BEEF CATTLE NUTRITION AND GROWTH --1980:

A SUMMARY OF RESEARCH

GROWTH RESEARCH Cl RCULAR 258

JULY 1980

ENERGY CONVERSION FROM STALKS TO STEAKS

OHIO AGRICULTURAL RESEARCH AND DEVELOPMENT CENTER U. S. 250 and Ohio 83 South

Wooster, Ohio

CONTENTS *** *** ***

Systems of Beef Cattle Feeding and Management to Regulate Composition of Growth, to Produce Beef Carcasses of Desired Composition, by F. M. Byers------------------------------------------------ l

Net Energy Value of Grain ·and Forage Diets for Beef Cattle, by F. M. Byers ____ 18

A System of Starting Small Calves on NPN Corn Sil.age with Bypass Protein, by H. Wilnam Newland and Floyd M. Byers ________ 26

Starting Lightweight Calves on NPN Corn Silage and the Effect of Protein in Excess of Recommended Levels Fed with Two Types of Corn Silage, by H. William Newland .and Floyd M. Byers ________ 29

All educational programs and activities conducted by the Ohio Agricultural Research and Develop­ment Center and the Ohio Cooperative Extension Service are available to all potential clientele on a nondiscriminatory basis without regard to race, color, national origin, sex, or religious affiliation.

AGDEX 420/51-53-54-55-58 7-80-6M

Systems of Beef Cattle Feeding and Management to ·Regulate Composition of Growth

to Produce Beef Carcasses of Desired Composit'ion F. M. BYERS1

INTRODUCTION Cattle of widely differing types and mature sizes

form the genetic resources of the beef cattle popula­tion. They are fed a variety of feedstuffs in calf pro­duction and cattle feeding systems which vary widely and· include the total. range of feeds fed to all kinds of livestock. · These feeds range from poor quality mature range grasses and crop residues to high en­ergy cereal grain diets, with all combinations in be­tween. Systems in the spectrum of beef production include wintering, backgrounding, summer grazing, growing, forage finishing, and feedlot finishing with forage and high energy grain diets. The end prod­ucts of these cattle/feed resource combinations are either ch.oice grade beef requiring 30-35% carcass fat or le~n ( 20-25 % fat) carcass beef to provide ground beef for the growing hamburger market.

The ability to use both feed and cattle resources to the best advantage depends on optimizing produc­tion systems to direct .growth of protein (muscle, lean) and fat to achieve desired carcass composition at marketable . carcass weights. Cattle differing in mature sfa;e and protein growth potential are best suited to differing "nutritional niches" for providing desired composition of growth to achieve needed ca~­cass composition and weight at slaughter. The ex-

1Associate Professor of Animal Science, Texas A&M ·University, College Station; formerly Assistant Professor of Animal Science, Ohio Agricultural Research and Development Center and The Ohio State University.

periments summarized involve recent OARDC re­search designed to determine how animal protein growth is regulated and how composition of growth can be controlled-in beef cattle production systems to most efficiently produce carcass be~f with cattle and feed resources available.

EFFECTS OF. NUTRITIONAL LEVEL ON COMPOSITION AT SLAUGHTER

Forage vs. Grain Diets Corn silage and shelled corn are the most com­

mon feedstuffs fed to feedlot cattle in the Midwest. Response of crossbred cattle of several mature sizes to corn silage vs. whole shelled corn diets is shown in Table 1. Small differences existed in rate of gain between small and large size cattle. The large size cattle, however, were not nearly as fat when termi­nated, especially those fed silage. Similar final weights were reached withill; c;:attle types fed either diet. Feed efficiencies were also similar between large and small types fed corn or silage.

If the large size cattle had been fed to a degree of fatness similar to the small size cattle, feed effi­ciency and rate of gain for the large size cattle would have been lower than observed, especially. on the si­lage diet. When adjusted to similGi:r carcass fat per­centage within size class and diet, small size cattle had 17 % heav~er carcasses and large size cattle had 34% heavier carcasses when fed corn silage thap. when

TABLE 1.-Effects of Cattle Size and Energy Level on Performance and Car­cass Composition.

Mature Size: Small Large

Corn Corn Ration Fed: Corn Silage Corn Silage

No. steers 15 16 16 16 Initial wt, kg 230 227 267 267 Final wt, kg 440 434 518 518 Av. No. days fed 17_6 256 195 266 Av. daily gain, kg l.19 0.82 1.29 0.94 Av. daily D.M. intake, kg 6.9 6.7 7.4 7.7 Dry matter/ gain 5.85 8.17 5.68 8.17 Av. carcass wt, kg 271 257 321 308 Av. carcass fat, % 32.6 29.5 27.8 24.0 Carcass wt. @ 30 % fat, kg 238 279 Carcass wt. @ 28 % fat, kg 323 434

Source: Byers et al. (11 ).

fed corn grain diets. This indicates that definite plane of nutrition effects existed and that large size cattle changed more in composition than small size cattle did when fed corn silage vs. corn grain diets. The smaller mature size cattle fattened much easier on corn silage than the larger cattle, indicating that small size cattle are likely better suited for finishing on lower energy corn silage diets.

Results of another study with cattle fed high si­lage or high grain diets are listed in Table 2. As is evident, cattle fed high grain diets were fatter at lighter weights than comparable cattle fed corn si­lage diets. The H~lstein steers responded the greatest in rate of gain to the additional energy and had 7 .8 % lighter carcasses at similar fatness when fed the grain diet rather than the silage diet.

TABLE 2.-Carcass Composition of Three Cattle Types Fed High Silage or High Grain Diets.

Breed: Hereford x Angus Hereford x Charolais

High High High Item Energy Level: Silage Grain Silage

No. cattle 10 10 10

Days fed 183 162 183

Average daily gain, kg 1.19 1.28 1.30

Initial wt, kg 241 240 290

Final wt. kg 462 453 525

Empty body wt, kg, 420 410 479

Carcass wt, kg 286 279 330

Empty body fat ( % ) 29.8 30.2 29.5

Carcass fat ( % ) 32.9 33.2 32.5

Weight* at similar carcass fat, percent within cattle types

Percent fat 33.2 32.5

.Carcass. weight* 290 279 330

Decrease with high grain energy level, % 3.8

kg carcass 10.9 kg live 18.2

-----··--··--· --- -·---- ---- --·-·-·- - _._ ______ *From regression of percent carcass fat on carcass weight within each treatment. Source: Newland et al. (5).

High Grain

10 162

1.35 288 507 464 318

29.4 32.5

318

3.3 10.9 18.2

Holstein

High High Silage Grain

10 10 204 183

1.34 1.48 306 306 581 574 499 496 344 342

22.5 24.2 25.l 26.9

26.9

371 342

7.8 29.l 48.6

TABLE 3.-Growth, Composition, and Efficiency of Various Cattle Types on Two Planes of Nutrition.

Size: Small Large

Item Nutritional Plane: Moderate High Moderate High

No. cattle 19 19 19 19 Initial wt, kg 210 214 249 246 Live wt, kg as slaughtered 548 515 588 572

Av. daily gain, kg* 0.83 l.21 0.80 1.31 Days fed 389 257 401 263 Dry matter/gain l 0.72 6.57 11.45 6.18 Final wt, kg* 533.9 525.7 570.1 591.4

Hot carcass wt, kg 325 320 347 360 Carcass fat, % 31.46 36.20 28.88 33.60 Empty body wt (EBwt), kg 472.8 466.3 502.9 519.l Empty body fat (EBF), % 28.81 32.94 25.97 30.51

range (19.4-35.7) (25.1-39.6) (16.2-32.4) (21.9-38.9)

E. Body wt == 472.6 E. Body wt == 511.2 Empty body fat at equal empty body wtt 28.8 33.49 26.46 Empty body protein, % 16.06 15.22 16.63

kg 75.93 70.97 83.63 Birth wt, kg 33.9 33.6 38.0

*Calculated from hot carcass weight with average (60.87) dressing percentage. tcalculated from regressions of fat on weight within groups. Source: Byers and Parker (8).

2

30.07 15.72 81.60 38.2

SEm

13.1 0.07

8.3 1.05

11.2 0.94

0.19

0.9

SEm

11.4 10.4 7.7 0.9 0.9

·Since experiments with fermented forage (corn silage) vs. dry corn grain diets indicated substantial effects of energy level on carcass composition at simi­lar final carcass weight, energy level effects were fur­ther evaluated with dry diets, eliminating possible fermentation effects. Two planes of nutrition were provided by 65 % .grain with 35 % ground corn stover (moderate energy) or shelled corn (high energy) . Crossbred cattle varying in mature size were group fed these two planes of nutrition (Table 3). Cattle of. both sizes fed moderate energy ( 65 % grain) diets gained similarly, with feed efficiency favoring. the small size cattle by 6.8%, even though they were r-.1

11 % fatter. Large size cattle gained 8.3 % faster and 6.3 % more efficiently than smaller cattle on the shelled corn high energy diet, due primarily to a lesser degree of fatness ( 30.5 vs. 32.9%) at slaughter. At similar final empty body weights, within cattle type, small and large size cattle fed the high energy diet had 16.3 and 13.6% more empty body fat ( % ) than similar cattle fed the moderate energy levels. These responses of increased fatness with higher energy levels with dry diets are similar to those noted pre­viously with corn vs. silage (fermented). diets.

The levels of nutrition fed regulated composition of the carcass at specified slaughter endpoints. These data lend credence to the concept of backgrounding or growing small mature size cattle to maximize ex­pression of genetic potential for total protein and lean tissue production and the rationale of feeding high energy "finishing" rations to large size cattle during the total feeding period to minimize time and carcass weight at desired carcass fatness. Thus, the breed type x nutrition interaction warrants careful consid-

eration in feeding programs where regulation of growth through level of nutrition would be feasible in more effectively utilizing feedstuff resources while optimizing growth patterns and attaining desired car­cass composition at acceptable carcass weights. The inherent ability of small size cattle to adequately fat­ten on low energy diets suggests existence of "nutri­tional niches" unique for given cattle types. Levels of Intake of a Common Diet

To evaluate energy level effects independent of dietary ingredients, shelled corn diets were full fed or limit fed to individually fed Angus-cross or Charolais steers. Results in Table 4 indicate level of nutrition effects, similar to those with forage vs. grain diets. The Angus X cattle fed either level were similar in final weight and the full fed Angus X steers were r-.1

20% fatter than their limit fed counterparts. Even though the limit fed Charolais steers were fed to 14% heavier weights than the full fed Charolais, full fed animals were still 20% fatter at slaughter. The large size cattle responded more in fat deposition to increased level of energy than the smaller size cattle did and as a consequence, at similar body weight the difference between full and limit fed Charolais in per­cent body fat was much greater than between full and limit fed Angus cattle.

These results indicate that large size cattle will respond to elevated energy levels with much greater ]ncreases in fat deposition than smaller sized cattle. While larger size cattle fed low energy diets will be extremely large when desired carcass fatness is reached due to their inherently high level of dally protein growth, their ability to greatly increase rates of fat deposition on high energy diets allows them to

TABLE 4.-Composition and Efficiency of Empty Body Growth of Charolais and Angus X Steers.

Angus X Charolais

Full Fed Limit Fed Full Fed Limit Fed SEm

No. cattle 4 4 4 4

Empty body wt, kg Initial 190.8 191.0 260.3 262.2 16.6 Final 394.5 401.8 478.5 544.3 25.2

Days fed 185.3 382.0 271 546.5 Protein, kg

Initial 35.3 36.5 48.2 49.9 2.9 Final 63.2 69.0 81.3 95.3 4.2

Fat, kg Initial 30.4 25.3 41.2 35.6 7.9 Final l 07.4 90.6 117.9 111.2 16.4

Growth, kg/ day Empty body l. l l 0.65 0.85 0.52 0.07 Protein 0.153 0.088 0.124 0.082 0.012

Fat 0.426 0.177 0.285 0.141 0.058

Source: Byers and Rompala (9).

3

achieve desired carcass fat~ess endpoints at much lighter and more marketable weights. Therefore, "nutritional niches" for ·small and large size cattle where rates of protein and fat deposition allow opti­mal composition of growth are provided by moder­ate (i.e.,, forage/ grain, corn silage) and high (shelled

corn) energy diets for small and large mature size cattle, respectively.

Full or limiting feeding corn silage provides yet another method for altering growth and composition in cattle. Data in Table 5 indicate effects of full vs. limit feeding corn silage on terminal empty body

TABLE 5.-Body Composition of Hereford Cattle Full Fed or Limit Fed a Corn Silage Diet.

Feeding Level

Item Full Fed

No. steers 60 Initial wt, kg 246.3 Final wt, kg 440.8U* Days fed 211 Average daily gain, kg 0.922a Empty body wt, kg 393.oa Empty body fat, % 30.l7a

Empty body composition at 395 kg Empty body fat, % 30.21a Empty body protein, kg 62.39a

*Means bearing different superscript letters differ, P < .01. Source: Byers (2).

70% of Full

60 247.0 4 l 2.2b* 253

0.653b 355.0b

24.69b

27.30b 64.90b

Fed SEm

17.4 3.6 0.37

0.31 0.16

TABLE 6.-Body Composition of Hereford Cattle Full or Limit Fed Control and Limestone Treated Silage.

Silage Control Limestone,

Intake Level Full Fed 70% Full Fed

No. steers 40 20 40 Initial wt, kg 241.5 239.6 239.9 flnal wt, kg 398.5 419.3 403.5 Days fed 202.3 269.5 218 Av. daily gain, kg 0.778 0.667 0.750 EmP,tY body wt, kg 356.6 353.5 359.l Empty body fat, % 31.17M 25.49b* 30.58a

*Means bearing different superscript letters differ, P < .01. Source: Byers (1 ).

NUTRITION AND GROWTH

Li'"'l.it

1%

70%

20 241.9 390.0 274

0.540 340.7

25.48b

Fu.lZ

SJ;m

0.015 5.0 0.91

Daily Fed. (I..) Fe.d. ff) lho.n~e

FAT ME/kg·75 190 230 150 ""'*' - E.B.Gain .92 1.13

* Protein(g) 129 138 ~ 7%

kg 100 Fat (g) 364 534 + 32,% TISSUE PROTEIN % Fa.t@ = 29.6 33.3 - L F

£.13. wt. - Days 219 196 50

L F E.B 415 434 wt NO. 40 40

FIG. 1.-Composition .of growth and of the empty body in steers full or Jimit fed shelled corn diets.

Source: Preston, Vance, and Cahill (16).

4

composition. Full fed cattle were 10.7% fatter at similar final empty body weight ( 395 kg) . Limit feeding. corn silage reduced fat deposition by 47% and protein by only 25 % , thus allowing cattle to "grow"and deposit more protein and lean.

In a similar. study with another group of Here­ford steers, limit feeding corn silage whether or not ensiled ~ith limestone also altered terminal composi-. tion (Table 6). Full fed steers were 21 % fatter (30.9 vs. 25.5% fat) than limit fed steers .at similar final empty body weight. Since similar responses were noted with either silage, and since the limestone extended silage fermentation, it can be concluded that extent of fermentation has no effect on thG composi­tion of growth response to dietary energy intake.

Data presented in Figure 1 show similar effects on body composition and growth with limit vs. full feeding shelled corn high energy diets to steers. Limit feeding reduced empty body gain by 19% and re­duced daily fat gain by 32% while reducing daily protein growth by only 7 % . Limit fed cattle had more protein and 13 % less empty body fat at empty body weights similar to full fed steers, conclusively documenting substantial level of nutrition effects on body composition.

Data of Moulton et al. ( 13) (Figure 2) obtained through serial slaughter techniques are in concert with more recent research and indicate that cattle fed on high planes of nutrition will have more empty body fat present at any weight than cattle fed on a lower nutritiona~ plane.

The similar effects of varying intake levels of the same diet, and varying dietary energy density with forage level, on carcass and empty body composition indicate that level of nutrition effects are related to energy intake rather than to specific feedstuffs in­cluded in the diet.

The clear "plane" or "level" of nutrition effects are obviously effects related to level of available en­e:r:gy intake,. where fat deposition is enhanced with high energy intakes. This implies existence of a biological limit on the physiological potential of an animal to de­posit protein, such that additional energy consumed is stored as fat. To determine this limit for protein growth and how it is approached, diets giving rise to a range in rates of growth were studied.

RATE AND COMPOSITION OF GROWTH WITH A RANGE IN FORAGE/GRAIN LEVELS

AND GROWTH RATES The studies previously discussed each involved

essentially two energy levels to evaluate the effects of level of nutrition on terminal body composition. Fur­ther research, with a variety of growth rates in each study, was conducted to more specifically determine

5

30

-C> ~ 200 w :::>

"' "' ,_

0 > ,_

i 100 < :::> a

ENERGY INTAKE TISSUE

{

ATER ·--· AT -

HIGH ROTEIN """"'" MINERAL ....... ----.1,.•• .,.,. .... --,.,.#fl''

{

ATER ·--- ,,,, .... ,;,; AT ··-·· ,,;' ;,;-'

L 0 W R 0 T EI N ·---· ,,. // i MINERAL-·-:.,."'"'/'/ /

_,. /; I

,.;"';I ,/ ,; 11 i

/ / i / / .' ,... I -'

// / /' / / // /

,'/ / ,,' ,1' _,-' -------------

, I ,.·"' --,)I /:.?:.:.::::: ............................................. .. // ..,.."'::~••;;\lV' •'

'1 .~~::~''' .. ~ ... '1 "";.... ·" 1? -~ .... ······: ..........

' .-.":.~ .,. . .,..... ------~~.:.;-·===·=·:-.::::::::::.::::: ........................... .

200 400 600 800

EMPTY SOOY WEIGHT (KGi

FIG. 2.-Body composition during growth of steers fed on two planes of nutrition.

Source: Moulton et al. (l 3J.

the relationship of rate of growth to composition of growth and to measure how protein growth changes as the biological limits for maximum protein growth are approached.

Feeding corn silage diets at a variety of intake levels to 120 Hereford steers resulted in composition of growth patterns indicated in Figure 3. Cattle groups averaged 350 kg at slaughter and feeding per­iods ranged from 197 to 274 days. As is evident, daily rates of protein growth approached maximum rates of r-J 8~ g/ day at r-J 0. 75 kg daily empty body gain. As rates of protein growth plateaued, rates of fat deposition a~celerated rapidly with rate of gain. Percentage protein ·in gain decreased with increasing rate. of gain.

In a study with a high forage corn silage, 180 Hereford calves initially averaging 268 kg were full or limit fed one of five levels of high moisture corn with forage. Rates of empty body gain ranged from 0.14 to 1.0 kg/ day and feeding periods ran from 110 to 264 .days. As indicated in Figure 4, rates of protein growth increased slowly with rate of gain, approaching maximum limits at r-J 1.0 kg/ day gain. Rates of fat deposition rapidly accelerated with increasing daily gain. The net result was a decrease in percentage protein in gain with increasing rate of gain. As a re­sult, composition at slaughter (Figure 5) reflected the effects of rate of growth on composition of gain. Emp­ty body fat ( % ) at 350 kg empty body weight in­creased from 23 % for cattle that had gained 0.4 kg/

~ ·~

~ ~14.20

~ ~ 13.80

~ ~ 13.40 ~ 'U ~ 13.00

•N

~ ·~ 12.60 \) ~

~ 12.20

~ ~ 11.80

~ ~ 11.40

~ ~ ~ 11.00 .....

~

450

400 -..... ~

350

~ 300·w

~

250%

t'\--l

20~

150~ "--1

FIG. 3.-Rate of gain and rate of empty body protein and fat deposition in Hereford steers fed a corn silage diet. Source: Byers (4)

...... ~ tmrcy. Bod/- Growt/z ~ 500

~

""' 450

-~ ~ 400

~ 20 \:t. 350

~ 19. % Prol:e.Z..ll Gai·1 300

x -. 18 250 ~

t:! N 17 160. 200 ~ ~

16. 140 150 ~~

. ~ tW .

0

l~ N 15 120 100 Ill

rN

~ CT: 14. 100 50

13. 80 0

12. 60 x

11 4 ?role io/_ ) j Day x

0

0 .2 A .6 .8 l.

Vai ?j tmpl1j- Bod'/- Gai17. , fc1 FIG. 4.-Rate and composition of growth in Hereford steers fed forage/ grain

diets. · Source: Byers (5).

35

% &mpl/ Bod7 Fa..t 30

~ 25 ~ ~ "\

~ ~ ·~ 20

~ "J

~ ~ 410 15 ~

'\5 ~

~ 380 0 t::)

0 0

I 0 0

10 ~ 350 a 0

~ 06 0 r1..J

!"\...:i 0 0 Q... 32 0

~ £~?cl Botl7 cJi:. ~

~ 0 /<;(' \>J 29

~ 0 0 0

260 0

0 .2 .4 .6 .8 1.0 1.2

DaiZ/ Ernpl"1 Body 6-az:a _, x-r· FIG. 5.-Rate of gain and final empty body composition of Hereford steers. Source: Byers (5).

7

650

-.,,

BodJ Grow?:Jc 600

~ €.mpt7 t

550

~ 500 '"> ~ 450 22 l'iJ

~ x 21 ~ x 400

20 3 Prcreil( Gaiq 350

~ 300 --..

·~ ~

250

~ ~ 200 ~ ·~

tN 16 150

~ r(! ~ 15 100

~ 14 50

Pro?:eifl/., , 1- 0 Da:1

x

0 .2 .4 .6 .8 1.0

1Jai2j tmflj. Body. Gai1 J kj

FIG. 6.-Rate and composition of growth of implanted Hereford steers fed forage/grain diets. Source:. Byers {2).

~ ~

·~

~ ~ ~ 450

~\,. 400 f'1....J ~ 350

ti ~ 300

25q_

0

0

0 0

.2

0

.4

0

0 0

.6

0 Io gR OQ 00

.8 1.0 1.2

JJai Zf £mp1:1f Body Gaitz , ''r

33

30

27 ~

24

21 ~

~ 18

15 ~ ~

12

~ rt..)

~.

~ \1,j

1.4

FIG. 7.-Rate of gain and body composition of implanted Hereford1 steers fed forage/grain diets. Source: Byers (2).

day to 31 % for cattle that gained at 1.0 kg/ day over the total feeding period.

Corn stalklage and high moisture corn in four diets were fed to 160 Hereford calves averaging 230 kg. Cattle were implanted with DES twice during feeding periods which lasted from 165 to 325 days. Growth patterns are shown in Figure 6. Rates of protein growth increased with rates of gain up to ,_, 1.0 kg/ day where the maximum limit for protein growth was reached and as a result, protein growth did not increase with faster rates of gain. Rates of fat deposition increased very rapidly with increasing rate of gain, especially with gains above 0.6 kg/ day. Per­cent protein in empty body gain decreased with rate of gain, reflecting changes in protein vs. fat deposition with rate of gain.

These changes in composition of growth modified body composition at slaughter as indicated in Figure 7. Percent empty body fat at slaughter increased linearly with rate of gain. Of cattle that reached similar final weight ( 410 kg) , cattle that gained at 0. 77 kg/ day had only 23 % fat while cattle that gained at 1.3 kg/day had 32% empty body fat. In this study

16 ~ 'Y

t,

~

~~ ·~

\J ~

15 t)J

% 'Prt:J-Ce1iz.. Gaitz ~ ~

l

~ .~ t'l

~ 14 150

.~ 140 l'\l

~ 13 130

~ ?rote.in/, I~ \\ Day ~o

ll

0 .7 .8

as in others, rate of growth regulated composition of growth and modified composition at slaughter. Rate and composition of growth and body composition at slaughter were predictable from rate of gain in these studies.

Other recent research documenting similar re­sponses between rate and composition of growth in­clude Michigan studies of Woody ( 17) and Cali­fornia research of Garrett ( 12). Data in Figure 8 show that daily protein growth in steers fed corn/ corn silage diets was maximized at ,_, 1.0 kg daily gain. Composition at slaughter (Figure 9) reflected the effects of accelerated fat deposition with rate of gain. Percent fat in the empty body at similar final weight changed from ,_, 28% to 31 % as rate. of gain in­creased from 0.95 to 1.13 kg/day.

Research of Garrett ( 12) with steers fed hay/ grain diets indicates similar effects. Rate of protein growth (Figure 10) maximized at ,_, 0.95 kg daily empty body gain, with faster rates of gain rapidly ac­celerating fat deposition with no additional protein growth. As a result, carcass composition at slaughter (Figure 11 ) reflected the changes in growth patterns.

rat/l1 ) ~ ~// 500

~

"'"""" 400 ~

~

~ 300 ~

~ x

x

.9 1.0 1.l 1.2

FIG. 8.-Rate of gain and composition of growth in steers fed corn/ corn silage diets. Source: Woody (17).

9

32

. . 31

~ i,,mpty lJodl rat 30

~ ~ 29

--. 28 ~ ~

'"\

~ 27 ctJ ....__

~ 26 ~

~o. 25 ~ ~

~ ~ 48 24

£m.pZ.' Body Ult. U1J ~460 cP ~ ~ - --z__;

9 I o 0 rtJ

().__ 0

~ ~ 440 0

0

~ 0 w 42Q 0

0 .7 .8 .9 l'.O 1:1 1.2

[)a i zy. tm?c/ :Pody Gain. ) K'J FIG. 9.-Rate of gain and body composition of steers fed corn/corn silage

diets. Source: Woody (17).

700

600

500 -... ··~

l~ 400

11 300

10

0 .7 .8 .9 1.0 1.1 1.2

lJa i Zf £mf1J Bad~ C-ai!Z , KJ FIG. 10.-Rate and composition of growth in implanted steers fed hay/ grain

diets. Source: Garrett (12).

Carcass fat at similar final carcass weight increased from 31 to 37% as rate of gain increased from 0.77 to 1.13 kg/ day. These observations are consistent with recent OARDC research discussed previously.

While the relationship of rate of gain to compo­sition of gain over a total feeding period can be deter­mined ifrom these experiments, intermediate composi­tion estimates are needed to determine age and stage of growth effects on the relationships of rate to com­position of growth at specific ages and weights. Fig­ures 12 and 13 indicate the effects of weight and rate of gain on daily protein growth in small and large mature size cattle. The data for these relationships

320

300

28

260

0

3 Ca.rca5.5 Fat

.7

Pai 221 .:/

a

.8 .9

were derived through use of the D20 dilution proce­dure for measuring body composition at specified in­tervals during growth in Charolais and in Angus X steers. As is evident, rate of protein growth de­creases with increasing body weight, indicating ef­fects of age and relative maturity on protein deposi­tion. Also, rates of protein deposition are greater for large (Figure 6) than small mature size cattle (Fig­ure 7) at any weight or rate of gain. Rates of pro­tein growth for either cattle size increase very little at rates of gain in excess of 1.0 kg/ day, documenting the existence of a biological limit for daily protein growth.

38

37

36

35

4

33

0 0

l'.O 1.2

FIG. 11.-Rate of gain and body composition of steers fed 'hay/grain diets. Source: Garrett (12).

1 l

AT 250 kg

- 1.0 kg gain contains 17.9% (179 g) protein, 18.9% fat

- Additional .5 kg gain has only 3.0% (15.2 g) protein and is 86.2% fat

---------------- .200

180

.160

.140

.120

.10 0

.080

.060

.040

c

0

C>

.020 0

Da;/y E mpty

1.so 1.oo

.0

.so

FIG. 12.-Rates of protein deposition in steers from 700 .kg dams as a function of empty body weight and rate of gain.

Source: Byers and Rampala (10).

12

0

AT 250 kg

- 1.0 kg gain contains 15.2% (152 q) protein, 30.9% fat

~ Addittonal .5 kg gain has only 2.8% (14 g) protein, and is 87.3% fat

Da;/y Empty

Body Ga; n, kg

---- ................... ___ _

..................

.200

.180

.160

.140

. J°20

. 100 m

.080

.060

.040

.020

000

..:.'.

c:

c: ·-QI -0 .. Q..

0 c

FIG. 13.-Rates of protein deposition in steers from 350 kg dams as a function of empty body weight and rate of gain.

Source: Byers and Rampala (l OJ.

13

TABLE 7 .-Effect of Growing and Finishing Phase Implants on Composition at Slaughter.

Anabolic Stimulus During None DES Ralgro Growing (Wintering):

Item Finishing: None DES None DES None DES SEm

No. steers 23 20 18 18 19 21 Live weight, kg 436.7 462.1 462.7 464.9 471.6 474.4 7.5 Hot carcass wt, kg 274.3 287.6 289.l 298.3 292.5 302.2 2.9

Carcass: Protein, % 14.09 14.25 14.29 14.57 14.30 14.40 0.14 Fat, % 35.5 34.8 34.7 33.5 34.7 34.2 0.6

Empty body: Weight, kg 403.9 421.9 424.1 436.6 428.6 441.8 8.1 Gain/day, kg 1.17 1.36 l.24 1.49 1.34 l.55

Protein, % 15.36 15.49 15.52 15.75 15.53 15.61 0.11 kg 6.2.03M 65.35b* 65.82b 68]6C* 66.56b 68.96C

Fat, % 32.3 31.7 31.6 30.4 31.5 31.1 0.6 kg 130.5 133.7 134.0 132.7 135.0 137.4

*Means bearing different superscript letters differ, P < .01. Source: Byers (3).

BIOLOGICAL AND PHYSIOLOGICAL LIMITS FOR NET PROTEIN GROWTH IN CATTLE

While mature size and genetic potential establish the maximum upper limits for daily protein growth, other factors determine the extent to which these theoretical limits will ever be achieved. The sex class of an animal establishes different biological limits for bulls, steers, and heifers that are similar in mature size, genetics, and nutritional adequacy. The use of anabolic implants (DES, Synovex-s, Ralgro) mimics endogenous estrogens, alters the actual physio­logical limit for protein growth at the cellular level, and allows an animal to deposit protein at rates closer to theoretical genetic limits. The effects of these agents in steers on body composition and protein growth are indicated in Tables 7-10.

The use of implants in growing calves to year­ling weight during a 175-day wintering period fol­lowed by use of implants in a 96-day finishing feed­ing period was studied with 120 Hereford steers. Calves of similar yearling weight from each winter-

TABLE 8.-Effect of Using DES Implants on Com­position of Growth.

Item Implant: None DES SEm

No. steers 60 59 Days fed 95 95 Protein gain, kg 9.88** 13.21 0.51

% of gain 8.12** 9.54 0.28 Fat gain, kg 80.68 82.00 1.79

% of gain 68.46** 61.38 1.44 Daily protein gain, g 103** 138 5 Daily fat gain, g 844 857 18

**Means differ, (P < .01). Source: Byers (3).

14

ing group were used in the finishing study. Data in Table 7 show effects of wintering/finishing implant combinations on body composition at slaughter. Use of either implant during the wintering period in­creased total protein production. Use of DES in the finishing period increased protein present at slaugh­ter by 3.1 kg. The response to wintering/finishing implants in protein storage was additive and steers that received either implant during the wintering phase and DES during the finishing period deposited a total of 6.9 kg, 11.1 % ) more total protein. These data indicate that anabolic effects of implants used in separate phases of animal growth are additive in increasing total protein, muscle, and lean meat pro­duction.

The mechanism of response is indicated in Table 8. DES increased daily protein growth by 38% with no alteration in daily fat retention. The physiologi-· cal limit for daily net protein growth was increased with DES. Similar responses were observed in an­other experiment (Table 9) with 64 Hereford year­ling steers. Use of DES in basal shelled corn diets increased rates of protein growth by 31 % at the ex­pense of fat growth which was reduced. With sup­plemental protein (soybean meal) in the diet, DES effected a 45% increase in daily protein growth with no change in fat deposition. Again, the primary ef­fect of DES was an increase in the physiological limit for daily protein storage, and effects on fat deposition simply reflect energy consumed above needs for pro­tein growth.

Data from an experiment with 159 Hereford steers (Table 10) further support wintering period implant effects on final composition following a sepa­rate finishing period with cattle of similar average

TABLE 9.-Body Composition and Growth of Cattle Implanted with DES

Implant: None DES

Item Protein: Basal SBM Basal SBM SEm

No. cattle 16 16 16 16 Days 89 89 89 89

Carcass

Weight, kg 247.2 260.0 253.0 275.8 2.8 Protein, % 14.66 14.64 14.99 14.83 0.16 Fat,% 33.1 33.2 31.8 32.4 0.7

Empty body

Weight, kg 366.9 384.4 374.8 405.9 6.8 Protein, % 15.82 15.80 16.07 15.96 0.13

kg 58.04 60.74 60.23 64.78 Fat, % 30.l 30.l 28.8 29.4 0.7 Gain

Protein, g/ day 89.7M l 06.3n, b* l 17.5b 153.7°* 7.2 Fat, g/day 748.4 821.4 720.6 844.3 38.9

*Means bearing different superscript letters differ, P < .01. Source: Byers and Mo'ffitt (7).

TABLE 10.-Wintering Period Implant Effects on Body Composition Following a Finishing Period.

Item None DES Synovex Ralgro SEm

No. steers 45 32 46 36 Days on finishing period 127 127 127 127 Carcass wt 291.0 292.3 295.6 289.3 3.0 Carcass fat, % 37.9n* 36.3b* 34.4C* 36.2b 0.55 Carcass protein, % l 3.53n 13.91? 14.36C 13.93b 0.12 Empty body weight

fol lowing wintering 299.3 300.2 299.l 296.4 1.3 Empty body parameters

following finishing period Weight, kg 426.6 428.4 432.9 424.3 4.1 Fat, % 34.56n 33.0b 3l .3C 33.0b 0.5 Protein, % 14.92n 15.22b 15.58C 15.24b 0.10 Protein, kg 63.65 65.20 67.45 64.66

*Means bearing different superscripts differ, P < .01. Source: Byers and Klosterman (6).

weight from all implant treatment groups. · All im­plants used in the wintering period ( 240 days) in­creased total protein present in the empty body fol­lowing a 127-day finishing period during which time no implants were used.

The effects of DES on diversion of energy from fat to protein growth are indicated in Figure 14. In two experiments with Hereford steers fed varying for­age/ grain levels (discussed with Figures 4 and 6) rate and composition of growth were evaluated. As is evident, DES implanted steers deposited more pro-

15

tein and less fat at any rate of gain, with the relative difference increasing with rate of gain.

These studies clearly indicate that anabolic im­plants alter the partitioning of energy between pro-. tein and fat and increase the physiological limits for daily protein growth in steers. Judicious use of these anabolic implants during the respective phases of beef cattle growing and finishing will effectively increase total lean beef production per steer provided suffi­cient dietary energy, protein, and other nutrients are available.

650

600

£n11ply Bod/ Growth 550

500

Fat/ 450

Dal~ I 400

---.,, 350

~ 300 ...........

~ 180 250 ~

~ 160 200 ~ (S

~ 140 150 "-.I ~ \)

100 <i-J '"'\-...I 120 ~

(~ ~ 100 50

80 Profei'%_ 0

60 Day'J 40

0 .2 .4 .6 1.0 1.2 1A

FIG. 14.-Effects of DES on tissue storage over a range of growth rates. Source: Byers (3).

MANIPULATING PROTEIN AND FAT GROWTH PATTERNS

TO OPTIMIZE CATTLE AND FEED RESOURCE USE IN BEEF PRODUCTION SYSTEMS Beef cattle feeding and management systems

commonly used include many aspects of growth pat­tern regulation addressed in these research investi­gations. Most systems include some phase of de­ferred feeding where animal growth rates are less than maximal. This restricts fat deposition and allows more total time for protein growth to occur, such that the animal is then older, has accumulated more total protein and muscle, and is heavier when slaughter condition (low choice grade) is eventually reached. Common terminology for such deferred systems of growth include: wintering, stockering, background­ing, summer grazing (as yearlings), growing, and forage finishing programs. As is evident from the research discussed, the more that growth rate and fat deposition are depressed or restricted, the greater is the increase in final slaughter weight needed to at­tain similar carcass fatness and finish. Also, the

16

amount of fat present in a steer's carcass at a com­mon final weight progressively decreases with degree of restriction in growth rate.

Common systems of deferred feeding include growing feeder calves after weaning on forage grow­ing programs either in feedlots (corn silage, haylage) or in extensive systems (wheat pasture, crop-residues, stocker grazing, wintering) until they reach yearling weights of 270-370 kg, after which they are normally shifted to high energy grain finishing feedlot rations. Average size steers handled in these deferred feeding systems will reach low choice grade and fatness at ,.._, 70 kg ( 150 lb) heavier weight than similar calves put directly on high grain feedlot rations as feeder calves at weaning. The research with energy levels and cattle of several mature sizes indicates that smaller mature size cattle are better suited to these growing­deferred feeding programs than large size cattle since large mature size cattle, :if fed in these deferred feed­ing systems, will yield unacceptably large carcasses when they finally reach low choice grade and fatness. While small and large mature size cattle will grow

with similar rates and efficiency of gain on grain diets, rate and efficiency of gain favor small size cattle on forage diets.

In best utilizing high energy cereal grain feed­stuffs for a total feeding program starting with weaned calves~ larger mature size calves appear most suitable. High grain diets fed to small and average mature size (frame size) calves will cause very rapid fat deposition and these steers will reach desired car­cass fatness at very light carcass weights and at very young ages, possibly before they have had adequate time to deposit adequate intramuscular fat ( marb­ling) to reach the low choice grade. Large size cat­tle have the inherent potential for depositing more pro­tein/ day and a high energy diet allows fat deposition such that they reach carcass fatness needed for slaughter at an acceptable carcass weight.

Therefore, smaller cattle types are favored on forage feeding systems, while grain feeding programs allow large type cattle to express their full potential for protein growth while enhancing rates of fat depo­sition such that desired carcass fatness is achieved at lighter and more desirable ·carcass weights.

Utilizing this nutrition x mature size interac­tion to ~c:lvantage will best optimize use of both feed and cattle resources for the most efficient production of carcass beef with desired fatness at acceptable car­cass weights.

In commercial practice, these systems usually involve deferred feeding programs followed by high grain finishing for "English" breeds of cattle (typical­ly Hereford, Angus, and their crosses) and shelled corn/protein-mineral supplement rations for Holstein and large mature size beef (Charolais, Simmental, Limousin, Chianiana, etc.) calves, starting at wean­ing or earlier.

The ultimate goal in these systems is to match feed resources with the physiological potential for nu­trient use in cattle to be fed, to improve the overall efficiency of beef production.

LITERATURE CITED 1. Byers, F. M. 1980. Determining effects of

monensin on energy value of corn silage diets for beef cattle with linear or semi-log methods. J. Anim. Sci., 51.

2. Byers, F. M. 1980. Diet net energy value and composition of growth of cattle fed a vegetative corn silage and high moisture corn. Nat. Amer. Soc. Anim. Sci. ( Abstr.).

3. Byers, F. M. 1979. Effect of anabolic stimuli on composition and efficiency of tissue growth in cattle. OARDC, Beef Cattle Research Re­port, Anim. Sci. Series 79-1, p. 83.

17

4. Byers, F. M. 1980. Effects of limestone, mon­ensin and feeding level on corn silage net energy value and composition of growth in cattle. J. Anim. Sci., 50.

5. Byers, F. M. 1980. Energy utilization and composition of growth in cattle fed corn stalk­lage and high moisture corn. Midwest Amer. Soc. Anim. Sci. ( Abstr.).

6. Byers, F. M. and E. W. Klosterman. 1979. Growth and estrogenic response to anabolic. im­plants. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 89.

7. Byers, F. M. and P. E. Moffitt. 1979. Physio­logical and nutritional modification of growth patterns with DES, monensin and wintering nu­tritional plane. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 75.

8. Byers, F. M. and C. F. Parker. 1979. Level of nutrition and composition of growth of cattle varying in mature size. OARDC, Beef Cattk Research Report, Anim. Sci. Series 79-1, p. 67.

9. Byers, F. M. and R. E. Rompala. 1980. Level of energy effects on patterns and energetic effi­ciency of tissue deposition in small or large ma­ture size beef cattle. Proc., 8th Int. Symposium on Energy Metabolism, Cambridge, England. Butterworths, pp. 141-146.

10. Byers, F. M. and R. E. Rompala. 1979. Rate of protein deposition in beef cattle as a function of mature size. and weight and rate of empty body growth. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 48.

11. Byers, F. M., C. F. Parker, V. R. Cahill, and R. L. Preston. 1976. Plane of nutrition re­sponse and mature size. OARDC, Beef Day Report, p. 1.

12. Garrett, W. N. 1979. Influence of time of ac­cess to feed and concentrate roughage ratio on feedlot performance of steers. California Feed­er Day, p. 11.

13. Moulton, C. R., P. F. Trowbridge, and L. D. Haigh.. 1922. Studies in animal nutritio:µ. III. Changes in chemical composition on differ­ent planes of nutrition. Missouri Agri. Exp. Sta., Bull. 55.

14. Newland, H. W., F. M. Byers, and D. L. Reed. 1979. Response of different cattle types to two energy levels in the feedlot. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 21.

15. Newland, H. W., F. M. Byers, and D. L. Reed. 1979. Response of three cattle types to two energy levels and two rates of energy feeding. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 15.

16. Preston, R. L., R. D. Vance, and V. R. Cahill. 1973. Energy evaluation of brewers grains for growing and finishing cattle. J. Anim. Sci., 37:174.

17. Woody, H. D. 1978. Influence of ration grain content on feedlot performance and carcass characteristics. Ph.D; Thesis, Michigan State Univ.

Net Energy Value of Grain and Forage Diets for Beef Cattle F. M. BYERS1

INTRODUCTION Corn and corn silage are the most common feed­

stuffs used in Midwest cattle feeding systems. They are currently fed in essentially all combinations of levels to growing and finishing cattle. Whether or not optimum ratios of forage to grain in silage (and in the ration as fed) exist is a concern that has re­ceived considerable attention in cattle feeding re­search. The primary concern is to maximize effi­ciency in beef production in use of all resources: feed, cattle, and management. Efficient use of energy harvested as grain and as forage in producing carcass beef is the principal objective in evaluating corn si­lage and grain feeding systems.

Concerns that need to be addressed include the relative net energy value of grain vs. forage, the en­ergy value of grain in corn silage, and the energy value of grain added to a corn silage or forage diet. Previous research in energy balance metabolism stud­ies ( 4) and in slaughter balance studies ( 14) indi­cates that the efficiency of use of forage and grain energy, and therefore forage, and grain net energy values may differ with the relative combination of forage and grain fed. Also, cattle feeding studies in­dicate that feeding silage and corn in separate phases

TABLE 1.-Energy Utilization of Corn Grain and Corn Silage with Feeds Fed at a Constant Level or in a Split Forage-then Grain Feeding System.

Feeding System: Two-Phase Constant

No. cattle 24 24 Initial wt, kg 282 282 Final wt, kg 543 541 Days fed 218 216 Av. daily gain, kg 1.20 1.20 DM/day, kg 8.10 8.26 Grain/day, kg 4.44 4.67 Corn silage DM/ day, kg 3.66 3.59 OM/gain 6.75 6.88 Efficiency of ME use for gain 42.5 39.2 NEg 1.20 1.14

Source: Newland, Byers, and Reed {11).

18

of cattle feeding ( 6, 10, 12) may result in more effi­cient feedlot gain, suggesting an improvement in effi­ciency of f eedstuff utilization.

One of the principal reasons for this response in­volves what are commonly called. "associative effects" of feeds where the addition of a readily available carbohydrate source (starch in corn grain) to a for­age diet reduces cellulose digestion and results in less energy digested from the forage and thus reduces for­age and possibly grain energy utilization.

SYSTEMS OF FORAGE AND GRAIN FEEDING Systems of forage and grain handling and proces­

sing were investigated in a series of growing-finishing cattle feeding energy balance studies to quantitate efficiency of forage and grain energy utilization and net energy value, when forage and grain are fed sepa­rately and in various combinations.

Split-Phase Feeding In addressing the timing of feeding corn silage

and grain, an experiment (Table 1) was conducted evaluating a split-phase feeding program vs. feeding shelled corn as a constant 56% grain diet throughout the feeding period. In the split-phase group, cattle were fed corn silage and protein supplement for 71 days and then were switched to a shelled corn/limited silage diet. While rate of gain was similar, efficiency of gain was enhanced with the split-phase system.

Energetic efficiency showed further response. Efficiency of energy use for gain was improved 8.4% and diet NEg value was enhanced by 5.3 % with the split-phase system where the silage was fed in the first part of the feeding period and the grain was fed later. These results are consistent with cattle feeding feed efficiency responses reported by Meiske and Goodrich ( 10), Dexheimer et al. ( 6), and Newland et al. ( 12) with split-phase feeding systems. Thus, energy utili-zation is improved by feeding forage and grain in

1Associate Professor of Animal Science, Texas A&M University, College Station; formerly Assistant Professor of Animal Science, Ohio Agricultural Research and Development Center and The Ohio State University.

separate periods during growing and finishing of cattle.

SEPARATION OF FORAGE AND GRAIN Corn silage as harvested contains variable

amounts of grain, with grain content commonly rang­ing from 10 to 50% of the dry matter. To determine the energy value of the grain in the silage, several sys­tems of separating grain and forage portions of the corn plant at harvest were evaluated.

Dry Corn and Cubed Stover The first involved harvesting dry shelled corn

and harvesting the corn stalks as soon thereafter as dry enough in large round bales ( 3). To improve the use of the energy in the stalk portion, the stalks were treated with calcium oxide ( CaO) at 4% of the dry matter and cubed in a John Deere 390 stationary cuher. This was one of several procedures studied to increase the cellulose and hemicellulose available for digestion by rumen microbes.

Net energy values of the stalks, grain, and sev­eral combinations are indicated in Figure 1. As is evident, net energy for gain (NEg) increased slowly with added grain up to 70% of the diet and increased rapidly to a NEg value of 1.63 kcal/ g for the 98.8% grain diet. Diet NEg value did not increase linearly with added grain, indicating that grain added in high

forage diets resulted in less efficient use of either the forage or grain energy with these combinations.

The CaO treatment of the stover increased the digestible energy (DE) level (9) from 60 to 62% when fed alone and increased the DE value of a stover/corn diet from 65.1 to 68.8%. A primary effect was on cellulose digestibility which was en­hanced with CaO treatment, especially when grain was also fed. Therefore, the associative effects . de­creasing the energy value of the mixed diets may have been somewhat greater if untreated stover had been fed.

Vegetative Corn Silage and High-Moisture Corn

Following the research with dry corn stover, a forage variety of corn planted at a high population resulting in few ears and little grain was evaluated with various levels of high-moisture corn. The ob­jective was to measure the energy value of good qual­ity, highly digestible corn plant forage as corn silage fed alone and the value of corn grain added to this forage.

One hundred a11d twenty Hereford feeder calves were fed 80, 60, 39, 18, or 3% of this ensiled forage ( DM basis), with protein supplement and high-mois­ture corn making up the remainder of the ration. Overall _results· are reported elsewhere ( 1 ) ·. The net

2.3

Al£l C1~1J} l,~?ue oJ Cu.bed Ca.O -C-rea.-2-ecr.1

Corr; Stove.r ar;d Con?

2.1

1.9

1.7

15

~l.3

" ~ 1.1

~ .9

\~ .7

.s

.3

100 90 80 70 60 50 40 30 20 10 0

Perce1?: For;e

FIG. 1 .-Net energy values of cubed CaO treated corn stover with several levels of whole shelled corn for cattle.

Source: Byers and Jones (3).

19

A{t £tzerjy o.f Ve7t:;ca-b.'ve Corl( Sila?e 2.2

2.1 aJZd liz?h ){ozsfure Corf!

1.9

1.9

l.

'-....~ 1.6 ""-.> ~

1.5 ~

~ 1.2

1.1

1.0

.9

.8

100 90 80 70 60 50 40 30 20 10 0

?erceflf: Foraje Fl.G. 2 .. -Net energy values of a high forage corn silage with several levels

of high moisture corn. Source: Byers (2).

2.2

2.1

2.0

1.9

1.8

1.7

16

15

\.4

1.0

~9 .8

.7

.6

.s

.4

.3

.2

100

Yet £11erjf Value ar Stal)d.aje a.l/d

Hij4 )(aislure. Corl(

90 80 . 70 60 50 40 30

'Percent Fora7e 20 10 0

FIG. 3.-Effects of NaOH treatment on net energy values of corn stalklage fed with several levels of high moisture corn. Source: Byers (l ).

energy values of this silage with several levels of corn were as indicated in Figure 2.

As is shown, the NEg value of the high forage diet with protein supplement was 0.98 kcal/ g, a value similar to the NRC table value for corn silage. NEg value increased very little with another 20% grain as high-moisture corn (NEg of 1.01 kcal/g) in the diet. Adding an additional 21 % corn (39% forage diet) resulted in an increase in NEg to 1.19 kcal/g. NEg value for the 18 % forage, 82 % grain diet was also somewhat greater, with a value of 1.31 kcal/ g. The net energy value ( NEg) for the high grain ( 3 % forage) diet was very much higher, with a NEg of 1. 72 kcal/ g. Therefore, it is obvious that levels of grain added to the forage diet at up to 50% of the dry matter had little effect on diet NEg value.

In essence, the value of the corn added in up to 50% grain diets was really no greater than the NEg of the forage to which it was added, which was ,_, 1.0 kcal/ g. This is perhaps why when corn silage is fed to cattle as the main f eedstuff, the level of corn in the silage does not have a big effect on growth and performance. Similar conclusions were reached by Woody ( 16) where NEg value of silage diets only in­creased from 0.94 to 1.04 as silage grain content in­creased from 30 to 50% of the dry matter. When grain is added to corn silage diets as fed, the grain in the silage would contribute just like the grain added in increasing total diet grain level to the point where it is more efficiently utilized (so+% grain) .

Stalklage and High-Moisture Corn Another approach was evaluated in a recent

OARDC study as a potential system in separately harvesting, storing, and feeding the grain and forage portions of the corn plant which involves harvesting the grain as whole shelled corn as early as feasible ( ,_, 30% moisturel) and immediately chopping and ensiling the stalks while they still are somewhat green and have sufficient moisture to ensile without the addition of water. The stalklage was ensiled either directly as harvested or with NaOH added at 4% of the dry matter to saponify oxygen ester bonds of ace­tyl groups on hemicellulose and similar chemical bonds between cellulose and lignin. The objective was to increase cellulose and hemicellulose digestion in the rumen to allow greater utilization of forage energy present in structural carbohydrate forms. The relative success of this approach is indicated in Figure 3.

In this study which is covered in more detail elsewhere ( 2), 160 Hereford steers were fed corn stalklage, either control or NaOH treated with sup­plement and high-moisture corn included at 20, 50, 75, or 95% of the diet dry matter. While the treat-

21

ment of stalklage with Na OH increased the NEm and NEg values of all diets, the response was greatest in the 80% forage diet where the diet NEg value was essentially doubled from 0.23 to 0.42 kcal/ g. With both untreated or NaOH treated stalklage, the NEg of the diet increased in a curvilinear fashion with level of added grain, indicating substantial negative "asso­ciative effects" with intermediate forage/ grain diets. Response to added grain in the untreated forage diets was less curvilinear, indicating fewer associative ef­fects and thus illustrating the concept that feeds that arc very indigestible. and have very low NEg value when fed alone will suffer little depression in digesti­bility and NEg value when available carbohydrate sources such as starch ·are added.

Treatment of stalklage with N~OH was most ef­fective in increasing diet energy value when the stalk­lage was fed without adding corn. NaOH treatment was not effective in preventing negative "associative effects" in mixed forage/ grain diets since observed NEg values in these diets were lower than would be predicted from the high forage and high grain diet NEg values measured.

In all avenues investigated, forage and grain combinations in mixed diets resulted in lower diet NEg values than would be anticip.ated from NEg values determined for forage and grain fed essentially alone in the same study. Therefore, no system ex­plored allowed complete utilization of forage and grain energy when fed in mixed diets, and negative associative effects persisted in all mixed diet feeding systems.

NATURE AND SCOPE OF ASSOCIATIVE EFFECTS WITH MIXED GRAIN/FORAGE DIETS­

IMPLICATIONS FOR CATTLE FEEDING SYSTEMS Associative effects involve a non-linear response

in digestibility and net energy value when two feeds or diets are combined. While all facets of the prob­lem are not completely understood, several mecha­nisms are clearly involved. Rate of digestion, rate of passage, and level of intake are three of the more critical factors determining the magnitude of associa­tive effects.

Rate of digestion is perhaps most critical. Feed­stuffs (primarily forages) with a high extent but low rate of digestion are most susceptible to depression in digestion when rapidly ferment~ble carbohydrates are added to a diet. When soluble carbohydrate is added to a diet, the rumen microbial population shifts emphasis from structural carbohydrate (cellu­lose and hemicellulose) digestion to fermentation of the soluble carbohydrates added, resulting in a reduc­tion in fiber digestion. Rumen pH is also reduced as a result of the soluble carbohydrate fermentation

which serves to further restrict activity of cellulolytic bacteria. As a result, when the rumen ingesta passes out to the lower tract, less of the cellulose has been digested. A compounding problem includes level of intake and effects on rate of passage.

Associative effects are scaled to level of intake. The reason for this is that as grain is added to forage diets, level of consumption usually increases. As level of intake increases, rate of passage of ingesta through the rumen also increases and further restricts the ex­tent of digestion of structural carbohydrates in for­ages. This effect is more critical for forages with large amounts of fermentable fiber with low amounts of lignin in the cell walls. Those forages containing very little fiber (high in solubles), containing fiber with fast rates of digestion, or with· indigestible fiber which is high in lignin and will not be digested in any event, suffer the least in depression of digestibility and energy value when grain is added.

As a result, feeds such as high quality alfalfa hay which have very fast rates of digestion will be mini­mally affected by combination with grain or other soluble carbohydrate sources. Feeds that are indi­gestible will have low energy values whether or not starch is present and will also be minimally affected by addition of grain. Forages including cereal grain

2.3

2.2

2.1

~~ 2.0

""" ~ \I 1.9 ~

1.8

~ 1.7

1.6

1.5

1.4

1.3

1.2

1.1

100 90 80 70 60 50

plant forage (corn silage, sorghum silage) and cereal seed by-products (brewers grains, distillers grains, bran) are among the most sensitive of all feedstuffs fed to "level of intake" mediated negative associative effects of soluble carbohydrate on feed energy diges­tion ( 15). These feedstuffs are typically high in cell walls and low in lignin, and digestible energy yield depends on extensive ruminal fermentation of the structural carbohydrates, which is restricted as rate of passage increases and ruminal pH decreases with higher levels of intake of mixed forage/ grain diets.

A classical example is illustrated (Figure 4) in data of Preston ( 13), which has been re-evaluated with respect to level of intake of mixed diets fed. The data as published document an extremely wide scatter of diet NEg values for either 15 or 35 % silage diets (from 1.2 to 1.6 kcal/ g) and perhaps the best conclu­sion might be that within this range of silage/ grain, there is no relationship between grain level and diet NEg value.

Further inspection reveals an explanation. Since level of intake determines the extent to which asso­ciative effects are manifested, the relationship of ME intake to the NEg value measured for 15% silage diets was determined through a linear regression of NEg value on ME intake. A similar relationship for

40 30 20 10 0

?ercer;f Conz 5i Zar:

FIG. 4.-Effects of level of intake on net energy values of corn and silage fed in various combinations.

Source: Preston (13).

22

the 35% silage diets was calculated. For the ,__, 15 % silage diets ( n = 5), the relationship was as fol­lows: NEg (kcal/g) = 4.045 - 0.0091 (ME, kcal/ kg0

•75/day); R 2 = 0.76. The same relationship for

the ,__, 35 % silage diets ( n = 7) was: NEg (kcal/ g) = 2.83 - 0.0053 (ME kcal/kg.o.75/day); R 2 = 0.67.

As is evident, the NEg values of these mixed diets, while at first glance appearing quite scattered, are in fact highly related to level of intake and clearly illu­strate the effect of level of intake on the magnitude of associative effects observed. Calculated NEg values from these regressions were plotted for 15 and 35% silage levels at two ME intakes and the lower curves indicate these relationships. Since little variation in 97+% grain diet or high silage diet NEg values existed, and since associative effects would be minimal in these diets in any case, little relationship of level of intake and NEg would be expected and in fact no rela­tionship existed on these diets. These data clearly illustrate the relationship of level of intake to associa­tive effects and depression in mixed diet net energy ( NEg) values in common beef cattle diets.

Data of Garrett ( 7) illustrated in Figure 5 docu­ment the effects of grain added to forages possessing rapid rates . of fermentation. As previously discussed, forages with rapid rates of fermentation will suffer

minimal depressions in energy utilization in the face of a hostile ruminal environment (soluble carbohy­

. drate, fast rate of passage, low pH). Alfalfa hay is low in total cell walls but high in

cell wall lignin content, which makes the cell walls rather indigestible. The low cell wall content and high level of cell solubles are responsible for the fast rate of dry matter digestion and respectable net energy value of alfalfa. For this reason, adding grain and readily f ermentable carbohydrate to an alfalfa hay based diet would have only minimal effect on digestion of available energy, and as Garrett's data indicate, this is exactly the response observed. A linear relationship of NEg to percent forage is probably as valid as the curvilinear quadratic function shown. Data in this study can be related only to grain/forage diets with similar rapidly fermentable low cell wall forages con­taining substantial lignin in the cell wall, and these re­sults are certainly not applicable to cereal grain forages and· other similar grasses.

Diet and individual feedstuff net energy values in cereal grain forages with respect to level of grain added are detailed in research of Byers et al. ( 4), illustrated in Figures 6 and 7. The reason for the non-linear diet NEg value with level of corn in Figure 6 is evident in Figure 7.

2.2

2.1

A/cd £177 Value o.T l[!Jal~a !la;r Conz Vz:et.s

2.0

1.9

1.8

1.7

0~1.6 t:t

~ 15

1.4

~ 1.3

1.2

1.1

1.0

.9

.8

100 90 80 70 60 50 40 30 20 10 0

FIG. 5.-Net energy values of alfalfa/sudan hay diets with various levels of corn.

Source: Garrett (7).

23

Net energy

Kcal/g

2.40

2.20

2.00

1.80

1.60

1.40

1.20

90 100

% total grain in diet (includes grain in silage)

FIG. 6.-Net energy for maintenance and gain of corn silage-corn grain diets in relation to the level of total grain in the diet.

Source: Byers et al. {5).

2.40

2.20

2.00

1.80

00 '- 1.60 <ii u

""' >. 1.40 llO Qi c (I)

a; 1.20 z

1.00

0.80

0.60

0.40

0 15 25 35 45 55 65 75 85 95

Total corn in diet,%

FIG. 7.-Net energy for maintenance and. gain of corn plant forag·e and corn grain vs. total· grain in diet, percent.

Source: Byers et al. {4).

24

As level of corn in the diet is increased, the net energy value of the forage portion decreases rapidly while the net energy value of the grain increases. Since forage particles in the small intestinal ingesta may limit intestinal starch disappearance, starch in grain passing from the rumen in forage diets may not be totally digested, and thus energy utilization of the grain may also be impaired ( 8), which is indicated in these data~

Therefore, with current technology, energetic ef­ficiency will be less than optimal when cattle are fed corn silage or similar type forages in diets with added grain. The only feasible approach is to separate the forage and grain to the extent mechanically possible and feed these separate feedstuffs during different phases of growing and finishing cattle.

F oi' a variety of reasons, the forage diets are bet­ter suited to early stages of feeding in growing rations for calves where intake relative to maintenance re­qui:rements is high and energy density of gain is low (primarily muscle, which is protein, mineral, and 74% water). The grain should subsequently be fed to finishing cattle as the primary ingredient with little forage in the diet. This split-phase or two-phase feeding system will maximize the efficiency of feed­stuff energy utilization in production of carcass beef.

LITERATURE CITED 1. Byers, F. M. 1980. Diet net energy value

and composition of growth of cattle fed a vege­tative corn silage and high moisture corn. Nat. Amer. Soc. Anim. Sci. (Abstr. No. 585).

2. Byers, F. M. 1980. Energy utilization and composition of growth in cattle fed corn stalk­lage and high moisture corn. Midwest Amer. Soc. Anim. Sci. (Abstr. No. 87).

3. Byers, F. M. and J. D. Jones. 1978. Level of grain and energy value of calcium oxide treated cubed stover. Nat. Amer. Soc. Anim. Sci., No. 287, p. 329 (Abstr.).

4. Byers, F. M., D. E. Johnson, and J. K. Matsu­shima. 1976. Associative effects between corn and corn silage on energy partitioning by steers. In M. Vermorel (Ed.), Energy Metabolism of Farm Animals, E.A.A.P. Pub. 19, p. 253.

5. Byers, F. M. J. K. Matsushima, and D. E. John-

25

son. 1975. Associative effects on corn net en­energy values. J. Anim. Sci.,- 41 :394.

6. Dexheimer, C. E., J. C. Meiske, and R; D. Goodrich. 1971. A comparison ·of four systems for feeding corn silage. Univ. of Minn. Beef Re­search Report, B-151.

7. Garrett, W. N. 1979. Relationships among diet, metabolizable energy utilization and net energy values of feedstuffs. J. Anim. Sci., 49: 1403.

8. Joaning, S. W., D. E. Johnson, and B. P. Barry. 1980. Nutrient digestibility depressions in corn silage-corn grain mixtures fed to steers. J. Anim. Sci. (in press) .

9. Jones, J. D. 1980. Level of grain and energy value of calcium oxide treated cubed corn sto­ver. M.S. Thesis, The Ohio State University.

10. Meiske, J. C. and R. D. Goodrich. 1969. A comparison of four different progi:ams for feed­ing a given amount of corn silage. Univ. of Minn. Beef Research Report, B-128~

11. Newland, H. W., F; M. Byers, and D. L. Reed. 1979. Response of three cattle types to two energy levels and two rates of energy feeding. OARDC, Beef Cattle Research Report, Anim. Sci. Series 79-1, p. 15.

12. Newland, H. W., R. L. Preston, and V. R. Ca­hill. 1972. Methods of feeding corn silage and shelled corn to finishing calyes. OARDC, Beef Cattle Res. Summary 53, p. 23.

13. Preston, R. L. 1975. Net energy evaluation of cattle finishing rations containing varying proportions of corn grain and corn silage. J. Anim. Sci., 41 :622.

14. Vance, R. D., R. L. Preston, V. R. Cahill, and E. W. Klosterman. 1972. Net energy evalua­tion of cattle finishing rations containing vary­ing proportions of corn grain and corn silage. J. Anim. Sci., 34:851.

15. VanSoest, P. J., J. Fadel, and C. J. Sniffen. 1979. Discount factors for energy and protein in ruminant feeds. Cornell Nutrition Confer­ence, p. 63.

16. Woody, H. D. 1978. Influence of ration grain content on feedlot performance and carcass characteristics. Ph.D. Thesis, Michigan State Univ.

A System of Starting Small Calves on NPN Corn Silage with Bypass Protein

H. WILLIAM NEWLAND and FLOYD M. BYERS1

SUMMARY Small calve~ averaging 415 lb were full fed urea­

treated corn silage (NPN) or regular silage the first week after arrival at the Northwestern Branch of the Ohio Agricultural Research and Development Cen­ter, near Custar. Hay was fed only during the first week. Bypass · (insoluble) protein added to the NPN corn silage inc:reased the total protein level above recommended levels and resulted in improved per­formance over calves fed regular silage and all na­tural protein sources.

INTRODUCTION Cattlemen ensiling corn silage with NPN fre­

quently have no other silage available and therefore must feed NPN silage to new cattle when they arrive. Iowa researchers ( 6) have suggested that calves un­der 600 lb are unable to utilize NPN adequately for

. proper protein nutrition. This suggests that cattle feeders starting small calves with NPN corn silaae will encounter less than desired performance until the calves reach heavier weights.·

TABLE 1.-Percentage Composition of Protein Supplements Fed During Adaptation Study with Feeder Calves.

Soybean meal, 44

Corn gluten meal*

Dicalcium phosphate

Limestone Salt

Normal

93.9

2.7 1.6 1.8

~~~~~~~~~~~~~~

Protein Type

Bypass (Less Soluble)

93.6 3.7 1.1 1.6

*Replaced with formaldehyde-treated soybean meal last one­half of experiment.

TABLE 2.-Percentage Composition of Silages Fed During Adaptation of Feeder Calves.

Dry matter

Crude protein

Phosphorus

Calcium

Potassium Magnesium

Regular*

31.71 7.39 0.17 0.28 1.13 0.17

*Average values on ·nine samples.

Urea-Treated NPN*

31.00 16.03

0.18 0.33 1.28 0.17

26

Natural protein sources vary considerably in protein solubility and the disappearance of dietary protein in the rumen increases with solubility ( 8) . Soybean meal protein is highly soluble and as a result, a high percentage of the protein is degraded in the rumen and does not reach the lower digestive tract for absorption. Treating soybean meal with for­maldehyde ( 10) and with dry heat (9) decreases its solubility and increases the amount of protein escap­ing, ruminal digestion, and reaching the small intes­tine.

Several natural protein sources including distil­lers dried grains, corn gluten meal, meat scraps, blood meal, and formaldehyde-treated soybean meal have a relatively high level of insoluble protein and are therefore slowly degraded in the rumen. Including sources of less soluble protein in cattle diets contain­ing NPN has improved gains and feed efficiency when compared to soluble protein such as soybean meal ( 1, 2, 3, and 12).

The purpose of this trial was to explore the fea­sibility of using less soluble protein sources for assist­ing in the adaptation of small calves to NPN corn silage.

EXPERIMENTAL PROCEDURES This trial was conducted at the Northwestern

Branch of OARDC. Southeastern Ohio Hereford steer calves were used. Calves were "gate cut" into four groups on arrival. The next day they were weighed, ear-tagged, vaccinated for IBR, wormed, and treated for grubs. The first day they were fed only hay. On the second day they were full fed either regular or NPN corn silage. Hay was gradu­ally decreased and was deleted entirely by 7 days. The diet ration consisted of corn silage (either regu­lar or NPN treated) and the appropriate protein sup­plement. With each kind of corn silage, a normal (soybean meal) or a high bypass protein supplement were fed (Table 1).

The level of supplement feeding was quite con­stant, and the energy level was similar between treat­ments. Protein was added to the regular silage groups at levels to meet the recommended (NRC) protein requirement. Since the NPN silage was ap-

1Professor of Animal Science, The Ohio State University and Ohio Agricultural Research and Development Center; and Associate Profes­sor of Animal Science, Texas A&M University, College Station; for­merly Assistant Professor of Animal Science, Ohio Agricultural Re­search and Development Center and The Ohio State University.

proximately 16% protein, adding the supplement to these groups resulted in protein levels of 19.7% com­pared to 13 .4% for the regular silage groups. The trial lasted 46 days.

Corn gluten meal was used for the bypass pro­tein during the first half of the trial, and formalde­hyde-treated soybean meal was used as the bypass source for the second half.

Corn silage (Table 2) was made from corn grown at the Branch. The NPN silage was made by adding urea at filling time at 20 lb per ton of silage.

RESULTS Results are presented in detail in Table 3. Calves

receiving the bypass protein with NPN silage (Lot 3) gained significantly faster than any other treatment. Performance of calves fed the bypass protein averaged 0.22 lb per day above those fed the normal protein ( 1.63 lb vs. 1.41 lb). Feed conversion was approxi­mately 17% better for calves fed the bypass protein compared to those fed the normal protein source.

The superior performance of calves fed NPN si­lage vs. regular silage and bypass protein is very in­teresting and deserves further research. Recent re­search ( 13) suggests that the combination of NPN and a bypass protein is highly efficient, particularly for high fiber rations. The reason is that the slowly degraded protein from corn gluten meal passes to the lower tract to become a source of amino acids neces­sary for growth, while the ammonia released in the rumen from NPN silage becomes a source of nitrogen for rumen microorganisms for synthesis into protein.

Peterson and Klopfenstein ( 11 ) showed a comple­mentary effect of corn gluten meal and urea in 500 lb calves.

A complicating factor in the present study was that the low protein level ( 13.4%) fed was likely in­adequate for calves this size, as indicated in the work · of Byers and Maxon ( 5) . The calves fed the NPN silage and bypass protein consumed the most protein/ day ( 818 g) and also gained the .fastest, indicating possibly that total protein intake as well as protein type were involved in the response.

Calves fed NPN silage with the conventional protein source were receiving a 19. 7 % protein diet and gained similarly to those fed a much lower pro­tein level with regular silage, indicating no value in combining NPN silage and soybean meal. It is pos­sible that so much of the protein from soybean meal was degraded in the rumen and thus unavailable for absorption in the lower tract that the resulting ration was essentially the same as an NPN corn silage.

Burroughs et al. ( 4) showed that approximately 7 5 % of the amino acids in soybean meal were de­graded in the rumen. One might speculate, however, that performance in these calves may have been re­duced even further without any protein above the NPN silage level. Fox .et al. ( 6) found a significant growth depression in calves fed NPN corn silage the first 28 days after arrival compared to calves started on untreated silage and soybean meal.

The results of this trial demonstrate a possible method of starting small calves on NPN corn silage by incorporating some form of bypass protein in the diet

TABLE 3.-Feedlot Performance of Calves Started on Regular or NPN Corn Silage with Soluble or Insoluble Protein.

Dietary protein, % (dry basis) Percent of total dietary protein from NPN No. days fed No. steer calves Initial wt, lb Final wt, lb Av. daily gain, lb

Average for protein types

Daily feed, lb: Hayt NPN silage Regular silage Protein supplement Daily dry matter, lb Dry matter/gain, lb Daily protein consumed, g

*Significant increase (P < .05). tAll of the hay consumed during first 7 days.

Normal Protein

NPN Regular Silage Silage

19.7 13.4 36.0 0.0 46 46 24 24

415 424 461 474

1.37 1.45 1.41

0.56 0.50 21.84

22.00 1.67 1.77 8.78 9.02 6.41 6.22

785 549

27

Bypass Protein

NPN Regular Silage Silage

19.7 l 3.4 37.0 0.0 46 46 24 24

403 413 455 471

1.75* 1.51 1.63

0.61 0.50 22.80

20.22 1.70 1.65 9.15 7.89 5.23 5.23

818 480

for a short time during the adjustment period. In principle, this procedure involves supplying adequate levels of ·protein in the lower digestive tract of calves on NPN corn silage. The less soluble protein is added in diets already at the "recommended" protein level. During this adjustment period the bypass protein en­sures adequate nutrition to the calf for growth, during which time the rumen microorganisms are becoming adapted to NPN utilization. After the adjustment period the extra protein may be discontinued. Fur­ther work in this area is planned.

LITERATURE CITED 1. Burroughs, W. and D. Moran. 1978. Natural­

ly protected protein (CG M) vs. unprotected protein ( SBM) in supplements for calves up to 600 lb weight. Iowa A.S. Leaflet R269.

2. Burroughs, W., E. Thomas, and D. Moran. 1977. Rumen-protected soybean meal plus urea combinations designed for superior cattle supplements. Iowa A.S. Leaflet R248.

3. Burroughs, W., E. Thomas, and A. Trenkle. 1976. Rumen protection of soybean meal with formaldehyde in feedlot cattle supplements con­taining urea. Iowa A.S. Leaflet R228.

4. Burroughs, W., A.H. Trenkle, and R. L. Vetter. 1974. Final report of second experiment demonstrating the variable feeding value of urea as predicted by the new metabolizable protein system of evaluating cattle feeds and rations in satisfying tissue amino acid requirements. Iowa A.S. Leaflet R192.

28

5. Byers, F. M. and A. L. Maxon. 1979. Protein and selenium levels for growing and finishing beef cattle. Ohio Animal Science Series 79-1.

6. Fox, D. G., H. D. Woody, M. L. Danner, and R. J. Cook. 1977. Starting new feeder cattle. on corn silage. Michigan Research Report 3 2.8 : 110.

7. Geasler, M. and W. Burroughs. 1974. Use of metabolizable protein and urea fermentation values in formulating feedlot rations. . Iowa A.S. Leaflet R191.

8. Hungate, R. E. 1966. The rumen and its mi­crobes. Academic Press, New York, N. Y.

9. Little, C. 0., W. Burroughs, and W. Woods. 1963. Nutritional significance of soluble nitro­gen in dietary proteins for ruminants. J ~ Anim. Sci., 22 :358.

10. Nishimuta, J. F., D. G. Ely, and J. A. Boling. 1974. Ruminal bypass of dietary soybean meal protein treated with heat, formalin, and tannic acid. J. Anim. Sci., 39:952.

11. Peterson, L. and T. Klopfenstein. 1977. A high bypass protein, corn gluten meal. Nebraska Beef Day Report EC-77-218.

12. Rock, D., J. Waller, T. Klopfenstein, and R_. Britton. 1979. Slowly degraded protein sources. Nebraska Beef Cattle Report EC-79-218.

13. Waller, J. C., J. R. Black, W. G. Bergen, and M. Jackson. 1980. Effective use of distillers dried grains in feedlot rations with emphasis on protein considerations. Proc. Dist. Feed Conf., 35:53.

Starting Lightweight Calves on NPN Corn Silage and the Effect of Prote'in in Excess of Recommended Levels

Fed with Two Types of Corn Silage

H. WILLIAM NEWLAND and FLOYD M. BYERS1

SUMMARY Lightweight Hereford steer calves were fed

either NPN or regular corn silage with one of two protein levels during growing and finishing. Seven­teen percent protein significantly improved perf or­mance in growing calves over 14% in conventional housing, but not in the slatted floor barn. Perfor­JJ?.ance of calves on NPN corn silage as their only pro­tein. source was surprisingly good, being almost com­parable to all natural protein and may be related to their treatment during the adjustment period before being placed on experiment.

Results during the finishing phase confirmed earlier work that 11 % protein ( 900 g daily) is ade­quate for finishing cattle.

INTRODUCTION Economicaly speaking, it is important that cat­

tlemen feed protein to meet but not exceed the pro­tein requirements of growing and finishing cattle. The NRC ( 5) lists protein requirements for 450 lb steer calves at 12.3% and 13.6% of the dry matter for.2.0 and 2.4 lb daily gain, respectively. Byers and Moxon ( 3) showed a significant growth response in Hereford steer calves by increasing the protein from 14.1 % to 16.5%. Feed· efficiency was also improved at the higher protein level.

Research at Iowa ( 2) showed that NPN was not as effective as a natural protein source in correcting protein def~ciencies in calves less than 600 lb.

The purpose of this study was to evaluate the need for higher protein.

EXPERIMENTAL PROCEDURES Hereford steer calves from south~estern Ohio

which had been used in a trial involving adjustment to NPN corn silage were reallotted for this experi­ment. The treatments during Phase 1 (growing period) were:

NPN Corn Silage, 14.% Dietary Protein (Dry Basis) NPN Corn Silqge, 17.% Dietary Protein (Dry Ba-sis) Regular Corn Silage, 14 % Dietary Protein (Dry Basis) Regular' Corn Silage, 17 % Dietary Protein (Dry Basis)

1Professor of Animal Science, The Ohio State University and Ohio Agricultural Research and. Development Center; and Associate Profes­sor of Animal Science, Texas A&M University, College Station; for­merly Assistant Professor of Animal Science, Ohio Agricultural Re­search and Development Center and The Ohio State University.

29

Calves in one replicate of each treatment were housed in a conventional enclosed barn with straw bedding and calves in the other replicate were fed in a slatted floor barn. Supplements used for both phases are shown in Table 1. During Phase II all protein levels were decreased to either 11 or 13.4%. The NPN corn silage was mixed with regular silage to provide the protein level for the 11 % groups.

The 11 % protein diets were fed in the conven­tional barn and the 13.4%' protein diets were fed to calves in the slatted floor barn during Phase II. Ad­justments in protein levels for both Phase I and Phase II were made by varying the level of soybean meal. Corn silage was full fed during both phases, and shelled corn added at approximately 0.8% of the body weight daily in Phase I and 1.25% during Phase IL Similar dietary energy concentrations were maintained between protein levels by varying the intake of corn in the supplements to compensate for soybean meal.

Calves were implanted with Ralgro at the start of the experiment and reimplanted in approximately 100 days. Monensin was fed to all groups through­out the entire trial. As th,e cattle reached approxi­mately low choice grade, they were slaughtered and carcass evaluations were made.

RESULTS Detailed results are presented in Table 2. Dur­

ing the growing phase, cattle fed in the conventional barn responded significantly in gain and feed effeci­ency to the 17% protein level ·with either NPN or regular corn silage. Cattle in the slatted floor barn did not respond to the higher protein level. Dry matter intake was also consistently lower in th~ slat­ted floor barn. In the conventional barn, dry mat­ter intake was greater for cattle fed the higher protein levels. Feed conversion was improved slightly with increasing protein levels in the conventional barn.

Performance patterns in Lots 1 and 5 deserve special mention. These calves received no supple­mental protein, thus deriving all of their protein from the NPN corn silage. Forty percent of their total daily protein intake was derived from NPN. Per­formance of these calves was almost comparable to those fed the 14% natural protein diets (Lots 3 and 6) . These results indicate that lightweight calves

can utilize non-protein nitrogen efficiently, contrary to what might be expected based on earlier reports.

Fox ,et al. ( 4) found that NPN (urea) signifi­cantly depressed gains and feed efficiency in 440 lb Holstein steer calves as compared to soybean meal for both high corn silage and high grain diets during the first 56 days· on feed.

The. calves fed NPN silage in this trial were pre­viously fed an .NPN source and may have started this experiment as adapted animals. The calves in Lots 1, 2, 5, and 6 had been on NPN corn silage during the adaptation. study which was apparently adequate for adaptation to NPN.

The positive response from the lightweight calves in this trial to protein levels exceeding the NRC recom­mendations for· protein agrees with the work of Byers and Moxon ( 3), who showed a response from a 16.5 % protein level with 500 lb calves. These work­ers suggested the protein requirement for c.alves in the 400 to 600 lb weight range may be in excess of 1000 grams daily. In this trial the calves on 14% protein were receiving approximately 900 grams, and those on 17% approximately 1150 grams daily. Braman et al. ( 1) also showed a response from 1100 grams daily fed to 500 lb calves.

During Phase II the objective was to evaluate the

effectiveness of maintaining higher protein levels dur­ing the finishing period. The protein levels were ad­justed to 11 and 13.4% within each kind of corn si­lage. As is evident in Table 2, there was no response to the higher protein level. The calves on the 11 % protein diets were receiving approximately 900 grams daily while those on the 13.4% diets were receiving ap­proximately 1100 grams. These results agree with Byers and Moxon ( 3) as well as Workman et al. ( 6) , who reported the absolute requirement for finishing cattle is in the neighborhood of 900 grams daily irre­gardless of the protein level in the diet.

Major treatment effects are presented in Table 3. Regular corn silage effected an increased gain ( 2.62 vs. 2.51 lb) and improved feed conversion (6.32 vs. 6.42). These differences were not statistically signifi­cast. Due to lack of response to 1 7 % protein in the slatted floor barn in Phase I, the overall effect was not significant. However, the positive response to higher protein during the growing period suggests a need for reevaluation.

Calves in conventional housing gained signifi­cantly faster during Phase I ( 2.27 vs. 2.52 lb); the ad­vantage disappeared during Phase II.

The various treatments had ·no effect on carcass traits evaluated (Table 2).

TABLE 1.-Composition of Supplements Fed During Growing and Finishing Periods.

Shel led corn Soybean mea I, 44 Dicalcium phosphate Limestone Calcium sulfate Salt Monensin (60 g/lb) Vitamin A (30,000 IU/g) Vitamin D (3,000 IU/g)

Shelled corn Soybean meal, 44 Limestone Calcium sulfate Salt Monensin (60 g/lb) Vitamin A (30,000 IU/g) Vitamin D (3,000 IU/g)

Protein Level:

Protein Level:

30

NPN Silage

14% 17%

% % 93.4 57.47

36.70 1.70 0.80 1.20 1.40 2.50 2.50 1.10 1.00 0.13 0.13 0.10 0.10 0.07 0.07

NPN Silage

11 % and 1 3.4 %

% 94.48

2.6 2.6 0.15 0.10 0.07

Phase I

Regular Silage

14 % 17 %

% % 32.0 65.3 97.4

1.60 1.50

1.00 1.00 0.13 0.13 0.10. 0.10 0.07 0.07

Phase II

Regular Silage

11 % 13.4%

% % 45.61 49,34 95.18

2.96 2.70

1.80 l.80 0.15 0.15 0.10 0.10 0.07 0.07

TABLE 2.-Effects of Protein Level and Type of Corn Silage on Performance of Growing and. Finishing Cattle.

PHASE I-GROWING PHASE

Protein Level

Percent of total protein from NPN

No. calves

No. days fed

Av. initial wt, lb Av. final wt, lb Av. daily gain, lb

Dry matter daily, lb Dry matter/gain, lb

PHASE II-FINISHING PHASE

No. cattle

No. days

Protein Level

Av. initial wt, lb Av. final wt, lb Av. daily gain, lb

Dry matter daily, lb Dry matter/gain, lb

Conventional Barn

NPN Silage

14% 17%

Lot l

40.0

12 122 461 774

2.56a* 14.34 5.60

Lot 2

32.0

12 122 461 793

2.73b*

14.86 5.45

Regular Silage

14% 17%

Lot 3

0.0

11 122 474 803

2.68a

15.00 5.60

Lot 4

0.0

12 122 474 817

2.81b 15.53 5.53

Conventional Barn

NPN Silage

11% 11%

Lot

12 119 774

1062 2.42

18.25 7.54

Lot 2 12

119 793

1080 2.41

18.71 7.76

Regular Silage __

11% 11%

Lot 3

11 103 803

1086 2.75

18.40 6.70

Lot 4 12

103 817

1089 2.64

19.23 7.28

SUMMARY PHASE I AND PHASE II

Protein Level Growing, Finishing

No. cattle

Days fed

Av. daily gain, lb Dry matter daily, lb

Dry matter/gain, lb

CARCASS EVALUATION Carcass wt, lb

Dressing percent Back fat, in Ribeye area, in2

Quality grade Yield grade

Conventional Barn

NPN Silage

14/11 % 17/11 %

Lot. 1 12

241 2.49

16.30 6.54

652.9 63.3

0.51 11.64 11.20 2.70

Lot 2 12

241 2.57

16.78 6.52

655.9 63.0

0.49 11.63 11.90 2.90

Regular Silage

14/11% 17/11%

Lot 3

11 225

2.71 15.55

6.03

681.0 62.6

0.60 11.80 12.80

3.00

Lot 4 12

225 2.73

17.22 6.31

685.7 63.09

0.57 12.08 11.91

2.64

*Means with different superscript letters are significantly different (P < .05).

31

Slatted Floor Bann

NPN Silage

14% 17%

Lot 5

40.0

12 122 455 768

2.57a 14.07 5.48

Lot 6

32.0

12 122 455 756

2.47a 14.08 5.71

Regular Silage

14% 17%

Lot 7

0.0

12 122 471 770

2.46a 14.32 5.83

Lot 8

0.0

12 122 471 785

2.58a 14.36 5.57

Slatted Floor Barn

NPN Silage

13.4% 13.4%

Lot 5 12

119 768

1077 2.60

17.58 6.77

Lot 6 12

119 756

1037 2.36

17.23 7.30

Regular Silage

13.4% 13.4%

Lot 7 12

103 770

1026 2.49

19.32 7.77

Lot 8 1,2

103 785

1051 2.58

17.73 6.93

Slatted Floor Barn

NPN Silage~

14/13.4% 17/13.4%

Lot 5 12

241 2.58

15.80 6.13

668.8 63.08

0.51 12.11 12.33 3.00

Lot 6

12 241

2.41 15~64

6.48

649.3 64.3

0.53 11.53 11.40 3.10

__!!!.~ular Sila_!!_e __

14/13.4% 17/13.4'%

Lot 7

12 225

2.47 16.61 6.72

64$.4 63.25

0.49 11.61 12.50 2.83

Lot 8 f 2

225 2.58

15.99 6.20

673.3 63.8

0.51 12.20 12.30 2.64

TABLE 3.-Summa'l'y ·of· Main Treatment Effects During Growing, Finishing, and Overall.

Av. Daily Gain lb Feed/Gain (D.M.)

PHASE I-GROWING Type of silage

NPN 2.58 5,56 Regular 2.64 5.63

Level of protein 14% 2.56 5.63 17% 2.65 5.57

Housing Conventional 2.69* 5.55 Slatted flobr 2.52 5.65

PHASE II-FINISHING Type of silage

NPN 2.45 7.34 Regular 2.62 7.17

Level of protein 11 % 2.56 7.32

13.4 % 2.51 7.18

Housing Conventional 2.56 7.32.

Slatted floor 2.51 7.19

OVERALL EXPERIMENT Type of silage

NPN 2.51 6.42 Regular 2.62 6.32

Level of protein

14 to 11 % 2.60 6.28 14 to 13.4 % 2.-?3 6.43 17 to 11 % 2.65 6.42 17 to 13.4 % 2.50 6.34

Housing Conventional 2.63* 6.35 Slatted floor 2.51 6.38

*Significant increase (P < .05).

1.

2.

3.

4·.

5.

6.

32

LITERATURE CITED Braman, W. L., E. E. Hatfield, F. N. Owens, and J. M. Lewis. 1973. P.rotein concentration and sources for finishing ruminants fed high concen­trate diets. J. Anim. Sci., 36 :782. Burroughs, W., A.H. Trenkle, and R. L. Vetter. 1974. Final report of second experiment demon­strating the variable feeding calue of urea as pre­dicted by the new metabolizable protein system of evaluating cattle feeds and rations in. satisfying tissue amino acid requirements. Iowa A.S. Leaf­let R192. Byers, F. M. and A. L. Moxon. 1979. Protein and selenium levels for growing and finishing beef cattle. Ohio Animal Science Series 79-1. Fox, D. G., C. L. Fenderson, and R. G. Cricken­berger. 1977. Sources of supplemental protein for growing and finishing Holstein steers. Michi­gan Res~arch Report 328:104. N.R.C. 1976. Nutrient requirements of domes­tic animals. No. 4, Revised 1976. Nutrient re­quirement of beef cattle. National Academy of Sciences, National Research Council, Washing­ton, D. C. Workman, B. L., F. M. Byers, A. L. Mo:xon, and R. L. Preston. Protein and potassium require­ments of feedlot cattle. Ohio Animal Science Series 79-1.

BETTER LIVING IS THE PRODUCT of research at the Ohio Agricultural Research and Development Center. All Ohioans benefit from this product.

Ohio's farm families benefit from the results of agricultural re­search translated into increased earnings and improved living condi­tions. So do the families of the thousands of workers employed in the firms making up the state's agribusiness complex.

But the greatest benefits of agricultural research flow to the mil­lions of Ohio consumers. They enjoy the end products of agricultural science-the world's most wholesome and nutritious food, attractive lawns, beautiful ornamental plants, .and hundreds of consumer prod­ucts containing i_ngredients originating on the farm, in the greenhouse and nursery, or in the forest.

The Ohio Agricultural Experiment Station, as the Center was called for 83 years, was established at The Ohio State University, Columbus, in 1882. Ten years later, the Station was moved to its present loca­tion in Wayne County. In 1965, the Ohio General Assembly passed legislation changing the name to Ohio Agricultural Research and De­velopment Center-a name which more accurately reflects the nature and scope of the Center's research program today.

Research at OARDC deals with the improvement of all agricul­tural production and marketing practices. It is concerned with the de­velopment of an agricultural product from germination of a seed or development of an embryo through to the consumer's dinner table. It is directed at improved human nutrition, family and child development, home management, and all other aspects of family life. It is geared to enhancing and preserving the quality of our environment.

Individuals and groups are welcome to visit the OARDC, to enjoy the attractive buildings, grounds, and arboretum, and to observe first hand research aimed at the goal of Better Living for All Ohioans!

7U State "!~ tU (34~ jo1t /l~t ~e4«Vtd ad'!)~

Ohio' major soil types and climatic conditions are represented at the Re­search Center's 12 locations.

Research is conducted by 15 depart­ments on more than 7000 acres at Center headquarters in Wooster, eight branches, Pomerene Forest Laboratory, North Appa­lachian Experimental Watershed, and The Ohio State" University. Center Headquarters, Wooster, Wayne

County: 1953 acres Eastern Ohio Resource Development Cen­

ter, Caldwell, Noble County: 2053 acres

Jackson Branch, Jackson, Jackson Coun­ty: 502 ;acres

Mahoning County Farm, Canfield: 275 acres

Muck Crops Branch, Willard, Huron Coun­ty: 15 'acres

North Appalachia'n Experimental "water­shed; Coshocton; Coshocton County: l 047 acres (Cooperative with Science and Education Administration/ Agri­cultural Research, U. S. Dept. of Agri­culture)

Northwestern Branch, Hoytville, Wood County: 247 acres

Pomerene Forest Laboratory, Coshocton County: 227 ocres

Southern Branch, Ripley, Brown County: 275 acres

Vegetable Crops Branch, Fremont, San­dusky County: l 05 acres

Western Branch, South Charleston, Clark County: 428 acres