.

With such a slow and steady removal infeed, it should be possible to prevent obesity inhens, while at the same time allowing ade-

quate energy and protein for the inevitable slowdecline in egg numbers. The reduction in feedintake is necessarily slow and involves small stepsbecause as shown in Table 6.23, the actualnutrients going into eggs are quite a small pro-portion of the hen’s total needs. Responding toa 5% decline in egg production, therefore,requires very small changes to the feed scale.

Some producers consider a 1 – 2 g/bird/dayreduction in feed intake hardly worth botheringabout, and either make no adjustment, or fewmuch larger reductions. Sudden large reductions�4 g/bird/day can often be very stressful and resultin sudden drops in egg production. Making noadjustments and continuing near peak allocationto 64 weeks, will be uneconomical in terms ofbirds becoming overweight with associated lossof egg production. In the example shown in Table6.24, a bird fed according to this suggestedschedule will eat about 22.8 kg to 65 weeks.Feeding 155 g through to 65 weeks, with no feedwithdrawal, will result in an extra 1.5 kg feedintake. This quantity of extra feed will likely resultin an additional 0.2 – 0.3 kg body weight gain,most of which will be fat.

Table 6.23 Protein and energy requirements of breeder hens at 32 and 55weeks of age at 24ºC

32 weeks of age 55 weeks of ageNutrient need Energy (kcal) Protein (g) Energy (kcal) Protein (g)

Growth 40 1 5 NoneEgg production 80 10 60 8Maintenance 310 10 350 11

Activity 40 None 25 NoneTotal 470 21 440 19



Egg production (%) Approx. age (wks) Daily feed intake (g/day)80 39 15579 40 15478 41 15477 42 15276 43 151

74 45 150

70 50 148

65 55 146

60 60 144

55 65 142

Table 6.24 Feed allocation program for heavy breeders after peak production

b) Body weightMaintenance represents the major need for

energy and hence feed by the breeder and soknowledge of body weight is important in allo-cating feed. All too often, the monitoring of bodyweight stops when birds are transferred to thebreeder house and so birds are fed solely accord-ing to egg production. The importance of bodyweight and body reserves of breeders through peakproduction has already been emphasized and thismeans continual monitoring of body weight. Itis essential that birds continually gain someweight through peak production. Loss of weightor stall-out in weight usually implies that birdsare not getting enough nutrients, and that loss inegg production will occur within 7 – 10 d. Inthis context, monitoring of body weight willgive an earlier indication of impending problems.From 20 – 32 weeks of age, pullets should ide-ally be weighed weekly.

Feeding to body weight assumes that birds areat ideal weight around 22 weeks of age (�2.2 kg).

If birds are over or underweight, then adjustmentsto intake must be made. If birds are underweight, then they should obviously be givenmore feed than the standard recommendedallowance in an attempt to stimulate growth.Overweight birds should also be given morefeed (Table 6.25). This apparent dichotomy of ideasis based on the fact that heavier birds have a larg-er maintenance requirement and so need morefeed to meet their overall energy (nutrient)requirement. This is a difficult concept for farmmanagers to accept since they are afraid of overweight birds getting even heavier. There is obvi-ously a fine line between over feeding and feed-ing to requirement for this overweight bird, butas previously discussed, the ideal 20 week-oldpullet is slightly overweight in comparison to mostprimary breeder guidelines. Under ideal conditions,pullets will not lose weight after 20 weeks of age,rather they show continued small increments ofweight gain each week and hopefully are around3.5 kg at the end of their laying cycle.



c) Feed clean-up timeFeed clean-up time should be used as an indi-

cation of adequacy of feed allocation. Majorchanges in clean-up time are an indication of over-or under-feeding and as such, are an early warn-ing of subsequent changes in body weight andegg production. As a routine management pro-cedure, the time taken to clean-up most of thefeed allocation should be recorded each day tothe nearest 30 minutes. If clean-up time variesby more than 60 minutes on a daily basis, thenbird weight should be measured immediately.However, major changes in feed allocationshould not be made solely on the basis of feedclean-up time, rather these values should be usedas a guide to investigate feed needs through moreprecise monitoring parameters. Feed clean-up time with high-yield strains of breeder hensis often greater (+ 1 hr) compared to the moretraditional strains and merely reflects a lessaggressive feeding behaviour.

Clean-up time for feed can vary considerablyfrom flock to flock for no apparent reason. Forexample, one flock may take 4 hours to clean-up feed, whereas a sister flock of the same ageetc. can take 2 hours. For this reason absolutetime taken to clean-up feed cannot be used asa management guide – the only useful param-

eter is change in clean-up time. Sudden changesin clean-up time often precede changes in bodyweight by 2 – 3 d, and changes in egg produc-tion by 10 – 12 d.

d) Morning vs. afternoon feedingChoice of feeding time of adult breeders

can influence the production of settable eggs,eggshell quality, fertility and hatch of fertiles. Inmost instances, these factors are a consequenceof feeding activity displacing other important dailyroutines, such as nesting and mating. Breederhens consume their feed in 2 – 6 hours each day.This large variation in feed clean-up time relatesto diet energy level, feed texture and perhaps mostimportantly, environmental temperature. In hotclimates breeders often take much longer toeat feed, and this is especially true of high-yield strains. Most managers consider thisextended feeding time to be advantageous,because it ensures more even allocation of feedacross the flock where even the most timidbirds have time to eat.

If breeders are fed early in the morning,then the most intense feeding activity will be overby 9 a.m. Again, this is ideal in terms of reduc-ing heat load in the early afternoon period. Thistiming is also ideal in terms of differentiating themain feeding time from nesting activity.

Depending upon when lights are switched onin the morning, most eggs are laid in the 9 a.m. –12 noon period. Feeding at say 8 a.m., would there-fore, induce birds to feed at a time when they areusually in the nests. In fact, eggs dropped in thearea of the feeder are a very good indication of late-morning feeding. Obviously some of these eggswill get broken or become too dirty for setting.

A few years ago there was interest in feed-ing breeders in the late afternoon. The main advan-tage is claimed to be an improvement in eggshell

Table 6.25 Example of energyallowance for breeders (kcalME/day)

Age Underweight Ideal Overweight(wks) Weight

18 230 240 25020 270 250 28022 310 295 32524 345 345 38026 430 430 470



thickness, and in fact in many field trials this isfound to be true. Improved shell thickness is like-ly a consequence of the bird eating calcium ata time when shell calcification is starting (for thenext day’s egg) and also the bird having more feedwith calcium in its crop when lights are switchedoff. If eggshell quality is a problem, then after-noon feeding seems a viable option. Alternatively,birds could be given a ‘scratch’ feed of large par-ticle limestone or oystershell in the late afternoon.

However late afternoon feeding has a num-ber of potential disadvantages. Firstly, there isincrease in shell thickness. This should not bea problem as long as incubation setter conditionsare adjusted so as to maintain normal moistureloss. In most situations this means reduction insetter humidity to accomodate less moistureloss through a thicker shell.

A greater concern with later afternoon feed-ing is potential loss of mating activity, andincrease in incidence of body-checked eggs.Mating activity is usually greatest in late after-noon. If hens are more interested in feeding atthis time, then there can be reduced matingactivity and also more aggression betweenmales. Body-checked eggs are characterized bya distinct band of thickened shell around the mid-dle of the egg (sometimes called belted eggs). Thisdefect is caused by the eggshell breaking duringits early manufacture in the bird’s uterus. The birdrepairs the crack, but does so imperfectly. Sucheggs have reduced gas and moisture-transfercharacteristics and usually fail to hatch. The mostcommon cause of body-checked eggs is suddenactivity, movement, stress, etc. on the bird. Thisextra activity takes place when feed is given inlate afternoon, and so there will likely be fewersettable eggs produced.

e) Environmental temperatureEnvironmental temperature is the major on-

farm factor influencing feed intake and energyneeds. Table 6.26 indicates partitioning of ener-gy requirements at various environmental tem-peratures.

Table 6.26 Peak feed needs ofbreeder hens at various environ-mental temperatures (g)

Feed need 18ºC 24ºC 34ºCGrowth 10 10 10Maintenance 140 125 110 (130)Eggs 30 30 30TOTAL 180 165 150 (170)

As temperature increases, so feed need isreduced. In this example, two values are shownfor maintenance feed need at 34ºC. The value inbrackets (130 g) represents feed need when thebird is under stress and panting etc., where sheneeds energy to drive the cooling mechanisms inthe body. In this situation, total feed needbecomes 170 g, which is actually greater than sug-gested at 24ºC. It is often difficult to get breed-ers to eat more feed under heat stress condi-tions, yet this increased energy intake is criticalif egg production is to be maintained. Table6.27 shows model predicted energy needs ofbreeders maintained at temperatures of from14ºC to 35ºC.

Depending upon acclimatization, birds willdie when temperatures reach 40ºC, while few birdscan survive for very long at temperatures below–10ºC. At –2ºC, the comb and wattles willfreeze. In most commercial houses today thereis concern with bird comfort in the range of 0ºC



to 38ºC depending upon the degree of envi-ronmental control. Breeder performance will beoptimized at around 22 – 24ºC and apart fromchanges in egg production, there is an incentivein optimizing feed efficiency by maintainingthis ideal temperature. While most discussionon environmental control of breeders focuses ontemperature, it must be remembered that the pre-vailing relative humidity is often the factor caus-ing distress to the bird. Conditions of high tem-perature and low humidity (e.g. 32ºC, 40% RH)are quite well tolerated by the bird, while hightemperature and high humidity (e.g. 32ºC, 90%RH) are problematic.

In discussion of the effect of environmentaltemperature on breeder performance, there issome debate about how temperature is actuallydefined. Measuring house temperature at firstglance seems to be a straightforward task.Thermometers or temperature probes can be posi-tioned at bird height and records collecteddaily. However, there is usually considerablefluctuation in temperature throughout the day.For example breeders can be subjected to a day-time high of 26ºC and a nighttime low of just 8ºC.

How do we reconcile this temperature fluctua-tion in trying to calculate maintenance energyand feed needs of the breeder? The traditionalapproach has been to simply take an average ofall readings or the average of the high and lowdaily temperatures e.g. (26º + 8º)/2 = 17ºC.However breeders do not behave in a similar man-ner during the day compared with nighttime dark-ness. During the day, most breeders are rarelyin contact with other birds and so the air aroundthem is at a temperature very similar to that record-ed on the thermometer.

When lights are switched off however, birdsinvariably sit down, and are usually huddledclose to their flockmates. Sitting, rather than stand-ing, will reduce heat loss of the bird, while hud-dling as a group has a great insulating effect. Thisbehavioural change in the bird has the effect oflessening the impact of the cooler night temperature.Simply averaging high and low temperatures, inorder to calculate feed need, may therefore be inac-curate. We therefore need a system that reducesthe relative significance of the night temperatures,and so propose the following solution:

Table 6.27 Model predicted energy needs of breeder hens as affected byenvironmental temperature (kcal/day)

Age B. wt (g) Egg mass Temperature(wks) (g/d) 14ºC 18ºC 24ºC 29ºC 35ºC

22 2320 - 284 256 229 201 17524 2450 3.5 300 272 254 215 18726 2565 18.0 350 320 290 260 23528 2665 44.3 439 409 379 348 32030 2758 53.7 475 444 413 382 35240 3100 53.6 490 456 423 390 35750 3310 48.0 482 445 411 376 34160 3425 41.0 464 428 393 357 32270 3500 34.0 445 410 373 337 302

Adapted from Waldroup et al. 1976



Effective temperature =[ (daytime high temper-ature x 2) + (nighttime low temperature)]/3

For the above example, the calculation becomes:

[(26 x 2) + 8]/3 = 20ºC

The ‘effective’ temperature becomes 20ºCrather than 17ºC as calculated by the tradition-al method. The nighttime low of 8ºC is given lessemphasis because birds get an insulative effectfrom sitting and huddling. These birds thereforeneed less ‘extra’ heat in order to keep warm thanis predicted from simple thermometer meas-urements. Table 6.28 shows calculations usingthis same formula, at various day and nighttemperatures. If we assume that 26ºC is an idealtemperature for breeders then we can calculatethe extra feed needed for maintenance as effec-tive temperature declines. If a diet provides 2850kcal ME/kg, a 3 kg breeder will need an extra 1.5g feed for each 1ºC decline in effective house tem-

perature. Table 6.28 shows such calculatedextra feed needed by breeders kept at various dayand night conditions relative to breeders kept inan ideal environment of constant 26ºC.

The deleterious influence of a cold nighttemperature is therefore not as significant as acomparable cold temperature during daytime.With a daytime temperature of 24ºC as anexample, we only have to feed an extra 12 g dailyin order to counteract a chilly night temperatureof 6ºC. Failure to make such an adjustment longterm will mean that the hen will either loseweight and/or reduce egg output in an attemptto conserve energy.

Another question often asked is how oftenshould feed intake be adjusted in order to accom-modate fluctuating environmental temperatures?Weather predictions can be notoriously inaccu-rate, and so day-to-day adjustments seem unwise,as well as being impractical for the farm staff. Thebird does have a quickly usable store of energy

Table 6.28 Effect of temperature on increased feed allowance relative to 26ºCstandard (gram/hen/day)1

Daytime Nighttime temperature (ºC)temperature 26 24 22 20 18 16 14 12 10 8 6 4 2 0 -2(ºC)

26 0 1 2 3 4 5 6 7 8 9 10 11 12 13 1424 4 5 6 7 8 9 10 11 12 13 14 15 1622 7 8 9 10 11 12 13 14 15 16 17 1820 10 11 12 13 14 15 16 17 18 19 2018 13 14 15 16 17 18 19 20 21 2216 16 17 18 19 20 21 22 23 2414 19 20 21 22 23 24 25 2612 22 23 24 25 26 27 2810 25 26 27 28 29 308 28 29 30 31 326 30 31 32 33

1Feed @ 2850 kcal ME/kg



in the form of body fat, and so, in the shortterm, it can use this as a supplement to feed ifenvironmental temperature declines on a dailybasis. However, there are limits to the bird’s abil-ity to mobilize large quantities of body fat overa prolonged period of time, the consequence ofwhich is usually loss in egg production. Suchloss in egg output may simply be a response relat-ed to energy conservation, although it may alsobe a consequence of change in hormone balanceof the bird. The latter effect is likely to have moreserious long-term consequences to egg pro-duction. As a generalization, it is estimatedthat the bird can use its body fat reserves to accom-modate the equivalent of a 6º – 8ºC drop in tem-perature over 4 – 5 consecutive days. Decreasesin house temperature that are greater than this,or that occur for a longer period of time shouldbe accommodated by appropriate increases infeed allowance. Feed changes in response to cool-er temperatures should therefore be accom-modated at least on a weekly basis.

Heat distress is a major challenge for breed-er managers. It is usually unwise to change dietspecifications in response to short-term changes(4 – 7 d) in the environment, yet ‘summer’ dietsare advantageous in many regions. Diets for hotweather conditions are usually higher in ener-gy (2950 kcal ME/kg minimum) and containminimal crude protein (<15.5%) with normal lev-els of essential amino acids. There are advan-tages to using at least 4% added fat together with250 mg/kg of vitamin C. Water intake should beencouraged, by adjusting diet salt levels to a max-imum commensurate with maintaining litterquality and egg cleanliness. Table 6.29 indicateswater balance of breeders at 22 vs. 35ºC wherethere is almost a doubling of water intake, dueto increased evaporative losses.

Table 6.29 Water balance in breed-ers at 22 vs. 35ºC (ml)

22ºC 35ºCWater intake 300 500Excreta loss 120 200Egg water 55 55Respiratory loss 125 245

Birds do not sweat and so this important cool-ing mechanism is unavailable to them. As an alter-native, birds lose heat by evaporation through pant-ing and loss of moisture in respired air. Evaporationis a very efficient means of heat-loss. For each1 g of water vaporized, about 600 calories of ener-gy are utilized. Much above 28ºC, evaporationbecomes the most important route of heat lossfor the bird. Unfortunately many conditions ofheat stress also involve high humidity, and thissituation adds increased difficulties on the birdfor dissipating heat. A practical solution is todisrupt the boundary layer of air immediately sur-rounding the bird, with increased air move-ment through mechanical systems such as cir-culating fans. Table 6.30 indicates the coolingeffect of increased air speed for breeders main-tained at 29ºC.

Another system used for reducing the heat loadis evaporative cooling. If air is passed over a finestream of water, then it heats and evaporates someof the water, which takes substantial quantitiesof heat from the air. The system obviouslyworks best in conditions of moderate humiditybecause the air must pick up moisture, and soat the extreme of 100% humidity in outsideair, evaporative cooling is not very effective.With incoming air at 20% RH, a 15º – 20ºC reduc-tion in temperature by evaporative cooling is the-oretically possible. At more normal levels of 60



– 70% RH, an 8º – 10ºC cooling effect is possible,while at > 75% RH, the cooling potential is about5ºC. Each 1ºC of cooling is associated with abouta 5% increase in RH.

drinking water – 300 IU/bird twice per week isrecommended. While feed is usually the onlysource of calcium and phosphorus consideredin meeting the breeder’s needs, it is known thatbirds eat litter which contains these nutrients. Suchlitter eating has been suggested as the reason forimproved shell quality of floor vs. caged birds underexperimental conditions. Controlled studieshave shown that breeders eating 20 g litter/day,consume an extra 7% calcium and 12% availablephosphorus. Unfortunately shell quality is influ-enced not only by levels of calcium in the diet,but also feeding time and also particle size.

Most of the shell material is formed in the dailyperiod of darkness, when the hen is not eating.During this time of rapid shell accretion, the birdrelies on the stores of medullary bone for almost50% of the calcium used to make a shell.Between successive calcifications, this bonemust be replenished, in the form of calcium phos-phate. One reason for decline in shell qualityover time is gradual loss in efficiency of this dep-osition and withdrawal of medullary bone.Although the medullary bone reserve is essen-tial to shell formation regardless of diet, its roleis somewhat reduced if the bird has some cal-cium being absorbed from the digestive tract atnight. This situation leads to the idea of afternoonfeeding of calcium, to provide a calcium sourcein the digestive tract that can slowly be releasedat night, and so aid shell formation. At the endof the day, the breeder will ideally have a few gramsof calcium in the digestive tract, that can slow-ly be digested and absorbed, and then directedto the shell gland. Farmer et al. (1983) determinedthe quantity of calcium remaining in various regionsof the digestive tract following a 7 a.m. feedingof a diet providing 4.27 g calcium/day (Table 6.31).

Table 6.30 Cooling effect of airmovement for breeders at 29ºC

Air speed Cooling effect (ºC)(meters/min)

15 0.530 1.045 2.060 3.075 4.090 5.0105 6.0

f) Eggshell qualityAs egg output increases, especially from 28

– 38 weeks of age, there is added pressure on shellsynthesis. Consequently, maintenance of shellquality is an emerging issue in breeder nutrition.Poor shell quality means potential loss of settableeggs and reduced hatch of fertiles due to changein moisture loss from the thinner shelled eggs.Nutritionally, the major nutrients of concernare calcium, available phosphorus, and vitaminD3. There may be an advantage to phase feed-ing both calcium and phosphorus, and provid-ing extra vitamin D3 as a water supplement.Calcium level can be increased over time by addingan extra 5 kg/tonne limestone to the diet at 45and 55 weeks of age. At the same time availablephosphorus levels can be reduced by at least0.05%. If shell quality is problematic, breederssometimes respond to vitamin D3 given in the



Time Crop Gizzard Small intestineUpper Lower

11 a.m. 1.64 0.53 0.22 0.327 p.m. 1.36 0.11 0.07 0.1411 p.m. 0.86 0.21 0.03 0.073 a.m. 0.24 0.20 0.09 0.097 a.m. 0.01 0.18 0.09 0.17

Table 6.31 Calcium remaining in various regions of the digestive tract following 7 a.m. feeding of a diet providing 4.27 g calcium/day (g)

Adapted from Farmer et al. (1983)

With lights out at 11 p.m. the breeders hadlittle calcium remaining in the digestive tractovernight. Time of feeding calcium, therefore,seems important. Because most breeders are fedearly in the morning and with clean up time ofonly 2 – 3 hours, then there is little potential forcalcium reserves remaining in the gut in theevening. When breeders are given experimen-tal diets containing just 0.4% calcium, they arefound to be able to maintain shell quality onlywhen an extra 3 g calcium is force fed at around4 p.m. Such force feeding at 8 a.m. resulted invery poor shell quality.

Feeding calcium in the late afternoon there-fore seems ideal if shell quality is problematic.This can best be done by simply broadcasting oys-tershell or large particle limestone directly ontothe litter at around 4 p.m. The feeding activityassociated with this technique also helps inbringing hens down from the slats, onto the lit-ter, which usually means greater mating activ-

ity at this time. This technique raises another con-cern about calcium source, namely particlesize. Usually, the larger the particle size, the slow-er the rate of digestion, and so the more prolongedthe metering out of calcium for shell forma-tion. The reason for poor shell quality follow-ing force feeding 3 g of calcium at 8 a.m., asdescribed previously, relates to the fact that thebird cannot utilize this sudden influx of calcium,and has no reserve other than the medullary bone.Large particle limestone and oystershell areusually digested more slowly, and this is the rea-son suggested for better shell quality with theseproducts. Ideally a mixture of fine and coarseparticles should be used because this gives bothrapid and slow metering of calcium for metabolicneeds. The disadvantage of both oystershelland large particle limestone is that they arevery abrasive to mechanical equipment. Table6.32 summarizes diet specifications aimed to opti-mizing shell quality.


SECTION 6.6Breeder male feeding programs

Breeder age25 wks 45 wks 55 wks

Calcium (%) 3.1 3.3 3.5Available phosphorus (%) 0.40 0.36 0.32Crude protein (%) 15.5 14.5 14.0Methionine (%) 0.35 0.32 0.30Water supplement

Vitamin D3 - 300 IU/bird/2 consecutive days per weekVitamin C - 20 mg/bird/2 consecutive days per week

Table 6.32 Diet specification aimed at optimizing shell quality

M ale condition is obviously criticalfor optimum yield of fertile eggs. Ifa breeder hen produces an egg, then

infertility is usually due to simple absence of spermin the oviduct, and this in itself is directly relat-ed to mating frequency and/or mating success.In many situations, therefore, loss of fertility iscaused by incorrect body condition of hensand/or roosters, such that mating activity isreduced. For hens, this is usually due to overfeedingand obesity, and in roosters is caused by both over-and under-feeding. Just as great care is taken tomeet the hen’s nutrient requirements with con-tinual adjustments to diet or feed allocation, sowe have to carefully monitor the male’s condi-tion and environment and to feed accordingly.In many respects, it is easy to predict the male’snutrient requirements, because we do not havethe complication of egg production as occurs withthe hen. The feeding program therefore has to meetjust two basic needs namely, growth and main-tenance of body functions. The major criteria ofour male feeding programs, therefore, are mon-itoring body weight and body condition andcontrolling frame size and uniformity.

The period during early maturity is probablythe most critical in the adult life of the breedermale. Up to about 30 weeks of age, the breed-er male is still expected to grow quite fast. Forexample a weight gain of around 1.4 kg isexpected between 10 and 20 weeks of age,and this is only slightly reduced to around 1.2kg weight gain between 20 and 30 weeks. It istherefore, very important to maintain this growthpotential through to 30 weeks, and so continuedmonitoring of body weight is critical.

The major complication of feeding the breed-er male at this time relates to the separate male-female feeding systems now commonly used.Grills on the female feeders are usually around43 mm in width. Unfortunately 19 – 21 weekold male breeders, when first moved to thebreeder facilities, will have head width slightlyless than this. The males will therefore, eatfrom the female feeders while they still have small-er head size. Individual males will grow at dif-ferent rates, and their head width will reach >43 mm, on average around 26 – 28 weeks.The larger birds usually have larger heads, and

6.6 Breeder male feeding programs



so there is a self-limiting system that evolves withexclusion over time of males from the female lines.However, we are faced with the problem oftrying to estimate the males’ feed and nutrientintake. One answer to this problem has been theuse of so-called ‘nose-bars’ which are plastic rodsinserted through the nostrils of the bird. This ‘nose-bar’ effectively excludes the male from thefemale line almost immediately, and so males willonly take feed from their own feed line. The effec-tiveness of nose-bars has been reported as quitevariable, and like many situations with broilerbreeders, there undoubtedly needs to be adesire by the flock supervisors to make the sys-tem work. Another potential solution to the prob-lem of male access to the hen feeders, is todelay placement of the males in the breeder houseuntil 22 – 23 weeks, when the male’s headwidth will naturally be wider. This managementdecision should not affect fertility, because eggsare rarely saved for hatching until 27 – 28 weeksof age, and by this time there will be normal maleactivity in the breeder house. If males are heldin the growing facilities until 22 – 23 weeks, itis important to still light stimulate them accord-ing to the hen lighting schedule. This willensure that roosters are as mature as the hens whenintroduced at this later date.

Leaving males un-dubbed also helps in earlierexclusion of males from the female line. Sometimesthis causes problems of roosters getting their combscaught in mechanical equipment, and here just dub-bing the back 20% of the comb seems beneficial,without really affecting the ‘size’ of the comb.Consideration of comb size raises another impor-tant consideration of feeder design. Much empha-sis has been placed on grill width (� 43 mm)although too often grills provide too much height,such that roosters will force their way into thehen feeders. If roosters are not dubbed, then grillheight should be no more than 70 mm, and ide-

ally closer to 65 mm. If roosters are dubbed, thengrill height should be no more than 60 mm.

The other major variable affecting breeder malefeed intake, is environmental temperature.Because maintenance plays such a major role innutrient needs, environmental temperature can great-ly influence the amount of energy needed tomaintain body temperature. Birds will needmore energy in cooler environments, and less ener-gy under warmer conditions. Unfortunately, it isdifficult to differentiate energy from the othernutrients in a diet, and so meeting fluctuating ener-gy needs can only be accommodated (practically)by varying overall feed intake.

Table 6.33 gives examples of feed intake forbreeder males, with emphasis on the criticalperiod up to 36 weeks of age. Because in mostcases males will have some access to the femalefeeders, we have emphasized this system in Table6.33 and shown suggested intakes under variousenvironmental conditions. Table 6.33 also showssuggested feed intake for males excluded fromfemale feeders, using techniques such as nose bars.Under comparable environmental conditions,these birds should be given more feed, becausethis allocation is their only source of feed.

When roosters have access to hen feeders, wehave a major feeding management decision to makeat around 28 – 30 weeks of age. At this time, almostall roosters will be unable to get into the henfeeder, and so they are suddenly faced with a poten-tial major reduction in feed intake. At this time,the roosters can start to lose weight and/or start tobecome very aggressive. One management deci-sion, as shown in Table 6.33, is to increase the roos-ter feed at this time, and then more graduallywean them off of this extra allowance over the nextfew weeks. Roosters that previously had accessto the hen feeder line are given more feed, espe-cially from 30 – 36 weeks, compared to those



Assuming males have access to hen feeders until approximately 28 weeks of age

Age (wks) > 35ºC 20 – 28ºC kcal ME/day2 < 15ºC20 108 110 (115)1 319 12022 110 115 (118) 334 12524 112 118 (120) 342 13026 120 125 (130) 363 13528 124 130 (135) 377 14030 130 135 (135) 392 15032 135 140 (130) 406 15534 130 135 (130) 392 15236 125 130 (128) 377 14840 125 128 (128) 370 14550 120 126 (126) 365 14060 120 126 (126) 365 140

Table 6.33 Examples of feeding schedules for male breeders consuming a diet of around 2900 kcal ME/kg (grams/bird/day)

1( ) assuming males totally excluded from hen feeders2 20 - 28˚C

birds with nose-bars etc. By 40 weeks of age,all roosters should be fed about the same amountof feed, regardless of whether or not they previouslyhad access to the hen feeders.

After 36 weeks of age, obesity is an ever-pres-ent problem with male birds. The critical nutri-ents at this time are again energy and pro-tein/amino acids. After 35 weeks of age, the roosterneeds only the equivalent of around 10% crudeprotein, albeit well balanced in important aminoacids. Energy needs are shown in Table 6.33although sample weighing of birds will quick-ly tell if the allocation is correct. If roosters becomeexcessively overweight/obese there should be anattempt at reducing their nutrient intake. Ifroosters are 200 – 400 g overweight, then bodyweight control can be achieved by reducing dailyfeed allowance by 5 g/bird/day each week untildesired weight and condition are achieved. Ifroosters are >500 g overweight, it may be essen-tial to use a low-nutrient dense feed (see next sec-

tion) as well as reducing allocation over time. Thereason for using a low-nutrient dense feed is tomaintain weight uniformity because propor-tionally more feed can be given daily (albeit atreducing quantities weekly). Any manager fac-ing these problems should seriously evaluate thefeeding management strategy of birds in thecritical 19 – 30 week period.

Male and female breeders will usually be fedthe same diets up to maturity. In the breeder facil-ities, there is the choice of using the breeder hendiet for all birds, or a separate diet specificallyformulated for males. Such male diets will usu-ally be much lower in crude protein, aminoacids and calcium compared to the breederhen diet. The advantage of a separate malediet is that it more closely meets the male’snutrient requirements and allows for a slightlymore generous feeding allowance. The proteinand amino acid needs of the mature male are verylow, being in the range of 10% CP. Such low pro-


SECTION 6.7Feed efficiency by breeders

tein diets are often difficult and expensive to for-mulate, but body weight control, and subsequentfertility, will usually be improved. A practical com-promise formulation is around 12% crude pro-tein or to use a 14 – 15% pullet grower diet. Whenlow protein diets are used, it must be rememberedthat protein quality is still very important. For theselow protein diets, methionine should be main-tained at 2% of the protein, and lysine at around5% of protein. Using a lower energy level,such as 2650 kcalME/kg, together with thelower protein, means that we can give males morefeed, which will prolong feeding time and help

maintain body weight uniformity. The calciumpresent in the hen breeder diet is also excessivelyhigh for the male. Because it is not producingeggshells, the male needs only 0.7 – 0.8% cal-cium in the diet. This extra calcium intake maypose additional stress on the kidney, although undermost farm conditions, the roosters can handle thisextra calcium load. However, when combinedwith other stressors to the kidney, such as highprotein, or high mineral intakes, or mycotoxinssuch as ochratoxin, there can be problems withthe general metabolism of the bird’s kidney.An example of a male diet is shown in Table 6.34.

M ost producers in the poultry meatbusiness could give a close approx-imation of feed efficiency in broilers,

but few managers or technicians have compa-rable values at their fingertips for breeder per-formance. To some extent this is a fault ofbreeding companies because virtually no man-agement guides contain this important information.

Table 6.35 shows the feed efficiency data forbreeders calculated in terms of feed or nutrientsper hatching egg or per chick. Data is shown to64 weeks of age, which is the most common age

for flock depletion. Values are also shown forbreeder hens alone or hens with 8% males.For hens alone to 64 weeks of age, feed usageis calculated at 300 g during the breeder phaseor 370 g including both grower and breeder phas-es, for each chick produced. Comparable num-bers per hatching egg are 260 and 320 g. Thereis considerable variation in the level of dietaryenergy fed to breeders worldwide, and so per-haps a more accurate assessment of feed efficiency,for comparative purposes, is feed energy usageper egg or per chick. To 64 weeks of age, totalenergy intake, including the carrying cost of

6.7 Feed efficiency by breeders

Metabolizable energy (kcal/kg) 2650 - 2750Crude protein (%) 10.0 – 12.0Calcium (%) 0.75Available Phosphorus (%) 0.30Sodium (%) 0.18Methionine (%) 0.28Methionine + Cystine (%) 0.44Lysine (%) 0.55Tryptophan (%) 0.13Mineral-Vitamin Premix As per breeder hens

Table 6.34 Male breeder diet specifications


SECTION 6.8Nutrition and hatchability

the males is 980 and 1130 kcal ME per hatch-ing egg and chick respectively. As a simplerule of thumb therefore, we expect an energy costof about 1000 kcal ME per hatching egg orchick. Because there are two values used in cal-culation of any measure of efficiency, the bot-tom line can be improved by maximizing one valueand/or minimizing the other. This means that intheory, efficiency can be improved by increas-ing egg and chick output and/or by reducing feed

intake. Unfortunately these two factors cannotbe changed that easily. It is difficult to increaseegg output per se because hopefully this isalready being maximized with the standard on-farm management practices. Likewise, we can-not simply reduce feed intake by an arbitraryamount without expecting some loss in per-formance. However, there may be some poten-tial for fine-tuning these parameters.

Females only Females + 8% males0 – 64 wks 24 – 64 wks 0 – 64 wks 24 – 64 wks

Per hatching egg:Feed (g) 320 260 345 280Energy (kcal) 915 750 980 800Protein (g) 50 40 53 43

Per chick:Feed (g) 370 300 400 320Energy (kcal) 1050 860 1130 920Protein (g) 60 50 62 50

Table 6.35 Feed efficiency of breeders

6.8 Nutrition and hatchability

S uccessful hatching of an egg dependsupon a fertile egg having adequate nutri-ents and environmental conditions, such

that the embryo can develop into a viable chick.From a nutritional point-of-view, hatchability canbe influenced by fertility of both male andfemale breeders, the nutrients deposited in theegg for the embryo, and certain physical egg char-acteristics that can affect gas and water exchangeduring incubation. Traditionally, vitamin statusof breeders is often considered the major nutri-tional factor influencing hatchability, althoughwe now know that imbalance or excess of a num-ber of nutrients can affect embryo viability. Inthe following discussion, it is assumed thatincubation conditions are ideal, and also that eggs

are stored and transported under ideal envi-ronmental and sanitary conditions.

a) FertilityThere is surprisingly little information available

on the effect of nutrition on fertility, and especiallyfor the hen. With hens it is assumed that if a birdis capable of producing eggs, and if viable spermare available, fertility will occur. Nutritionaleffects on female fertility are, therefore, assumedto be quite minor in relation to nutritional effectson egg formation per se. While this is true for nutri-ents such as vitamins and minerals, it may not betrue for nutrients affecting general body size andbody composition, such as diet protein and dietenergy. Protein level of the diet of breeder henscan have a significant effect on fertility (Table 6.36).



In these diets, methionine and lysine levelswere kept constant, as was energy level, and onlydiet crude protein was varied. All roosters werefed a separate male diet at 12% CP, and so thedata shown in Table 6.36 is a true female effect.Lopez and Leeson (1995) concluded that thisapparent crude protein effect was simply due tobody weight, because hens on the lower proteindiets were smaller throughout the experiment.Birds fed 10% CP were some 500 g smallerthan birds fed 16% CP at 64 weeks, even thoughfeed and energy intakes were similar for alltreatment groups. Limiting excess body weightafter peak production is, therefore, important inmaintaining greater mating activity of thesesmaller more active birds. In this respect, over-feeding both protein and energy is expected toreduce fertility, simply by making birds obese,and so less willing to mate with the roosters.

This same concept also applies to roosters,where overfeeding of protein and/or energy is like-ly to result in reduced fertility. Overfeeding ofmale Leghorn breeders results in a dramaticdecline in total sperm production with associ-ated increase in production of dead spermato-zoa. The introduction of separate male feedingsystems has also resulted in better fertility, sim-ply because of better control over feed intake ofthe rooster. However, even with separate malefeeding, it seems advantageous to use low pro-tein diets (McDaniel, 1986, Figure 6.4).

Table 6.36 Diet protein and femalefertility to 64 weeks of age

Diet protein (%) Fertility (%)16 91.6b

14 93.3a

12 95.1a

10 95.4a

Males Hatch Sperm Testesproducing of set penetration wt.semen (%) day 2

kcal 38 42 46 (%) (#) (g)ME/d wk wk wk

290 100 55 36 61 20 9330 100 73 64 66 100 12370 100 100 82 65 160 26

Feeding inadequate amounts of energy alsohas a deleterious effect on semen production byolder males (Table 6.37).Table 6.37 Adult male performance

in relation to energy intake

Adapted from Bramwell et al. (1996)

Fig. 6.4 Diet protein level and percentageof roosters producing semen (fromMcDaniel, 1986).



b) HatchabilityNutritional effects on hatchability of fertile

eggs are not easily quantified, apart from the effectof gross deficiencies of vitamins and some othernutrients. Table 6.38 provides a summary of com-mon embryo deficiency symptoms for selectedvitamins and minerals. It should be emphasizedthat classical deficiency symptoms of individualvitamins are rarely seen. More often, multiplevitamin deficiencies occur when vitamin premixesare inadvertently omitted from the diet, or morecommonly, deficiencies are induced by some othernutrient or toxin. These latter effects are obvi-ously difficult to diagnose, since diet analysis revealsa correct vitamin level, even though a defi-ciency of that vitamin is evident.

In situations of complex vitamin deficiency,caused for example by accidentally failing to addthe vitamin premix, then riboflavin deficiency isoften the first to appear. This has the most dra-matic effect on breeders, with hatchability reach-ing very low levels in 3 – 4 weeks (Table 6.39).

In this study hens were fed corn-soy diets wherethe premix was formulated without individual vita-mins as detailed. For some vitamins, therefore,corn and soybean meal will provide some baselevel of vitamins and this may be the reason fordifferential results within the diets. As already indi-cated, the response to riboflavin is most severe,with hatchability down to zero in seven weeks.After 15 weeks of deficient diets, we reintroduceda regular fortified diet, and as shown in Table 6.39,for all treatments hatchability returned to normalwithin 4 weeks. Hatchability problems related

to vitamin deficiencies therefore seem reversibleonce adequate diets are fed, and there seems tobe no longlasting effect.

A practical problem with on-farm nutri-tional deficiencies is that hatchability declinesare not seen until three weeks after deficient dietsare consumed. For this reason, weekly checkson embryo survival will give a much quicker indi-cation of potential problems. There is an excel-lent correlation between feeding vitamin defi-cient diets, and incidence of mid (7 – 14 d) embryomortality. Using regular diets, 7 – 14 d embryomortality is very rare being in the order of 0.1%.However, as vitamin deficiencies progress, thereis a dramatic increase in mid-term embryo mor-tality and so this can be used as a diagnostic toolin troubleshooting problems with hatchability.Observations on malformations and malpositionedembryos indicate no clear trend, inferring lim-itations of these parameters as diagnostic indi-cators of practical-type vitamin deficiencies inbreeder diets.

Vitamin deficiencies, of course, should notoccur under commercial conditions becauseall requirement needs should be met with syn-thetic sources in the premix. In fact, breeder dietsoften contain the highest levels of supplemen-tal vitamins of any class of poultry, and this is sometimes questioned as being too costly. In feedingbreeders we not only want to prevent signs of defi-ciency as detailed previously, but also to ensureoptimum production and hatchability. Thesuperior performance of breeders that we rou-tinely see today, with peaks of 85 – 88% will onlybe achieved by feeding relatively high levels



Nutrient Deficiency symptomsVitamin A Early embryo mortality (48 hours) with failure to develop circulatory system.Vitamin D3 Depending on reserves in dams, stunted chicks and soft bones. Usually associated with shell

defects and hence changes in porosity of the shell.Vitamin E Usually see early embryo mortality at 1 – 3 d.

Encephalomalacia may be seen in the embryo and exudative diathesis is common.Riboflavin Excessive embryo mortality 9 – 14 or 17 - 21 days. Embryos show edema and clubbed down.

Chicks may show a curling of the toes.Pantothenic acid Subcutaneous hemorrhages in unhatched embryos.Biotin Reduced hatch without reduced egg production. Peak in embryo mortality during first week

and last 3 days of incubation. May see skeletal deformities and crooked beaks.Vitamin B12 Embryo mortality around 8 – 14 days, with possibly edema, curled toes and shortening of the beak.Thiamin There are two stages of embryo mortality – one very early and the other at 19 – 21 d. Many

dead chicks appear on the trays although there are few, if any, deformed chicks. Mortality can be high for 10 – 14 days for those chickens that do hatch. Injecting the chicks with thiamin results in an almost instantaneous recovery. Certain types of disinfectants, anticoccidials and poor quality fish meal have been implicated in thiamin deficiencies. There is also recent evidence to suggest that thiamin requirements are increased in the presence of some Fusarium molds.

Calcium and phosphorus As maternal deficiency progresses, embryo mortality shifts from later to earlier stages of incubation. Shortened and thickened legs are seen with shortened lower mandible, bulging forehead, edema of neck and protruding abdomen. Shell quality is usually affected.

Zinc Numerous skeletal deficiencies, and feather down may appear to be ‘tufted’.Manganese Late embryo mortality (18 – 21 days). Embryos show shortened wings and legs with abnormal

head and beak shape. Edema is common and feather down is usually abnormal.

Table 6.38 Common embryo deficiency symptoms for vitamins and minerals

Vitamin omitted from control dietWeek None Biotin B12 E Folacin Niacin Pantothenate Riboflavin

on diet (control)1 95 86 97 97 97 96 94 953 97 83 95 84 89 87 81 555 98 63* 84 67 30* 61* 74* 19*7 92 54* 61* 62* 19* 69 26* 1*13 88 52 27* 95 38* 50 54 0*

15** 90 96 21* 75 70 38* 56 0*17 95 90 50 58* 85 61 40* 57*19 97 99 99 92 99 98 97 96

Table 6.39 Hatchability of eggs produced by caged breeders fed corn-soybean diets devoid of supplemental vitamins (% fertile eggs)

* Significantly different from control (P < 0.05).** Vitamins reintroduced.


SECTION 6.9Caged breeders

of vitamins as part of a balanced nutritionalprogram.

One reason for higher vitamin fortificationsrelative to standards, such as NRC (1994), is theloss in potency of vitamins that can occurbetween feed manufacture and consumption bythe bird. Different vitamins are susceptible to var-ious stresses to varying degrees, but as a gen-eralization it can be stated that the major caus-es of loss of vitamin potency are storage time,storage temperature, and storage humidity of thepremix before mixing, and of the feed aftermixing. Another major loss of vitamins occursif they are premixed with minerals and stored for

3-4 months prior to incorporation in feed. Also,conditions within the premix and feed cancause loss of potency. For example, some vita-mins are acidic whereas others break downunder acidic conditions. Finally, to really causeproblems to vitamin stability, we sometimespellet feed, and here the temperature and humid-ity can cause vitamin breakdown. Most com-panies consider high levels of vitamin fortifica-tion to be essential and economical for optimumhatchability and early broiler performance. Inmost locations, vitamins E, A, biotin and riboflavinare the most expensive vitamins within a premix,representing 60 – 70% of total cost.

6.9 Caged breeders

T he dwarf bird seems an ideal candidatefor cage management although thereare serious problems seen when regular

size breeders are caged for any length of time.Commercial trials with regular breeders, involv-ing artificial insemination, have generally provenunsuccessful due to lack of uniformity and footpad lesions. Both of these problems seem to relateto feeding management, and the propensity ofthe regular sized breeder to become overweight.Few mechanical systems are able to accurate-ly dispense feed to each cage, and so over/under-nutrition becomes a problem. Our experienceswith field trials indicate that most often, in a cagecontaining three breeder hens, while ‘averageweight’ may be ideal, there will often be three

distinct sized birds which is likely related to aggres-sion and dominance behavior within the group.

Feed allocation is also difficult to regulate asmortality progresses, since for most systems, itmeans physically moving birds so as to maintaina constant number per cage. Footpad lesions oftendevelop after 35 weeks of age, especially withoverweight birds. Until a simplified and accu-rate feed allocation system is developed forcage systems, it is doubtful that they can be madeto operate economically under commercialconditions. We have experienced similar prob-lems with a new colony cage system involvingtwenty breeder hens and two roosters per cage.Again foot pad lesions become problematicafter peak egg production.


Attia, Y.A., W.H. Burke, K.A. Yamani and L.S.Jensen (1995). Daily energy allotments and per-formance of broiler breeders. 1. Males. Poult. Sci.74:247-260.

Attia, Y.A., W.H. Burke, K.A. Yamani and L.S.Jensen (1995). Daily energy allotments and per-formance of broiler breeders. 2. Females. Poult. Sci.74:261-270.

Bartov, I. (1994). Attempts to achieve low-weightbroiler breeder hens by severe growth depressionduring various periods up to 6 weeks of age andfood allocation below the recommendations there-after. Br. Poult. Sci. 35:573-584.

Bennett, C.D. and S. Leeson (1989). Water usage ofbroiler breeders. Poult. Sci. 68:617-621.

Bennett, C.D., S. Leeson and H.S. Bayley (1990).Heat production of skip-a-day and daily fed broilerbreeder pullets. Can. J. Anim. Sci. 70:667-671.

Bowmaker, J.E. and R.M. Gous (1989).Quantification of reproductive changes and nutrientrequirements of broiler breeder pullets at sexualmaturity. Br. Poult. Sci. 30:663-675.

Brake, J., J.D. Garlich and E.D. Peebles (1985).Effect of protein and energy intake by broiler breed-ers during the prebreeder transition period on sub-sequent reproductive performance. Poult. Sci.64:2335-2340.

Cave, N.A.G. (1984). Effect of a high-protein diet fedprior to the onset of lay on performance of broilerbreeder pullets. Poult. Sci. 63:1823-1827.

Fancher, B.I. (1993). Developing feeding programsfor broiler breeder nutrition. Poult. Digest. P. 18.

Fontana, E.A., W.D. Weaver and H.P. VanKrey (1990).Effects of various feeding regimens on reproductionin broiler breeder males. Poult. Sci. 69:209-216.

Harms, R.H. (1992). A determination of the order oflimitation of amino acids in a broiler breeder diet. J. Appl. Poult. Res. 1:410-414.

Harms, R.H. and G.B. Russell (1995). A re-evalua-tion of the protein and lysine requirement for broilerbreeder hens. Poult. Sci. 74:581-585.

Hocking, P.M. (1993). Optimum size of feeder gridsin relation to the welfare of broiler breeder femalesfed on a separate sex basis. Br. Poult. Sci. 34:849-855

Hocking, P.M. (1994). Effects of body weight at pho-tostimulation and subsequent food intake on ovari-an function at first egg in broiler breeder females. Br.Poult. Sci. 35:819-820.

Hocking, P.M., D. Waddington, M.A. Walker andA.B. Gilbert (1989). Control of the development of theovarian hierarchy in broiler breeder pullets by foodrestriction during rearing. Br. Poult. Sci. 30:161-174.

Leeson, S., B.S. Reinhart and J.D. Summers (1979).Response of White Leghorn and Rhode Island Redbreeder hens to dietary deficiencies of synthetic vita-mins. 1. Egg production, hatchability and chickgrowth. Can. J. Anim. Sci. 59:561-567.

Lopez, G. and S. Leeson (1994). Nutrition and broil-er breeder performance. A review with emphasis onresponse to diet protein. J. Appl. Poult. Res. 3:303-312.

Lopez, G. and S. Leeson (1995). Response of broilerbreeders to low-protein diets. 1. Adult breeder per-formance. Poult. Sci. 74:685-695.

Lopez, G. and S. Leeson (1995). Response of broilerbreeders to low-protein diets. 2. Offspring perform-ance. Poult. Sci. 74:696-701.

Reis, L.H. (1995). Extra dietary calcium supplementand broiler breeders. Appl. Poult. Res. 4:276-282.

Samara, M.H. (1996). Interaction of feeding time andtemperature and their relationship to performance ofthe broiler breeder hen. Poult. Sci. 75:34-41.

Spratt, R.S. and S. Leeson (1987). Broiler breederperformance in response to diet protein and energy.Poult. Sci. 66:683-693.

Selected Readings

345

SECTION 7.1Commercial turkeys

345

7.1 Commercial turkeys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

7.2 Turkey breeder feeding programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

a. Hens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

b. Toms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

c. Model predicted nutrient needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366

Genetic potential for growth rate ofturkeys continues to increase, andstandards for male turkeys are now close

to 1 kg per week of age at marketing weightsof 18 – 20 kg. Unlike most other meat birds,there are distinct differences in the marketweights of males and females and so it isaccepted that the sexes must be grown sepa-rately. Male turkeys are now commonlygrown to 18 – 24 weeks of age, and femalesto 15 – 16 weeks of age. A proportion of femaleswill be sold as whole carcasses, while malesare usually further processed in some way. Agrowing concern with these large turkeys isintegrity and quality of the breast meat, sincePSE (pale soft exudative) meat, as sometimesoccurs in pigs, is now raised as an issue dur-ing processing. There has been no majorchange in carcass fat:protein over the last fewyears, and so meat quality is the main concernregarding carcass quality. Other carcassdefects, such as breast buttons and other skinabnormalities are often a factor of managementrather than genetics or nutrition per se.

There still needs to be some flexibility indeveloping feeding programs for turkeys.

The diet specifications shown in Table 7.1 aregeneral guidelines that can be used for both maleand female turkeys. Depending on the marketingage of hens, the diets will perhaps be scheduleda little more quickly and/or the last diet usedis a compromise between the Developer #2 andFinisher as shown in Table 7.1. The turkey willgrow quite well on a range of diet nutrient den-sities, although grow-out time will increase andclassical feed utilization will decrease, with lowernutrient dense diets. Poorer performance thanexpected with some high energy diets is oftena consequence of not adjusting amino acid lev-els to account for reduced feed intake. Examplesof diets based on corn and soybean meal areshown in Table 7.2 and growth standards areshown in Table 7.3.

Breast muscle deposition is now maxi-mized at around 18 weeks of age in large toms,with deposition of about 65 g/d. Depositionof leg and thigh muscle on the other handplateaus early, at around 14 weeks of age whenthere is a maximum daily deposition ofabout 45 g. Nutrient specifications from thecommercial breeding companies are detailedin Tables 7.4 and 7.5.

Page

7.1 Commercial turkeys

FEEDING PROGRAMS FOR TURKEYS 7

CHAPTER

346 CHAPTER 7FEEDING PROGRAMS FOR TURKEYS


Starter Grow 1 Grow 2 Dev 1 Dev 2 FinisherAge (wks) 0 – 4 5 – 8 9 – 11 12 - 14 15 - 16 17+Crude Protein (%) 28.0 26.0 23.0 21.0 18.0 16.0Metabolizable Energy (kcal/kg) 2850 2900 3050 3200 3250 3325Calcium (%) 1.40 1.25 1.15 1.05 0.95 0.85Available Phosphorus (%) 0.75 0.70 0.65 0.60 0.55 0.48Sodium (%) 0.17 0.17 0.17 0.17 0.17 0.17

Methionine (%) 0.62 0.56 0.52 0.48 0.42 0.35Methionine + Cystine (%) 1.05 0.93 0.84 0.75 0.68 0.58Lysine (%) 1.70 1.60 1.45 1.30 1.12 1.00Threonine (%) 0.90 0.87 0.82 0.76 0.68 0.61Tryptophan (%) 0.28 0.26 0.23 0.21 0.19 0.16Arginine (%) 1.75 1.65 1.55 1.40 1.20 1.10Valine (%) 1.20 1.10 1.00 0.90 0.78 0.65Leucine (%) 1.90 1.80 1.65 1.50 1.25 1.10Isoleucine (%) 1.10 1.00 0.94 0.82 0.72 0.65Histidine (%) 0.60 0.55 0.50 0.44 0.35 0.30Phenylalanine (%) 1.00 0.90 0.82 0.73 0.63 0.55

Vitamins (per kg of diet) 100% 100% 90% 80% 70% 60%Vitamin A (I.U.) 10,000Vitamin D3 (I.U.) 3,500Vitamin E (I.U.) 100Vitamin K (I.U.) 3Thiamin (mg) 3Riboflavin (mg) 10Pyridoxine (mg) 6Pantothenic acid (mg) 18Folic acid (mg) 2Biotin (µg) 250Niacin (mg) 60Choline (mg) 800

Vitamin B12 (µg) 20


Table 7.1 Diet specifications for growing turkeys

347CHAPTER 7FEEDING PROGRAMS FOR TURKEYS


Starter Grow 1 Grow 2 Dev 1 Dev 2 FinisherCorn 473 535 535 605 680 690Soybean meal 350 350 349 266 195 180Corn gluten meal 80 26Meat meal 60 60 60 60 60 60AV Fat 31 46 44 55DL-Methionine* 1.2 1.2 1.3 1.3 1.1 0.5L-Lysine 2.5 1.6 0.2 1.4 1.9 0.9Salt 2.3 2.3 2.4 2.4 2.4 2.4Limestone 15.0 10.3 9.4 7.9 6.6 6.0Dical Phosphate 15.0 12.6 10.7 9.0 8.0 4.2Vit-Min Premix** 1.0 1.0 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000 1000 1000

Crude Protein (%) 28.7 26.0 24.2 21.0 18.2 17.5ME (kcal/kg) 2890 2900 3050 3200 3250 3325Calcium (%) 1.50 1.25 1.15 1.05 0.95 0.85Av Phosphorus (%) 0.75 0.70 0.65 0.60 0.55 0.48Sodium (%) 0.17 0.17 0.17 0.17 0.17 0.17Methionine (%) 0.62 0.56 0.52 0.48 0.42 0.35Meth + Cys. (%) 1.05 0.95 0.89 0.75 0.68 0.60Lysine (%) 1.70 1.60 1.45 1.30 1.10 1.00Threonine (%) 1.10 1.06 1.00 0.87 0.76 0.74Tryptophan (%) 0.35 0.34 0.33 0.28 0.23 0.22

Table 7.2 Examples of turkey diets (kg)


Table 7.3 Performance standards for commercial turkeys

Weight Age F:G ADGMale 15 kg 18 wk 2.60 110 – 130 g1

Female 7.5 kg 14 wk 2.25 77 – 90 g

1Higher value denotes European standardsusing higher nutrient dense diets.



Starter (0-4 wks) Finisher (16 – 20 wks)BUT Hybrid Nicholas BUT Hybrid Nicholas

ME (kcal/kg) 2900 2850 2910 3300 3520 3420CP (%) - 27.5 25 – 27.0 - 16.0 14 – 17.0Ca (%) 1.40 1.40 1.45 1.07 0.90 0.85Av P (%) 0.78 0.75 0.74 0.62 0.45 0.38Na (%) 0.16 0.17 0.17 0.18 0.18 0.18

Methionine (%) 0.70 0.69 0.58 0.49 0.36 0.34Meth + Cys (%) 1.25 1.17 1.02 0.88 0.65 0.56Lysine (%) 1.92 1.80 1.70 1.04 0.80 0.80Threonine (%) 1.22 - 1.04 0.66 - 0.53

Nutrient /kg BUT Hybrid NicholasVitamin A IU 15,000 10,000 14,000Vitamin D3 IU 5,000 5,000 5,000Vitamin E IU 50 100 50Vitamin K mg 5 4 4Folic acid mg 3 2.5 4Niacin mg 75 100 55Pantothenic acid mg 25 25 28Riboflavin mg 8 15 10Thiamin mg 5 4.5 4Pyridoxine mg 7 5 6Biotin µg 300 300 200Choline mg 400 1,200 1,600Vitamin B12 µg 20 40 20

Copper mg 20 15 25Zinc mg 100 160 100Iron mg 50 80 45Manganese mg 120 160 120Selenium mg 0.2 0.3 0.4Iodine mg 2 3 3

Table 7.4 Strain comparison for commercial heavy male turkeys

Table 7.5 Vitamin and trace mineral needs of commercial turkeys (0-4 weeks)



a) Starter diets and poult viability

Feeder management and feed texture are justas important as feed formulation in influencingearly poult growth. Poults are much morereluctant to eat mash rather than crumbledfeed, and this phenomenon is most evident in the7 – 14 d growth period (Table 7.6).

Quality crumbles and then quality pellets areimportant to ensure optimum feed intake. Duringthe first week, poults should not have to movetoo far to find feed and water. It is good man-agement practice to ‘overfill’ feeders at thistime, to ensure easy access to feed, even thoughthis creates some feed wastage.

There has always been higher mortality in thefirst week in turkeys compared to chickens.Mortality of 1 – 2% in the first 7 d is still com-mon, and in part, this may relate to feedingprogram. As its name implies ‘starve-out’ iscaused by failure of poults to eat and/or drink,even though feed is apparently readily accessi-ble. For whatever reasons, metabolic conditionscause lethargy in some poults and they seem reluc-tant to feed and drink. The situation may be com-pounded by hatchery conditions such as beaktrimming, vaccinating, detoeing and desnood-ing of male poults.

Intentionally depriving poults of feed for 48hr on average has little effect on 7 – 10 d bodyweight or intestinal morphology at this time.Certainly 3 – 4 d body weight and intestinal growthare affected by such starvation, although com-pensatory growth seems to occur if conditionsare ideal for such growth. Under commercial con-ditions where multiple stressors are possible, thenit may take longer than 7 – 10 d for growth com-pensation to occur.

The poult is hatched with very low availableenergy reserves, and glycogen is most likelysynthesized by gluconeogenesis from protein.Attempts at improving glycogen/energy reservesin the poult have generally had little beneficialeffect. In the past, poults have been given glu-cose solutions prior to transport from the hatch-ery. Recent data suggests that while this may havevery short-term benefits (2 – 3 hrs maximum) theglucose uptake likely suppresses key enzymes,so suppressing glycogen synthesis, and this canbe detrimental to subsequent longer-term healthstatus. Injecting alanine, a non-essential aminoacid, has been shown to elevate blood glucoselevels without the concomitant reduction inglycogen reserves. However, the long-term ben-efits with alanine injection are difficult to quan-titate, even in terms of 7 d mortality. Propionateis also a precursor of glucose, and has been fedto young poults. However propionate is also ananorexic agent, and so this is counterproductiveto ensuring long-term benefits for the poult.

Table 7.6 Effect of feed texture on growth rate of poults (g)

Poult age (d) Mash Quality crumbles Difference (%)7 117 140 2014 250 320 2821 450 600 3028 780 1020 30

Adapted from Nixey (2003)



49 d digestibilityBird type Nitrogen (%) Fat (%) AMEn (kcal/kg)

Non-infected 64.6a 85.9a 3470a

Infected – large wt. 59.1b 80.8ab 3270b

Infected – medium wt. 61.4ab 78.5b 3190b

Infected – small wt. 58.4b 78.3b 3180b

Table 7.7 Nutrient digestion of 49 d old turkeys previously infected withPEMS at 5 d of age

There has also been concern about the vita-min E status of the young poult. Vitamin E lev-els in the liver and serum of poults reach alarm-ingly low levels 2 – 3 weeks after hatch. Forexample, while poults may show 80 µg vitaminE/g liver at hatch, the normal levels at 21 d arecloser to 0.5 µg/g. Sell and co-workers at IowaState have investigated this problem, and whilesignificant treatment differences are sometimesseen, normal blood and liver values are still inthe order of magnitude as described previous-ly. For example, feeding the medium chainfatty acids as found in coconut oil, rather thantallows or even sucrose, does seem to change vita-min E status, yet after 21 d, liver levels are stillless than 1 µg/g tissue. It therefore seems verydifficult to stop this ‘natural’ decline in vitaminE status, and obviously, the poults’ immune sta-tus is being questioned relative to these changes.Because vitamin E plays a number of roles in thebody, it is possible that fat levels and fat oxida-tion may influence general health status of theyoung poult. However adding extra antioxidantshas not generally been beneficial. Likewiseadding bile salts to the diet does little to improvevitamin E status of the poult, and so absorptionper se is not thought to be a limiting factor.

There are a number of health issues thatinfluence early poult development, and per-

haps the formulation of starter diets. Poultenteritis and mortality syndrome (PEMS) hasbeen a serious problem in isolated regions of theworld. The condition is likely caused or accen-tuated by the presence of viruses, and poults canbe artificially infected by dosing with intestin-al contents from other infected birds. While highmortality is sometimes experienced, there is a sec-ondary problem of stunting, where affectedbirds do not show compensatory growth. Recentdata suggests that turkeys that recover fromPEMS have impaired digestion/absorption ofmost nutrients (Table 7.7). At 49 d, turkeyswere selected as large, medium or small depend-ing on their recovery characteristics from PEMSinfection at 5 d. Regardless of turkey size,there was a general trend for reduced nutrientdigestion, suggesting that early PEMS infectionhas a long lasting detrimental effect on intestinalmorphology.

There is some controversy regarding the useof fat in diets for young poults. High fat diets have been advocated to ease the shift towards glycolysis after hatching and there is the suggestionthat this situation improves early growth rate.Advocates of high fat starter diets indicate thatdiet energy levels should not be increased, andthat fat merely replaces carbohydrate as a sourceof energy.

Adapted from Odetallah et al. (2001)



Variable results to such formulations may berelated to saturation characteristics of the fat beingused. The young poult seems somewhat betterthan the chick in digesting saturated fatty acids,yet when these predominate, overall digestibil-ity is quite low (Table 7.8).

The saturates C16:0 and C18:0 are fairly welldigested when in the presence of a large quanti-ty of unsaturates as occurs in soybean oil. This syn-ergism likely relates to ease of micelle forma-tion, which is a necessary prerequisite of transportfrom the lumen to the brush border of the epithe-lium, digestion and subsequent absorption. Whenthere are minimal unsaturates available for micelleformation, then digestion of saturates is exceptionallylow, not getting much over 50% by 21 d of age.Since medium chain unsaturates such as C8:0 andC12:0 in ingredients like coconut oil, do not nec-essarily need prerequisite micelle formation or actionof bile salts then they are better absorbed byyoung birds (Table 7.9).

The digestion of medium chain fatty acids isexceptionally high, even for very young poults,and so these provide a viable alternative toother, possibly more expensive, vegetable oilscontaining unsaturates. There is also someresearch suggesting that three week old turkeysmetabolize corn with about 10% less efficien-cy compared to 17 week old birds.

So-called Field Rickets continues to be an on-going problem at certain farms. Since some farmsseem to have greater occurrence than do others,there has always been suspicion of an infectiousagent. However, when homogenates from thedigesta of affected poults are fed to normalbirds, there is no effect on poult liveability or skele-tal development. Obviously, dietary levels of cal-cium, phosphorus and vitamin D3 come underclose scrutiny, but rickets does not seem to bea simple deficiency of any one of these nutrients.There are reports of prevention from using25(OH)D3 rather than vitamin D3, while other

Table 7.8 Digestibility of C16:0 and C18:0 fatty acids within soybean oil and tallow (%)

C16:0 C18:0Soybean oil Tallow Soybean oil Tallow

Poult 7d 96 65 51 5021d 99 59 51 36

Chick 7d 81 35 73 621d 94 54 88 31

Adapted from Mossab et al. (2000)

Table 7.9 Fat digestion by young poults

Lipid digestibility (%)Diet 3-5d 6-8d 9-11d

1. Corn-soy 74b 76b 78b

2. 1 + 10% AV-fat 69c 72b 71c

3. 1 + 10% MCT1 90a 92a 90a

1Predominantly C8:0Adapted from Turner et al. (1999)



workers claim the condition is caused by an asyet unidentified antinutrient.

Formulating high protein/amino acid starterdiets using only vegetable proteins presentssome unique challenges. When animal proteinsare excluded from the diet, the most commonchange in formulation is to use more soybean meal.In order to achieve 28 – 29% CP and associat-ed levels of amino acids, then it is necessary touse around 50% soybean meal in these all-vegetable diets. When meat meal is available,the level of soybean is closer to 35% of the diet.While 50% soybean ensures that amino acid needscan be met, this high level of inclusion does poseproblems with elevated levels of potassium andoligosaccharides. Because soybean meal is a lowenergy ingredient, a high inclusion level also posesproblems of ‘space’ within the formulation.The levels of threonine and arginine in the dietalso need more careful scrutiny. There is littlethat can be done to resolve the problem ofindigestible oligosaccharides, since as yet, thereare not any really effective exogenous enzymesthat can be used to aid digestion of these com-plex carbohydrates. High levels of potassium leadto wetter litter and more problems with footpadlesions. It is possible to maintain electrolyte bal-ance by using less salt, more sodium bicarbon-ate and in extreme cases, by adding ammoniumchloride to the diet. Maintaining electrolyte bal-ance by these means may be most beneficial whenround heart disease (spontaneous cardiomy-opathy) is problematic since occurrence canbe limited by maintaining MEq at 230 vs. 250-320 as often occurs in high soybean mealprestarters.

With the high levels of lysine needed inprestarter/starter diets, there is often concern aboutthe need for arginine. The usual recommenda-

tion is to have arginine at 110% of lysine, andso when lysine is at 1.7%, arginine needs are closeto 2% of the diet. This level of arginine may bedifficult to achieve with higher levels of animalprotein, and under these situations, arginine at102% of lysine is more economical.

b) Heavy turkey programsWith continued improvement in genetic

potential of large strain turkeys, there is thepossibility to continually extend market weight.Most large white male strains today are capableof sustained high ADG through to 23 – 24 kgliveweight. At this end of the spectrum, nutri-tional programs aimed at sustaining skeletalintegrity and manipulating the balance of car-cass fat:protein become more critical. As ageneralization, the young turkey is most respon-sive to amino acids, while economic growth ofthe larger bird is more related to energy intake.There have been major changes over time in thetype or genetics of turkeys available for production.Today, such differences are less evident as all breed-ing companies strive to aim for larger birdsgrown to older market ages. This later maturingtype of turkey, which has been very common inEurope for many years, is now becoming the stan-dard ‘type’ worldwide, and so today, there is lessemphasis on ‘strain-specific’ feeding programs.

In diets composed essentially of corn and soy-bean meal, methionine and/or TSSA are likelyto be the limiting amino acid. Requirement formethionine will obviously vary with energylevel of the diet, although it is possible to makegeneral recommendations of around 2.4, 2.1 and1.7 mg methionine per kcal ME for starter,grower/developer and finisher diets respective-ly. With later maturing turkey strains that are nowused almost exclusively, higher levels of lysine



seem beneficial. Lysine levels are thereforearound 6.5, 5.5 and 3.5 mg/kcal ME for starter,grower and finisher diets respectively. Mostnutritionists consider the turkey to be veryresponsive to lysine levels, although as a percentageof crude protein, the levels used in practice arelittle different than for other meat birds. There issome evidence to suggest that toms and hens arenot too responsive to higher levels of lysineassuming a balanced protein is being used.

Traditionally, the concept of optimum ener-gy:protein has been considered for most class-es of turkeys. Recent evidence suggests that thisconcept is no longer applicable, or at least notalways economically viable. Sell and co-work-ers in an extensive series of studies, working withgrowing tom turkeys from 9 – 20 weeks of age,concluded that increasing CP or ME improvedweight gain and feed:gain, but that the CP effectwas independent of ME. It is perhaps pertinentthat the energy response in this work in fact relatesto added fat. Increasing the energy concentra-tion of the diet reduced the quantity of proteinconsumed per kg of body weight gain, althoughit had no effect on ME consumed per kg ofgain. Increasing the protein content of the dietreduced protein efficiency in relation to gain,although efficiency for ME was improved.Interestingly, these changes in diet specificationhad little effect on carcass composition. Theseworkers conclude that optimum CP:ME as aconstraint in formulation may be inappropriate,and that it may be better to consider inde-pendent effects for both protein and energy.

In meeting the nutrient requirements ofturkeys, changes in diet specification with ageare obviously a compromise in attempting toaccommodate reduced requirements of older birds.With an 18 – 24 week growing period, thepotential for diet change is much greater although

they must obviously be balanced against prac-tical considerations of feed manufacture and on-farm handling of many feeds. Many research stud-ies in fact suggest that the number of dietchanges, from as little as 2, up to 10, over an 18week period have little effect on turkey per-formance. With fewer diet changes, there hasto be more ‘over formulation’ to ensure that birdsare not faced with deficient diets at the beginningperiod of feeding any one diet. Changing diet each3 – 4 weeks seems to be a practical compromise.Fewer diet changes do pose problems in adjust-ing diet texture. While young poults require qual-ity crumbles, the transition through to largerpellets is critical over the first 8 weeks of growth,and can only really be achieved with at least twochanges in feed texture. Too large a pellet intro-duced too early invariably results in reducedfeed intake and increased feed wastage.

Utilization of fats in diets for turkeys has alwaysbeen a controversial topic and certainly one thathas received considerable attention in recent years.In many instances, research protocols fail todifferentiate between the effects of fat and ener-gy. Considering the dominant role that energyplays in controlling growth, it is perhaps not toosurprising that turkeys respond to supplementaldietary fat. At fixed energy levels, there is oftenimprovement in feed:gain with added fat and thiseffect increases with increase in age of the bird.From 0 – 12 weeks, F:G is improved by about 1.5%for each 1% added fat. From 12 – 20 weeks, acorresponding value of 3.5% is seen. It is oftennoted that if fat is removed from the diet ofolder birds, then any improvements to that timeare often lost. These data suggest little return inuse of fat for young birds, and that economicresponse is maximized after 8 weeks of age. Theage response is likely a reflection of improveddigestibility of more saturated fatty acids coupledwith the improved efficiency associated with direct



deposition of absorbed fats into body fat depots.The turkey’s response to energy is to someextent influenced by environmental temperature.

Maximum weight gain for market weightbirds is achieved at 10 – 16˚C. At 27˚C and 35˚C,gain is reduced by about 6% and 12% respectivelyalthough feed:gain is improved by 1.2% for each+1˚C up to 27˚C. It is generally recognized thatamino acid levels in the diet should increase astemperature increases, because feed intake willdecline. There are also advantages to increasingthe fat and perhaps the energy content of diets forturkeys older than 12 weeks of age and necessarilymaintained at >22˚C. As genetic potential increas-es, so the upper critical temperature for opti-mum growth rate will likely decline. In their pub-lication, British United Turkeys predict that themaximum environmental temperature required forrealizing maximum growth rate is declining by 2– 3˚C each 10 years and for large toms nowstands at close to just 10˚C. It seems that marketweight declines by about 100 g for each 1˚Cincrease in environmental temperature abovethis 10˚C ideal. However, this increased growthis achieved by stimulation of feed intake and sofeed efficiency will deteriorate at lower temper-atures (Table 7.10).

25ºC 15ºC134 d B.wt.(kg) 17.72 18.83Feed intake 43.64 49.05F:G 2.41 2.53Breast (% carcass) 31.9 33.3

Table 7.10 Performance of maleturkeys grown at 15 or 25ºC

Adapted from Veldkamp et al. (2000)

In this study, growth rate and breast meat yieldcould not be sustained when birds at 25˚C werefed diets supplemented with additional methio-nine, lysine and threonine.

The large turkey would seem to be an idealcandidate for compensatory gain and in fact, theearly work on such feed programs was demon-strated with turkeys. However, modern strainsof turkeys do not seem to perform adequately onsuch diets, and growth compensation is rarelyachieved. It seems as though slow initial growthbrought about by using low nutrient densestarter diets compromises the bird to such an extentthat 18-week weight is 5 – 7% below standard.With lower protein starter diets, there is a sug-gestion that amino acid levels other than methio-nine and lysine should be more closely studied.With starter protein levels as low as 22% CP, thre-onine and valine levels may be equally asimportant as lysine, and interaction amongbranched-chain amino acids may be problem-atic. For example, high levels of leucine seemto cause growth depression in low protein starterdiets, and this effect is only partly alleviated byadditions of valine. Such data suggest cautionin the use of high leucine ingredients such as corngluten or blood meal in compensatory growthtype feeding programs. More recent studieson compensatory gain have generally failed toshow any distinct advantage in terms of overallfeed usage or cost/kg gain, and in fact completegrowth compensation to a specific age is some-times not realized. For example, feeding low pro-tein starter diets for just the first 3 weeks, followedby normal diets, has been shown detrimental to18-week body weight. It seems as though thelater maturing strains common today are not idealcandidates for compensatory growth. Theirgenetically inherent slower initial growth, in



effect, parallels the concept of compensatorygrowth and it appears that these birds are unableto fully recover from a period of early under-nutrition. For market ages of 16 – 20 weeks, com-pensatory growth therefore has limited application.The concept will likely be re-visited as marketweights increase further.

There have been numerous research projectslooking at low crude protein, amino acid forti-fied diets, ostensibly as a means of reducing feedcost or in order to reduce manure nitrogen con-tent. When diets are formulated to 80% ofnormal levels of crude protein, then body weightcan often be normalized by supplementing withmethionine, lysine and threonine. However, inmost of these studies, even though growth maybe normal, there is often loss in breast meat yield.With low protein diets there is usually loss in feath-er cover. The length of tail feathers is oftenused as an indicator of feather development, andit seems that there is a linear relationshipbetween this characteristic and diet protein/aminoacids. It seems that tail feather length decreas-es by about 2 mm/1% CP by 6 weeks of age. Thisis equivalent to about 2% loss in tail feather lengthper 1% CP. However, since such diets often impairgrowth rate per se, it is not clear if this delayedfeathering is merely a correlate of reducedgrowth. Of the amino acids tested to date feath-er development seems most responsive tomethionine.

Two reoccurring problems in the industry areso-called flushing syndrome, which appears asdiarrhea, and turkey knockdown, which dis-ables older turkeys. Both problems may have anutritional component, although it is obvious thatother, yet unknown factors, are also involved. Asits name implies, flushing syndrome is charac-terized by wet, runny excreta that is seen in com-

mercial flocks from 6 – 14 weeks of age, althoughmost commonly during 8 – 12 weeks. Becausethis timing coincides with removal of anticoc-cidials from the diet, there has been speculationabout associated changes in intestinal microflo-ra. The wet litter increases the potential for legdisorders and breast blemishes. Wetter excre-ta can be caused by high levels of mineralsand especially salt and also by excess protein whichboth relate to increased water consumption.However, the flushing syndrome is associated witha ‘sticky’ type of excreta, whereas extra saltand protein usually cause watery and urate-dense excreta respectively.

Surprisingly, diet fiber level and source havelittle effect on cecal and excreta appearance. Theoccurrence of flushing at 8 – 12 weeks coincideswith increase in fat content of the diet and so var-ious levels and sources of fat, and also fats withvarious degrees of rancidity have been tested, againwithout any consistent effect. The only dietnutrient that consistently affects the degree andconsistency of cecal excreta, is copper. Adding500 g copper sulphate/tonne feed results ingreater cecal evacuation and the cecal excretaare of much greater viscosity. Cecal excreta con-tains as much as 14,000 ppm copper. Certainlynot all turkeys are fed additional copper sulphate,although it does appear to contribute to abnor-mal excreta consistency. Other attempts at dietmodifications used to treat or prevent flushingsyndrome have generally met with little success.There are some reports of benefit to adding 2 kgbetain/1000 litres of drinking water.

Turkey knockdown also occurs at around 10– 14 weeks of age where affected birds areunable to stand or walk. The condition resem-bles ionophore toxicity, but this has largelybeen ruled out as a single causative factor.



Knockdown is most severe when there is arepetitive on-off lighting program and turkeys areseen to ‘gorge’ feed when lights are turned onafter a prolonged period of darkness. This lat-ter situation is especially relevant when turkeyshave limited access to water. Because of the impli-cations of high feed intake over a short periodof time, associated high intakes of ionophoreshave been suspected. However, under con-trolled studies when turkeys are encouraged togorge on feed containing even 140 ppm mon-ensin, no knockdown was observed.

With large turkeys there is now concernabout quality of breast muscle. A condition com-parable to Pale Soft Exudative (PSE) meat seenin some pigs, now appears in breast meat of largeturkey males. In pigs, PSE is known to be an inher-ited trait. The changes to the breast meat are obvi-ous with visual examination, and there are dis-tinct microscopic alterations to breast musclemorphology. The condition becomes mostproblematic during further processing and slic-ing of breast meat. There does not seem to bea direct effect of nutrition. PSE is only seen inconjunction with fast growth rate, and the con-dition can be eliminated by slowing downgrowth by various means. PSE is not likely a fac-tor of size of individual muscle fibers, becausewhen restricted fed birds eventually catch up inweight, their fiber size is similar, yet PSE is rare.

Muscle creatine kinase, which is an indicator ofmuscle ‘damage’ is greatly increased with con-ventional ad–lib feeding and in birds of similarweight, is always higher in ad-lib vs. restrictedfed birds. In the swine breeding industry, the reac-tion of the pig to the anesthetic halothane wasused as a screening test. This test does notseem to work with turkeys. The swine industrynow uses a genetic marker test to screen carri-ers of the gene.

c) Broiler turkeysThere has been a decline in production of broil-

er turkeys, essentially due to competition withlarge roaster chickens. None of the commercialbreeders now have a strain specifically designedfor this market.

Feeding programs for small females essentiallyentail quicker scheduling of diets with earlier movesto higher energy diets. It is very difficult toobtain sufficient fat depots on males for this 6 –6.5 kg broiler category and so they are rarely usedfor this purpose. Turkey hens will be around 5kg at 10 weeks and 6.5 kg at 12 weeks with feedconversion at 1.8 – 2.0. The male of thesestrains is commonly taken to 10 –12 kg liveweight,again for the whole bird market. A feedingprogram for turkey hens to 12 weeks of agewith 6.5 kg liveweight, is shown in Table 7.11.



d) Carcass compositionWith an increased proportion of large turkey

carcasses being cut-up or further processed,there is a continued demand for information oncarcass yield and composition of turkeys. Dueto dramatic changes in weight-for-age of the turkey,information regarding carcass composition forspecific ages of bird becomes virtually redundantovernight. For this reason, we have presentedthe following carcass data based on expectedchanges related to age of turkey hens and toms(Table 7.12). In order to use this information, the

coefficients for a particular parameter are mul-tiplied by ‘age-in-days’ and ‘(age-in-days)2’.

eg: % total viscera for a 100 d tom is calculated as

17.87 – (0.158 x 100) + (0.00054 x 1002)

= 17.87 – 15.8 + 5.4

= 7.47%

Similarly, Table 7.13 gives expected changesin cut-up yields for toms and hens.

Table 7.11 Diet specifications for broiler turkey hens

Starter Grower I Grower II Developer Finisher0 - 4 wk 5 – 6 wk 7 – 8 wk 9 – 10 wk 11 – 12 wk

CP (%) 29.0 26.5 24.0 21.0 19.0ME (kcal/kg) 2850 2975 3075 3200 3300Ca (%) 1.4 1.3 1.2 1.1 1.0Av P (%) 0.80 0.75 0.65 0.55 0.50Na (%) 0.17 0.18 0.18 0.19 0.19

Methionine (%) 0.65 0.62 0.58 0.52 0.45Meth + Cys (%) 1.20 1.10 1.00 0.92 0.85Lysine (%) 1.80 1.70 1.60 1.45 1.25Threonine (%) 1.20 1.10 1.00 0.90 0.80



Constant ± Age ± Age2 CoefficientAge Age2

As % of body weight:Total viscera 17.870 - .158 + .000544 ** **

18.696 - .180 + .000772 ** **Liver 2.792 - .0204 + .0000673 ** **

3.023 - .0247 + .0000824 ** **Heart .798 - .00653 + .0000267 ** **

.766 - .00681 + .0000284 ** **Alimentary tract 14.168 - .129 + .000400 ** **

14.924 - .152 + .000548 ** **Gizzard + proventriculus 5.089 - .0284 + .0000258 ** NS

5.455 - .0458 + .000134 ** **Carcass fat (g) 62.990 - 5.309 + .0929 ** **

-55.970 + .749 + .0596 NS **Carcass CP (g) -103.10 + 8.738 + .0357 ** **

-122.46 + 10.704 - .00863 ** NSViscera fat (g) 3.516 - .421 + .0173 NS **

-26.375 + .737 + .0182 NS **Viscera CP (g) -32.15 + 3.478 - .00524 ** **

-21.23 + 2.806 - .00733 ** **Total body fat (g) 66.506 - 5.729 + .110 ** **

-82.344 + 1.486 + .0778 NS **Total body CP (g) -135.269 + 12.216 + .0305 ** **

-143.692 + 13.510 - .0160 ** NSTotal body fat (%) 5.708 - .0565 + .000698 ** **

4.704 + .00588 + .000724 NS **Total body CP (%) 15.438 + .102 - .000545 ** **

15.250 + .0996 - .00577 ** **

Table 7.12 Relationships between turkey age (days) and body weight andorgan proportions. For each parameter, the first line represents toms, thesecond line hens


SECTION 7.2Turkey breeder feeding programs

Constant ± Age ± Age2 Coefficientsignificance Age Age2

% Neck 9.126 - .0267 + .000121 ** *9.141 - .0199 + .0000192 * NS

% Drumsticks 14.498 + .00183 - .000115 * NS14.158 - .0108 - .0000366 NS NS

% Thighs 16.013 - .0194 + .000104 NS NS16.471 - .0287 + .000183 ** **

% Wings 14.852 + .0458 - .000493 ** **16.067 + .00711 - .000285 ** NS

% Back 18.398 - .113 + .000468 ** **19.203 - .131 + .000652 ** **

% Breast 26.653 + .1233 - .000167 ** NS26.525 + .172 - .000502 ** **

% Yield 58.260 + .352 - .00123 ** **55.932 + .426 - .00170 ** **

Table 7.13 Relationships between turkey age (days) and body weight andcarcass proportions. For each parameter, the first line represents toms, thesecond line hens.

Nutrition and feeding management play a sig-nificant role in attempting to meet the proces-sor’s demand for leaner turkey carcasses/meat.While previous discussion has detailed theimportance of energy and protein, rather than ener-gy:protein in terms of conventional growthparameters, one must be aware of the importanceof this balance in finisher diets as it influencescarcass fat deposition. There seems little doubtthat the turkey responds in a classical manner in

this respect, in that wider energy:protein will leadto increased carcass fat and vice versa. Inreducing the ratio of energy:protein, one obvi-ously has the option of increasing protein/aminoacids in relation to energy, or reducing energywhile maintaining normal protein levels. For broil-er turkey hens, widening the ratio of energy:pro-tein ensures early deposition of subcutaneous fat,and hence higher grade.

W ith increased genetic potential forgrowth rate of hens, as well as tombreeders, it is often necessary to prac-

tice some degree of nutrient restriction during thegrowing period. It is difficult to control body weightthrough use of very low nutrient dense diets, andso feed restriction is becoming a viable alterna-tive. Diet specifications for juvenile breeders are

shown in Table 7.14, and for adult breeders in Table7.15. Examples of corn-soybean adult breederdiets are detailed in Table 7.16. For the larger strains,the hens will weigh around 12.0 – 13.0 kg at 30weeks and eat 50 – 55 kg feed. Toms will like-ly be close to 23 kg at 30 weeks, and eat 100 kgin this growing period.

7.2 Turkey breeder feeding programs



Starter Grower 1 Grower 2 Develop HoldingAge (wks) - Hens 0 – 3 4 – 7 8 – 11 12 – 14 15 - lighting

- Toms 0 –4 5 – 8 9 – 12 13 – 17 18 - 30

Crude Protein (%) 26.0 23.0 21.0 16.0 12.0Metabolizable Energy (kcal/kg) 2750 2800 2850 2850 2800Calcium (%) 1.40 1.30 1.10 1.00 0.90Av. Phosphorus (%) 0.80 0.70 0.60 0.50 0.45Sodium (%) 0.17 0.17 0.17 0.17 0.17

Methionine (%) 0.65 0.60 0.46 0.35 0.30Methionine + Cystine (%) 1.15 1.00 0.85 0.64 0.58Lysine (%) 1.70 1.55 1.25 0.95 0.60Threonine (%) 1.10 0.95 0.75 0.55 0.48Tryptophan (%) 0.28 0.24 0.20 0.16 0.14

Vitamins (per kg of diet) 100% 100% 90% 80% 80%Vitamin A (I.U.) 10,000Vitamin D3 (I.U.) 3,500Vitamin E (I.U.) 100Vitamin K (I.U.) 3Thiamin (mg) 3Riboflavin (mg) 10Pyridoxine (mg) 6Pantothenic acid (mg) 18Folic acid (mg) 2Biotin (µg) 250Niacin (mg) 60Choline (mg) 800Vitamin B12 (µg) 20


Table 7.14 Diet specifications for juvenile turkey breeders



Breeder 1 Breeder 2 Tom dietCrude Protein (%) 16.0 14.0 13.0Metabolizable Energy (kcal/kg) 2950 2900 2850Calcium (%) 2.60 2.80 0.85Av. Phosphorus (%) 0.40 0.35 0.25Sodium (%) 0.17 0.17 0.17

Methionine (%) 0.34 0.30 0.28Methionine + Cystine (%) 0.58 0.50 0.42Lysine (%) 0.80 0.72 0.60Threonine (%) 0.60 0.50 0.45Tryptophan (%) 0.18 0.16 0.15Arginine (%) 0.90 0.70 0.60Valine (%) 0.64 0.55 0.50Leucine (%) 1.05 0.85 0.75Isoleucine (%) 0.65 0.55 0.50Histidine (%) 0.30 0.25 0.22Phenylalanine (%) 0.60 0.45 0.42

Vitamins (per kg of diet)Vitamin A (I.U.) 9,000Vitamin D3 (I.U.) 3,500Vitamin E (I.U.) 100Vitamin K (I.U.) 4Thiamin (mg) 3Riboflavin (mg) 8Pyridoxine (mg) 5Pantothenic acid (mg) 18Folic acid (mg) 1Biotin (µg) 300Niacin (mg) 70Choline (mg) 900Vitamin B12 (µg) 16


Table 7.15 Diet specifications for turkey breeders



Breeder 1 Breeder 2 Tom dietCorn 700 755 560Soybean meal 211 160 61Wheat shorts 350AV Fat 12.5DL-Methionine* 0.5 0.4 0.6L-Lysine 0.8 1.0Salt 3.2 3.2 3.0Limestone 60.1 70.0 21.0Dical Phosphate 11.7 9.6 2.4Vit-Min Premix** 1.0 1.0 1.0

Total (kg) 1000 1000 1000

Crude Protein (%) 16.0 14.0 13.0ME (kcal/kg) 2950 2900 2890Calcium (%) 2.60 2.88 0.90Av Phosphorus (%) 0.40 0.35 0.25Sodium (%) 0.17 0.17 0.17Methionine (%) 0.34 0.30 0.28Meth + Cystine (%) 0.58 0.50 0.46Lysine (%) 0.80 0.72 0.60Threonine (%) 0.70 0.62 0.52Tryptophan (%) 0.22 0.18 0.17

Table 7.16 Examples of turkey breeder diets (kg)


a) HensAs with any female bird, body weight and con-

dition at maturity seem to be the key to successfulreproductive performance. For most strains ofLarge White hens, it is no longer possible to usecommercial-type meat bird rearing programs,because birds become overweight within the first4 – 6 weeks of growth. The type of program asshown in Table 7.14 is commonly used for moststrains of turkey hens. If slower early growth rateis required, then it is tempting to start birds onlower-nutrient dense grower diets. This concepthas been used successfully with broiler breed-

er pullets. However, for the young breeder poult,we are faced with large changes in specificationof many nutrients in grower, compared to starterdiets. This is most critical with levels of calciumand phosphorus and so a common consequenceof starting poults on grower diets, is the occur-rence of rickets. If slower early growth is requiredin breeder hens, then it is necessary to formulatespecialised low protein/energy diets.

There are conflicting reports of the benefitsto accrue from restricted feeding of juvenilebreeder hens. Reducing body weight by up to 40%at 16 – 18 weeks of age is often claimed to result



in more settable eggs. This situation assumes thathens are allowed to compensate in the 18 – 30week period and attain 12.0 – 13 kg weight atthis age. If hens are underweight at 30 weeksof age, there is invariably poorer adult per-formance. One major variable seems to be theseason in open-sided houses, since restricted feed-ing is most beneficial for breeders maturing inthe warmer summer months.

The key to successful rearing of the breed-er hen lies in monitoring of body weight, andscheduling diets according to weight-for-age, sim-ilar to the concept previously described forLeghorn pullets. Depending upon individual flockcircumstances, managers should be flexible indiet selection within a program (Table 7.14). Forexample, if hens do not gain weight for two weeks,then it may be necessary to feed a higher pro-tein diet until desired weight-for-age is achieved.Due to its large body size, the breeder hen hasa very large maintenance energy requirement.It is for this reason that the bird is greatly influ-enced by changing environmental conditions.For example, a small Leghorn bird is expectedto be slightly smaller when grown in hot vs. coolenvironments. However, the same environ-ment for the turkey breeder hen can mean thedifference between the need to restrict feed vs.the need to stimulate growth. Managers shouldbe acutely aware of this effect and be preparedfor flexibility in feeding programs with changingenvironmental conditions.

If hens are to start producing eggs at around32 – 33 weeks of age, then it seems necessary toinduce a partial molt at 20 – 22 weeks of age, andto light stimulate all birds around 30 weeks of age.Such a molt is best achieved with a suddenreduction in day length from 14 – 16 hours downto 6 – 8 hours for a 10 – 11 week period. Duringthis molt, hens should ideally lose all primary wingfeathers, although in practice, the 10th primary isoften carried over. During this period of molt, henswill invariably eat some of the dropped feathers,especially if straw is not used as litter. Thisbehavior seems normal, and is not indicative ofa sulfur-amino acid deficiency. Obviously, birdsshould be fed insoluble grit at this time.

The use of a pre-breeder diet is open tosome debate. High nutrient dense pre-breederdiets are often used on the assumption thatthey will advantageously pre-condition the birdimmediately prior to lay. This may be true if birdsare underweight at this age, due to poor rearingmanagement. However, for birds of ideal weightand condition, there seems no advantage tousing pre-breeder diets. With other classes of stock,pre-breeder diets are often used in an attempt tostimulate medullary bone development as apre-requisite to shell calcification. However, inrelation to shell output, the turkey consumes sig-nificant quantities of calcium from breederdiets, and so there is likely less emphasis onmedullary bone calcium. The turkey hen doeshowever exhibit an unusual pattern of feedintake in relation to egg production (Figure 7.1).



Fig. 7.1 Feed intake pattern of adult breeder turkey hens.

Fig. 7.2 Dry egg biotin content (Robel, 1983).



As the hen increases her egg production upto peak, she consumes a diminishing quantity offeed. In extreme cases, she may reduce feed intakefrom a peak of 300 g/d down to close to 200 g/d.At the same time, she is obviously increasing eggmass output, and so she will be in negativeenergy balance in terms of feed input:egg out-put. Such imbalance is obviously accommodatedfor by loss in body weight (Figure 7.1). The abil-ity to lose up to 1 kg of body weight seems crit-ical for optimum egg output, and this emphasizesthe reasoning behind the importance of bodyweight and condition of the hen at 30 weeks ofage. Unless nutritionists are aware of this inher-ent problem in breeder hens, and of the impor-tance of tailoring diets according to matureweight, then variable responses to diets can berecorded. The positive response of turkey hensto added fat in the diet agrees with the generalassumption of energy insufficiency at this time.

In addition to egg production, the feeding pro-gram must also accommodate optimum hatch-ability and poult quality. So-called ‘first-AI’syndrome is common with the first few hatch-es from young flocks, where hatchability is sub-optimal, and poult quality quite variable. Sometenuous relationships between this condition andnutrition of the breeder have been developed,although the condition invariably persists regard-less of feeding program. The condition seems muchworse with underweight birds, where presum-ably nutrient supply is limited. Under suchconditions, vitamin supply is often questioned,although response to extra vitamins in the dietor water seems quite variable. There is some log-ical basis for extra vitamin supplementation atthis time, because the content of some vita-mins in the egg, such as biotin, seem suboptimalfor the first few eggs produced by the turkey hen(Figure 7.2, Robel, 1983). Such changes in egg

vitamin content may, however, be independentof nutritional status of the bird. Robel (1983) con-cludes that vitamin levels in the diet may be inad-equate to sustain the original nutrient levels ineggs of turkey hens over the reproduction sea-son, and that such inadequate levels may becausative in seasonal declines in hatchability.

A considerable number of turkey hens arebeing force-molted and used for a second cycle.An example of a molting program is given in Table4.45. Guidelines to be followed during such aprogram are similar to those involved in rearingyoung hens, since body weight and condition atthe start of the second cycle are again important.As shown in Figure 7.1, the hen regains weightafter peak production, such that at the end of thefirst cycle she may be 0.75 – 1 kg heavier thanher 30-week body weight. Ideally, the moltingprogram will ensure that this weight is lost, sothat the second cycle starts with a body weightonce more at around 11-12 kg. In practice,hens are often heavier than this weight.

b) TomsConsidering the genetic potential of the

male breeder turkey, it is obvious that someform of restricted feeding is essential. Suchrestriction results in smaller toms that are easi-er to handle in stud pens as well as birds of supe-rior reproductive capacity. Restricted feeding pro-grams usually involve diets of relatively lownutrient content (Table 7.14).

Seasonal decline in semen quality and quan-tity experienced with breeder toms can often belargely prevented through restricted feedingduring rearing. Such males are easier to handle,and up to a 50% reduction in feed intake can be achieved. Hulet and Brody (1986) also



observed that toms were easier to handle followingrestriction to achieve 80 or 60% of the body weightof control-fed birds. These reductions in bodyweight were achieved with approximately 30 and50% levels of feed restriction. These authorsrecorded no loss in reproductive performance.

Studies have been conducted with young grow-ing tom breeder candidates in which protein lev-els have varied significantly. As expected, thelower the protein content, the smaller the bird,yet effects are not pronounced until diets ofless than 12 – 13% CP are used after 10 weeksof age. Most turkey multipliers carry out quitesevere selection at 16 – 17 weeks of age, at whichtime only 50 – 60% of toms may be consideredas potential breeder candidates. Such selectionis based on body weight, leg condition andgeneral conformation. A criticism of using toosevere a feed restriction program prior to this timeis that there can be no selection against those birdsexhibiting adverse characteristics associatedwith fast growth – the assumption being that theiroffspring may also show such characteristics. Itis obviously more difficult to control growthafter 17 weeks of age if high nutrient densediets are used prior to this time in an attempt tosimulate commercial growing conditions. Lower-protein diets used during rearing of toms also delaysthe onset of semen production, and this shouldbe taken into account in placement time oftoms and hens.

A problem sometimes encountered withbreeder toms, is production of so-called yellowsemen. Such semen is of inferior quality, and anincidence of up to 15% has been recorded in com-mercial flocks. There is some evidence linkinga higher incidence with those toms fed lowprotein, low energy diets although the rela-tionship is far from clear. When a high incidence

of yellow semen occurs other environmental fac-tors should also be investigated.

In those situations where physical daily feedrestriction is not possible, then slowing growththrough use of low nutrient dense diets after selec-tion must be considered. It seems that 8 – 10%CP diets, of adequate amino acid balance, aresuitable, although such specifications are oftendifficult to achieve in many geographical loca-tions. Such low protein diets are most easilyachieved with corn, and it is likely that this is thebasis for recommending high energy levels(3000 kcal ME/kg) for such diets. While low pro-tein-high energy diets may temper growth of tomsin warm climates, these birds often overconsumeenergy in more temperate environments. Underthese latter conditions, lower energy (2800 kcalME/kg) levels are recommended.

In the stud pens, physical feed restriction isagain an ideal management practice wheremost Large White strains will consume about 400– 450 g each day. However, body weight mon-itoring must continue throughout this period, sinceit seems advantageous that the breeder tomgain weight, albeit very little (150 g/wk after 40wks age). This can best be achieved by very small,but gradual increases in feed allowance each week.

c) Model predicted nutrientneeds

An alternative system for defining nutrientrequirements of breeders is to make predictionsbased on simple assumptions of need accordingto known inputs. For both breeder hens and tomsbody weight and growth are by far the largest input,and for the hen there is need to account fornutrients required for egg production.



In the following calculations, maintenancenutrient requirements were taken from datapresented by Moran et al. (1983) and for the henestimates of egg size, egg production and egg com-position are used to calculate corresponding pro-duction requirements. Predictions for majornutrient needs of hens are shown in Table 7.17and for toms in Table 7.18. Hens were assumedto have a body weight of 12.5 kg and be at 60%production with a 100 g egg. Tom needs werecalculated based on body weight of 24 kg.

Data in Tables 7.17 and 7.18 show twomajor discrepancies between predicted levels andthose provided by a typical commercial diet. Forboth hens and toms we seem to be overestimatingneeds for crude protein and greatly underestimatingrequirement for the amino acid cystine. The sit-uation with cystine is of greatest concern, andthe model prediction estimates are high becauseof the extensive need for maintenance related tofeather regeneration. If these values are correct,then the only practical way of meeting such arequirement is to include feather meal in the dietand/or to use more synthetic methionine.

Table 7.17 Predicted daily nutrient requirements of turkey breeder hens

Nutrient Prediction Diet specifications @ Typical diet 250 g daily feed intake

ME 850 kcal/d 3400 kcal/kg 2970 kcal/kgCP 24.9g 10.0% 17.0%Arginine 1.9g 0.76% 0.95%Isoleucine 1.5g 0.60% 0.75%Lysine 1.3g 0.52% 0.85%Methionine 0.5g 0.20% 0.42%Cystine 1.3g 0.52% 0.24%Meth + Cyst 1.8g 0.72% 0.66%Threonine 1.2g 0.48% 0.55%Tryptophan 0.3g 0.12% 0.14%

Table 7.18 Predicted daily nutrient requirements of turkey breeder toms

Nutrient Prediction Diet specifications @ Typical diet 450 g daily feed intake

ME 1150 kcal/d 2550 kcal/kg 2750 kcal/kgCP 36.2g 8.00% 12.0%Arginine 2.8g 0.62% 0.61%Isoleucine 2.2g 0.69% 0.53%Lysine 1.7g 0.38% 0.60%Methionine 0.5g 0.11% 0.20%Cystine 2.2g 0.49% 0.18%Meth + Cyst 2.7g 0.60% 0.38%Threonine 1.7g 0.38% 0.42%Tryptophan 0.3g 0.07% 0.11%


Suggested Readings

a) Market TurkeysDonaldson, W.E. (1994). Administration of propi-onate to day-old turkeys. Poult. Sci. 73:1249-1253.

Donaldson, W.E. (1995). Carbohydrate, hatcherystressors affect poult survival. Feedstuffs: p. 16.

Frame, D.D., D.M. Hooge and R. Cutler (2001)Interactive effects of dietary sodium and chloride onthe incidence of spontaneous cardiomyopathy (RoundHeart) in turkeys. Poult. Sci. 80 (11):1572-1577.

Hocking, P.M., G.W. Robertson and C. Nixey (2002).Effects of dietary calcium and phosphorus on miner-al retention, growth, feed efficiency and walking abil-ity in growing turkeys. Br. Poult. Sci. 43 (4):607-614.

Hurwitz, S., Y. Frisch, A. Bar, U. Elsner, I. Bengaland M. Pines (1983). The amino acid requirementsof growing turkeys. Model construction and param-eter estimation. Poult. Sci. 62:2398-2042.

Jackson, S. and L.M. Potter (1984). Influence ofbasic and branched chain amino acid interactions ofthe lysine and valine requirements of young turkeys.Poult. Sci. 63:2391-2398.

Kagan, A. (1981). Supplemental fats for growingturkeys: A review. World’s Poult. Sci. J. 37:203-210.

Kamyab, A. and J.D. Firman (1999). Starter perioddigestible valine requirements of female Nicholaspoults. J. Appl. Poult. Res. 8 (3):339-344.

Kidd, M.T. and B.J. Kerr (1998). Dietary arginineand lysine ratios in large white toms. 2. Lack ofinteraction between arginine-lysine ratios and elec-trolyte balance. Poult. Sci. 77:864-869.

Kidd, M.T., P.R. Ferket and J.D. Garlich (1998).Dietary threonine responses in growing turkey toms.Poult. Sci. 77:1550-1555.

Leeson, S. and J.D. Summers (1978). Dietary self-selection by turkeys. Poult. Sci. 57:1579-1585.

Leeson, S. and J.D. Summers (1980). Productionand carcass characteristics of the large white turkey.Poult. Sci. 59:1237-1245.

Lilburn, M.S. and D. Emmerson (1993). The influ-ence of differences in dietary amino acids during theearly growing period on growth and development ofNicholas and British United Turkey toms. Poult. Sci.72:1722-1730.

Mamputu, M. (1992). Performance of turkeys sub-jected to day and night feeding programs duringheat stress. J. Appl. Poult. Res. 1:296-299.

Moran, E.T, Jr. (1995). Performance of turkeys at 110vs. 115% of NRC (1994) protein recommendation. J.Appl. Poult. Res. 4:No. 2, 138-147.

Mossab, A., J.M. Hallouis and M. Lessire (2000).Utilization of soybean oil and tallow in youngturkeys compared with young chickens. Poult. Sci.79:1326-1331.

Nixey, C. (2003). Nutrition and management of theyoung turkey. Poult Conf. Flori, Italy. Oct. 2003.

Noy, Y., A. Geyra and D. Sklan (2001). The effect ofearly feeding on growth and small intestinal devel-opment in the posthatch poult. Poult. Sci. 80:912-919.

Odetallah, N.H., P.R. Ferket, J.D. Garlich, L.Elhadri and K.K. Kruger (2001). Growth and diges-tive function of turkeys surviving the poult enteritisand mortality syndrome. Poult Sci. 80 (8):1223-1230.

Oju, E.M., P.E. Waibel and S.L. Noll (1988). Earlyprotein undernutrition and subsequent realimenta-tion in turkeys. 1. Effect of performance and bodycomposition. Poult. Sci. 67:1750-1759.

Owen, J.A., P.W. Waldroup, C.J. Mabray and P.J.Slagter (1981). Response of growing turkeys todietary energy level. Poult. Sci. 60:418-424.

Plavnik, I., B. Makovsky and D. Sklan (2000).Effect of age of turkeys on the metabolisable energyof different foodstuffs. Br. Poult. Sci. 41 (5):615-616.

Renema, R.A., F.E. Robinson, V.L. Melnychuk, R.T.Hardin, L.G. Bagley, D.A. Emmerson and J.R.Blackman (1994). The use of feed restriction forimproving reproductive traits in male-line largewhite turkey hens. 1. Growth and carcass charac-teristics. Poult. Sci. 73:1724-1738.


Rivas, F.M. and J.D. Firman (1994). The influence ofenergy and protein on turkeys during the finisherperiod. J. Appl. Poult. Res. 3:327-335.

Turner, K.A., T.J. Applegate and M.S. Lilburn(1999). Effects of feeding high carbohydrate or highfat diets. 2. Apparent digestibility and apparentmetabolizable energy of the posthatch poultry.Poult. Sci. 78 (11): 1581-1587.

Veldkamp, T., P.R. Ferket, R.P. Kwakkel, C. Nixeyand J.P.T.M. Noordhuizen (2000). Interactionbetween ambient temperature and supplementationof synthetic amino acids on performance and carcassparameters in commercial male turkeys. Poult. Sci.79 (10):1472-1477.

Veldkamp, T., R.P. Kwakkel, P.R. Ferkett and M.W.A. Verstegen (2002). Impact of ambient temperatureand age on dietary lysine and energy in turkey pro-duction. World’s Poult. Sci. J. 58 (4): 475-491.

Vukina, T., H.J. Barnes and M.N. Solakoglu (1998).Intervention decision model to prevent spiking mor-tality of turkeys. Poult. Sci. 77 (7):950-955.

Waibel, P.E., C.W. Carlson, J.A. Brannon and S.L.Noll (2000). Limiting amino acids after methionineand lysine with growing turkeys fed low-proteindiets. Poult Sci. 79:1290-1298.

Waibel, P.E., C.W. Carlson, J.A. Brannon and S.L.Noll (2000). Identification of limiting amino acids inmethionine and lysine-supplemented low-proteindiets for turkeys. Poult. Sci. 79:1299-1305.

Waldroup, P.W. (1993). Effects of amino acid restric-tion during starter and grower periods on subse-quent performance and incidence of leg disorders inmale large white turkeys. Poult. Sci. 72:816-828.

Watkins, K.L. (1993). Effects of feed restriction andsubsequent gorging with limited access to water onmale turkeys fed graded levels of monensin. Poult.Sci. 72:677-683.

Wylie, L.M., G.W. Robertson and P.M. Hocking(2003). Effects of dietary protein concentration andspecific amino acids on body weight, body composi-tion and feather growth in young turkeys. Br. Poult.Sci. 44 (1):75-87.

b) Breeder TurkeysCecil, H.C. (1984). Effect of dietary protein and lightrestriction on body weight and semen production ofbreeder male turkeys. Poult. Sci. 63:1175-1183.

Crouch, A.N., J.L. Grimes, V.L. Christensen andJ.D. Garlich (1999). Restriction of feed consumptionand body weight in two strains of large white turkeybreeder hens. Poult. Sci. 78 (8):1102-1110.

Crouch, A.N., J.L. Grimes, V.L. Christensen and K.K.Krueger (2002). Effect of physical feed restriction dur-ing rearing on large white turkey breeder hens. 2. Reproductive performance. Poult. Sci. 81 (1):16-22.

Crouch, A.N., J.L. Grimes, V.L. Christensen andK.K. Krueger (2002). Effect of physical feed restric-tion during rearing on large white turkey breederhens. 3. Body and carcass composition. Poult. Sci.81(12):1792-1797.

Fairchild, A.S., J.L. Grimes, M.J. Wineland and F.T.Jones (2000). A comparison of the microbiologicalprofile of poults from young versus old turkeybreeder hens. J. Appl. Poult. Res. 9:476-486.

Fairchild, A.S., J.L. Grimes, M.J. Wineland and F.T.Jones (2000). The effect of hen age on antibioticresistance of Escherichia coli isolates from turkeypoults. J. Appl. Poult. Res. 9:487-495.

Ferket, P.R. and E.T. Moran, Jr. (1986). Effect ofplane of nutrition from starting to and through thebreeder period on reproductive performance of henturkeys. Poult. Sci. 65:1581-1590.

Harms, R.H., R.E. Buresh and H.R. Wilson (1984).The influence of the grower diet and fat in the layerdiet on performance of turkey hens. Poult. Sci.63:1634-1637.

Leeson, S., L.J. Caston and B. Rogers (1989).Restricted water access time as a means of growthcontrol in turkey tom breeder candidates. Poult. Sci.68:1236-1238.

Owings, W.J. and J.L. Sell (1980). Effect of restrict-ed feeding from 6 to 20 weeks of age on reproductiveperformance of turkeys. Poult. Sci. 59:77-81.

Robel, E.J. (1983). The effect of age of breeder henon the levels of vitamins and minerals in turkeyeggs. Poult. Sci. 62:1751-1756.

371

SECTION 8.1Ducks

FEEDING PROGRAMSFOR DUCKS & GEESE

8.1 Ducks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

8.2 Geese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

T he waterfowl industry has been rel-atively static in terms of overall pro-duction and marketing opportuni-

ties. There are now very few internationallyrecognized commercial breeders and sothis leads to more standardization of per-formance. Asia, and particularly China,continue to be major producers of bothmeat and eggs, while eastern Europe is a majorcenter of goose meat production. Interestinglythe growth potential of Pekin type duckstrains continues to still outperform that ofmodern broiler chickens.

Growth rate of meat ducks continues toimprove on an annual basis, with malesbeing around 3.2 kg at 42 d. Nutritional pro-grams are aimed at finding a balance betweenexpression of this growth rate vs. control ofcarcass fatness. Diet specifications for bothcommercial and breeder ducks are shown inTable 8.1, while examples of corn-soybeandiets are shown in Table 8.2.

In formulating diets for meat ducks, caremust be taken in adjusting the balance of pro-tein:energy to try and minimize carcass fat dep-osition. The duck seems to respond in a sim-ilar way to protein:energy as previously

described for the broiler chicken and turkey,such that higher protein diets in relation to ener-gy generally result in less carcass fat. The duckseems to be able to digest fiber slightly betterthan does the chicken, and as such, metabi-lizable energy values for ducks may be 5 – 6%greater than corresponding values for chick-ens – such differences should be consideredin setting energy specifications of diets.

Methionine and lysine are likely to be themost limiting amino acids in diets for ducks,and the normal base level of 2 and 5% of crudeprotein respectively seem applicable to theduck. Growth characteristics of Pekin ducksare shown in Table 8.3.

In developing feeding programs for ducks,carcass composition must be taken intoaccount, especially for late-grower and fin-isher diets. Table 8.4 outlines the yield andcommercial portions of Pekin ducks, whileTable 8.5 details the fat and protein deposi-tion in the carcass at 49 d of age. At 49 d ofage, abdominal fat represents only some2% of body weight, which is comparable tothat found in chickens – this data confirmsthat the major problem with fat in the body of the duck is subcutaneous fat depots.

Page

8.1 Ducks

8CHAPTER

372 CHAPTER 8FEEDING PROGRAMS FOR DUCKS & GEESE

SECTION 8.1Ducks

Starter Grower/Finisher Holding BreederAge (wks) (0 to 3) (4 to 7) (8 – lighting) (Adult)

Crude Protein (%) 22 18 14 16Metabolizable Energy (kcal/kg) 2950 3100 2750 2850Calcium (%) 0.85 0.75 0.75 3.0Available Phosphorus (%) 0.40 0.38 0.35 0.38Sodium (%) 0.17 0.17 0.16 0.16Methionine (%) 0.48 0.38 0.3 0.40Methionine + Cystine (%) 0.85 0.66 0.58 0.68Lysine (%) 1.15 0.90 0.70 0.80Threonine (%) 0.78 0.55 0.48 0.58Tryptophan (%) 0.22 0.18 0.14 0.16

Vitamins (per kg of diet): 100% 90% 80% 100%Vitamin A (I.U) 6000Vitamin D3 (I.U) 2500Vitamin E (I.U) 40Vitamin K (I.U) 2Thiamin (mg) 1Riboflavin (mg) 6Pyridoxine (mg) 3Pantothenic acid (mg) 5Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 200Vitamin B12 (µg) 10


Table 8.1 Diet specifications for commercial and breeder ducks

373CHAPTER 8FEEDING PROGRAMS FOR DUCKS & GEESE

SECTION 8.1Ducks

Grow/Starter Finish Holding Breeder

Corn 560 741 304 662Soybean meal 275 184 200Wheat Shorts 100 8.7 647 51Meat meal 50 55 30DL-Methionine* 1.6 0.9 1.9 1.6L-Lysine 1.9Salt 2.4 2.4 2.1 2.8Limestone 10.0 7.0 12.1 71.4Dical Phosphate 10.2Vit-Min Premix** 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000

Crude Protein (%) 22.0 18.0 14.0 16.0ME (kcal/kg) 2950 3100 2750 2850Calcium (%) 0.87 0.75 0.75 3.00Av Phosphorus (%) 0.41 0.39 0.35 0.38Sodium (%) 0.17 0.17 0.16 0.16Methionine (%) 0.52 0.40 0.40 0.44Methionine + Cystine (%) 0.85 0.66 0.58 0.68Lysine (%) 1.23 0.94 0.70 0.80Threonine (%) 0.91 0.76 0.50 0.69Tryptophan (%) 0.29 0.23 0.18 0.22

Table 8.2 Diets for commercial and breeder ducks (kg)


Table 8.3 Growth rate, feed efficiency and feed consumption of Pekin ducks

Average weight (g) Feed intake:body weight gainWeeks

1 500 490 1.2 1.22 1200 1140 1.6 1.63 1620 1570 1.7 1.84 2300 2100 1.8 2.05 2800 2600 1.9 2.16 3200 3100 2.0 2.27 3600 3400 2.2 2.3


SECTION 8.1Ducks

Table 8.4 Yield and commercial cuts of Pekin ducks

35 d 42 d 49 d

Eviscerated carcass (g) 1950 1850 2300 2150 2600 2350Carcass yield (%) 70.5 72.0 73.0 74.0 75.0 76.0% Thighs 14.0 12.4 13.7 13.0 12.2 11.2% Drumsticks 13.7 13.5 12.5 12.2 10.6 10.3% Wings 12.1 12.4 12.3 11.8 11.5 11.6% Breast 17.0 18.9 20.5 21.7 25.7 26.5

Table 8.5 Carcass composition of male Pekin ducks

35 d 42 d 49 dCarcass fat (g) 480.3 632.1 785.0Carcass CP (g) 100.3 66.4 72.8Offal fat (g) 90.5 140.6 160.0Offal CP (g) 98.2 94.5 106.5Total body fat (g) 570.9 772.8 945.0Total body CP (g) 343.3 394.7 459.0Total body fat (%) 24.4 28.7 35.0Total body CP (%) 14.8 14.6 17.0Carcass fat as % body fat 84.2 81.8 83.0Carcass CP as % body CP 71.3 76.0 76.7

The nutrient needs of the growing duck mayvary depending upon consideration for weight gain,feed efficiency or carcass yield (Table 8.6).

If fast growth rate is desired, then thereseems to be a distinct advantage to feedinggood quality pellets. Ducks do not performadequately on mash diets, a factor likely relat-ed to their inability to efficiently pick-up feed,and to do so without causing major feed wastage.The trend towards higher energy diets over thelast few years, through use of dietary fat and high-er levels of corn, leads to more problems in cre-ating quality pelleted feed. Studies with ‘wet’ mashdiets suggest improvements of liveweight and feedefficiency of around 5%. However these advan-

tages are somewhat offset by the ‘dirty’ condi-tion of the ducks, especially around the vent area.

High energy diets are often blamed for thehigh levels of fat seen in the carcass. However,the duck seems to eat to its energy requirementover quite a wide range of diet energy levels, andso it is not so obvious that high diet energy lev-els will lead to increased energy intake. Inmost instances, such high energy diets are notadjusted for crude protein content, and it is thebalance of protein to energy that is most oftenthe culprit that leads to increase in carcass fat-ness observed with high energy diets. There isreason to believe that the net energy of fat isincreased when considerable portions of fatare being deposited in the carcass, and this


SECTION 8.1Ducks

Table 8.6 Estimated amino acid needs of Pekin ducks (% of diet)

situation does detract from the use of high energy diets. Due to the duck’s apparent supe-rior utilization of crude fiber, and the duck’s abil-ity to adjust feed intake to diet energy concentration,there seem to be advantages to using diets of medi-um-low energy concentration. In addition totempering diet energy concentration as a meansof controlling carcass fat content, there havealso been reports of restricted feeding regimes, espe-cially in the late-grower and finishing periods. Feedrestriction per se does not seem to be as useful forcontrolling carcass fat as does attention to pro-tein:energy in the diet, although a combinationof the two systems may be feasible. As with anyrestricted feeding program, growth rate will bereduced, therefore producers must realize high-er monetary returns from such leaner carcasses.

Discussion on the nutrition of ducks invari-ably includes their need for water. Water intakevalues are shown in Table 2.29. Ducks do haverelatively high water requirements, and this is like-ly associated with the increased rate of pas-sage of digesta. Reducing access time to wateras a means of controlling litter moisture most oftenresults in reduced feed intake and reducedgrowth rate, although two 4-hour periods ofwater access seems to be a compromise situa-tion. Contrary to popular belief, there is no need

to provide water such that ducks can eitherswim or immerse their heads, and so bell-typeor even nipple drinkers are acceptable.

While most discussion to date has centeredon the Pekin-type strains of meat bird, there is grow-ing interest in the production of Muscovy ducks.This genetically distinct strain is most easilyidentified by the large sexual dimorphism inbody weight (Table 8.7) with the male being atleast 50% heavier at a slightly later marketing age.Muscovy ducklings seem to have a slightly lowerprotein requirement of around 21 and 19% CPrespectively in starter diets for males and females.Requirements seem to decline to 14 – 17% CPin finisher diets for both sexes, although femalesare usually marketed some 2 – 3 weeks earlierthan males in order to limit carcass fat deposition.The Muscovy may be an ideal candidate for pro-grams involving compensatory growth.

Mule ducks have gained in popularity overthe last few years, being a hybrid cross betweenPekin and Muscovy. The main advantage of thesterile hybrid is that the males and females areof comparable weight, so removing the main obsta-cle associated with marketing of smaller Muscovyfemales. Typical growth rates of such hybrids areshown in Table 8.8.

0 – 21 d 21 – 49 dParameter Lysine TSAA Threonine Lysine TSAA Threonine

Body weight 1.16 0.76 >0.99 0.83 0.73 0.62Feed efficiency 1.03 >0.87 0.98 0.73 >0.84 0.62Breast yield - - - 0.90 0.77 0.66Feed cost/kg gain 0.94 0.87 0.82 0.74 >0.84 0.69Gross margin >1.21 >0.87 >0.99 0.87 >0.84 0.69

Adapted from Lemme (2003)


SECTION 8.1Ducks

Table 8.7 Performance of Muscovy ducks

Age Body weight (g) Feed intake:body

(wks) weight gain

1 160 150 1.10 1.102 500 450 1.20 1.203 1000 900 1.40 1.424 1600 1300 1.60 1.755 2250 1800 1.80 1.906 2800 2100 1.95 2.057 3500 2350 2.10 2.158 4000 2500 2.20 2.309 4500 2700 2.32 2.5010 4800 2900 2.40 2.6211 5100 - 2.45 -12 5400 - 2.60 -

Table 8.8 Growth and feed efficiency of hybrid Mule ducks

Age Body weight (kg) Feed efficiency(weeks)

3 1.0 0.9 1.32 1.544 1.6 1.4 1.41 1.635 2.2 1.9 1.54 1.756 2.8 2.5 1.63 1.847 3.4 3.0 1.71 1.908 3.9 3.5 1.82 2.009 4.2 3.8 1.91 2.1410 4.6 4.1 2.04 2.26

All ducks are very susceptible to mycotox-ins, and in particular aflatoxin. Levels as low as30 – 40 ppb have been shown to impair proteinutilization, while levels of 60 – 80 ppb cancause a dramatic loss in growth rate. With lowprotein diets, the symptoms are greatly accen-tuated, and onset occurs more quickly. Heavymetal toxicity has also been studied extensive-ly with ducks, although much of this research seemsdirected at application of natural contaminationin wild species. Most species of ducks seem very

susceptible to such heavy metals as cadmium,lead and arsenic, although toxic levels shouldnot normally be encountered in uncontami-nated commercial feeds. There are few researchreports detailing the nutrient requirements of egg-type duck strains such as the Khaki Campbell andIndian Runner. In fact, a review of the literaturesuggests that strains such as the Khaki Campbellcan be offered diets comparable to brown eggstrain chickens and that feeding management isalso similar.


SECTION 8.1Ducks

There seems to be an advantage to feedrestriction in growing breeder candidates. Mostbreeding stock is selected from within com-mercial flocks at normal market age, and sothere is a great challenge to ‘hold’ birds up to timeof sexual maturity. Low nutrient dense holdingdiets (Table 8.1) fed on a restricted basis accord-ing to desired body weight seem to be the onlypractical method of both delaying sexual matu-rity and controlling mature body size. Withoutsuch control, egg production is often very poor,and fertility of males may be virtually non-exis-tent. Under such conditions, breeder candi-dates should be fed according to body weight aswas previously described for broiler breederstock (Table 8.9).

Restricted feeding of juvenile breeders from3 – 20 weeks results in greater numbers of set-table eggs and some 10% improvement in fertility.As occurs with turkeys, ducklings from young breed-ers do not grow as well as do those from olderbirds, and this situation cannot be resolved by sup-plements to breeder diets (Table 8.1). Heavy breed-er strains can also successfully be molted asdiscussed previously for chickens and turkeys. Table4.45 gives a general outline of a molting program.As with other species the initial requirement is forloss of 25 – 30% of body weight, and this isachieved by feed withdrawal and reduction in daylength. The body reserves of the breeder, and herovary and oviduct are then re-established throughgradual return to ad-lib intake of a breeder dietover a 5 – 6 week period.

Table 8.9 Effect of restricted feeding of juvenile breeders on the perform-ance of breeders from 20 – 60 weeks of age

Feeding system to 20 weeks of ageAd-lib 75% ad-lib 50% ad-lib

Feed intake (kg) 3 – 8 wk 7.4 5.6 3.78 – 20 wk 17.3 13.0 8.7

Body wt (kg) 8 wk 3.1 2.8 2.120 wk 4.0 3.4 2.560 wk 4.3 4.1 3.8

Eggs 20 – 60 wk 163 180 187Fertility (%) 20 – 60 wk 83 92 92

Adapted from Olver (1995)


SECTION 8.2Geese

8.2 Geese

W hile geese can exhibit the most rapidgrowth rate of all domesticated poul-try species, a major limitation of

expanded commercial production is undoubtedlycarcass quality. As for most waterfowl species,the goose has a propensity to deposit fat in thebody, and it is evident that a large proportion ofthis very rapid growth appears as skin, feathersand body fat. When economically feasible,such concerns must be accommodated in the devel-opment of feeding programs. Diet specificationsfor commercial meat-type geese and breeders areshown in Table 8.10 while corresponding diet exam-ples are shown in Table 8.11.

As most production systems for geese involvesome time spent on pasture, then the actualchoice of feeding program must accommodatethe availability and quality of pasture. Regardlessof rearing system, early growth rate is best opti-mized through use of pelleted starter diets for 3– 4 weeks during which time goslings are usu-ally confined. Subsequent grower and finisherdiets can be fed as sole dietary sources, and itis under such conditions that optimum growthrate is often achieved. Differences in perform-ance of Chinese x Embden geese related torearing system is shown in Table 8.12

Growth rate and feed intake data for sexedPilgrim geese reared under confinement are

shown in Table 8.13. While confinement rear-ing, involving the sole use of complete diets, mayresult in the most rapid growth, extensive systemsmay be more economical. Alternate systems ofteninvolve a period on pasture and/or supplemen-tal grain feeding. Because geese have vora-cious appetites, they are able to consume largequantities of forage, and in eating such large quan-tities their nutrient intake from this poorer qual-ity feed is maintained at near normal levels.Nutrient intake under such conditions will obvi-ously depend upon both quantity and quality ofpasture, and in the latter context pasture man-agement, as it relates to ruminant animals, canbe applied. Geese seem to accept a range of qual-ity roughages, including clovers, mixed grasses,cereals and corn-silage.

Depending upon the time of year, it is oftendifficult to get adequate finish on ‘younger’birds on pasture. Full-feeding of finisher dietsfor the last 10 d is often necessary to provide ade-quate feathering with a minimum of pin-feath-ers. When weaning geese from, or to pasture sys-tems, the allocation of complete feed should notchange abruptly, rather the transition shouldoccur over a 2 – 3 d period. For geese on pas-ture, or for birds supplemented with wholegrains, insoluble grit should be offered at about1 kg/100 geese/wk.


SECTION 8.2Geese

Table 8.10 Diet specifications for commercial and breeder geese

Starter Grower/Finisher Holding BreederAge (weeks) (0 - 3) (4 - market) (7 – lighting) (Adult)


Vitamins (per kg of diet): 100% 80% 70% 100%Vitamin A (I.U) 7,000Vitamin D3 (I.U) 2,500Vitamin E (I.U) 40Vitamin K (I.U) 2Thiamin (mg) 1Riboflavin (mg) 6Pyridoxine (mg) 3Pantothenic acid (mg) 5Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 200Vitamin B12 (µg) 10



SECTION 8.2Geese

Table 8.11 Diets for commercial and breeder

Starter Grow/Finish Holding Breeder

Corn 504 613 514Soybean meal 315 198 25 137Wheat shorts 150 150 500 267Barley 450Meat meal 15DL-Methionine* 1.7 1.0 0.6 1.8L-Lysine 0.5Salt 3.3 3.1 2.9 2.9Limestone 16.4 12.7 15.0 67.0Dical Phosphate 8.6 6.2 5.0 9.3Vit-Min Premix** 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000

Crude Protein (%) 21.7 17.7 14.0 15.0ME (kcal/kg) 2870 2970 2600 2750Calcium (%) 0.90 0.80 0.80 2.80Av Phosphorus (%) 0.40 0.38 0.35 0.38Sodium (%) 0.18 0.18 0.16 0.16Methionine (%) 0.51 0.40 0.27 0.43Meth + Cystine (%) 0.85 0.66 0.48 0.64Lysine (%) 1.20 0.90 0.60 0.70Threonine (%) 0.90 0.74 0.49 0.61Tryptophan (%) 0.30 0.24 0.21 0.20


Table 8.12 Growth rate and feed consumption of White Chinese x Embdengeese (mixed sex)

Confinement reared Range reared (excludes pasture)Cumulative feed Cumulative feed Feed intake:

Age Average consumption Feed intake: Average consumption body wt.(wks) wt. (kg) (kg) body wt. gain wt. (kg) (kg) gain

3 1.68 2.6 1.55 1.59 2.6 1.666 4.20 8.4 2.00 3.80 6.0 1.609 5.74 17.1 2.99 4.98 9.6 1.9312 6.71 23.8 3.56 5.80 16.2 2.7514 7.10 28.6 4.03 5.95 18.6 3.14


SECTION 8.2Geese

Table 8.13 Growth rate and feed consumption of Pilgrim geese

Average Cumulative Feed intake:Age weight(kg) feed(kg) body wt. gain

(wks)

2 0.70 0.70 0.88 0.88 1.26 1.264 2.20 2.10 3.20 3.40 1.45 1.616 3.60 3.00 6.70 7.00 1.86 2.338 4.70 3.90 11.70 11.60 2.48 2.9710 5.00 4.50 15.10 15.00 3.02 3.3312 6.10 5.10 20.00 18.50 3.27 3.6314 6.45 5.40 25.00 23.00 3.87 4.26

Table 8.14 Effect of diet protein and amino acid levels on performanceof Embden geese

Diet crude Body wt. (kg) Carcass fatprotein Methionine Lysine 21 d 63 d (% DM)

(%) (%) (%)

22 0.36 1.25 1.76 1.68 4.8 4.3 49 5420 0.34 1.10 1.80 1.63 5.0 4.4 50 5318 0.31 0.96 1.75 1.64 4.9 4.4 49 5016 0.29 0.81 1.60 1.55 4.7 4.4 51 53


SECTION 8.2Geese

The energy level of all diets should be con-sidered in relation to the propensity for carcassfat deposition. It appears as though growthrate, and hence carcass fat content, are more sen-sitive to diet energy concentration than to inputsof protein and/or amino acids (Table 8.14).

In this study, Embden geese fed single diet pro-grams varying in protein content from 22 –16% exhibited comparable body weights and car-cass composition at 9 weeks of age. Even whenall diets were supplemented with additionalmethionine and lysine, there was no responsein these performance characteristics. Failure toshow a response to amino acid supplementationbeyond 3 weeks of age suggests that with a16% protein, corn-soybean meal diet the lysinerequirement for maximizing subsequent gain isno higher than 0.8%. In this study, calculationof the ratio of protein consumed to proteinappearing as edible carcass protein gave valuesranging from 5 to 9% for the various diets,which is markedly lower than the values ofaround 15 and 21% reported for the chicken broil-er and turkey, respectively. While feed wastagewas relatively high in this study (Table 8.14), itwould be expected to account for only a rela-tively small portion of the difference in proteinutilization. Thus, while geese may be very fastgrowing animals, they appear to be extremelyinefficient in converting dietary protein to edi-ble carcass protein. However, it is obvious thatin this particular study, as well as many otherreports, the level of dietary protein fed was in excessof that required for optimum gain.

Geese seem to derive about the same amountof energy as do chickens from most feedstuffs. Theirability to perform adequately on high fiber dietsis therefore a factor of increased feed intake,

rather than improved digestibility. Geese arequite sensitive to a number of mycotoxins aspreviously described for ducks, and are alsogreatly influenced by anti-nutrients such as the trypsininhibitor found in raw soybeans. This increasedsusceptibility to anti-nutrients is manifested asdecreased feed efficiency rather than any directeffect on feed intake. In situations of reduced per-formance, such as occurs with raw soybeans, poorfeathering is often an early indicator of potentialproblems. As with most species of waterfowl, stageand degree of feathering can have economicsignificance in terms of yield of feathers and/or inci-dence of pinfeathers. Most data suggest thatgeese are able to perform most economicallyon low energy, high fiber diets. This scenario usu-ally implies access to pasture and/or whole grainas well as complete feeds. The capacity of the gooseto consume large quantities of dry matter enablesit to meet its nutrient requirements from a diet veryhigh in fiber. The goose might provide an inter-esting alternative to ruminant animals in utilizinghigh fibrous forages.

Because geese produce relatively few eggs, theirnutrient requirements for egg production are notgreatly increased over maintenance – or at leastnot increased for any sustained period. In orderto control body weight, breeder candidates shouldbe offered holding diets soon after selection,and this feed offered on a restricted basis up to timeof maturity. Specialized breeder diets can be intro-duced 2 – 3 weeks prior to anticipated first egg,or alternatively the birds fed increasing quantitiesof the holding diet together with 3 – 4 g calcium/das large particle limestone or oyster shell. Ifbreeders are retained for subsequent breeding sea-sons, then holding diets and/or grains with min-erals and vitamins should be allocated accordingto maintenance of body weight.


Selected Referencesa) DucksAdams, R.L., P.Y. Hester and W.J. Stadelman (1983).The effect of dietary lysine levels on performanceand meat yields of White Pekin ducks. Poult. Sci.62:616-620.

Bons, A., R. Timmler and H. Jeroch (2002). Lysinerequirement of growing male Pekin ducks. Br. Poult.Sci. 43 (5):677-686.

Braun, C.M., S. Neuman, P.Y. Hester and M.A.Latour. (2002). Breeder age alters offspring per-formance in the Pekin duck. J. Appl. Poult. Res. 11:(3):270-274.

Elkin, R.G. (1986). Methionine requirement of maleWhite Pekin ducklings. Poult. Sci. 65:1771-1776.

Elkin, R.G. (1987). A review of duck nutritionresearch. World Poult. Sci. 43:84-106.

Farhat, A., L. Normand, E.R. Chavez and S.P.Touchburn (2001). Comparison of growth perform-ance, carcass yield and composition, and fatty acidprofiles of Pekin and Muscovy ducklings fed dietsbased on food wastes. Can. J. Anim. Sci. 81:107-114.

Farrell, D.J. (1995). Table egg laying ducks:Nutritional requirements and current husbandrysystems in Asia. Poultry and Avian Biology Reviews6 (1):55-69.

Farrell, D.J. and P. Stapleton (1985). Duck produc-tion-science and world practice. Publ. Univ. of NewEngland, Armidale, Australia.

Jeschke, N. and P.E. Nelson (1987). Toxicity to duck-lings of Fusarium moniliforme isolated from cornintended for use in poultry feed. Poult. Sci. 66:1619-1623.

Leeson, S., J.D. Summers and J. Proulx (1982).Production and carcass characteristics of the duck.Poult. Sci. 61:2456-2464.

Lemme, A. (2003). Reassessing amino acid levels forPekin ducks. Poult Int. April 2003 p. 18.

Olver, M.D. (1995). Effect of restricted feeding dur-ing the rearing period a ‘forced moult’ at 40 weeks ofproduction on productivity of Pekin breeder ducksBr. Poult. Sci. 36:737-746.

Plavnik, I. (1988). Protein requirements of Muscovymale ducklings. Nut. Rep. Int. 39:13-17.

Stadelman, W.J. and C.F. Meinart (1977). Some fac-tors affecting meat yield from young ducks. Poult.Sci. 56:1145-1147.

Wilson, B.J. (1975). The performance of male duck-lings given starter diets with different concentrationsof energy and protein. Br. Poult. Sci. 16:617-625.

Yalda, A.Y. and J.M. Forbes (1995). Effect of wetfeeding on the growth of ducks. Br. Poult. Sci.36:878-879.

b) GeeseHollister, A.G., H.S. Nakaue and G.H. Arscott(1984). Studies with confinement reared goslings. 1.Effects of feeding high levels of dehydrated alfalfaand Kentucky Bluegrass to growing goslings. Poult.Sci. 63:532-537.

Nitsan, Z. and I. Nir (1977). A comparative study ofthe nutritional and physiological significance of rawand heated soya beans in chicken and goslings. Br. J.Nutr. 37:81-87.

Serafin, J.A. (1981). Studies on the riboflavin, pan-tothenate, nicotinic acid and choline requirements ofgrowing Embden geese. Poult. Sci. 60:1910-1915.

Storey, M.L. and N.K. Allen (1982). Apparent andtrue metabolizable energy of feedstuffs of mature non-laying female Embden geese. Poult. Sci. 61:739-745.

Summers, J.D., G. Hurnik and S. Leeson (1987).Carcass composition and protein utilization ofEmbden geese fed varying levels of dietary proteinsupplemented with lysine and methionine. Can. J.Anim. Sci. 67:159-164..

Veltmann, J.R. and J.S. Sharlin (1981). Influence ofwater deprivation on water consumption, growthand carcass characteristics of ducks. Poult. Sci.60:637-642.

Vernam, J. (1995). Assessing the mule duck as ameat producer. World. Poult. Sci. 11: No. 5, p. 44.

385

SECTION 9.1Game birds

9.1 Game birds

Pheasants, Quail, Guinea fowl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385

9.2 Ratites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

9.3 Pet birds and pigeons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

Page

9.1 Game birds

W hile there is some recent infor-mation on nutrient requirements ofquail and pheasants, there is still

a tendency to rely on trends occurring inturkey nutrition. A challenge in designingdiets for game birds is varying market needs andespecially commercial meat production vs. grow-ing birds for hunting preserves or release.Birds grown for release generally do not needto grow at maximum rate and in many instancesthis is, in fact, a detriment to flying ability. Nutrientrequirements and examples of diets shown inTables 9.1 and 9.2 relate only to commercialmeat production. For release programs, thensome type of low nutrient dense holding dietis usually fed for example after 7 – 9 weeks ofage with pheasants.

Pheasants – Table 9.1 outlines starter,grower, holding and breeder diet specificationsfor pheasants. The pheasant starter diet shouldbe fed to 4 weeks of age, followed by the firstgrower diet to market age or until they are select-ed for breeding. Diets shown in Table 9.2 arecomplete diets and need not be supple-mented with grain. However, the feeding of5 to 10% cracked grain can be utilized after

12 weeks of age for birds that are to bereleased for hunting. The grain portion shouldbe switched to whole grain at 16 weeks of ageat which time one half of the feed allotmentcan be grain. Such a feeding program resultsin a stronger, hardier bird and one that ismore able to forage for itself when released.

The pheasant breeder diet should be fedto the birds starting at least 2 weeks beforeeggs are expected. Again, this is a completediet and no supplements should be added toit. Table 9.3 indicates weight gain and feedintake data for male and female pheasants to18 weeks of age.

Quail – Quail diet specifications areshown in Table 9.4. The quail starter diet shouldbe fed as a complete feed up to 6 weeks of age.At this time, the birds should be placed on thegrower diet either until they are marketed asmeat or until one week before table or hatch-ing eggs are expected from the females. Asmentioned above, a small percentage ofscratch grain may be employed. Table 9.5 showsbody weight and feed intake data for both maleand female quail to 10 weeks of age.

FEEDING PROGRAMS FOR GAME BIRDS,RATITES AND PET BIRDS

9CHAPTER

386 CHAPTER 9FEEDING PROGRAMS FOR GAME BIRDS, RATITES AND PET BIRDS


Table 9.1 Diet specifications for commercial and breeder pheasants

Starter Grow/Finisher Holding BreederAge (wks) 0 to 4 4 to market 12 – lighting Adult


Vitamins (per kg of diet): 100% 80% 70% 100%Vitamin A (I.U) 7000Vitamin D3 (I.U) 2500Vitamin E (I.U) 40Vitamin K (I.U) 2Thiamin (mg) 1Riboflavin (mg) 6Pyridoxine (mg) 3Pantothenic acid (mg) 5Folic acid (mg) 1Biotin (µg) 100Niacin (mg) 40Choline (mg) 200Vitamin B12 (µg) 10


387CHAPTER 9FEEDING PROGRAMS FOR GAME BIRDS, RATITES AND PET BIRDS


Table 9.2 Diets for commercial and breeder pheasants (kg)

Starter Grow/Finish Holding Breeder

Corn 480 580 300 566Soybean meal 418 247 14 177Wheat shorts 96 615 180BarleyMeat meal 55 55 55Av Fat 17DL-Methionine* 2.6 1.7 2.1 1.5L-Lysine 1.3Salt 2.7 2.6 2.3 3.3Limestone 15.5 13.6 9.3 60.0Dical Phosphate 8.2 3.1 11.2Vit-Min Premix** 1.0 1.0 1.0 1.0

Total (kg) 1000 1000 1000 1000

Crude Protein (%) 27.0 21.0 15.5 16.0ME (kcal/kg) 2950 2950 2750 2800Calcium (%) 1.30 1.10 0.85 2.60Av Phosphorus (%) 0.60 0.48 0.45 0.42Sodium (%) 0.18 0.18 0.18 0.18Methionine (%) 0.69 0.51 0.44 0.42Meth + Cystine (%) 1.10 0.82 0.64 0.65Lysine (%) 1.60 1.16 0.78 0.79Threonine (%) 1.10 0.87 0.55 0.67Tryptophan (%) 0.37 0.28 0.19 0.22


Table 9.3 Growth rate, feed consumption and feed efficiency of ring-neckedpheasants

Cumulative feed Average weight (g) consumption (g) Feed efficiency

Age (wks) Male Female Male Female Male Female 2 85 85 144 144 1.71 1.714 220 200 430 416 1.98 2.076 380 350 866 794 2.23 2.288 620 520 1496 1352 2.43 2.61

10 830 660 2161 1915 2.61 2.8812 1050 820 3136 2747 2.97 3.3314 1300 960 4092 3640 3.15 3.7816 1475 1025 5163 4709 3.51 4.5918 1530 1080 6338 5827 4.14 5.40



Quail will likely be mature at around 7 – 8weeks of age when body weight is around 150 -160 g. Over a 15 week laying cycle, the breed-ers will produce about 80 eggs with hatch of thoseset around 80%.

Guinea Fowl – Although guinea fowl productionhas increased in North America over the last 10– 15 years, the industry is still quite small com-pared to some parts of Europe and especially France.Diet specifications for growing and breeding

guinea fowl are shown in Table 9.4. The starterdiet is used to 4 weeks of age, followed by grow-er to market age of around 12 – 15 weeks depend-ing upon needs of various weight categories.Growth rate and expected feed intake of male andfemale guineas are shown in Table 9.6.

Breeding females are switched to the guinea breed-ing diet shown in Table 9.4 approximately 2 weeksbefore eggs are expected. This is a complete dietand no grain or grit supplements need to be fed.

Table 9.4 Diet specifications for quail and guinea fowl

Quail Guinea FowlStarter Grower Breeder Starter Grower Breeder

Crude Protein (%) 28 17 18 26 18 16Metabolizable Energy (kcal/kg) 2900 2900 2950 2900 2950 2900Calcium (%) 1.3 1.1 3.1 1.2 0.95 3.0Av Phosphorus (%) 0.60 0.48 0.45 0.5 0.42 0.40Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18Methionine (%) 0.60 0.51 0.52 0.55 0.48 0.41Methionine + Cystine (%) 1.10 0.80 0.82 0.92 0.82 0.75Lysine (%) 1.30 0.90 0.85 1.20 0.95 0.80Threonine (%) 1.10 0.85 0.78 1.00 0.85 0.71Tryptophan (%) 0.24 0.22 0.22 0.22 0.21 0.18

Vitamins and trace minerals as per Table 9.1

Table 9.5 Mean body weight and feed intake of male and female Japanesequail to 10 weeks of age

Male FemaleAge Body Cumulative Body wt. Cumulative

(wks) wt. (g) feed intake(g) (g) feed intake (g)2 40 50 40 504 90 180 100 1906 120 300 130 3308 130 350 160 45010 140 400 170 510


SECTION 9.2Ratites

Table 9.6 Growth rate and feed intake of guinea fowl

Body weight (g) Feed intake (g/d)Age (wks)

1 70 90 13 182 140 175 23 273 250 270 36 394 400 400 50 506 750 700 58 568 1200 1000 65 6010 1420 1300 75 7012 1650 1550 75 7016 1900 1800 75 70

O strich and emu are the species mostcommonly farmed for meat, skin, feath-ers and other products such as preen gland

oil. Traditionally South Africa has dominatedworld production of ostrich products, although inthe mid 1980’s there was great interest in ostrichfarming in Europe and North America.Overproduction and limited market opportunitieshave now resulted in considerable reduction inratite farming in these newer regions.

Ostriches are by far the largest birds of this group with adults reaching in excess of 150 kg.Hens can produce 20 to 40 eggs per year, eachaveraging around 1.25 kg.

Emus are about half the size of ostrichesand while they produce a similar number of eggsas do ostriches, they are only about half the size.Emus are more docile than the ostrich and so eas-ier to handle in confinement housing.

The large intestine of the ostrich is approx-imately 3 times the size of the small intestine, withfood transit time of about 40 hours. The ostrich’sdigestive system is therefore adapted to handle

large quantities of roughage material allowing itto obtain a significant portion of its energy fromhind gut fermentation. The emu’s digestive sys-tem, unlike that of the ostrich, is more like thatof poultry, with rate of food passage beingaround 5 to 6 hours. Despite the apparent lim-itation in fermentation sites, there are reports sug-gesting that emus can digest more fibrous mate-rial than do other types of commercial poultry.Ostriches do not have a crop, and any feedstorage occurs in an elongated proventriculus,which becomes prone to impaction with long stemfibrous ingredients. Diet specifications forostriches are shown in Table 9.7.

Ostrich diets usually contain 6 to 15% fiber,depending on the age of the bird, while diets sim-ilarly vary in protein from 23 to 15%. It has beenreported that the ostrich will metabolize 30 to 40%more energy from a diet than will poultry. Thiscould account for some of the obesity problemsseen in breeders fed ‘poultry diets’. Metabolizableenergy values for selected ingredients are shownin Table 9.8, confirming that ostriches havegreater ability to digest high fiber ingredients.

9.2 Ratites


SECTION 9.2Ratites

Table 9.7 Diet specifications for ostriches

Starter (0 – 8 wks) Breeder1

Crude Protein (%) 18.0 15.0Metabolizable Energy (kcal/kg) 2750 2650Methionine (%) 0.36 0.30Methionine + Cystine (%) 0.70 0.62Lysine (%) 0.90 0.72Calcium (%) 1.40 1.80Av Phosphorus (%) 0.70 0.45Sodium (%) 0.18 0.17

1 Plus free choice forage – actual energy level therefore reduced toequivalent of around 2300 kcal/kg

Table 9.8 TMEn of selected ingredients for mature ostrich and cockerels(kcal/kg)

Ostrich CockerelWheat bran 2844 2040Common reed 2070 666Lupins 3490 2240Soybean meal 3210 2160Sunflower meal 2600 2120Fish meal 3620 3330

Adapted from Cilliers et al. (1999)

Table 9.9 Growth rate and feed intake of ostriches fed commercial diets

Age Body wt. Feed intake (wks) (kg) (g/d)

6 5.8 35010 15.5 55018 38.0 130026 55.0 200034 75.0 250042 90.0 220052 100.0 2000


SECTION 9.2Ratites

Both the ostrich and the emu are prone to legproblems as well as apparent vitamin E andselenium deficiencies. Consequently, mineralfortification should be closely monitored, espe-cially if forage or dehydrated alfalfa makes up asignificant proportion of their diet. Vitamin E for-tification of up to 80 IU/kg of diet is usually rec-ommended, while selenium supplementation mustremain within approved levels. At one week ofage, ostrich chicks should weigh around 1 kg andby 4 weeks of age be close to 3 kg in weight. Table9.9 details subsequent growth rate and feedintake.

After 4 to 6 weeks of age, liberal quantitiesof green forage can be offered to the birds eitheras a supplement or from pasture grazing. At 6months of age, dietary protein level can bereduced to 13 to 15% with energy level remain-ing at 2700 – 2800 kcal ME/kg. Since ostrich-es make relatively good use of high fibrousfeedstuffs, their diets can contain up to 20% fiber.Thus, liberal quantities of forage or alfalfa hay canbe fed along with the prepared diet. Emus can-not handle as much fiber as do ostriches, and sotheir fiber intake should not make up morethan 10 to 15% of their diet. Because of this highfiber intake, it is common practice to supply gritto the birds at least once a week.

Young ostrich and emu chicks have the ten-dency to search for and pick up any appropriatesize material in their surroundings and so litter eat-ing can be a problem in commercial units. To avoidthis occurrence, chicks can be started on some typeof rough paper or burlap. However, care must betaken to avoid anything with a smooth surfacebecause ratite chicks are prone to leg problems.During the first week, the young chicks have a rel-atively slow rate of growth and growth rate is notconstant as occurs with other meat birds. Growthin the first 7 – 10 d is quite slow and then this peri-od is followed by maximum growth rate up to about6 months of age. Subsequent slower growthcontinues up to maturity at around 30 months ofage. Ostrich chicks suffer from leg problemssimilar to those seen with broiler chicks, althoughdue to the relative size of the leg bones, such dis-orders are more easily noticed. Supplemental cal-cium feeding, as calcium borogluconate solution,seems useful for severely affected individuals, sug-gesting perhaps that attention should be given tocalcium levels in the diet, and especially calciumavailability of forages.

There is relatively little information availableon carcass composition of ratites. Table 9.10 showssome carcass and body composition data ofostriches killed at 100 kg live weight.

Table 9.10 Carcass composition of 100 kg ostrich

% Yield of live weightFeathers 1.8Blood 3.0Hide 7.0Feet 2.5Carcass 60.0Heart 1.0Liver 1.5Abdominal fat 4.0Viscera 8.5


SECTION 9.3Pet birds and pigeons

During the breeding season, the femalesmarkedly reduce their feed intake somewhat likea turkey breeder. Thus, it is important that theybe in good condition carrying sufficient nutrient

reserves, so that quality eggs are produced,leading to potentially healthy offspring. Table 9.11shows gross composition of eggs from ostrich-es and emus.

Table 9.11 Ratite egg components

M ost pet birds are fed diets based onwhole seeds rather than completefeeds as pellets. Feeding birds along

the guidelines outlined in Table 9.12 would seemmore logical from a nutritional viewpoint, althoughnutrition per se does not always seem to be themajor factor involved in diet selection by owners.

Use of complete pelleted feeds has been metwith resistance by owners, and not all species ofbird readily accept conventional pellets. However,by using extruded pellets and incorporation ofcolor/taste/smell additives both the owner and birdcan be coaxed into using such complete feeds. There

is increased demand for hand-reared birds due tobetter behavioral disposition and the potential fora ban in trade in exotic species. Consequently thereis increased demand for information on diets forhand feeding of newly hatched birds. Whilemany such hatchlings are fed on baby food/peanutbutter mixes, a gruel formulated to the specificationsshown in Table 9.12, and composed of moreconventional ingredients, should prove moreeconomical for large-scale operations. However,due to the monetary value of many of these petbirds, economics of nutrition is not always amajor factor, especially when one considers theactual feed intake of these very small birds.

9.3 Pet birds and pigeons

Weight (g) Albumen (%) Yolk (%) Shell (%)Ostrich 1200 54 32 14Emu 600 53 34 13

Table 9.12 Diet specifications for pet birds

Budgie Parrots HandYoung Adult Young Adult feeding

Crude Protein (%) 23.0 15.0 21.0 14.0 26.0Metabolizable Energy (kcal/kg) 3000 2900 2900 2800 3200Crude fat (%) 5.0 5.0 5.0 4.0 10.0Crude fiber (%) 3.0 3.0 4.0 3.0 3.0Calcium (%) 1.2 1.0 1.0 0.9 1.4Av Phosphorus (%) 0.45 0.45 0.45 0.4 0.7Sodium (%) 0.17 0.17 0.16 0.14 0.18Methionine (%) 0.50 0.30 0.43 0.25 0.60Methionine + Cystine (%) 0.92 0.61 1.00 0.52 1.20Lysine (%) 1.30 0.75 1.20 0.68 1.40

Mineral-vitamin premix as per turkey with 200 mg/kg Vit. C


SECTION 9.3Pet birds and pigeons

For adults and young birds, that are self-feeding, then conventional ingredients as detailedin Chapter 2 can be considered. Fruit flavors maybe an advantage with some of the more exoticspecies. Feed wastage can be a major problemwith many pet birds, especially when pelletedfeeds are first introduced to birds that are moreaccustomed to whole grain diets. Under theseconditions, feed wastage can approach 10xthat of the actual feed intake. Due to the diffi-culty of measuring feed wastage, and the obvi-ous problem of equating feed intake with feeddisappearance from the feeder, monitoring of bodyweight becomes the most rigorous criterion tobe used in assessing any new feeding program.Regardless of the feeding program used, behav-ioral problems are often reduced if birds haveaccess to other appropriate nutrient sourcessuch as cuttle fish bones and/or fresh fruit etc.

Pigeon meat is often derived from squab, whichis the name given to young pigeons that have beenfed directly by the parents. Under the action ofprolactin hormone, adult pigeons produce asecretion from the crop that is regurgitated andused by the hatchling pigeon. Pigeons are bornblind and with few feathers, and rely soley onthis crop milk for nourishment. The milk isaround 25% solids, composed almost entirelyof protein (18%) and lipid (7%). This very richsource of nutrients results in very rapid growthrate, measured at 4 times the rate of young

‘broilers’. The squab will be around 500 g liveweight at 28 d. There is an indication that cropmilk production is reduced by feeding much lessthan an 18% CP diet to the adults. There are alsoreports of increased crop milk production followingsupplementation of their drinking water with L-carnitine. No one has yet been able to successfullygrow squabs on a synthetic crop milk.

Adult pigeons are often fed mixtures of wholeor cracked grains and protein feeds. The wholeseeds are metabolized quite efficiently (Table 9.13).

Table 9.13 AMEn of various ingre-dients fed as whole seeds to adultpigeons

AMEn (kcal/kg)Corn 3530Barley 2950Sorghum 3315Peas 3350Sunflower 5300

Adapted from Hullar et al. (1989)

The adult pigeons need a diet providingaround 18% CP and 2900-3000 kcal ME/kgwhile producing crop milk; 16% CP and 2800kcal ME/kg during other times of the breeding sea-son and 12 – 14% CP and 2600 kcal/kg as a hold-ing diet between breeding seasons.


Chah, J.C. (1982). Scientific formulation of diets forcaptive birds. In Proc. 2nd Dr. Scholl Conference onNutrition of Captive Wild Animals. Lincoln ParkZoo, Chicago, Illinois.

Cilliers, S.C., F. Sales, F.P. Hayes, A. Chwalibog andF.F. Du Preez (1999). Comparison of metabolisableenergy values of different foodstuffs determined inostriches and poultry. Br. Poult. Sci. 40:491-500.

Cooper, R.G. (2000). Management of ostrich(Struthio camelus) chicks. World’s Poult. Sci. 56(1):33-44.

Earle, K.E. and N.G. Clarke (1991). The nutrition ofthe budgerigar. J. Nutr. 121:S186-192

Flegal, C.J. (1993). Diets for growing and breedingostrich. Proc. Multi-state Big Bird Conf., April 24-25.

Gandini, G.C. M., R.E. J. Burroughs and H. Ebedes(1986). Preliminary investigation into the nutritionof ostrich chicks under intensive conditions. J. SouthAfrican Vet. Sci., March 1986 pp 39-42.

Hullar, I., I. Meleg, S. Fekete and R. Romvari (1999).Studies on the energy content of pigeon feeds. I.Determination of digestibility and metabolizableenergy content. Poult. Sci. 78(12):1757-1762

Muirhead, S. (1995). Ratite gastrointestinal physiol-ogy, nutrition principles explored. Feedstuffs, Oct.2., pp 12.

Roudybush, T. (1986). The nutrition of altricialbirds. In Proc. 6-7th Dr. Scholl Conference onNutrition of Captive Wild Animals. Lincoln ParkZoo, Chicago, Illinois.

Sales, J. and G.P. J. Janssens (2003). Nutrition of thedomestic pigeon (Columba livia domestica).World’s Poult. Sci. J. 59(2):221-232.

Sales, J. and J.J. Du Preez (1997). Protein and ener-gy requirements of the Pearl Grey guinea fowl.World’s Poult. Sci. J. 53:381-385.

Tables, A.E.C. (1987). Nutrient requirement tablesfor various game bird species. A.E.C. Rhone-Poulenc. Paris, France.

Van Niekerk, B. (1995). The science and practice ofostrich nutrition. Proc. AFMA Forum, June 1995,Sun City, South Africa.

Vohra, P. (1992). Information on ostrich nutritionalneeds still limited. Feedstuffs, July 13, p. 16.

Selected References

395APPENDIX

Appendix Table 1Basic nutrient composition

Ap

pen

dix

1.

Bas

ic n

utr

ien

t co

mp

osit

ion

Ingr

edie

ntC

rude

D

iges

tibl

e M

etab

oliz

able

C

rude

fat

Cru

de fi

ber

Cal

cium

(%

)A

vaila

ble

Lino

leic

aci

dpr

otei

n (%

) pr

otei

n (%

)en

ergy

(kc

al/k

g)(%

)(%

)ph

osph

orus

(%

)(%

)

Yello

w C

orn

8.5

7.8

3300

3.8

2.5

0.01

0.13

1.9

Whe

at13

.011

.631

501.

52.

70.

050.

200.

5O

ats

12.0

9.9

2756

4.0

12.0

0.10

0.20

1.5

Bar

ley

11.5

9.3

2780

2.1

7.5

0.10

0.20

0.8

Milo

9.0

7.9

3250

2.5

2.7

0.05

0.14

1.0

Rye

12.5

8.4

2734

1.7

2.4

0.05

0.18

0.4

Trit

ical

e15

.413

.231

101.

04.

50.

050.

190.

4R

ice

(rou

gh)

7.3

5.5

2680

1.7

10.0

0.04

0.13

0.6

Whe

at b

ran

15.8

11.7

1580

4.8

10.4

0.10

0.65

1.7

Whe

at s

hort

s15

.114

.322

004.

05.

00.

070.

301.

6W

heat

scr

eeni

ngs

#115

.011

.730

004.

13.

00.

050.

200.

7R

ice

bran

13.0

7.7

1900

5.0

12.0

0.06

0.80

3.4

Ric

e po

lishi

ngs

11.0

8.5

2750

15.0

2.5

0.06

0.18

6.2

Bak

ery

by-p

rodu

ct10

.59.

835

009.

52.

50.

050.

133.

0M

olas

ses

(can

e)3.

02.

119

62-

-0.

500.

03-

Deh

ydra

ted

alfa

lfa m

eal

17.0

9.5

1647

2.0

26.0

1.40

0.10

0.3

Can

ola

mea

l37

.534

.020

001.

512

.00.

650.

450.

5Fu

ll-fa

t ca

nola

see

d22

.019

.746

2040

.06.

00.

380.

278.

0So

ybea

n m

eal (

48%

)48

.044

.025

500.

53.

00.

200.

330.

4Fu

ll-fa

t so

ybea

ns38

.033

.438

8020

.02.

00.

150.

370.

3C

orn

glut

en m

eal

60.0

54.4

3750

2.51

2.48

0.10

0.28

9.0

Cor

n gl

uten

feed

22.0

14.3

1830

2.5

10.0

0.40

0.21

1.22

Cot

ton

seed

mea

l41

.033

.223

500.

514

.50.

150.

401.

0P

eanu

t m

eal

47.0

35.7

2205

1.0

13.0

0.20

0.45

0.21

Pea

s23

.520

.725

501.

35.

50.

100.

300.

3Sa

fflow

er m

eal

42.0

32.9

1630

1.1

14.5

0.37

0.20

0.9

Sesa

me

mea

l44

.030

.619

845.

05.

00.

200.

630.

5Su

nflo

wer

mea

l46

.835

.622

052.

911

.00.

300.

752.

0Lu

pins

34.5

29.8

3000

6.3

16.0

0.20

0.50

1.8

Flax

22.0

18.1

3500

34.0

6.0

0.25

0.20

3.0

Mea

t M

eal

50.0

45.0

2500

11.5

2.5

8.00

0.17

5.2

Fish

mea

l (60

%)

60.0

55.4

2750

2.0

1.0

6.50

4.00

1.82

Pou

ltry

by-p

rodu

ct m

eal

60.0

52.5

2950

8.5

1.9

3.60

3.50

0.3

Blo

od m

eal

80.0

71.2

2690

1.0

1.0

0.28

2.10

2.5

Feat

her

mea

l85

.075

.730

002.

51.

50.

200.

280.

1D

ried

Whe

y13

.012

.419

180.

5-

0.80

0.70

0.1

396 APPENDIX

Appendix Table 2Total amino acid composition

Ap

pen

dix

2.

Tota

l am

ino

acid

com

pos

tion

Ingr

edie

ntM

ethi

C

ysti

ne

Lysi

neH

ist

Tryp

t T

hre

Arg

Is

oLe

uP

heny

lV

al-o

nine

%(%

)-i

dine

-oph

an-o

nine

-ini

ne-l

euci

ne-c

ine

-ala

nine

-ine

%%

%%

%%

%%

%

Yello

w C

orn

0.2

0.11

0.2

0.2

0.1

0.41

0.4

0.5

1.0

0.5

0.4

Whe

at0.

20.

210.

490.

20.

210.

420.

70.

30.

90.

60.

5O

ats

0.2

0.2

0.4

0.2

0.2

0.4

0.7

0.5

0.9

0.6

0.6

Bar

ley

0.21

0.21

0.39

0.3

0.19

0.4

0.5

0.5

0.8

0.6

0.6

Milo

0.12

0.17

0.31

0.3

0.09

0.32

0.4

0.5

1.5

0.5

0.5

Rye

0.2

0.2

0.5

0.3

0.1

0.4

0.5

0.5

0.7

0.6

0.6

Trit

ical

e0.

20.

20.

40.

30.

10.

30.

80.

51.

00.

70.

7R

ice

(rou

gh)

0.12

0.11

0.22

0.2

0.11

0.34

0.6

0.3

0.7

0.3

0.5

Whe

at b

ran

0.1

0.1

0.6

0.3

0.3

0.4

1.0

0.6

0.9

0.5

0.7

Whe

at s

hort

s0.

210.

190.

610.

20.

210.

50.

90.

71.

00.

60.

7W

heat

scr

eeni

ngs

#10.

210.

210.

530.

20.

20.

420.

60.

30.

90.

50.

5R

ice

bran

0.29

0.11

0.51

0.3

0.18

0.38

0.5

0.4

0.8

0.4

0.6

Ric

e po

lishi

ngs

0.21

0.29

0.50

0.2

0.12

0.32

0.6

0.3

0.7

0.4

0.7

Bak

ery

by-p

rodu

ct0.

210.

190.

290.

30.

130.

30.

50.

40.

80.

60.

5M

olas

ses

(can

e)-

--

--

--

--

--

Deh

ydra

ted

alfa

lfa m

eal

0.3

0.4

1.8

0.4

0.4

0.5

0.7

0.7

1.3

0.8

0.9

Can

ola

mea

l0.

690.

612.

211.

10.

51.

722.

21.

42.

71.

51.

9 Fu

ll-fa

t ca

nola

see

d0.

50.

41.

30.

60.

31.

01.

30.

81.

60.

91.

1So

ybea

n m

eal (

48%

)0.

720.

793.

221.

30.

711.

963.

62.

63.

72.

52.

5Fu

ll-fa

t so

ybea

ns0.

490.

632.

410.

90.

491.

532.

72.

02.

81.

91.

9C

orn

glut

en m

eal

1.61

0.91

0.90

1.4

0.3

1.7

2.2

2.4

8.1

3.2

2.6

Cor

n gl

uten

feed

0.4

0.5

0.6

0.7

0.2

0.9

1.0

0.6

2.4

0.7

1.0

Cot

ton

seed

mea

l0.

490.

621.

671.

00.

51.

314.

61.

32.

42.

21.

9P

eanu

t m

eal

0.4

0.7

1.6

1.2

0.5

1.5

4.9

2.0

3.0

2.7

2.8

Pea

s0.

30.

21.

60.

70.

20.

91.

41.

11.

81.

91.

3Sa

fflow

er m

eal

0.4

0.7

1.3

0.4

0.3

0.6

2.9

0.6

1.2

1.2

1.1

Sesa

me

mea

l1.

50.

61.

41.

20.

81.

75.

12.

33.

22.

32.

5Su

nflo

wer

mea

l0.

80.

71.

61.

00.

91.

63.

31.

82.

41.

92.

2Lu

pins

0.3

0.6

1.7

0.9

0.4

1.2

4.5

1.4

2.4

1.3

1.4

Flax

0.41

0.41

0.89

0.4

0.29

0.82

2.1

1.0

1.3

1.0

1.1

Mea

t M

eal

0.71

0.61

2.68

0.7

0.36

1.52

3.0

1.3

3.3

1.6

2.4

Fish

mea

l (60

%)

1.82

1.1

5.28

1.6

0.58

3.01

4.0

4.1

5.0

2.7

3.6

Pou

ltry

by-p

rodu

ct m

eal

1.3

2.0

3.4

1.0

0.4

2.2

3.5

2.1

4.5

1.8

3.0

Blo

od m

eal

1.0

1.4

6.9

4.2

1.1

3.7

3.5

1.0

10.0

6.0

7.0

Feat

her

mea

l0.

65.

51.

720.

50.

64.

516.

44.

36.

54.

37.

4D

ried

Whe

y0.

20.

31.

10.

20.

20.

80.

40.

91.

40.

40.

7

397APPENDIX

Appendix Table 3Available amino acid composition

Ap

pen

dix

3.

Ava

ilab

le a

min

o ac

id c

omp

osti

on

Ingr

edie

ntM

ethi

C

ysti

ne

Lysi

neH

ist

Tryp

t T

hre

Arg

Is

oLe

uP

heny

lV

al-o

nine

%(%

)-i

dine

-oph

an-o

nine

-ini

ne-l

euci

ne-c

ine

-ala

nine

-ine

%%

%%

%%

%%

%

Yello

w c

orn

0.18

0.09

0.16

0.18

0.07

0.33

0.35

0.44

0.8

0.42

0.33

Whe

at0.

160.

170.

400.

180.

170.

320.

560.

260.

810.

540.

42O

ats

0.18

0.18

0.37

0.18

0.18

0.34

0.64

0.45

0.81

0.55

0.50

Bar

ley

0.16

0.16

0.31

0.26

0.15

0.29

0.41

0.41

0.73

0.53

0.48

Milo

0.09

0.15

0.23

0.26

0.06

0.24

0.28

0.42

1.30

0.40

0.40

Ric

e (r

ough

)0.

090.

060.

170.

170.

110.

270.

500.

260.

560.

280.

41W

heat

bra

n0.

080.

070.

420.

240.

240.

280.

790.

480.

720.

410.

55W

heat

sho

rts

0.16

0.14

0.48

0.16

0.15

0.41

0.71

0.56

0.84

0.49

0.57

Ric

e br

an0.

150.

070.

390.

240.

130.

280.

400.

310.

540.

300.

46R

ice

polis

hing

s0.

160.

080.

410.

180.

080.

250.

480.

270.

570.

310.

52B

aker

y by

-pro

duct

0.18

0.16

0.19

0.24

0.08

0.21

0.40

0.32

0.71

0.51

0.40

Deh

ydra

ted

alfa

lfa m

eal

0.21

0.16

1.00

0.29

0.28

0.35

0.56

0.51

1.00

0.55

0.70

Can

ola

mea

l0.

610.

471.

760.

930.

381.

301.

921.

042.

401.

301.

55

Full-

fat

cano

la s

eed

0.40

0.26

1.00

0.48

0.24

0.81

0.98

0.62

1.28

0.72

0.81

Soyb

ean

mea

l (48

%)

0.64

0.63

2.87

1.07

0.53

1.75

3.20

2.30

3.20

2.10

2.20

Full-

fat

soyb

eans

0.41

0.52

2.00

0.74

0.39

1.27

2.31

1.72

2.20

1.70

1.70

Cor

n gl

uten

mea

l1.

440.

780.

811.

140.

211.

582.

072.

307.

903.

102.

40C

orn

glut

en fe

ed0.

330.

350.

420.

560.

140.

650.

870.

482.

120.

630.

83C

otto

n se

ed m

eal

0.35

0.40

1.18

0.69

0.35

0.90

3.68

0.95

1.72

2.00

1.70

Pea

nut

mea

l0.

330.

551.

280.

960.

381.

204.

001.

802.

702.

302.

40Se

sam

e m

eal

1.30

0.54

1.30

1.00

0.60

1.43

4.60

2.00

2.80

2.10

2.30

Sunf

low

er m

eal

0.72

0.55

1.30

0.80

0.65

1.20

2.64

1.28

1.90

1.55

1.75

Lupi

ns0.

270.

541.

400.

810.

261.

004.

101.

202.

201.

101.

20Fl

ax0.

330.

300.

720.

320.

260.

651.

760.

721.

100.

760.

95M

eat

mea

l0.

620.

332.

090.

560.

261.

172.

781.

002.

601.

301.

90Fi

sh m

eal (

60%

)1.

620.

804.

721.

400.

482.

503.

623.

704.

502.

303.

20P

oultr

y by

-pro

duct

mea

l1.

11.

202.

700.

800.

31.

83.

001.

703.

801.

402.

40B

lood

mea

l0.

901.

105.

903.

400.

802.

802.

900.

788.

905.

306.

10Fe

athe

r m

eal

0.47

2.38

1.10

0.35

0.41

3.15

5.05

3.60

5.00

3.50

6.10

398 APPENDIX

Appendix Table 4Mineral composition

Ap

pen

dix

4.

Min

eral

com

pos

itio

n

Ingr

edie

nts

Chl

orid

eM

agne

sium

So

dium

P

otas

sium

Iron

M

anga

nese

Cop

per

Zin

cSe

leni

um(%

)(%

)(%

)(%

)(%

)(m

g/kg

)(m

g/kg

)(m

g/kg

)(m

g/kg

)

Yello

w C

orn

0.05

0.15

0.05

0.38

0.01

43

290.

04W

heat

0.08

0.16

0.09

0.52

0.01

487

400.

50O

ats

0.10

0.17

0.06

0.37

0.01

385

310.

30B

arle

y0.

180.

120.

080.

480.

0116

740

0.30

Milo

0.07

0.17

0.05

0.32

0.01

149

260.

04R

ye0.

370.

120.

020.

260.

0166

730

0.45

Trit

ical

e0.

410.

150.

040.

410.

0151

635

0.43

Ric

e (r

ough

)0.

280.

140.

030.

340.

0115

310

0.17

Whe

at b

ran

0.30

0.15

0.06

1.24

0.02

115

1289

0.95

Whe

at s

hort

s0.

100.

260.

070.

840.

0110

49

990.

80W

heat

scr

eeni

ngs

#10.

050.

150.

080.

550.

0148

740

0.57

Ric

e br

an0.

170.

850.

101.

300.

0242

514

300.

19R

ice

polis

hing

s0.

170.

650.

101.

170.

0231

08

300.

17B

aker

y by

-pro

duct

0.48

0.20

0.53

0.62

0.02

307

410.

30M

olas

ses

(can

e)0.

650.

400.

303.

500.

0250

2035

0.08

Deh

ydra

ted

alfa

lfa m

eal

0.45

0.34

0.16

2.40

0.03

509

410.

06C

anol

a m

eal

0.05

0.51

0.09

1.45

0.02

617

440.

90Fu

ll-fa

t ca

nola

see

d0.

030.

310.

010.

810.

0235

626

0.52

Soyb

ean

mea

l (44

%)

0.05

0.25

0.05

2.61

0.02

3235

540.

12So

ybea

n m

eal (

48%

)0.

050.

270.

052.

550.

0127

3652

0.11

Full-

fat

soyb

eans

0.04

0.21

0.05

1.50

0.01

2027

410.

10C

orn

glut

en m

eal

0.06

0.05

0.10

0.04

0.04

728

660.

30C

orn

glut

en fe

ed0.

200.

290.

950.

600.

055

4745

0.17

Cot

ton

seed

mea

l0.

030.

390.

051.

100.

0118

1640

0.06

Pea

nut

mea

l0.

550.

040.

071.

100.

0329

680

0.12

Pea

s0.

060.

120.

031.

100.

0118

1620

0.05

Saffl

ower

mea

l0.

030.

270.

100.

690.

0324

980

0.13

Sesa

me

mea

l0.

050.

500.

041.

200.

0448

427

0.06

Sunf

low

er m

eal

0.03

0.75

0.02

1.00

0.10

153

100

0.25

Lupi

ns0.

010.

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AAflatoxin 98Air movement, chilling 184Alfalfa 67Alimet“ 76Alimet“, egg size 198, 200Alkaloids 106Alkalosis 185Alkalosis, shell strength 186Amino acid:

analyses 79breeders 302ducks 375dye-binding 83geese 375layers 184synthetics 74

Antibiotics 88, 271Anticoccidials 86Antifungals 90Antioxidant 206Arginine 75Ascites: 251, 253

broiler 273feed restriction 276

Assay:crude protein 78fat 78gizzard erosion 83gossypol 84metabolizable energy 80rice-hull 85tannin 84

Autointoxication 106

BBacterial toxins 106Bakery meal 28Barley 21Beak trimming 215Bioplex“ minerals 293Biotin, eggs, turkey breeder 364Blood glucose 281Blood meal 68

Body fat, layer 183Body weight, layer 170Bone:

ash 280breakage, layers 219medullary 194

Botulism 107Breeder:

ducks 377geese 382

Broiler: ascites 273breed specifications 301carcass composition 281chick weight 259diet dilution 251diet energy 247, 248efficiency 260energy balance 263environment temperature: 261

electrolytes 265feed change 265protein 265

feathering 285feed:

allocation 240-242efficiency 259intake 239intake, temperature 263withdrawal 255

feeding programs 238growth:

30 yr pattern 249breeder age 258efficiency 257egg weight 258restriction 248, 251temperature 264water system 266

gut health 270heavy birds 233high nutrient density 231lighting 267, 269low nutrient density 232, 246

INDEX

maintenance needs 250mash diets 255minerals 244, 256necrotic enteritis 272nutrient management 289nutrition 230prestarter 244SDS 276skeletal disorders 277skin integrity 285spiking mortality 281stock density 257strain specific diets 243vitamin needs 244vitamins 244, 256

Broiler breeder: 297cage systems 340calcium metabolism 312challenge feeding 321choking 309coccidiosis 308diet ME 318egg production 320egg weight 314eggshell quality 332energy balance 316, 318, 329environmental temperature 330feed:

clean-up time 327efficiency 337grills 335program 305, 315, 336reduction 326restriction 304

fertility 338growth standard 303hatchability 314, 338, 340prebreeder 311protein needs 319rooster feeding 308, 334semen production 339sperm penetration 339temperature 328uniformity 304vitamin deficiency 340water management 309, 331weight adjustment 307wind chill 332

Bulk density 77

CCage layer fatigue 217Cage systems, breeder 340Calcium: 69

balance 152balance, breeders 333balance, layer 195balance, pullet 152bone composition 218breeders 312eggshell 193layers 184manure moisture 153metabolism, breeder 312prelay 149retention 151solubility 85water intake 153

Canola:meal 37seed 67tannins 104

Carcass composition:broilers 281chemical composition 283components 282ducks 374fat profile 284flaxseed 285turkey 357weights 283

Cardiomyopathy, turkey 352Carotenoids 206Challenge feeding, breeders 321Chelates, mineral 73Choking, breeders 309Cholesterol, copper, yolk 211Cholesterol, egg 210Cinnamamide 97Cobalt 72Coccidiosis, breeders 308Coccidiostats 86Coconut oil 59Collagen 288Compensatory growth 250Competitive exclusion 91, 271Conjugated linoleic acid 60Copper: 72

turkey 355yolk cholesterol 211

Corn: 11gluten meal 40phosphorus 224

Cottonseed 105Cottonseed meal 42Crotalaria 108Crude protein assay 78Cyanides 99Cyclopropenoid fatty acids 105

DDehydration 117DHA – carcass 284DHA – egg composition 208Diet:

dilution, broiler 251energy, broilers 247, 248layer 164prelay 129pullet 126pheasant 386turkey breeder 360turkey 346

Digestion, lysine, bird age 245Ducks: 371

amino acid needs 375breeder 377carcass composition 374diet specifications 372growth rate 373

EEgg:

cholesterol 210composition 203composition, DHA 208deposition, lutein 206minerals 204omega-3 207, 210production, breeder 320production, curve 176production, energy response 175

size: 198manipulation 154maturity 138methionine 198, 200taint 37, 102

vitamins 204, 212, 213weight, breeder 314

Egg, yolk colour 205Eggshell:

calcium 193quality: 193

breeder 332vitamin D3 196

Electrolyte: 265balance 156, 185feed ingredients 187

Energy:balance, breeders 316, 318, 329balance, temperature 263broilers, diet 247, 248efficiency 260intake prediction 171response, egg production 175

Enzymes – additives 92Enzymes – NSP 93EPA – carcass 284Ergot 100Expanders 113Extrusion 113

FFat: 57

assay 78digestion – turkey 351hydrogenation 63iodine titre 84oxidation 61poultry 59quality 84variable AME 64

Fatty acid profiles 58, 62Fatty Liver Syndrome (FLS) 216Feather cover – layers 181Feather meal 52Feathering, broiler 285Feathering, keratin 286

Feed allocation, broiler 240-242broiler breeder 305, 336challenge, breeder 321clean-up time 327efficiency, broiler breeder 337efficiency, broiler 259grills, broiler breeder 335ingredients, electrolytes 187intake:

broiler 239layer 171, 172methionine deficiency 202turkey breeder 364

manufacture 110production 7programs, breeder 315reduction, breeder 326restriction:

ascites 276broiler breeder 304pullets 160

texture 183, 192texture, turkeys 349withdrawal, broiler 255

Feeding programs, broiler 238Fertility, broiler breeder 338Fish meal 54Fish oils 59, 208Flavouring agents 96Flax 207Flaxseed 44Flaxseed, carcass composition 285FLS (Fatty Liver Syndrome) 216Flushing Syndrome, turkey 355Free choice feeding 17

GGame birds 385Geese: 378

amino acid needs 375breeder 382diet specifications 379growth rate 380

Gizzard erosion 57Gizzard erosion, assay 83Glucosinolates 101

Glycine 75Gossypol 42, 105Gossypol, assay 84Groundnut 67Growth promoters 88Growth rate:

ducks 373geese 380 ratites 390

Growth restriction, broiler 248, 251Growth, compensatory 250Growth, standard, turkey 347Guinea fowl 388Gut health – broiler 270

HHalofuginone 287Hatchability 314, 338, 340Heat distress, layers 177, 189Heat stress 261Heat stress, strategies 267Humidity 178Hy-D“ 197, 279Hysteria, layers 214

IIodine 73Iodine, titre, fat 84Ionophores 87Iron 73

KKeratin 286Knockdown, turkey 355

LLactobacilli 91Lathyrism 104Layer:

amino acids 184body fat 183body weight 170bone breakage 219calcium 184calcium, balance 195cannibalism, protein 173

diets 164energy balance 174, 179feather cover 181feathering, protein 173feed intake 171, 172feeding activity 182heat distress 177, 189hysteria 214low energy diet 172molting 220nutrient needs 171, 182phosphorus 185protein 184vitamin D3 185water balance 188

Lectins 32Lighting:

broilers 267, 269maturity 159mortality, broiler 268pullets 147, 157step down 159

Limestone 69Limestone, solubility 195Linoleic acid, conjugated 60Linoleic acid, egg size 201Linolenic acid 44Lipase 94Liver fat, layer 217Low energy layer diets 172Lupins 68Lutein, egg deposition 206Lysine digestion, bird age 245Lysine 75

MMagnesium 73, 214Maintenance needs, broiler 250Management, manure 148Manganese 73, 280Mannanoligosaccharides 89Manure:

Composition: 222broilers 289minerals 293

disposal 225management 148moisture, calcium 153

nitrogen losses 223Mash diets, broilers 255Maturity, egg size 138ME ingredients, ratites 390Meal:

bakery 28blood 68canola 37corn gluten 40cottonseed 42feather 52fish 54meat 47poultry by-product 50soybean 31

Medullary bone 194Metabolizable energy, assay 80Methionine: 75, 191

deficiency, feed intake 202egg size 198, 200needs, layers 203

Milo 19Mineral:

Bioplex“ 293broilers 244, 256eggs 204requirements, turkeys 348

Model prediction, turkey breeder 365Molasses 66, 182Mold inhibitors 90Molting, layers 220Molting, schedule, turkey breeder 365Monensin 86Mortality, broiler lighting 268Mycotoxins 98

NNear Infra Red Analysis (NIRA) 80Necrotic enteritis, broiler 272Nicarbazin 107, 212Nitrofurans 107NSP enzymes 93Nutrient management 148, 222, 290

OOats 65Ochratoxin 99

Odour control 97Odour, yucca 97Oil: 57

coconut 59fish 59, 208, 284palm 59vegetable 59

Oily Bird Syndrome (OBS) 288Oligosaccharides 33Omega-3, carcass 284Omega-3, eggs 207, 210Ostrich 389Ostrich, carcass composition 391Oxidation – fat 61Oystershell 69

PPalm oil 59Particle size 13Peas 68Pellet binders 86Pelleting 112PEMS, turkey 350Pet birds 392Phase feeding 190Pheasant 385Pheasant, diet specification 386Phosphorus: 69

corn, soybeans 224layers 185manure 291

Phytase 94Pigeon 392Pigments 96Poult Early Mortality Syndrome 350Poult, viability, turkey 349Poultry by-product meal 50Poultry fat 59Prebiotics 91Prelay diets 129Prelay, nutrition, pullets 149Premixes 110Prepause nutrition 155Prestarter diets, broiler 244Probiotics 91Production:

egg, curve 176

egg, energy response 175feed 7world 4, 6

Prolapse 215Protein:

dye-binding 83layer 184layer, feathering 173solubility 32, 35, 82

Proximate analysis 78Pullet:

body weight 132, 136, 145calcium balance 152diets 126feed:

intake 136management 137restriction 160

feeding examples 144growth, temperature 142lighting 147, 157maturity 138nutrient intake 141prelay, body weight 153prelay, nutrition 149programs 123requirements 124, 125strain requirements 129vitamins 133, 137water intake 153

QQuail 385Quail, Japanese 388

RRancidity 61Ratites: 389

diet specifications 390growth rate 390ME ingredients 390

Restaurant grease 60Rice: 23

bran 30by-products 29hull assay 85

Roasters 252, 254Rooster feeding 334Rooster, feeder 308, 334Rye 65

SSafflower 68Salmonella 48Salt 71SDS 251, 253Selenium 73Semen, production, breeder 339Serine 281Sesame 68Shell quality 193Shell strength, alkalosis 186Sinapine 37Skeletal disorders: 277

broilers 277tibia 277, 280vitamin D3 279

Skin integrity:broiler 285, 287collagen 287halofuginone 287Soap formation 64Soapstock 60Sodium 69Sodium, bicarbonate 71, 187Sorghum tannins 103Soybean 35Soybean, meal 31Soybean, phosphorus 224Sperm penetration, breeder 339Spiking mortality 281Strain comparison, turkey 348Sudden Death Syndrome 251, 253, 276Sulfonamides 107Sulfur-canola 37

TTallow 57Tannin 102Tannin, assay 84Temperature:

breeder 328broiler growth 264energy balance 263environment, broiler 261feed intake, breeder 330feed intake, broiler 263pullet growth 142turkey 354

Thermal cooking 113Threonine 75Tibial dyschondroplasia 277, 280Toxic seeds 107Toxin, T2 286Toxins, bacterial 106Trace minerals 71Trans fatty acids 65Tricothecenes 99Triticale 66Trypsin inhibitor 32, 45Tryptophan, hysteria 215Tryptophan 75Turkey breeder: 359

Biotin, eggs 364diet specifications 360feed intake 364model prediction 366molting schedule 363, 365

Turkey 345broiler 356carcass composition 357cardiomyopathy 352copper 355diet specifications 346fat digestion 351feed texture 349Flushing Syndrome 355growth standard 347heavy 352knockdown 355mineral requirements 348PEMS 350poult viability 349strain comparison 348temperature 354vitamin requirements 348

UUniformity, breeders 304Urease 32Urease, testing 82Urolithiasis 156

VVanadium 214Vegetable oil 59Vitamin:

broilers 244, 256deficiency, breeder 340eggs 204, 212, 213premixes 110requirements, turkeys 348stability 112, 114Vitamin A 279Vitamin C 185, 287Vitamin D3: 278

CLF 219eggshell quality 196layers 185

Vitamin E 216

WWater: 115, 188

balance: 117layers 188breeder 309, 331

consumption 116intake, calcium effect 153

pH 273pullet, intake 153quality 119restriction 118system, broiler growth 266temperature 118

Weight adjustment, breeder 307Weight, pullet prelay 153Wheat: 15

bran 25by-products 25screenings 26shorts 25

Wind chill, breeders 332World production 4, 6Worming compounds 97

XXanthophyll: 96

yolk colour 205

YYeasts 92Yolk mottling 212Yolk sac 244Yucca, odour 97

ZZearalenone 100Zinc 73, 279Zinc, molting 221

commercial poultry nutritio

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