cobb broiler nutrition guide

COBBBroiler

NutritionGuide

Broiler Nutrition Guide

This new and completely revised Broiler Nutrition Guide has been produced by Dr. RobertTeeter, Professor at Oklahoma State University (OSU) and Dr. Chet Wiernusz, Nutritionistin the Cobb-Vantress World Technical Support Group.

Data for the guide utilizes the extensive research on Cobb birds carried out over the last 20years by Dr. Teeter’s group at OSU and various other research institutes. The formattherefore includes much explanatory material to allow better utilization of the data to matchthe wide range of nutritional and growing strategies with varying environmental conditions forbroiler production worldwide.

Cobb-Vantress wishes to acknowledge this significant cooperation and contribution.

2003

Nutritional Guide

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ContentsPage

1. Broiler Nutrition

INTRODUCTION AND DEFINITION OF OBJECTIVES

2. The Bird Environment and Growth Interface

COMPENSATORY GAIN

3. Interfacing Management, Environment, and Growth

MAINTENANCE

BMR AS A MAINTENANCE COMPONENT

MAINTENANCE ACTIVITY AND WASTE HEAT COST

MAINTENANCE EXACERBATION COSTS

AMBIENT TEMPERATURE & RELATIVE HUMIDITY COST

MAINTENANCE & IMMUNE CHALLENGE COST

TISSUE GAIN

MANAGEMENT

4. Quantifying the Production-Management Value

5. Optimizing the Performance Environment

NONPATHOGENIC STRESS

AIR QUALITY

AMBIENT TEMPERATURE

LIGHTING

FEED FORM

HYGIENE

6. Feed Conversion

7. Growth as Proportion of Mass Versus Yield

8. Nutrient and Energy Recommendations

BASIC NUTRIENT RELATIONSHIPS

ENERGY

REQUIREMENTS

PROTEIN NEEDS

9. Feeding for Yield and Lean Meat Production

OPTIMIZING THE NUTRITIONAL APPROACH

APPARENT CRUDE PROTEIN MAXIMUM

FEEDING REDUCED CRUDE PROTEIN RATIONS

SUMMARY BROILER CRUDE PROTEIN NEED

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Page10. Vitamin and Trace Elements

RECOMMENDED NUTRIENT LEVELS

FREE RANGE CHICKEN PRODUCTION

YELLOW SKINNED BIRDS

11. Feed Manufacture

RAW MATERIAL QUALITY

FEED HYGIENE

FAT QUALITY

PROTEIN QUALITY

MICRO NUTRIENT AND MEDICINAL INCLUSIONS 12. Feed 12.

12. Feed Management

RAW MATERIALS QUALITY AND TESTING

FEED TESTING

SAMPLING

WHOLE WHEAT FEEDING

13. Physiological Stress

HEAT STRESS (HS) GENERAL CONCERNS

HS / THERMOBALANCE

HS / EVAPORATIVE COOLING

HS / HEAT PRODUCTION

HS / MANAGEMENT OPTIONS

HS / WATER MANAGEMENT

HS / OTHER CONSIDERATIONS

HS / HYGIENE

ASCITES

OXYGEN AS A NUTRIENT

ACTIVITY

BASAL METABOLIC RATE

TISSUE ACCRETION AND NEEDS

EXCEEDING MAINTENANCE

DIETARY SODIUM

BIRD ABILITY TO CONSUME OXYGEN

OTHER MEASURES

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1. Broiler Nutrition

Cobb broiler chickens are grown all over the world, under a broad range of agriculturalconditions, to produce numerous products. The agronomic conditions encountered byproducers include a diverse array of environmental, nutritional, mechanical andimmunological combinations. Due to these conditions, unique challenges may arise thatrequire nutritionist, veterinarians and facility managers working together to provide thebest possible production environment. Birds must be provided adequate housing,hygiene, management, and nutrition to achieve their genetic potential and/or optimalprofitability. Despite the environmental challenges faced by some, successful broilerproduction occurs every day throughout the world.

The purpose of this manual is to provide a guide containing the general specifications asto the feeding and manufacture of broiler feeds that are applicable to a diverse array globalsettings faced by producers. The tables of recommended nutrient levels are intended toreflect the nutritional requirements of Cobb broilers under the most common as well assome unique managerial and environmentally challenging production scenarios. The dataherein are directed towards interactivity between nutritional and managerial approaches foroptimizing bird performance. These recommendations are based upon a combination ofour own research, academic publications and practical experience of working withcustomers around the world. We provide this guide as a supplement to your own skills infeed manufacture and broiler management, to work in conjunction with your knowledge andjudgment to attain the best results possible. If the guide raises any questions and/or issuesthat you wish to discuss, please contact Technical Services at Cobb-Vantress, Inc.

Introduction and Definition of Objectives


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2. The Bird Environment & Growth InterfaceA bird’s ability to grow is determined by a combination of genetic, nutritional, environmentaland managerial variables. All aspects of providing broilers essential housing, dietary needsand management should be related to their age influenced growth curve (Figures 1-3). Asthe bird grows and matures, it’s environmental and nutritional needs change in proportion toits age, body size, body composition and tissue accretion rate. The final productivityoutcome will be the summation of the bird’s genetic-environmental interactions as influencedby the managerial and nutritional decisions made. The bird’s general growth andperformance curves improve each year. To optimize these curves management teamsendeavoring to provide the best possible environment, within the constraints of the region,are apt to achieve the best possible results.

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BWT (g)

Figure 1. Live Body Weight vs. Age

Birds Age (days posthatch)

Figure 1. A plot of bird live body weight (BWT) vs. day of age illustrates a rapid growthpotential. Though growth appears slower in the early days, a day-old chick has thepotential to more than double its live body weight after just a few days of life. During thistime bird dependency upon its environment is greater than at any other point in theproduction cycle.

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Figure 2.The shape ofthe growth curvechanges whenviewed versus feedc o n s u m p t i o n .Though age isimportant, manycompanies feedbirds according to apreset amount offeed to establishproduction phases.

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BWT (g)

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Figure 2. Live Weight vs. Feed Consumption

Feed Consumption (g)

Typical Bird Age (days)

Body

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ADG (g)

Figure 3. Average Daily Gain vs. Feed Consumption

Feed Consumption (g)

Figure 3. As the bird matures, its rate of daily gain (ADG) rises to a near maximallevel and plateaus. These values are actual daily gain, not merely ending weight perday of age. Beker & Teeter, OSU


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Figure 4. Growth ResponseFollowing Stress Removal

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Days Posthatching

Body Weight (g)CG

HS

TN

When growth is suppressed due to stress, it is possible for at least a partial recovery underthe right conditions. For example, high ambient temperature can subsequently reduce theperformance of poultry and livestock classes. However, if the stressors are alleviated, thereis potential for compensatory gain or catch-up growth. The birds referenced in Figure 4 wereraised under hot conditions from days 19 to 31. Taking a sub-sample of the birds and placingthem in a thermoneutral environment for days 31-49 enabled them to nearly reach the liveweight of their continually thermoneutral housed counterparts and exceed the performanceof the continually heat stressed group.

Compensatory Gain

Figure 4. Male broilers reared under heat stress conditions have suppressed growth.Moving the birds to an acceptable environment enables them to nearly catch thecontinually thermoneutral housed birds. Qureshi, Daskarin and Teeter, OSU

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3. Interfacing Management, Environment & Growth Many aspects of management classically referred to as animal husbandry, merge withenvironment to influence expression of genetic growth potential. Numerous studies havebeen conducted to identify critical variables. Though the number of variable candidates ishigh, they can be grouped to simplify the application process. A working model relating thepractical aspects is as follows:

ENERGY & NUTRIENTS REQUIRED FOR PERFORMANCE= + MAINTENANCE + TISSUE GAIN + MANAGEMENT

The maintenance (M), tissues gain (TG) and management (MGT) terms are interactive andmultifaceted; however, this does not preclude their quantitative measure or producerinfluence to enhance both the rate and efficiency of production. Terms are written as + toreflect the fact that each is a variable and should be viewed with the potential to enhance orhinder performance. Tissue gain is written after maintenance to reflect that maintenancecomponents will generally be satisfied prior to tissue accretion. As such, an elevation in birdmaintenance needs will divert nutrients away from growth, unless feed intake is alsoenhanced. Management is included as a variable. Relative to the current production statemanagerial decisions can have a positive or negative influence on both M and TG. As such,certain aspects of management are quantifiable components that have influence upon boththe extent and efficiency M and TG. The quantitative values expressed in this writing, as inFigure 5, are written relative to performance in a generally good production environment andmay be viewed as benchmarks of relative value differences between production scenarios.Each term will be the focus of discussion at various segments throughout this manual.

BMRACTIVITY & SUBSTRATE

EFFICIENCYSTRESS

Ambient TemperatureImmune ResponseExcitability

SUBSTRATEEFFICIENCY

ACTIVITY

HOUSINGNUTRITIONHEALTHHUSBANDRY

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A working definition of maintenance is the amount of energy and nutrient required to sustainan animal with no net gain or loss of body tissues. Housed within the maintenance categoryis basal metabolic rate (BMR; energy expended by a broiler at rest and performing nothermal work due to environment), activity energy expended by the bird to attain sustenance,inefficiency of consumed nutrient oxidation for satisfying maintenance needs (waste heatproduction) and stress defined as any challenge necessitating extra energy expenditure tomaintain homeostasis. The maintenance value is the sum of its components and is therebyinfluenced by each contributing factor. On average, in a good production environment,maintenance is about 36% of MEn consumption.

Figure 5. Consumption of MEn (green), under good growing conditions, is partitioned askcal live retained energy (yellow) and kcal energy utilized for maintenance (red). Eachcomponent is multifaceted with potential to enhance or hinder performance. Diversion ofenergy into maintenance reduces energy for gain and increases FCR. Likewise,inefficient dietary substrate conversion into body tissue will increase the FCR ratio.Management will strongly influence maintenance and tissue gain proportions to MEnconsumption. Beker and Teeter, OSU

Maintenance

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Figure 5. Consumed ME Partioned into TissuenME Consumption (kcal)n

ME Consumption (kcal)n

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The building blocks of energy metabolism start with homeostasis of existing tissue. Asdisplayed in Figure 6, basal metabolic rate (BMR) increases linearly with cumulative MEnconsumption and averages about 36% of consumed MEn. Basal metabolic rate (kcal),however, is curvilinear with respect to body mass as heat dissipation is related to surfacearea (Figure 7).

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Figure 6. Maintenance Energy Partioned by ComponentsME Consumption (kcal)n


Figure 6. The kcal needed to satisfy the maintenance fraction (yellow), lying withinoverall kcal of MEn consumption (green), may be partitioned into the major classes ofBMR (black) and kcal expended for activity + waste heat associated with substrateoxidation (red) expended in satisfying maintenance. Maintenance in a good growingenvironment is about 52% BMR and 42% waste heat. This corresponds to 19 and 17 %of overall MEn consumption, respectfully. Beker and Teeter, OSU

BMR as a Maintenance Component

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A portion of the maintenance energy expended is related to the activity required to attainsustenance. Additional energy expenditures in this category include waste heat associatedwith the digestion and substrate metabolism to the needed form. In the current model theyare combined as their fractional estimation is speculative. Energy expenditures here enablethe bird to compete in the production environment. Managerial decisions related to housedesign, feeder and waterer space, distance between feeders and waterers, stocking densityand lighting are among the many variables potentially influencing this component. Acombined estimate of maintenance energy and waste heat costs generated within anadequate production environment, is 17% of MEn consumption.

Various stress categories have the potential to adversely reduce performance. Amongvariables included in this category are factors such as ambient temperature and relativehumidity extremes, immunological response, atmospheric contaminants (ammonia, dust,brooder gases), fear and discomfort. Managerial factors influencing these components ofmaintenance range from overall house design and ventilation to the hygienic environmentand general husbandry.

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Figure 7. BMR Versus Body Weight

BWT (g)

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Figure 7. Energy expended to satisfy bird BMR, increases in a curvilinear fashion withlive bird weight. This energy value may be impacted by numerous factors. Beker andTeeter, OSU

Maintenance Activity and Waste Heat Cost

Maintenance Exacerbation Costs

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From a practical vantage, divergence of ambient temperature (AT) from the zone ofthermoneutrality can significantly elevate maintenance cost. Relative humidity has thepotential to exacerbate the AT impact. Managerial decisions regarding housing design,brooder application and day to day regulation of ventilation equipment will each influence themagnitude of the AT + RH challenge to the chick. Figure 8 illustrates the impact of ambienttemperature deviation from the thermoneutral environment at constant RH on bird energyexpenditure for body weight homeostasis of 5 day-old chicks.

Though the extent of energy expended by immune challenge varies, the data in Table 1indicates that an E. coli challenge diverts energy away from performance. In this study,chicks were limit fed at 5% of their initial 7 day body weight such that variation in feedconsumption with challenge would not mask heat production differences. The E. coli

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Figure 8. Maintenance Heat ProductionDue to Temperature Change

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TCHANGE (C)

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Figure 8. Heat production (HP, kcal/day/kg) of 5 day old chicks, fed at maintenance,increases under conditions of changing ambient temperature. Both decreasing andincreasing ambient temperature from TN (TCHANGE=0) results in elevated heatproduction. Maintaining the environment at TN will improve FCR as less energy isdiverted from growth. In this example, a 5 C temperature change elevated maintenanceenergy expenditure by 30% for the 5 day old chicks. This would divert nearly 11% ofconsumed MEn to nonproductive purposes if feed consumption remained constant.Beker and Teeter, OSU.

Ambient Temperatures & Relative Humidity Cost

Maintenance & Immune Challenge Cost

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challenge resulted in an 8% elevation in heat production and a 7.3% increase in O2consumed. However, analysis over additional feed consumption levels estimated themaintenance MEn elevation at just 2.9%. The disparity between the two measures mayreflect differences in retained tissue composition. Nonetheless, it is clear that immunechallenge has a calorific and oxygen consumption cost.

Table 1. E. coli challenge effects in limit fed chicks.

The energy available for gain may be computed as MEn consumption minus maintenanceenergy cost as displayed in Figure 5. This energy gain must support all activities andmetabolic needs exceeding maintenance for tissue accretion. The result, as displayed inFigure 9, is the lean tissue + water and lipid accrued. Note that once water is removed fromlean tissue that the actual amount of protein gain is markedly lowered. This is why thefractional gain for protein and fat has a significant impact upon feed conversion. On average,for a corn-soybean based ration, approximately 66% of MEn consumption is available fordirect deposition in lean and lipid tissues.

Though the energy and nutrient content of tissue may be directly measured, the efficiencyof nutrient conversion into tissue varies with the type of tissue being synthesized and thesubstrate being employed. For example, energetic efficiency of converting digestible protein,carbohydrate and lipid into de novo lipid is 45, 78 and 84%, respectively. Managerialdecisions regarding ration composition influence overall efficiency of substrate conversion totissue, as do the managerial decisions impacting activity exceeding maintenance. Tissuegain is the purpose of poultry production; however, it is the component occurring virtually bydefault after maintenance activity and waste metabolic heat have been removed.

Managerial influences, under the proposed model, strongly impact both the M and TGcategories. As shown in Figure 5, maintenance energy expenditure accounts for approximately36% of MEn consumption under good growing conditions. Data displayed in Figure 5 alsosuggests that this amount may increase by 30% under conditions of AT stress to divert asmuch as 10% energy from TG unless feed intake is elevated. However, if managerial inputthrough enhanced ventilation and/or evaporative cooling reduces the elevated AT rise then theloss will be partially ameliorated. Ambient temperature is merely one aspect of themanagerial and maintenance interaction that impacts TG. Other managerial influencesmay range from such simple factors as stocking density and feeder space to minimizingwaste heat production via control over dietary nutrient balance and/or lighting program.

Tissue Gain

Treatment

Control

E. coli

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-19

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2.97b

3.17a79.9

Gain (g) FeedConsumption (g)

O2 Cons(L/h) 1

Heat Productionkcal/h

1Liters/hourBeker, Daskarin and Teeter, OSU

Management

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Figure 9. Live Body Weight Partitioned intoLean, Protein and Lipid Tissues vs. MEn Consumption

(in thousands)


Figure 9. Approximately 66% of MEn consumption is available for live weight accretion(black, g). Within the live mass, energy deposition occurs as lean + water (yellow),protein (green) and lipid (red) components. Metabolizable energy not utilized foraccretion is largely used for maintenance and activity. Beker and Teeter, OSU

Various lighting programs have been applied to laying and breeding poultry to optimize egg production. More recently such programs have also been applied to broiler rearing.Light availability in duration and intensity have been observed to impact the efficiency ofproduction with reports of improved FCR, body weight gain and the lowered incidence ofmetabolic disorders. The underlying mode of action may be reduced energy expenditurefor activity. When the lighting is reduced, birds are almost immediately observed toreduce their activity, consume less oxygen and produce less heat. Conversely, whenbirds under a state of BMR (usually measured in the dark), are exposed to light theiroxygen consumption rises by nearly 3% when feed is not present. The data presented inFigure 10 displays the reduced heat production observed for a flock on a program of 12hours light followed by 12 hours of dark. These differences were entirely eliminated whena program of 23 hours of light with 1 hour of dark was utilized.

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Figure 10. LighteningProgram Affects onOxygen Consumptionfor broilers in thegrowing phase

Figure 10. Lighting programshave the potential to conserveenergy by reducing activityexpenditures. However, note thatlighting programs differ markedlyin their impact upon the bird’soxygen consumption (liters/hour).The plot at the top is for birdsexposed to 23 hours of light perday and 1 hour of dark. Thelighting program at the bottom isfor birds experiencing 12consecutive hours of lightfollowed by 12 hours of dark.Birds managed with 12 hours ofdarkness had the same final liveweight and significantly improvedFCR. Lighting programinteraction with environment andstocking density should beanticipated as time must beallowed for all birds toadequately consume feed. Bekerand Teeter, OSU

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4. Quantifying the Production-Management ValueChief among management decisions is the intent of enhancing profitability. This can be aquite challenging process, as performance improvements must be transferred into aneconomic picture. In most companies, final bird performance is commonly expressed as alive weight and feed conversion. Managerial decisions, in turn, must be quantified as to theirimpact upon live body weight and feed conversion. If the live weight and/or feed conversionconsequence of a stressor is known; and the management cost of solving the issue can bequantified, this value may be compared with the projected nutritional cost for eliciting thesame production change. The relationship, displayed in figure 11, enables the live bodyweight-feed conversion variable to also be expressed as a dietary caloric density responsethroughout the growth curve. The basis for this relationship is that both body weight gain andfeed conversion are responsive to caloric density (constant calorie/protein ratio). Theserelationships allow field data and management decisions to be transformed into an interactivepicture of environment, bird performance, management and nutritional cost. In this mannerdecisions impacting production cost and output benefits may be judged as nutritionalequivalence. As such, calorific value may be applied to managerial decisions regardinglighting programs, feed form, ventilation and hygiene among others. Thus providing theopportunity to make improvements by multiple methodologies, or enabling the relaxation ofnutritional specifications due to improved management.

The mathematical equation describing the relationship illustrated in Figure 11 is shown below. This may be applied as an aid to assign relative nutritional values to managerial decisions impacting live body weight and FCR. Note data applicable to 500 g through 2,800 grams live bird weight.

Cumulative feed conversion ratioCD1 = 7017.65491 + (1.3773 _ BWT) – (0.00009006 _ BWT2) + ((5.247565 _ 10-8) _BWT3) – (5200.87308 _ CFCR) + (1566.92696 _ CFCR2) – (0.75909 _ (BWT _CFCR))

[P < .0001; R2 = .9391]

Daily feed conversion ratio3CD = 4180.202 + (1.667 _ BWT) – (0.00029675 _ BWT2) + ((1.359715 _ 10-7) _BWT3) – (1408.89875 _ DFCR) + (272.21113 _ DFCR2) – (0.37068 _ (BWT _ DFCR))

[P < .0001; R2 = .8834]

1CD=caloric density (kcal/kg2BWT=body weight (g)3Graphical representation not shown

McKinney and Teeter, OSU

The mathematical equation describing the relationship illustrated in Figure 11 is shownbelow. This may be applied as an aid to assign relative nutritional values to managerialdecisions impacting live body weight and FCR. Note data applicable to 500 g through2,800 grams live bird weight.

By inserting values into the equation with and without the managerial decision, one mayestimate the “nutritional change” that would be benefited by the response as thedifference between the two values.

Cumulative feed conversion ratioCD1 = 7017.65491 + (1.3773*BWT) – (9.006*10-5*BWT2) + (5.247565*10-8*BWT3) –(5200.87308*CFCR) + (1566.92696*CFCR2) – (0.75909*(BWT*CFCR))

[P < .0001; R2 = 0.9391]

Daily feed conversion ratio3

CD = 4180.202 + (1.667*BWT) – (2.9675*10-4*BWT2) + (1.359715*10-7*BWT3) –(1408.89875*DFCR) + (272.21113*DFCR2) – (0.37068*(BWT*DFCR))

[P < .0001; R2 = 0.8834]

1CD=caloric density (kcal MEn/kg diet)2BWT=body weight (g)3Graphical representation not shown

McKinney and Teeter, OSU

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The Figure 11 equation may also be rearranged to predict FCR for a field production scenariounder a presumed “near ideal” standardized environment. This will provide an FCR indicatorof combined differences existing between the field feed evaluation matrix and the generalizedstress consequence encountered, versus the standardized production environment.

FCR = 24.152 + 2.3700*10-4*BWT -7.65*10-8*BWT2 + 2.91*10-11*BWT3 -0.014*CD + 2.26* 10-6*CD2

Generally the predicted standardized FCR value will be lower than the observed field estimate.For example, under standardized conditions a cumulative FCR of 1.61 was obtained for broilersreared to 2.36 kg on a diet with 3250 kcal of MEn/kg ration. Conversely, under an applied fieldapplication with the same caloric density and different environment, broilers were observed tohave an FCR of 1.84. If the formulization matrixes are similar then, from a nutritional vantage,the FCR discrepancy reflects environmental differences. By employing the caloric densityequation from figure 11 the costs may be further quantified as caloric value. In this case aneffective dietary caloric density difference of 362 kcal MEn/kg exists. Further examination mayassist the producer by identifying areas whereby managerial input may enhance the productionenvironment and pay dividends. By examining performance measures in this manner, decisionsimpacting production costs and output benefit, may be evaluated as a nutritional equivalence.

Figure 11. Dietary caloric density (kcal MEn/kg diet), under defined conditions, may beexpressed as the combination of body weight (g) and feed conversion, this may beutilized to build a data base of seasonal, managerial, feed milling and nutritionalinfluences for decision making. McKinney and Teeter, OSU

Figure 11. The Body Weight, FCR and Caloric Density Relationship

FCR

BodyWeight (g)

Caloric Density(kcal ME n/kg diet)


Air Quality

Ambient Temperature

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5. Optimizing the Performance EnvironmentProviding satisfactory environmental conditions will enable the broiler to achieve the bestpossible performance. Poultry performance has the potential to be maximized when theoverall production environment is also optimized. Stress consequences can begin in thehatchery and/or hatchery to farm transport with consequences that far exceed the originalstress duration period. Growth, feed conversion, disease susceptibility and processing plantcondemnations may all be compromised because of problems stemming from the hatcheryand/or subsequent transport to rearing facilities. Personnel must work at every phase of birdhandling and rearing to minimize perturbations that negatively impact bird health and wellbeing. Only in this manner can the genetic potential of today’s poultry be approached.

A nonpathogenic stressor is defined as any environmentally based insult necessitatingphysiological response to sustain homeostasis. Such stresses may include ambienttemperature, the gaseous atmosphere (ammonia, relative humidity, oxygen at a minimum),feed and water availability, noise, lighting and interactions of these with other variables.

Air naturally contains nitrogen (78.1%), oxygen (20.9%), argon (0.93%), carbon dioxide(0.03%) and various trace elements (0.01%) at sea level. However, in the normal productionprocesses concentrations of these components vary considerably. Though poultry have theability to contend with a broad range of gaseous conditions they are particularly susceptibleto low oxygen content, by-products of heating systems and gaseous production productsoriginating from the litter. As altitude increases oxygen becomes a limiting nutrient for alllivestock classes. Birds exposed to poor air quality can exhibit reduced performance.

A study exposed day-old chicks to various atmospheric oxygen concentrations (8.60, 12.60,16.60, 20.60%) for 8 hours simulating inappropriate transport stress. Study results indicatedthat short term oxygen deprivation impacts both subsequent growth rate and ascites risk.Mean growth rate declined incrementally as atmospheric oxygen declined. Contrasting thetwo lowest oxygen levels with the two highest resulted in reduced (P=.03) 42 day growthrates (by 7 points). Ascites incidence significantly rose (P=.055) from 2.48 to 4.5% at 42days of age.

Since homeothermy is only achieved after chicks generally reach a week of age, stressconsequences for the first week differ from later periods. Any time ambient temperatureexceeds the birds TN zone; heat production, and consequently oxygen consumption, areelevated. This occurs because the bird must expend energy to generate heat, if cold, or todissipate heat if too hot. Young broilers are most susceptible to cold stress as they have ahigher surface area per unit weight. Increased susceptibility to heat stress occurs in olderbirds because the surface area available for heat dissipation is reduced. The projectedthermoneutral midpoint temperature, for full fed broilers, declines from a 32.2 C at hatchingto approximately 22 C for a 2.5 Kg bird. These numbers are influenced by a variety of factorsincluding body composition, altitude, ventilation rate (air velocity), ration consumption andcomposition as well as relative humidity.

Nonpathogenic Stress

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Any time the bird is exposed to ambient temperature deviations from the thermoneutralzone, management and housing alterations should be considered. Failure to do so willforce the bird to adjust, and such adjustments are usually at the expense of feedconversion and/or growth rate. Figure 13 illustrates the caloric cost on bird maintenanceneeds that can be associated with ambient temperature deviations from the birds zone ofthermoneutrality.

Figure 12. Estimated thermoneutral ambient temperatures (TN) for birds to 2.5 kgbody weight housed at 40-70% relative humidity under minimized stress conditions.

TN (C) = 31.896 - (4.625*BWT) Beker and Teeter, OSU

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Figure 12. Projected Zone of Thermoneutralityfor broilers to 2.25 kg. mass

Body Weight (kg)

TN Temperature

Linear (TN Temperature)

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Feed Form

Lighting programs have been reported to impact growth rate, feed conversion and ascitessusceptibility. When considering a lighting program it is important to provide ample time,during lighting periods, to enable the flock to react. For example, changing lighting inincrements that are too short would not allow enough time for all birds to consume feed andwater. Lighting impacts feed efficiency, when sufficient time is allowed for adequate feedconsumption, primarily by reducing maintenance energy needs.

Broiler rations must be fortified with the correct amounts of energy and nutrients. Thephysical form of the diet, however, must also be considered and should not be viewed disjointfrom nutrient specifications as both impact ration value. Diet physical form can vary frommash to pelleted or extruded forms. In some cases these products may be mixed withvarious amounts of whole grain just prior to feeding. Beneficial aspects of further processingrations include both managerial and bird benefits. On the management side feed handlingcharacteristics are improved. On the bird side, improvements in growth rate and/or feedconversion have been noted. Though many companies further process their feeds, what isactually delivered to the bird may well be a varying mixture of fines, pellets and/or crumbles.Only the physical form of the ration placed in front of the bird for consumption will have theopportunity to impact performance. A decline in the integrity of the processed formproportion almost always occurs in the handling-transport-storage-delivery processes.

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Figure 13.

Temperature Elevation Temperature Reduction

Age (Days) Age (Days)

Dai

ly H

P (

kcal

) Total Fed HP @ TNMaintentance HP @ TNMaintentance HP @ TN + 2.5CMaintentance HP @ TN + 5C

Total Fed HP @ TNMaintentance HP @ TNMaintentance HP @ TN - 2.5CMaintentance HP @ TN - 5C

Figure 13. Caloric expenditure of male-full fed-broilers and birds maintained at bodyweight homeostasis while housed at their projected TN midpoint, note that exposingbirds to either a 2.5 and 5 C AT change, elevates maintenance energy cost, divertingenergy away from production. Beker and Teeter OSU.

Lighting


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If pellet or crumble durability is low, then the amount of fines increases and the furtherprocessing value decreases. Figure 14 displays the potential impact of pellet quality on theenergy sparing value as caloric density. This relationship may be applied to assign value tofurther processing itself and / or the overall consequence of feed handling. In those situationswhereby a producer may desire to slow growth by reducing dietary caloric density of the diet,physical form of the ration offered should also be considered as an option.

Independent of pathological disease, the bird is impacted by its hygienic environment.Though it would be simpler to view broilers as independently functioning entities, theycompete with numerous microorganisms found within the body and immediate environment.Specific microbial affects may be either beneficial (vitamin synthesis, toxin destruction etc.)or detrimental (toxin production, infection, nutrient destruction, immunological based energywasting). Birds reared in germ free environments have been reported to have as much asa 15% overall elevation of energetic efficiency. Reducing the birds’ microbial load has thepotential to enhance growth rate, feed conversion, dressing percentage and elevate breastyield as well as reduce consequence any physiologic stress where improved energeticefficiency is a potential therapeutic (heat stress, ascites). Under practical conditions, caloricvalue of nonpathogenic hygiene management ranges from 50 to 200 Kcal/kg diet.

150

225

75

00 20 40 60 80 100

Diet Pellet Percentage

En

erg

y S

par

ing

Kca

l ME

n P

er K

g D

iet1

Figure 14. Physical form ofrations presented to broilershas an impact upon thediet’s calorific value. Energysparing responses to 20%pellets appear to be feedconsumption mediated, whileresponses between 60-80%appear to be activity related.The equation may be appliedto estimate calorific value ofprocessing or consequenceof handling mediated feedform degradation.

1 PQ caloric value (kcal MEn/kg ration) = 1480.202 + (1.16673*BWT) - (2.9675 x 10-4

*BWT2) + (1.359715*10 -7*BWT3) - (1408.89875*DFCR) + (272.21113*DFCR2) -(0.37068*BWT*DFCR); R2 = 0.88, P < .01; Mckinney and Teeter, OSU

BWT = body weight (g)DCFR = daily feed conversion ratio

Hygiene


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6. Feed ConversionFeed conversion, the compilation of feed consumption divided by live bird weight, is animportant aspect of overall performance. For this calculation the initial weight of the chick isusually ignored, while more precise measures would subtract that mass and report feed perunit gain (Figure 15). Nonetheless, the feed to body weight ratio is influenced by a plethoraof interacting components. Major determinants of FCR include bird age-body size,environment, appetite, management and ration form-composition among others (Figure 16).As birds age their feed conversion ratio increases due to increasing maintenance cost, andthe increasing proportion of gain accrued as lipid. Therefore, younger birds will have a betterFCR than older, and the FCR for “starter, grower and finisher” periods will be significantlyinfluenced by bird ages. Since FCR is a weight ratio, unadjusted for water content, birdssynthesizing lean will have a better FCR, as lean mass is 75.4% water and lipid mass is just9%. Birds accruing lipid, however, will still have a positive FCR as it represents massaccretion for a feed input. Important aspects of ration composition relate to the efficiency ofsubstrate utilization for tissue synthesis and the composition of tissues being synthesized.Though feed and energetic efficiency are correlated, the fact that water and mass, in lieu ofenergy, are included in the determinations can make the values less meaningful.


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204060

100120140160180200220

80

0 10

Daily Feed

Day

Figure 16. Daily Feed Consumption Versus Day of Age

20 30 40 50 60

Consumption (g)

Figure 16. Daily feed consumption increases with age. Optimization of production-management will help to maximize conversion of consumed feed into body mass. Oftenbirds with the best FCR consume the same amount of feed as the poor converters,however, they gain more body weight. Beker and Teeter, OSU

3.02.82.62.42.22.01.81.61.41.21.0

0 10000 20000

FCR

Figure 15. Cumulative and DailyFCR Versus MEn Consumption


Figure 15.The relationship betweenfeed conversion, expressedon a daily basis (yellow)and on a cumulativebasis (green) versusenergy consumption.Note as the bird maturesthat the amount of feedrequired to achieve aunit of gain increasesmarkedly for the dailyvalue and in a bufferedfashion for thecumulative value. Thesevalues are interactivelyimpacted by managerialand ration compositiondecisions. Beker andTeeter, OSU.


7. Growth as Proportion of Mass Versus YieldThe concept of growth and yield may be examined in several ways. Growth as grams ofmass is straight forward and easy to measure; however, yield is often viewed as apercentage and can be misleading. When tissue growth is viewed as mass, output is astraight forward and quantitative measure that serves well to guide the production process.When yield is the criteria of growth and viewed as a percentage of overall products,misconceptions may arise. For example, a nutritional change intended to manipulate aspecific output may only alter the mass of another component. As a result, this could havethe appearance of impacting the intended result in a manner that did not increase massoutput. Consequence here would be unrealized tissue output with a potentially needlessdietary cost elevation. This is illustrated by feeding elevated concentrations of dietary proteinto enhance breast or lean yield. Increasing protein consumption may indeed increase theproportion of breast meat and lean tissue in the carcass. This elevation may however be dueto the fact that the efficiency of lipogenesis, via dietary protein, is less than that forcarbohydrate or lipid. Consequently, the enhanced percentage of breast and/or lean mayonly reflect a reduced carcass fat mass. If that is the desired result, it is usually more costeffective to simply lower a ration’s caloric density. Feeding elevated dietary crude proteinlevels, also has the impact of reducing metabolic efficiency. And, under stressed conditions,feeding excess dietary protein has the potential to elevate the incidence of metabolicdisease. Yield is best viewed as mass, especially when coupled with the efficiency ofmetabolizable energy use for overall gain.

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Basic Nutrient Relationships

8. Nutrient and Energy RecommendationsSince feed expenditures frequently comprise the largest component of bird production cost,decisions regarding ration composition have a significant impact upon profitability. However,ration composition is just one of the many interactive components that must be met forefficient production. Any management, housing, environmental or hygienic inadequacy canreduce bird performance. Indeed, interactivity between nutrition and the aforementionedvariables is illustrated by the caloric values placed upon feed form, lighting, ambienttemperature and hygiene among others. Managerial decisions that impact bird energyexpenditure have the impact of effectively altering dietary calorie/nutrient ratio. The astutepoultry grower will combine managerial, environmental and dietary interactivity to producethe most efficient bird possible. The principle goal of dietary guidelines is to provideacceptable combinations of energy + dispensable nutrients along with the complete array ofindispensable nutrients enabling the broiler to reach its genetic potential.

The overall broiler production objective is the creation of lean tissue with acceptable lipidcontent. Production efficiency is the balance of appetite driven feed inputs with wastageoutputs. Portions of the wastage points, such as maintenance energy expenditures underthermoneutral conditions, are obligatory. In contrast, other portions of energy expenditureare determined by the birds’ environment and producer managerial decisions. Aside fromexpenditures for maintenance and activity, the cost of lean tissue accretion is relativelyconstant for a reasonably fed and housed bird. Variations in production efficiencymeasures, excluding low feedstuff quality and obligatory cost, are usually associated withmaintenance variables and rations with divergent calorie/protein ratio via their impact uponenergy metabolism. The role of the nutritionist is to examine such interactions andprescribe feedstuff-nutrient combinations to optimize the performance characteristicschosen by the company.

The performance characteristics chosen for optimization vary considerably amongcompanies, and as discussed in the following sections, have a marked impact upon rationformulization goals. Performance objectives can range from body weight and feedconversion, to breast yield or even survivability under stressed conditions. Once these arechosen then the measures for success may be created. The best data source for nutritionalmodifications is feedback from the overall production system. This feedback should includenot only live performance and survivability data, but also accurate carcass compositionalinformation from the processing plant. Combined with the stated company objectives, thisinformation guides the formulization decisions to make the best diets possible.

Bird energy needs may be expressed in numerous ways. Historically, the metabolizableenergy (ME) system has been the most widely developed and applied. As a result, birdnutrient requirements are usually qualified as pertaining to a diet of stated MEn or in aratio to MEn. As the ME system does not account for heat losses, any variability in heatproduction will result in varying nutrient/energy ratios at the cellular level. Ideally, acoupling of bird energy expenditure with indispensable requirement would guide theformulization process. However, with the current system nutritionist are forced to rely onproduction system feedback as their benchmark for environmental and managerial

Energy


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influences upon ration utilization. Calorific values of aforementioned managerial-environmental influences should help to fine tune the nutritional-managerial interface.

Aside from direct energy expenditures, nutrients in excess of that utilized for lean accretionwill be converted to lipid. Substrate use for lipid synthesis varies and can have a directimpact upon feed conversion, carcass composition, dressing percentage and apparentbreast yield. For example, estimates suggest that it will take 3.1 g dietary protein, 2.3 gdietary carbohydrate and 1.2 g dietary lipid to synthesize just 1 gram of body fat. This makesthe pattern of dispensable nutrients used as energy sources have a significant influenceupon final carcass composition and feed conversion.

Though nutrient requirements are traditionally expressed in phases, this is more a matter ofmilling and feed handling constraints than of truly segmented nutrient needs. For example,the protein requirement for a ration containing 3,200 kcal MEn/kg, is 23% for a 1-21 day oldchick, 20% for 21-42 days and 18% for 42 to 56 days (NRC, 1994). Bird nutrient needs donot change abruptly on these specified days, but rather they change continuously over time.Therefore, the time frame can have a significant influence on the estimated requirement. Asmany companies feed at periods differing from classical recommendations, alternativeexpressions of requirements are needed. However, cautions are warranted: if producersinitially feed exactly at the bird’s requirement, before long they are feeding above the bird’sneed and expensive nutrients are wasted. Conversely, if birds are fed below their nutrientrequirement till they “grow into” the ration, then rations are deficient for a period of time(Figure 17) and performance can wane. In either case, neither feed nor energetic efficiencyis optimized.

Requirements

Figure 17.

Broiler Age

Nu

trie

nt

Inta

ke

Underfeeding

Overfeeding

Theoretical Nutrient

Starter Grower Finisher

Nutrient Intake vs. Broiler Age Figure 17. The impact ofphase feeding broilerspotentially results inperiods of either over orunder feeding growthdetermining (rate limiting)nutrients (Corzo andTeeter, OSU).

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Considerable information exists regarding protein requirements. Data suggests that oncethe dietary protein requirement-amino acid needs are reached, that minimal additionalenhancement in carcass protein occurs with further fortification. In addition, it is observedthat a reduction in dietary protein (within reason and with indispensable amino acidsmaintained) has minimal impact on overall growth and final carcass protein yield. Exceptionsto these general tendencies include the subtle enhancement of breast yield with fortificationof some indispensable amino acids and the enhancement of bird appetite and with subtledietary protein reduction. Therein lies a portion of the art of nutrition, with the greaterappetite one may attain a larger bird with a subtle protein deficiency. Conversely, fortificationof some amino acids in a ration that has satisfied the “protein requirement” may result ingreater yield of desired parts. For companies simply monitoring live body weight, themotivation to feed reduced protein diets is clear. However, specific amino acid fortificationwithin an adequate protein level may potentially result in better breast yield. Indeed, thecompany feeding the reduced protein level, depending upon feed intake, may get as muchbreast (on gram basis), but at a reduced percentage as the birds contain more carcass fat.

Protein Needs

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9. Feeding For Yield and Lean Meat ProductionWithin a satisfactory production environment, carcass and lean-breast mass may beenhanced via nutrition. To effectively utilize nutrition to enhance production, it isadvantageous to simultaneously lower the diversion of feed nutrients to body homeostasis-immunological response via housing and management. Reducing a diversion of feednutrients can have the same impact on carcass composition as diet modification.Conversely, failure in this area can also negate expensive dietary changes. Once asatisfactory environment for the intended growth is prepared, then nutrient specificationsmay be optimally modified to impact carcass yield and lean meat proportions. Making subtlechanges in the ratios of various essential amino acids to energy and dietary crude proteinlevels can indeed impact final carcass characteristics and proportional masses. It isbeneficial to attain data from the processing plant such that the overall picture (carcass massand proportions) may be continually monitored and seasonal strategies evolved. In thismanner one can avoid the illusion of elevated lean proportions simply at the expense ofmetabolic efficiency and carcass fat.

For optimization of lean mass, all indispensable as well dispensable nutrients plus energymust be at the accretion location simultaneously. Any deficiency of nutrients required in thesynthesis-maintenance of lean tissues will result in a reduced final lean mass. This alsodictates a reduced proportion of lean mass if lipid synthesis is maintained or elevated.Fortunately, the combined ration-bird metabolic characteristic does not necessitate that wecontinuously monitor all 40+ nutrients. In most situations it is sufficient to identify the 3-4 ratelimiting nutrients in each nutrient category for monitoring. Insuring that the rate limitingnutrients are contained along with sufficient energy supply will create the opportunity forefficient lean accretion.

Formulating diets to supply specified levels of the most common rate limiting amino acids(lysine, methionine, threonine, arginine, tryptophan), within a fixed level of dietary crudeprotein, is usually sufficient to maintain generalized lean accretion. The critical amino acidsare determined by feed ingredient composition and amino acid bioavailability. In typicalgrain-soybean based diets the bird may, assuming adequacy of the housing environment,deposit lean tissue in response to increasing the levels of lysine. Others have suggestedthat an increase in the levels of sulphur amino acids (methionine and cystine) is correlatedto a reduction in fat deposition. However, these are not disjoint processes and should not beviewed as such. In order to obtain maximum meat yield with minimum carcass fat levels bothlysine and sulphur amino acid levels must be simultaneously optimized. Other essentialamino acids, along with the substrates utilized for lipogenesis (protein, lipid, carbohydrate,dispensable amino acid) also play a role in this highly interactive area. It is important toremember that, although fat can be regarded as a waste product, a minimum level of carcassfat is required to prevent the meat becoming dry and tasteless when cooked.

Phase feeding conventional rations typically results in under and over consumption ofnutrients during the early and latter periods of the phase interval, respectively. Ideally,a more refined working model would guide the formulization processes. It is possible;using qualitative on-farm feed blending techniques, to match the ration composition withthe birds’ daily nutrient requirements. Though such blending is not generally available,

Optimizing the Nutritional Approach


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a working model is desirable for company analysis of feeding intervals. Today,considerable variation exists between company feeding interval variation and thecomposition of interval rations.

Description of daily nutrient and energy needs, as defined by the environment-managerialinterface, is mathematically possible. These can be used in turn coupled with bird productiondata to best evolve ration formulization standards. As far as protein nutrition is concerned,more is not always better, and less is not always worse. Nutritional balance in relationshipto daily need and dietary energy is the objective. The following equations and tables provideexamples of estimates, under a low stress environment, for daily energy, crude protein andlysine allowances to support lean tissue accretion of the Cobb broiler.

Maximum may be an incorrect use of the term, as successful boiler production can occurwith greater amounts of protein consumption than indicated here. However, research hasfound through experimenting with various ration types a set of daily quantitative intakevalues, beyond which further consumption does not generally elevate protein accretion. Inthese studies levels of critical amino acids were fixed with the only variable being crudeprotein primarily in the form of dispensable amino acids. Dietary crude protein consumption,independent of critical indispensable amino acids, is listed in Table 2 and predicted byequations 1-8.

EQUATION 1: Predictive equation for cumulative protein intake based upon day of age.Limitations of this approach are failure of the production environment to produce a growthcurve match to the one utilized. In most feeding situations this would result in anoverestimation of protein need.Highest crude protein need with satisfactory indispensable amino acids = 1.97747 + 1.60348*day + 0.55084*day2 - 2.51236*10-3*day3;

As an example, the total protein consumption for 15 and 35 day old birdswould be about 141 and 625 grams, respectively.

One may also utilize this equation to estimate the quantity of protein needed for anyproduction interval as follows: Where B (dayb) is the day farthest along the growth curveand A (daya) is the earliest day. Similar to equation 1, accuracy here is determined by theproduction growth curve matching the standard. With this assumption, the approachenables determination of maximal protein need with respect to the desired time interval(Equation 2).

EQUATION 2: Estimation of protein need for a specified time interval.Initial day = IntdayaFinal day = IntdaybProtein needed for the interval= (1.97747 + 1.60348*Intdayb + 0.55084*Intdayb2 - 2.51236*10-3*Intdayb3

-(1.97747 + 1.60348*Intdaya + 0.55084*Intdaya2 - 2.51236*10-3*Intdayb3

As an example, the total protein consumption for birds 15 and 35 days of age would beabout 484 grams.

Apparent Crude Protein Maximum


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EQUATION 3: Alternatively, bird protein need may also be related to body weight.The advantage here is that the necessity for the production growth curve to match the standard is reduced.

Prediction of cumulative protein consumption need (g) based on body weight (g).

= -15.8598 + 0.28746*BWT + 3.9642*10-5*BWT2 - 1.736*10-9*BWT3

As an example, the total protein consumed for birds weighing between 508 or 814 grams would be 140 or 626 grams, respectively.

EQUATION 4: Alternatively, bird protein need may also be determined for a body weight differential. In the following example, the first body weight is bwta and the second bwtb.Similar to the cumulative equation above, the advantage for the technique is the reduced necessity for the production and standard growth curves to match.Dbwta = Initial body weight (g)Dbwtb = Final body weight (g)Protein consumption for body weight interval.= (-15.8598 + 0.28746*Dbwtb + 3.9642*10-5*Dbwtb2 - 1.736*10-9*Dbwtb3)-(-15.8598 + 0.28746*Dbwta + 3.9642*10-5*Dbwtb2 - 1.736*10-9*Dbwta3)

As an example, the total protein consumed for birds weighing between 508 and 1814 grams would be 486 grams.

Excess broiler protein consumption serves essentially no benefit. The added nutrient mayelevate ration cost, and it will reduce metabolic efficiency. The average conversion efficiencyof amino acid energy into lipid is just 45% (including cost of nitrogen metabolism), while theefficiency for absorbed carbohydrate and lipid is estimated at 78% and 84%, respectfully. Asdiscussed, any elevation in carcass yield by feeding excessive protein may well be viareduced energetic efficiency and hence lowered carcass fat. Consequently, the most costeffective ration in terms of MEn calories consumed will be the one with sufficient, notexcessive protein content. Studies have been conducted to examine the extent to whichcrude protein may be reduced. In these studies levels of critical amino acids were fixed withthe primary variable being reduced crude protein mostly in the form of dispensable aminoacids. Reduced dietary crude protein consumption, independent of critical indispensableamino acids, is also listed in Table 2 and predicted by equation 5-6.

EQUATION 5: Predictive equation for cumulative protein intake based upon day of age.Limitations of this approach are failure of the production environment to produce a growthcurve match to the one utilized. In most feeding situations this would result in anoverestimation of protein need.Reduced crude protein need with satisfactory indispensable amino acids = 0.40025 + (1.18418*day) + (0.50083*day2) - (1.955947*10-3*day3)As an example, the total protein consumption for 15 or 35 day old birds would be about124 and 572 grams, respectively.

Feeding Reduced Crude Protein Rations

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Ultimately, there are an assortment of factors that will influence decisions regarding proteinlevels that are fed. Paramount among these is the optimization of conversion efficiency andproduction of a finished product that is of uniform quality. Under practical feeding situations,the need for dispensable and some indispensable amino acids may be reduced as long asthe specified critical 4 amino acids are maintained. This occurs without apparent loss of leanaccretion potential. Requirement estimates are provided in Table 2.

One may also utilize this equation to estimate the quantity of protein needed for anyproduction interval as follows: Where B (dayb) is the day farthest along the growth curveand A (daya) is the earliest day. Similar to equation 5, accuracy is determined by theproduction growth curve matching the standard. With this assumption, the approach enablesdetermination of maximal protein need with respect to the desired time interval (Equation 6).

EQUATION 6: Reduced protein need for a specified time interval.Initial day = IntdayaFinal day = IntdaybProtein needed for the interval= (0.40025 + (1.18418*Intdayb) + (0.50083*Intdayb2) - (1.955947*10-3*Intdayb3)) - (0.40025 + (1.18418*Intdaya) + (0.50083*Intdaya2) - (1.955947*10-3*Intdaya3))

As an example, the total protein consumed for birds between 15 and 35 days of age wouldbe about 447 grams.

EQUATION 7: Alternatively, reduced bird protein need may also be related to body weight.The advantage here is that the necessity for the production growth curve to match thestandard is reduced.Reduced cumulative protein consumption need based on body weight (g)= -16.73268 + 0.25588*BWT + 4.001*10-5*BWT2 -1.21809*10-9*BWT3

As an example, the total protein consumed for birds weighing 508 or 814 grams would beabout 123 or 572 grams, respectively.

EQUATION 8: Alternatively, reduced bird protein need may also be determined for a bodyweight differential. In the following example, the first body weight is bwta and the second bwtb.Similar to the cumulative equation above, the advantage for the technique is the reducednecessity for the production and standard growth curves to match.Dbwta = Initial body weight (g)Dbwtb = Final body weight (g)Protein consumption for body weight interval =(-16.73268 + 0.25588*Dbwtb + 4.001*10-5*Dbwtb2 -1.21809*10-9*Dbwtb3

-(-16.73268 + 0.25588*Dbwta + 4.001*10-5*Dbwta2 -1.21809*10-9*Dbwta3)As an example, the total protein consumed for birds weighing between 508 and 1814grams would be about 449 grams.

Summary Broiler Protein Need

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Companies must use sound decision making in the utilization of recommended dietaryguidelines, as ultimately the optimal ration form will be determined by the environment-managerial decision-nutrition interface. The calorific value of such managerial effects aslighting program, feed form, hygiene level, ambient temperature and feedstuff matrixassignment will each impact the final result. Indeed, the quantitative value placed uponfeedstuff energy value is also a variable that makes recommendations qualitative. The MEnvalue for a given feedstuff can range considerably from one source to another. Despite theseconstraints, however, coupling the principles expressed in these writings with end product(bird carcass composition) feedback should provide the poultry producer with sufficientinformation to make sound decisions and enable successful poultry performance within theregional constraints encountered.

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Table 2. Energy and protein needs to 55 days of age.

12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455

5973951131411681952272592953313724174635085586126677217808449039711,0341,1021,1701,2381,3111,3791,4521,5241,5881,6691,7421,8141,8911,9642,0412,1182,1912,2682,3452,4222,5042,5812,6582,7402,8172,8982,9763,0573,1343,2163,2933,375

Day ofAge

BodyWeight

183351741011331692092543033564144775436146907708549431,0361,1331,2351,3411,4511,5661,6851,8081,9352,0672,2022,3422,4852,6332,7852,9403,1003,2633,4303,6013,7753,9534,1354,3204,5094,7004,8965,0945,2955,5005,7075,9186,1316,3476,5656,786

FeedIntake(g)

101419232732364045495358626771758084899397102106110115119123127131136140144148152156159163167171174178182185188192195198201204207210213216219221

Daily Feed

EnergyIntake(kcal Men)

561001562263094065156387749241,0871,2641,4541,6571,8742,1042,3482,6052,8753,1593,4563,7764,1104,4584,8195,1935,5815,9826,3966,8237,2637,7168,1818,6599,1499,65110,16610,69211,23011,77912,34012,91213,50414,10714,72115,34615,98016,62517,27917,94318,61619,29819,98920,68921,396

48121723313948587082951101251411591771962172382612813023243473713964214474745025315615916226546877207547898258618949289639981,0341,0701,1071,1441,1821,2201,2591,2981,338

HighProteinIntake (g)

4.13.24.35.46.47.48.49.410.411.412.313.314.215.116.016.917.718.619.420.221.021.822.623.324.124.825.526.226.927.528.228.829.430.130.631.231.832.332.833.433.934.334.835.335.736.136.536.937.337.738.038.338.739.039.3

DailyProtein(g)

258131925334150617283961101241401561731902092282482692903123353593834084344604875155435716016316616927247567898228568909249599951,0311,0671,1041,1411,1791,2171,255

ReducedProteinIntake (g)

2.33.34.25.26.17.07.98.89.710.611.512.313.214.014.915.716.517.318.118.819.620.321.121.822.523.223.924.625.325.926.627.227.828.429.029.630.230.731.331.832.332.833.333.834.334.735.235.636.036.436.837.237.637.938.3

ReducedDaily ProteinIntake (g)

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10. Vitamins and Trace ElementsThe vitamin and trace element requirements for various ages of broiler are now defined. Toensure that adequate amounts are provided, diets must be supplemented according to boththe level and availability of the vitamin and trace element in the various feed ingredients.

Table 3. Recommended supplementary levels of vitamins and trace elements (pertonne of feed) 1

1Successful production has been observed with these values, however numerous factorssuch as feed processing, bird stress, feedstuffs used among others impact the required level.Optimum profitability should also be considered.

The following nutrient specifications are intended to provide information that will contributeto the optimization of performance, under a diverse array of production situations (Table 4).These tables should be used as a guide of the general nutrient requirements of broilersgrown to 55 days of age or less. The specifications are for chickens reared in temperateclimates under good conditions. Various discussions contained in this manual providegeneral information for conditions that deviate from the norm. When the mean diurnaltemperature exceeds this range, or insufficient oxygen consumption occurs, the birds’nutrient requirements change and modifications should be made. Additional specificationshave been provided for free range chicken production.

Vitamin AVitamin D3

Vitamin EVitamin K (a)Vitamin B1 (thiamin)Vitamin B2 RiboflavinVitamin B6 PyidoxineVitamin B12BiotinCholineFolic AcidNicotinic AcidPantothenic AcidManganeseZincIronCopperIodineSelenium

(MIU)(MIU)(KIU)(g)(g)(g)(g)(mg)(mg)(g)(g)(g)(g)(g)(g)(g)(g)(g)(g)

12.04304494201504001.5601512010040201.00.30

10.04303284151203501.0501212010040201.00.30

9.03303283151203001.0501212010040201.00.30

Starter Grower Finisher

Recommended Nutrient Levels


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The Cobb broiler can be successfully grown under an extensive range of productionsystems. Free range chickens are invariably grown at a slower rate than intensively rearedstock in order to produce meat with a more mature flavor. They require specialized diets,which may be based entirely on vegetable ingredients, and are often reared using controlledfeeding management techniques. Feed control may be necessary, depending on thespecific conditions in which the birds are grown.

Free Range Chicken Production

ProteinLysine-totalLysine-digestibleMethionine-totalMethionine-digestibleM+C-totalM+C-digestibleTryptophanThreonineArginineCalciumAvailable PhosphorusSodiumChloridePotassiumAcid: Base balanceLinoleic AcidEnergy

Feeding Programs

A/H21.51.331.170.560.500.980.860.210.851.390.900.450.200.200.65201.2512.6530231374500

A/H18.01.100.970.480.430.880.770.170.731.200.840.400.160.200.65201.2513.40320214552800

A/H17.01.040.910.440.400.800.700.160.701.110.780.350.160.200.65201.2513.4032021455to marketing

Starter

A/H19.51.251.100.530.480.960.840.190.801.300.880.420.170.200.65201.2513.25316614391400

Grower

(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)(%)meq/100g(%)(MJ/kg)(Kcal/kg)(Kcal/lb)(g/bird)

Finisher 1 Finisher 2

Table 4. Recommended Broiler Nutrient Specificationsin Finished Feeds

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The Cobb broiler is a naturally yellow skinned bird, but eliminating all the sources of pigmentfrom its feed will produce a white skinned, white fleshed chicken. In regions of the worldwhere wheat is the staple cereal, consumer preference tends to be for a white fleshedproduct. In regions of the world where maize (corn) is the staple cereal consumer preferencefrequently slants towards a yellow skinned product. In order to produce yellow skinnedbroilers, the birds have to be fed a diet that includes pigments.These pigments may be eitherxanthophylls that occur naturally as a component of some feedstuffs or they may be addedas a feed supplement. The intensity of the yellow color in the bird products depends entirelyon the amount of pigment included in the diet and deposited in the flesh. Natural materials(e.g., corn, corn gluten meal, dehydrated alfalfa, grass meal, lucerne meal) can be used toproduce birds with pigmented flesh, but the result is often variable. The reason for thisvariability is the natural variation in the level of pigmenting xanthophylls and their pigmentingpotency in the feed raw materials. To achieve a uniform color it is usually necessary tosupplement the natural xanthophylls with extracted or synthetic pigments.

Yellow Skinned Birds

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11. Feed Manufacture

Correct nutritional specifications are an essential pre-requisite for any diet. However, it mustbe recognized that the quality of the diet is entirely dependent on the quality of the rawmaterials. Textbook feeding values for raw materials are only a guide to the actualcontribution that a particular ingredient may make to the final diet. For major raw materials itis essential to monitor their actual composition. The quality of the diet is affected by:

• total nutrient level and availability of essential nutrients;• metabolizable (MEn) or true metabolizable energy (TME);• the proportion of saturated to unsaturated fats for starter diets (due to the limited

ability of chicks to digest saturated fats);• anti-nutritional factors, e.g., histamines (biogenic amines) in fish meal,

trypsin inhibitors in field beans;• toxins, e.g., mycotoxins produced in the field (ergot and fusarium in

wheat) or in storage (aflatoxin);• the addition of enzymes to improve the digestibility of wheat or other

raw materials;• the development of novel raw materials, e.g., processed vegetable

protein products or new varieties of cereals with characteristics intended to make them especially suitable for feed manufacture.

\

Feed may be contaminated by a number of disease organisms, but those of primaryconcern are Salmonella and Campylobacter because of their importance to humanhealth concerns. It is widely recognized that feed plays an important role in the spreadof such organisms throughout the chicken industry. To achieve the objective ofminimally contaminated broiler feed, a number of important steps must be taken. Allincoming raw materials should be selected on the basis of routine bacteriologicalmonitoring. This involves regular sampling based on the volume and frequency withwhich each material is purchased. Storage warehouses and dock discharge facilitiesshould be periodically inspected to ensure that adequate attention is paid to vermincontrol. The construction and management of the feed mill should be designed toensure that there is no possibility of cross contamination from untreated materials.Feed processing lines should be discrete and the flow of product should always run tominimize final product contamination. The mill facilities must be clean. Subjecting themixed raw materials to high temperatures by using specialized milling equipment suchas expanders, extruders and conditioners contributes significantly to a reduction inbacterial contamination. The degree of bacterial kill is dependent on a combination oftemperature, moisture and time. Total bacterial elimination is achievable, but it may beat the expense of important macro and micro nutrient availability. Recontamination ofheat treated feed must be prevented. The critical mill area is post pelleting. The hotpellets should be cooled as rapidly as possible by blowing only clean, filtered, cold airthrough the stream of product. Condensation in this area should be eliminated, sinceit provides an environment that will allow bacteria to survive and multiply. Organicacids and formaldehyde can be used to help control the growth of bacteria and

Raw Material Quality

Feed Hygiene

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molds in both raw materials and finished feed. They are an important tool in the mill hygieneprograms, but the critical areas for bacteria contamination control are heating and cooling.Feed delivery vehicles are also an important link in the chain of bio-security. It is anadvantage to use vehicles specifically dedicated to the delivery of feed, rather than general-purpose haulers or farm vehicles. All vehicles must be regularly and thoroughly cleaned,both inside and outside, including in particular the discharge system.

Neo-natal chicks are not capable of digesting saturated fats properly, so the fat in the starterfeed should be largely unsaturated (e.g., soybean oil). The ability of chickens to metabolizefats improves as they develop, so the grower and finisher diets can be formulated to includeincreasing amounts of saturated fat (e.g., palm oil, and tallow).

Fats, particularly long chain unsaturated fats, are damaged by heating and oxidation. Fatblends often include waste products from commercial frying operations and the by-productsfrom chemical processes, such as distillation residues from oil refining. Fats such as thesewill reduce growth rate and may have an adverse effect on the health of the birds as well astheir carcass quality. The use of anti-oxidants in the fat and feed can have an importantmitigating effect on fat quality.

Soybean meal is the major protein source used in broiler feed and it can, and does varyconsiderably in nutrient content. The causes of this variation are diverse: the soybean cropnutrient profile may vary in quality from year to year and area to area; products with the samenominal specification will vary in their nutrient content depending on the manufacturingconditions used to cook the meal and extract the oil. Cooking is an especially importantprocess because it is necessary to heat the beans to destroy an anti-nutritive factor calledTrypsin Inhibitor (TI). TI lowers the digestibility of the total protein fraction of the feed andimpairs the growth rate of the chickens. Under cooking leads to poor protein digestion dueto the TI, whereas over cooking causes both the protein and fat in the meal to be extensivelydenatured and potentially reduces their digestibility. Regular monitoring of either TI or ureaseactivity is very important. Samples of every new intake of each soybean product should besubject to colorimetric comparison with previous batches and random samples should besent for chemical analysis. Acceptable urease values, using the colorimetric test, fallbetween 0.05-0.20.

Fishmeal can be included in broiler starter diets to provide a good source of digestible aminoacids. Fishmeal also contributes Omega-3 PUFAs, organic selenium and other valuablenutrients, but as with soybean meal, either over or under cooking will reduce its nutritionalvalue. Regular quality control is very important. The levels of available lysine, salt, mineralsand oil stability should all be monitored.

Cereals not only contribute a large proportion of the energy to a broiler ration, but theyalso provide approximately 30% of the crude protein. A change in the level of crude proteinin feed wheat from 11.5% to 10.5% can reduce the crude protein level in the finished feedby up to 2-3% points. The quality of cereals clearly needs to be regularly monitored. In thecase of feed wheat, starch and available starch levels will change with conditions duringgrowing and harvest. Although not directly correlated to energy or protein availability, thehigher levels of non-starch polysaccharides (NSP) often found in wheat indicate that theenergy values may be reduced. The use of xylanase enzymes to break down the non-starch

Fat Quality

Protein Quality

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molecules is now common practice in all major wheat using countries. Periodic assessmentof the nutritional value of wheat should be undertaken, as wheat variety, harvest conditionsand xylanase enzyme activity can vary, leading to differences in available levels of proteinand energy.

The importance of controlling and monitoring the use of feed additives, particularly vitaminsand anticoccidials is all too frequently understated. Vitamins and trace elements are involvedin all the metabolic processes of the body and, while deficiency symptoms are rarely seentoday, sub-optimal performance caused by a marginal deficiency in just one of thesenutrients is not uncommon. Anticoccidials and other medicinal products must beincorporated in feed at the correct levels to ensure their efficacy.

Table 6. Assessing Broiler Feed Analysis

Micro-nutrient and Medicinal Inclusions

Nutrient

Protein 17-24% 98% A test of quantitynot quality

Oil/Method A 8-10% 92% Ether extract method

Starch 35-45% 98% Necessary for energycalculations

Sugar (sucrose) 3-6% 95% Necessary to calculateenergy content of feed

Manganese 100-150 mg/kg 95% Inexpensive method ofassessing vitamin/traceelement supplementinclusion, since baselevels are 15-20 mg/kgand supplement levels80-100 mg/kg

Calcium 0.85-1.15% 95% Errors may be high dueto separation. Pelletingreduces separation.

Phosphorus 0.65-0.75% 95% Availability isapproximately (total %)60-65% of total.

Vitamins A-10 - 14 iu/gE-40 - 150 iu/g

95%95%

Vitamin analysisexpensive. Vitamin A iseasiest to assess andmay be used to indicatecorrect supplement levels.

Oil/Method B 8-10% 92% Acid hydrolysis (e.g. forphospholipids) valueshigher by 0.7%-0.8%.Test enables energyvalue to be calculated

Normal Range(depending onnutrient specification

Analytical precision Additional Information

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12. Feed Management

Ensuring that broiler feeds will successfully meet nutrient specifications begins with theassurance that the raw ingredient composition matrix is accurate. The matrix must reflectthe actual nutrient content of an ingredient for energy, protein, essential amino acids,minerals, vitamins and trace element content. Only then may the ingredients be accuratelyselected and formulated to provide the correct levels of nutrients to be contained in thebroiler feed. In this regard, the feed is only as good as the raw materials themselves, theymust meet specification and our knowledge of their composition must be complete. Manynutritional problems arise due to lack of attention to the quality of raw materials used toprepare the desired rations. Ensuring the quality of the finished feed involves attention to thedetail of raw material nutrient composition, freedom from toxic factors as mycotoxins,bacterial contamination, biogenic amines and rancid fat as well as quality feed formulation,manufacture, delivery, farm storage and presentation to the bird. Accurate testing of rawmaterials and finished feed allows quality control to close the loop.

SamplingGood feed sampling technique is as important as good laboratory practice if the results ofthe analysis are to reflect the real nutrient content of the feed. The majority of variationbetween the results of the same analysis from two different samples of the same feed,analyzed at the same laboratory, is likely due to poor sampling technique. The sample mustbe representative of the feed from which it was taken, and this cannot be achieved by“grabbing” a sample of feed from the feed trough. A 20 ton bulk load of finished feed will bemade up from a number of different mixed batches of raw materials. It is unlikely that thesebatches will be identical in composition, so to get a representative sample of feed it isnecessary to take a number of sub-samples and combine them to make a compositesample. Take at least 5 sub-samples from any size of load. These sub-samples should becombined to form a composite sample for analysis. Always record details of the date, thelocation at which the sample was taken, the feed type, and the batch number. Make sure thatthe laboratory understands which tests are required and where the results should be sent.

Whole wheat feeding is undertaken in a number of countries. The benefits include areduction in feed manufacturing cost, reported improvements in gizzard development andthe efficiency of digestion. Feeding whole wheat also provides the ability to manipulatenutrient intake. The disadvantages may be poorer uniformity, lower growth rates and areduction in lean meat yield, as well as a potential loss of bio-security. Wheat can beadded either at the point of dispatch from the feed mill, or the point of feeding. Addingthe wheat at the point of feeding is technically preferable, but a feed proportioningsystem is essential if the technique is to be successful. The cereal is added to the feedin quantities ranging from 5-30%, starting usually from 4-7 days of age. The overallusage of wheat is 10-12% of the total volume of feed consumed. Whole cereals otherthan wheat may be used, but grains as large as maize (corn) must be milled beforethey are presented to the birds. When wheat feeding is undertaken it is important totake account of the dilution effect on the nutrient specification of the whole feedpresented to the birds. In par t icular, i t is essential to ensure that medicines

Raw Materials Quality and Testing

Feed Testing

Whole Wheat Feeding

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such as cocciostats are fed at the correct levels. The successful use of controlled feedingtechniques requires a significant management input. The birds should be regularly weighedand adjustments to the feeding program may be necessary. Feeding to meet daily nutrientrequirements can be a useful technique and has been shown to have benefits, but it relieson the nutrient levels in the finished feed meeting their expected values.

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13. Physiological StressTwo types of physiologic stress, high ambient temperature-relative humidity combinationsand inadequate atmospheric oxygen, center on metabolic perturbations with overlappingtherapeutics. In the case of heat stress, birds are compromised from waste heat production.In the case of ascites, oxygen needs exceed the bird’s ability to consume. In both situations,improving energetic efficiency and/or slowing growth can assist with survival.

Mean diurnal temperature has a significant effect on the physiology of broiler chickens andwill affect their agricultural performance. The thermoneutral comfort zone for poultry declinesfrom 32 C at hatching to 24 C at 5 weeks of age. When ambient temperature rises andnecessitates heat dissipation via evaporative cooling, elevated humidity makes pantinginefficient and further elevates bird heat production. The birds’ thermoneutral comfort zone,with regard to humidity, lies between 50% and 70% relative humidity (RH). When the RHrises from 70% to 95%, at a constant temperature, feed intake, growth rate and survivabilitymay decline. Optimizing broiler production during heat stress necessitates that theappropriate combination of nutritional and management therapies be applied.

Heavier birds generally have more of a problem with heat stress since they have less surfacearea for heat dissipation per unit weight. In temperate regions hot weather may cause heatstress (acute heat exposure) when a period of high temperatures coincides with a flocknearing slaughter age. These conditions are sporadic and unpredictable, makingtherapeutics difficult. In hot regions of the world the problem is more of chronic exposure tohigh mean diurnal temperature. In such situations the birds will somewhat adapt to the hightemperature in which they are kept, though performance is generally less.

Studies indicate that birds exposed to heat stress retain the potential for enhanced growthrate. If feed intake is elevated during the stress bout, or once the ambient temperature hasfallen, bird growth rate will increase. Several management options are available to elevatefeed consumption during heat stress, but to do so without impacting heat dissipationcapacity, potentially elevates mortality. This is important because it demonstrates thatsuccessful manipulation of energy consumption will improve growth rate, but it alsodemonstrates that increased energy consumption can be devastating during survival limitingheat stress. Producers need to decide how much emphasis to place on growth during thestress event. Allowing, or encouraging growth to slow during the highest temperature periodof the day may be desirable if survivability becomes an issue. During the cooler portions ofthe day compensatory growth may help to offset losses.

HS/Thermobalance:Physiologically, the heat stress dilemma is an issue of energy balance. Thermobalance is acomposite of heat production and its dissipation. Of the two heat dissipation routes(evaporative and nonevaporative), the potential for nonevaporative heat loss is reduced asambient temperature increases above TN. Consequently, for the heat stressed broiler toavoid overheating it must increasingly rely on respiration rate mediated evaporative coolingand/or reduced feed consumption. Nonevaporative cooling is the most energetically efficientmeans to dissipate heat and its optimization will enhance feed conversion efficiency. Byoptimizing ventilation the poultry manager can enhance nonevaporative cooling and therebyaid heat dissipation most efficiently. In summer stress periods ventilation is critical during

Heat Stress (HS)/ General Concerns

41COBB


the day, however, it also has a marked impact during the evening hours by removing wasteheat as quickly as possible and ensuring maximal time for compensatory growth.

HS/Evaporative Cooling:Evaporative cooling usually becomes the principle heat dissipation route during heat stress.Though the bird can dramatically increase evaporative cooling by increasing respiration rate,the efficiency of this process is variable. As the relative humidity rises, both the extent andease with which the bird can support evaporative cooling declines. These relationships mustbe considered for optimal management of ventilation and in-house evaporative coolers suchas foggers and cooling cells.

HS/Heat Production:Broiler heat production averages approximately 45% of MEn consumption. Ambienttemperatures at, or below, the thermoneutral zone, have no adverse heat productionconsequence other than wasted nutrients. Under heat stress conditions however, bird heatproduction has consequences. Birds lower heat production by consuming less feed andslowing growth rate. Feed conversion efficiency also deteriorates as feed consumptiondeclines. Management decisions must keep these factors in mind.

HS/Management Options:In order to achieve consistent performance it is important to maintain feed consumption andnutrient intake. The importance of adequate poultry housing can not be overemphasizedand should be the focal point of an effective heat stress management program. The greatestproportion of economic loss associated with heat stress is usually the result of lowered feedintake, though mortality can be excessive. While the heat stressed bird increases its growthrate as feed consumption increases, and the potential for a near normal growth rate is stillpresent, elevating feed consumption without impacting heat dissipation capacity canincrease mortality. Caution must therefore be utilized in management decisions directedtowards manipulating feed and energy intake, and in fact, they should be coupled with heatdissipation management.

Several options exist for enhancing feed and energy consumption of heat stressed broilers.It is important to utilize lighting to the fullest extent possible without limiting time forconsumption due to lighting program. Continuous lighting or 23 hours light:1 dark should beconsidered. Anything that draws the birds’ attention to the feed, such as running automaticfeeders or physically shaking feeders will elevate consumption. Feed forms as pelleted andextruded products enhance the feed density and generally elicit a greater consumptionduring heat stress. Other avenues of enhancing density, such as improved feed digestibilityand increasing nutrient density help to maintain consumption. Fat addition to the dietincreases nutrient density and enhances growth under high ambient temperature conditions.Using more fat not only improves palatability but reduces heat production per calorieconsumed. However, with fat and with the other techniques discussed, it is critical to realizethat if successful, heat production will likely become elevated. This is also true for theinclusion of fat as it tends to enhance consumption more than it’s heat increment reduction.Dietary caloric value may also be increased with pellet quality.

In hot conditions it may be beneficial to feed the birds only during the coolest part of the dayand night. Removing feed and fasting chicks reduces the birds’ heat load. Under acute highambient temperature-relative humidity stress this management tool can increase survival.However, at least 3 hours is required for the feed to clear the digestive tract and reduce

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metabolism so one must plan ahead as removing feed after the onset of heat stress is of littlevalue. Fasting birds for 3 hours prior to heat stress initiation, coupled with a 6 hour heatstress period, can increases the time without feed to 9 hours. This does reduce timeavailable for consumption and fasting, during cool time periods will reduce growth rate.Consequently, this management avenue should be used only when mortality risk is high. Itis important to provide enough feeder space so that birds do not become overexcited andbruise or scratch themselves during the early re-feeding phase. When properly applied,evidence suggests that compensatory gain during the evening hours will offset reducedgains during the day.

HS/Water Management:Water consumption by the heat stressed bird is a critical consideration as over 80% of theirheat production is dissipated via evaporative cooling. A supply of cool water must beavailable at all times. Reducing water temperature from 30.0°C to 12.4°C has been shownto lower body temperature by as much as 0.5°C with minimal impact upon water intake. Ifthe litter can tolerate added urinary output, encouraging water consumption by addingNaHCO3, NaCl or KCl may have benefits as evaporative heat dissipation extent andcalories dissipated per breath are correlated with water intake. Birds in positive waterbalance are better able to maintain body temperature homeostasis and performance.

HS/Other Considerations:Since feed consumption declines with heat stress, nutrient fortification should be considered.The levels of supplemental vitamins and minerals in the feed should be adjusted to offset thereduction in feed intake. Withdrawing the finisher period vitamin premix from heat stressedbroilers results in a greater performance reduction than withdrawing such premixes whenbirds are housed within a thermoneutral environment.

Lowering the dietary protein, while maintaining essential amino acid fortification levels,has been observed to improve bird growth rate and survivability. Indeed, such anapproach is one of the few observed to simultaneously improve both growth rate andsurvivability. The crude protein levels must be adequate for anticipated growth, but theyshould not be increased in line with the calculated decline in feed intake. Instead, the birds’requirements for the essential amino acids lysine, methionine, arginine and threonineshould be met by forcing increased levels of synthetic amino acids into the feedformulation. This will have the effect of satisfying the birds’ requirement for these nutrientswithout increasing their heat burden.

HS/Hygiene:Optimizing the bird’s hygienic environment has the potential to improve heat stressperformance since the gastrointestinal tract represents a significant source of metabolicheat. Lowered heat production, with reduced microbial loads, occurs due to reducedgastrointestinal tract mass and reduced immune challenge. Such broilers have beenobserved to produce less heat (~7%; Table 1) and consume less oxygen per calorie ofmetabolizable energy consumed.

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Ascites is commonly known to poultry producers as waterbelly, altitude disease or avianedema. Ascites is the result of a physiologic syndrome of multiple causes and generallyattributable to insufficient oxygen consumption. Historically, ascites was viewed as being ahigh altitude disease with its occurrence being more common in countries where regionscontaining poultry production exceeded 1,500m. However, combinations of disease, toxinsand/or insufficient management and/or nutrition can either interfere with chick ability toconsume oxygen or elevate its requirement to the point that ascites can occur at virtually allaltitudes. When oxygen consumption falls below metabolic need, compensatory physiologic-cardiovascular alterations are made. These changes, however, are the triggers that sendthis syndrome down a progressive path. Proper nutritional and environmental managementcan do much to avoid the ascites issue.

The ascites syndrome in poultry is a clinical manifestation of oxygen insufficiencyprecipitated by a divergent oxygen requirement and cardiovascular ability to supply it. Birdoxygen need increases with tissue accretion rate and proportion as lean mass. Broilershoused in metabolic chambers have been observed to consume 3.1 liters O2 per gramprotein gain vs. just 0.82 liters O2 per gram fat over a 35 day production period. As a resultone might conclude that various managerial and nutritional concepts presented to improveFCR and/or cope with heat stress also have the potential to modulate ascites incidence.

Oxygen as a Nutrient:All tissues are supported by an obligatory oxygen driven metabolism. Oxygen is required forgrowth, maintenance and activity. Figure 18 partitions the cumulative oxygen consumptionprofile for a growing broiler, under reasonable growing conditions, into its gross components.The production of a 3.4 Kg broiler necessitates that the bird consume approximately 2,500liters of oxygen during the production period. Of this 19% is utilized to support BMR, 36%for a combined BMR, activity and waste energy associated with converting consumed MEninto maintenance needs.

Ascites

Figure 18. Broiler totaloxygen consumption in liters(green) partitioned into thatutilized to support gain (black)and total maintenanceneed partitioned intoBMR (red), BMR + lightson activity (blue) as wellas oxygen consumed tosupport maintenance (yellow)metabolism associated withgain is displayed. BMR,activity and oxygen requiredfor the production process arenearly of equal magnitude.Beker and Teeter, OSU

0

-1000

1000

2000

3000

0

10000 20000

O2 Consumption (L)

Figure 18. Partitioning of OxygenConsumption vs. MEn Intake


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An evaluation of the 3 distinguishable expenditures for oxygen merit discussion as they offerpotential interaction via management and nutrition:

Activity:The activity components associated with maintenance, tissue gain and social behaviorwarrant discussion. Ideally, for optimized utilization efficiency of both energy and oxygen, thebird would have enough activity to acquire needed sustenance followed by reducedlocomotion expenditures. From a managerial perspective, proper administration of lightingcycles and intensity has the potential to lower bird activity. Reduced day length and/orlighting intensity is well documented to lower bird activity (see previous discussion). Fastedbirds housed under conditions of BMR elevate their oxygen consumption when the lightscome on. Reducing lighting intervals within the day provides broiler producers’ a means oflimiting activity that results in energy + oxygen expenditure. Consequently, it is of littlesurprise that lighting program application enhances FCR and lowers mortality incidence.

Basal Metabolic Rate:Previous discussion indicates that the amount of energy needed for maintenance can bemarkedly elevated by ambient temperature. For example, a change in ambient temperatureof 5 C will elevate the maintenance oxygen needs by approximately 10%. Ambienttemperature, consequently, is a significant determinate of total bird oxygen need. Rearingbroilers within the TN zone will help to reduce ascites. Ambient temperatures deviating fromTN have the potential to elevate mortality at all altitudes, but are particularly detrimental atelevations exceeding ~610 m or 2,000 feet.

Tissue Accretion and Needs Exceeding Maintenance:The combination of management and ration balance continue to impact bird oxygen needsonce maintenance aspects have been addressed. Managerial decisions, independent ofration composition, that worsen FCR will generally elevate the bird oxygen requirement andascites susceptibility. This is particularly true under conditions of AT deviation from TN andelevated altitudes. Managerial decisions related to environmental definition (stockingdensity, housing design, ventilation, brooder management, hygiene) have an increasedimportance when dealing with the ascites issue.

Ration composition also influences bird oxygen need, especially when environmentalconditions fail to provide a reasonable growing condition. The combination of poor housingenvironment and excess dietary crude protein can elevate ascites incidence. When dietaryprotein is utilized as a source of energy, exceeding needs for lean tissue accretion, energeticefficiency is lowered and more oxygen consumption is needed. As shown in Table 7, theinfluence of caloric density and calorie protein ratio, though not as significant as altitude,contribute to worsening the cardiovascular challenge. This is evidenced by blood hematocrit,right ventricular mass and ascites heart ratio. Such occurrence is the result of the metabolicefficiency for converting dietary protein MEn into lipid being just 45%. This is in contrast tohigher efficiencies for carbohydrate(78%) and lipid (84%). An additional consideration forlipid is that it generally places the bird in a higher growth plane, further exacerbating oxygenneed. Lipid consumption will thereby not only elevate carcass fat but also oxygen need.Therefore, a reasonable ration to minimize ascites is similar to one for minimizing mortalitydue to heat stress perturbation, where added heat production via lipid and proteinexacerbate environmental consequence. Ultimately, the producer will need to decidethe ration composition warranted to cope with the specific environmental risk level(determined by altitude, AT, brooder efficiency, ventilation, environmental toxins, etc).

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Dietary SodiumExcessive consumption of sodium, via the diet or from drinking water, places additionalstress upon the cardiovascular system. The combination of sodium source andbioavailability can make sodium delivery to the bird uncertain. Often times, nutritionistattempt to error on the side of feeding excessive sodium amounts so as to avoid thepossibility of deficiency. In the case of ascites, this approach can needlessly elevate ascitesrisk. The bottom line is that serum sodium should not be allowed to exceed 155 meq. Insituations where ascites is a significant concern, attaining serum samples and testing forserum sodium can provide information to see if Na is being over fortified.

Bird Ability to Consume Oxygen:Altitude certainly plays a potential role in bird ability to consume oxygen. As elevationincreases the concentration of oxygen per liter air declines, and the effort expended toconsume it increases. In addition to altitude, other air quality and disease factors such asammonia, dust and respiratory infection are among the many contributing factors that have thepotential to lower bird ability to consume oxygen. Under generally good growing conditions,with the exception of elevation, the altitude associated with physiological changes related to theprogressive ascites syndrome, appears to be approximately 1200 meters (Figure 19). It shouldbe noted, however, that this estimate is attained by using hematocrit, the earliest respondingcomponent of the progressive array of cardiovascular changes associated with

O2 (%)

HCT (%)

1720.6

CD (kcal/kg)28803200

CPR113140

38.25a

32.62b

35.2535.62

36.26a

34.61b

RV (g)

0.42a

0.40b

0.40b

0.42a

0.42a

0.40b

AHR

23.14a

21.56b

22.4722.23

22.81a

21.88b

Table 7. Altitude, caloric density (CD) and calorie-protein ratio (CPR) effects onhematocrit (HCT), right ventricular mass (RV) and ascites heart ratio (AHR=RV/totalheart weight (g)/100) of chicks reared to 2 weeks of age. Vanhooser, Swartzlander,Beker & Teeter, OSU


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ascites development. Other criteria such as ascites score, right ventricular mass and ascitesheart ratio do not appear to change as early as hematocrit (Table 8). Nonetheless, diligenceis recommended for oxygen concentrations falling below ~19.4%. This corresponds to analtitude of ~610 m or 2,000 feet. It is important to keep in mind that other environmentalfactors such as ammonia, ambient temperature, stocking density, poor ration balance andinsufficient ventilation rate would be expected to impact such results. Unfortunately, thesefactors result in physiologic adjustments occurring at lower altitudes.

Vanhooser, Beker & Teeter, OSU

Table 8. Physiological Changes Under Varying PercentAtmospheric Oxygen Percentage

32

34

36

38

40

42

44

46

48

50

0 1000 2000 3000 4000

0 3280 6560 9840 13120

Figure 19. Altitude Effects on Percent Blood Hematocrit

Altitude

Meters

Feet

HCT

Hematocrit (HCT), ascites score (Ascore), right ventricular (RV) mass and ascites heartratio (AHR=RV/total heart weight (g)/100) of broiler chicks reared to 14 days of age atvarying atmospheric oxygen concentration. Vanhooser, Beker & Teeter, OSU

Variables

a-d Means in a row with unlike superscript differ

20.618161412

HCT (%)

Ascore

RV (g)

AHR

48.92 ± 0.46a

3.00 ± 0.39a

0.79 ± 0.04a

52.36 ± 2.00a

42.24 ± 0.46b

2.23 ± 0.19b

0.82 ± 0.04a

43.37 ± 2.00b

35.77 ± 0.57c

0.67 ± 0.14c

0.46 ± 0.03b

24.00 ± 1.74c

32.60 ± 0.40d

0.38 ± 0.14c

0.38 ± 0.03b

22.91 ± 1.74c

31.88 ± 0.98d

0.25 ± 0.14c

0.34 ± 0.08b

20.99 ± 4.25c

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Nutritional GuideBroiler Nutrition Guide

Other Measures:Once practical environmental and dietary management of ascites has been addressed, aswith heat stress survivability, one may choose to therapeutically slow growth. Slowinggrowth reduces the overall need for birds to consume oxygen, thereby enabling thegrowth-maintenance-bird ability to consume oxygen balance to normalize. Growth may beslowed via utilization of feed restriction, reduced caloric density rations, mash diets andlighting program.

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Notes

Cobb-Vantress Inc.PO Box 1030, Siloam Springs, Arkansas 72761

Tel: +1 479 524 3166 Fax: +1 479 524 3043

Email: [email protected]

Cobb EuropeMidden Engweg 13, 3882 TS Putten, The Netherlands

Tel: +31 341 36 08 80 Fax: +31 341 36 05 24


Cobb-Vantress Brasil, Ltda.

Rodovia Assis Chateaubriand, Km 10

Cep: 15110-000/Caixa Postal 2, Guapiaçu-SP-Brasil

Tel: +55 (17) 3267 9999 Fax: +55 (17) 3267 9992


Website: www.cobb-vantress.com

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cobb broiler nutrition guide

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