L I E> R.AR.Y OF THL UNIVERSITY OF ILLINOIS G30.7 tio.499-513 cop. 2 MRICULTURE The person charging this material is responsible for us return to the library from which it was withdrawn i or before the Latest Date stamped below. n, and underlining of books are reasons for discioli- Vo7enern n T TK ""!? '" diSmi8Ml ' TOm the ""'versity. TO renew call Telephone Center, 333-8400 RARY AT URBANA-CHAMPAIGN LI61 O-I096 .' 605012-4428583 if ec ^ l PREGNANCY QUALITY OF BEEF By R. R. Snapp and Sleeter Bull Bulletin 508 UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION CONTENTS INTRODUCTION 431 PLAN OF THE EXPERIMENT 432 DISCUSSION OF RESULTS 434 Live Animals 434 Carcasses 439 SUMMARY 451 CONCLUSIONS . .452 Urbana, Illinois December, 1944 Publications in the Bulletin series report the results of investigations made or sponsored by the Experiment Station EFFECT OF PREGNANCY ON QUALITY OF BEEF By R. R. SNAPP, Chief in Beef Cattle Husbandry, 1 and SLEETER BULL, Chief in Meats IN THE LIVESTOCK and meat industry the effect of sex on the quality of beef has always been a subject of considerable contro- versy. On the livestock market heifers usually sell for two or three cents a pound less than steers of equal grade, and heifer beef usually sells for less in the wholesale house than steer beef. There is, however, no price distinction in the retail market. Altho sex differences are not discernible in retail cuts, most consumers believe that heifer beef is inferior to steer beef and will not knowingly buy it except at a cut price. For this reason the retailer usually sells heifer beef as steer beef and at the same price. The Illinois Station made a comparison of the beef from steers and open heifers in 1926-27, from which the following conclusions were drawn : 2 . . . the much vaunted superiorities of the steer over the non-pregnant heifer as a butcher's beast are not so great as has been claimed by many in the beef trade. As a matter of fact, light heifers (weighing around 700 pounds after 140 days of feeding) proved to have distinct advantage over steers of similar feeding, breeding and weight in the matter of finish and they cut out almost as well. There would seem to be no logical reason for a price discrimination against the light heifer on account of her sex. Heavier heifers (weighing 800 to 900 pounds after 200 days of feeding) are slightly inferior to steers of equal weight, being a little over-done. The heavy steer cuts out to slightly better advantage than the heavy heifer, owing to the excessive condition which is oftentimes found in the heifer, but the superiority of the heavy steer is not sufficient to justify the usual price discrimination of 1 to 3 cents a pound in favor of the steer carcass. If the producer will market heifers after a shorter feeding period and at lighter weights than steers of equal age and quality, it will be to his financial advantage. There were no differences in dressing percentages between steers and heifers slaughtered in feeder condition nor when slaughtered after 140 days of feeding. There is an indication that the heifers dressed a little better than the steers when fed for 200 days. . . . As slaughter cattle the heifers graded about the same as the steers. When both were fed 140 days, the heifer carcasses, however, graded some- what higher than the steer carcasses. When fed for 200 days, the slaughter ] On leave for military service. "Effects of sex, length of feeding period, and a ration of ear-corn silage on the quality of baby beef. 111. Agr. Exp. Sta. Bui. 355. 1930. 431 432 .BULLETIN No. 508 {December, steers graded slightly higher than the heifers. The carcass grades were about the same; however, considering the usual discrimination against any except light heifers, it is probable that the carcasses of the heifers fed for 140 days would have sold better than those of the heifers fed for 200 days. The palatability committee did not detect any particular differences in the palatability of the roasted beef that could be attributed to sex. Since many heifers are bred before they are marketed, an experi- ment was conducted in 1930-31 to study the effect of pregnancy on the quality of beef. That pregnancy has an important effect on the feeding and killing qualities of cows and heifers is commonly believed by feeders and butchers. Many farmers have an aversion toward heifers for feeding purposes, because they believe that the frequent heat periods (every three weeks) give rise to considerable disturbance among feedlot cattle, which is detrimental to good gains. It is largely to lessen such disturbances that the breeding of heifers soon after they are started on feed is a rather common practice. Feeders are inclined also to believe that the gains are increased by the presence of the young in utero ; consequently they favor the breeding of cows and heifers which are being fattened for market on the theory that preg- nancy induces more rapid and economical gains. On the other hand, buyers and butchers object to heifers largely on the grounds that many of the heifers marketed are pregnant and hence have a relatively low dressing percentage. Sometimes the claim is made that heifers slaughtered while pregnant do not bleed out well and consequently produce dark-cutting carcasses. Thus buyers con- sider that they have good reasons for making severe price discrimina- tions against female cattle that are old enough to be several months along in gestation. Feeders, on the other hand, believing that their cows and yearling heifers will be bought on a pregnancy basis, feel fully justified in marketing them in a pregnant condition. Thus a circle of cause and effect exists, futile in nature if the alleged benefit of larger and cheaper gains credited to pregnancy is largely offset by decreased dressing percentage, lower quality of carcass, and lower selling price. PLAN OF THE EXPERIMENT For the experiment 10 Hereford heifers were selected from a car- load of choice yearlings bought in the fall of 1930 in northern Texas: Their exact age was unknown, but their weight and general appearance indicated that they were about 16 or 18 months old when purchased. 1944~\ EFFECT OF PREGNANCY ON QUALITY OF BEEF 433 The paired feeding method, a method first described by Armsby 1 in 1917, was used. The animals were compared by pairs, each pair consisting of one open and one bred heifer as nearly alike as possible in age, type, weight, condition, and other items which presumably affect their feeding and killing qualities. The animals were started on feed November 7. The original plan of the experiment was -to feed each pair of heifers a maintenance ration of about 4 pounds of shelled corn and 6 pounds of clover hay per head until one of the pair was observed to be in heat, whereupon this heifer was to be bred. Then she and her paired mate were to be fed a fattening ration for 150 days. At the end of this period both animals were to be slaughtered. Since none of the heifers, how- ever, had shown any signs of estrum after two weeks on the low level of feeding, the ration was increased to a full feed of grain and one pound of linseed meal per head daily. Apparently the improved ration was effective, for at least one heifer of each pair came in heat during the next thirty days. The dates when the heifers conceived (Table 1) are considered the beginning of the experiment for each pair. All the heifers, haltered and tied to separate mangers for two hours each morning and evening, were fed individually. Both heifers of each pair were fed identical rations, the amount of feed being determined by the animal with the smallest appetite. Since some of the heifers would not eat all their hay, it was replaced in all rations on December 19 by about 10 pounds of corn silage. Except at feeding time the heifers were allowed to run loose in their sheds, which adjoined open lots. As soon as five heifers were bred, the bred and open heifers were kept in different lots in order that observations might be made of the relative activity of the two groups. At 28-day intervals each animal was weighed and ten body measurements were taken. One hundred and fifty days after the breeding of a heifer she and her paired mate were slaughtered (Fig. 1). This period of time was chosen because yearling heifers are seldom fed longer than six months for the open market. If it takes three or four weeks of rather liberal rations in the feedlot before thin range-bred heifers show signs of heat, as was true in this experiment, few heifers that are open when put into the feedlot will be more than five months in calf when sold for slaughter. Consequently, the effects of gestation observed in this experi- ment may be regarded as the maximum effects to be expected in year- ling heifers bred after being placed in the feedlot. The effects of 'Cooperative experiments upon the protein requirements for the growth of calves. Bui. Natl. Res. Council 12, 219-288. 1921. 434 BULLETIN No. 508 [December, gestation after 150 days would, of course, be more marked in heifers that were well advanced in pregnancy when started on feed. All data were analyzed statistically by Student's method for the interpretation of paired experimental data. When the value of "P" was greater than .05, the results were regarded as insignificant. DISCUSSION OF RESULTS Live Animals Activity. The pregnant heifers showed a little more tendency to lie down than did the open heifers, and when lying down they were less inclined to rise when being approached. These differences, how- ever, were not statistically important. Of more importance were the differences in temperament. The pregnant heifers were more easily caught and tied than were the open heifers and appeared to be more content. The more quiet disposition of the pregnant heifers was ap- parent each month when body measurements were being taken. It was comparatively easy to measure the pregnant heifers, but the open heifers resented being handled and frequently became nervous and excited. Close observations were made of the five open heifers to determine the extent to which they were disturbed by one of them being in heat. Signs of heat were not easily detected, however, particularly during the last half of the feeding period. Only on three occasions was a heifer in heat ridden repeatedly by other heifers in the lot. 1 Appetite. The amount of feed consumed could not be taken as a measure of appetite, since the bred and the open heifers 'were given the same amounts of feed. Accordingly observations were made to de- termine how rapidly and completely each animal consumed its feed. The pregnant heifers possessed keener appetites than their open mates, as was evident from both the speed and completeness with which they ate their feed. At practically all stages of the test the bred heifers would have eaten somewhat more feed if it had been given to them. 2 Rate of gain. Altho all heifers made fairly g-ood gains, the gains of the pregnant heifers were not significantly larger than those of the open animals (Table 1). Apparently the (continued on page 439) 'In experiments at the California Station it was concluded that "activity of open heifers in riding each other at estrual periods is not serious." Cal. Agr. Exp. Sta. Bui. 645. 1940. "These results do not agree with those of the California Station (Bui. 645), from which it was concluded that "pregnancy in cattle does not cause increased appetite." Fig. 1. Heifers at the time of slaughter. The bred heifers (B) are shown at the left; their open mates (O), at the right. 436 BULLETIN No. 508 [December, S -~-- --- E jnificance rease ^ 8 c o 8- ts -to 04 1 ,. 00 *-H ^T T -tCNOO^-*P<)'-'-'*TfSOOC-''^ *-( "3 t! u w 00 ' O 00 00 f*5 fa (2 SQ en en w Q cs o ig -|a -82 sj 3 OS O en en J to X . J, *C r^- to *o '-'csiooo;^ ^o -o o* ^ 10 w 1 u Q o ^2^2 2* ^^ u _f 1 M ^lO 00 l^ 5 05 O fa o en O |pi N l s " 2s i %s ENTAG '3 o :Ss N S S 5 2 -l a . !fl o O uis c &O'1 < >O(SVO Hd04 i/lioOO^OO^Ou^O icant are I j -S 5 -0 i C/3 J S O tSCSf) ^1 '3 S ' _>> fl ; a X " to ts k '3 cs cn CS E # w S c/) 03 rt u W rt to u 3 *-' E ,u 5^ M w 2 A c O g 9 & 5| Q ' W T3 I to )s C3 U EFFECT OF PREGNANCY ON QUALITY OF BEEF 439 increase in the weight of the bred heifers due to the developing fetus was largely balanced by slower body growth. These results agree closely with the findings of other investigators who kept open and bred heifers on the same level of feeding during the first half of the gesta- tion period. 1 Had the bred heifers been fed to the limit of their appe- tites instead of being limited to the amounts of feed consumed by their unbred mates, it is likely that the bred heifers would have shown larger gains. 2 Growth. The growth made by each animal during the test was determined by 10 body measurements taken at 4- week intervals. The parts of the body measured were those believed most likely to be affected by the devoloping fetus. Pregnancy had little effect on most of the body measurements taken, but it did have a marked effect on some (Table 2). If height at withers be taken as the best single mea- sure of growth, pregnancy retarded growth approximately 11 percent during the first five months. The measurements most noticeably affected by pregnancy were width of loin and width of hip. Thru the loins the bred heifers grew only 72 percent as much as their open mates, and thru the hips, only 62 percent as much. Carcasses Slaughter data. Pregnancy had a significant effect upon the weights of the liver, uterus and contents, stomach, thymus, spleen, and shanks (Table 1). The livers of the bred heifers were 6 percent heavier than those of the open heifers. This difference, altho small, is signifi- cant (odds 41 to 1). As would be expected, the uteri and contents were much larger in the bred heifers, averaging 30.2 pounds per 1,000 of empty live weight 3 compared with 1.6 pounds per 1,000 in the open heifers. The percentages of spleen, stomach, and shanks (expressed in per- centage of empty live weight) in the pregnant heifers were significantly less (10 to 20 percent) than in the open heifers. In view of other results of this experiment (see above) it seems logical to conclude that the lighter weights of these organs were due to the general retarding effect which pregnancy had on growth. The (continued on page 445) 'Eckles, C. H., and Swett, W. W. Some factors influencing growth of dairy heifers. Missouri Exp. Sta. Bui. 31, 1918. "At the California Station (Bui. 645), bred heifers made slightly larger and more economical gains than open heifers. "Empty live weight is the live weight just before slaughter minus the weight of the contents of the digestive tract. C t-C o x rt U CO bi) to bub o ns O bi 444 BULLETIN No. 508 [December, W 3 ta f T) < O en ti < -a s| ? U-3 u &x . *t m . ooooo * o . m ts ..... Hfj . t- . . . oo ** ooooo OO . fsov ..... ws . cs So 5 : ^ -i ^ -*"> ..... oo .-H (MO ' CM c >O fn ' ^-O O- O>~* ..... "100 -~H\O r^^j"! i.. Tf\O- ) 1O f>lO O O> 00 ^HfSin OOOOCS -^O") OO'* 5 -H i/> m-O >** MrOfO VOCN^^ ID f*5 1/5^^- TffO^H 't't^H m OOr^O 10^*0 i/)-Ocs-< iO'-'f*5 -^fi^H rj-Tf Tf^tr- IO^O^-H VOCN f^5*o mfO^H r^- t ^H -"Oul OOO>O O^t^ GO*-** *t *? >-i O">*O r^t-O * >O fO <"5 * O "> 00 O>OfN -tf^O >OOrO OO>O O*OO r^GCM OOOOfC m -* vOiOt- i/5O> in rs ^H 10 '-i f*5 ^l 4 f^ *+ *& <# PO in ^ Tf -^ -( m cs -< cst^ TJ*C^*H \o^^^ m fo <* ^H o t>- re o o o PN ^ o ^t 4 -> o o NO o ^^ ^o o o in >omo i^.oo*t vo^t\o ^ro rnt^o oomt^ ^ts-H oooo r~t^m oomes OOOOCN ^cso fo ^^ fo r>i CM in ~ n in ^ooo t^o?s fo - csin^^ ooo rooooo oo^Of^ O-4in- o^O"^ o> o "too o-mfo in cs *H in ~* f*5 ^f PC - fc in '^ ^ -^ ^* info^- VOCS^H CM*O * ro ^H \O^HT- ot^ro >mo "tcsoo ooot^ -rc >O O n * * * intsts r^ ~ 00 O O r-100 * t- 00 fS ro rO ' -^ ' '.'.'. '.'.'. '.'.'. '.'.'. '.'.'. '.'.'. '.'.'. '.'.'. c . . ....... c . . ......... a . . ... . . .-- . . .T3 . . . ... ... ... \j O s-S O fi c v c.nj^n.u C-^CC.D e-n> c v, K v JU.CQ.2 feffl 1944] EFFECT OF PREGNANCY ON QUALITY OF BEEF 445 development of the thymus of the pregnant heifers was less (35 per- cent) than in the open heifers. If the size of the thymus is, as is gen- erally believed, an index of potential growth, it appears that pregnancy hastens maturity. Dressing percentages. Pregnancy did not affect the dressing per- centages. Apparently the larger weights of the uteri and contents in the pregnant heifers (24 pounds on the average at the time of slaughter) were approximately balanced by the lighter weights of other offal and the higher condition of the bred heifers. 1 Carcass grade. Two days after a pair was slaughtered, the car- casses were graded. The carcass grades ranged from Good- to Choice (Table 1). Altho four carcasses of the bred heifers were assigned higher grades than those of their open mates, statistical analysis did not show that the differences were significant. The carcasses of the bred heifers, however, were without exception more highly finished than were those of the open heifers. 2 Cutting percentages. One side of each carcass was divided into ordinary wholesale cuts according to the methods recommended by the Committee on Cooperative Meat Investigations of the State Agricul- tural Experiment Stations and the U. S. Department of Agriculture. 3 The loin ends of the open heifers were about 7 percent heavier than those of the bred heifers (Table 3). Statistically this difference is highly significant (odds 88 to 1). The rounds also (shanks on, rumps off) of the open heifers were 11 percent larger than those of the bred heifers. This difference too is statistically significant (odds 2,500 to 1). There were no significant differences between the percentages of other cuts. Physical composition of carcasses and cuts. The wholesale cuts were separated with the knife into lean, fat, tendon, and bone, and the percentage composition of the cuts and of the entire carcass was cal- culated. Since there was only a small percentage of tendon in any cut, it is not included in the published tables. Pregnancy had no greater or more significant effect on any other of the major items studied in this experiment than on physical compo- sition of the carcass and cuts (Tables 4 and 5). On the average, the carcasses of the bred heifers contained approximately 20 percent more *In the California Station experiments (Bui. 645), pregnancy up to the fifth or sixth month did not affect dressing percentage. 2 No significant differences in the carcass grades of bred and open heifers were observed in the California experiments (Bui. 645). 3 A study of the factors which influence the quality and palatability of meat. Issued for the cooperators by the Anim. Husb. Div., Bur. of Anim. Indus., U. S. Dept. of Agr. Mimeo. Rev. ed. Feb., 1927. 446 BULLETIN No. 508 [December, 1 o <5 IO * o> (M (N O C S QJ J2 1) W >> c O t t-- Os f5 .9 tj 2; -_> c . o & f*5 ^" ^-t = 0-0 S 1 + 1 " !-, 1- o a O <*5 00 Tf 1/5 00 10 o n 10 tO H h '3 u PL, 03 00 \O O z "5~ Tf C z "- 1 o w H CL, " Q , O CN "5 W5 CS u-) ro <-i Q .5? '3 U- ^ 03 00 10 O H & U Z-< 00 00 s AFFE carcass O 00 IT) rt I < -, ^ C> 10 ^l 1 a> -H W) >O fO *-H tisticallj rt H O f^ rt "o u -5 "> en - CO O * ON V5 u * o\ 00 \O (*5 2 >o es -H CO 01 n &H 2 03 ro r^ fO is 3 10 cs * cs ts *O f*5 i-, "3 c B J k 03 i /j " 'o c 01 5 o II Z JS a 1 n Q C t> 2 3 J [x. CQ o o 01 u O . ro c CS o t^ cs * * S -" O Ol o s i, O ir> 00 o "5 if) trt cc ^ ^ 00 o ii PQ TC rt rt rt Ol Q is a a CL, *^ H o a Ed CQ i/^ in i^ Tj- Tj< 00 "6 u, '^ -t C < ^ a T. O 00 IO (S t^ Ol H fj O IO W5 a i. r^ rt ^ ^H" 'c a u K*" '5 (C i] PM vO f*5 '5 5 CQ fi 00 .5? 2 O 10 *o cs "Z 2 " - - a _^ ^ < O CS (S cd IO IO 00 4 fS * t t tn j , ^H ^ U < c h 3 J3 3 n OH 03 l/i 1/5 O O 2 /i ^ ^ ^ S u 5 j o> a -< - O i * 00 1 5 _H rt "5 : .h o j c2 3 CQ s J 1O ** 00 E -i ^1 ' a a o II O Ol S T) 1 "8 Z ^ S ^ 3 ^ S n **"* ** c >> .2 03 i ill 1944] EFFECT OF PREGNANCY ON QUALITY OF BEEF 447 separable fat than the carcasses of the open heifers, 5 percent less lean, and 10 percent less bone. Statistically these differences are highly sig- nificant. The chucks, ribs, navels, briskets, short loins, loin ends, and rounds of the bred heifers contained significantly more fat than those of the open heifers, and all these except the rounds contained less lean. The carcasses and wholesale cuts of the bred heifers were notice- ably better finished than those of the open heifers (Figs. 2 to 7). The marked differences in physical composition of the carcasses and cuts of the bred and open heifers show that pregnancy does have a pronounced effect on the feeding and killing qualities of heifers. Preg- nancy shortens the time required to attain a satisfactory market finish, as is indicated by the higher percentage of fat in the carcasses of pregnant heifers. Because of their lighter bone, pregnant heifers have a larger quantity of edible meat and a better quality of carcass. On the other hand the greater deposition of fat in the carcasses of preg- nant animals may result in wasty carcasses if the heifers are fed too long. The desire of the feeder to sell bred heifers before they show unmistakable signs of pregnancy, however, usually insures their being marketed before they are too fat. Firmness of fat. From the open and bred heifers samples were taken of the back and kidney fat, and the refractive index (Nd) of each was determined as a measure of firmness. 1 Pregnancy apparently softened the back fat slightly but not the kidney fat (Table 6). That this difference in firmness of fat is appreciable is evidenced by the fact that the graders assigned lower scores on firmness of fat to the carcasses of the bred heifers in four of the five pairs, and the same score to the carcasses of the other pair. Color of lean. Butchers frequently claim that pregnant heifers and heifers in heat do not bleed out so thoroly as steers and that their carcasses therefore cut dark or off color. Since none of the open heifers of this experiment was in heat when slaughtered, no data were ob- tained on the effect of heat on the color of lean. Altho graders assigned slightly higher scores on color of lean to the carcasses of the bred heifers in four of the five pairs, spectrophotometric analyses 2 of samples of lean disclosed no significant differences in color which could be attributed to pregnancy (Table 7). None of the carcasses was criticized for cutting dark or being in any way off color. 'For an explanation of the relationship between refractive index and firm- ness of fat see Bulletin 366 of this Station, pages 49-50. 1931. 2 For an explanation of the significance of these color determinations see Bulletin 355 of this Station, pages 219-225. 1930. 31529*?- ' Fig. 6. Light end of ribs. Note the thicker covering and better marbling of the ribs of the bred heifers. Fig. 7. Heavy end of ribs, bred and open heifers. The ribs of the bred heifers are fatter. 450 BULLETIN No. 508 [December, 1 00 fO vO l-~ rt o\ 10 ** U1 !H '3 PH PQ 00 rs re t^ C\ tN ~ * O ts : ^H rf 2 1 CQ o 4 ""* S ft -i O >0 5 2 ^ oo ^ C w 10 'rt ^ PH x| 1) eq * v 6 J "^ S 3 z 'c ^ o 8 e ^ 5 >; 43 5 M E -r 'C O g 03 Q PH 1944} EFFECT OF PREGNANCY ON QUALITY OF BEEF 451 SUMMARY Bred heifers spent more time lying down, were less active, and had more quiet dispositions than open heifers. Undue activity caused by open heifers riding each other during estrual periods was not serious. Bred heifers had better appetites than open heifers. Since their feed consumption was limited to the amount eaten by the open heifers, the extent of this difference in appetite was not determined. When kept at the same level of feed consumption, bred and open heifers showed no significant difference in rate of gain. The bred heifers increased less in height at withers, width of loin, and width of hips than the open heifers. In other measurements there were no significant differences due to pregnancy. The bred heifers had significantly heavier livers than the open heifers but lighter spleens, stomachs, and shanks. The average weight of the thymus gland of the bred heifers was 290 grams; that of the open heifers, 443 grams. The uteri and contents averaged 3 percent of the empty live weight of the bred heifers. In dressing percentages there was no significant difference between the bred and the open heifers. Except that the carcasses of the bred heifers were noticeably better finished, there was no significant difference in carcass grade. The loin ends of the open heifers were 7 percent heavier than those of the bred heifers, and the rounds were 11 percent heavier. Otherwise there were no significant differences in cutting percentages. The carcasses of the bred heifers contained 20 percent more fat than those of the open heifers, 5 percent less lean, and 10 percent less bone, indicating that pregnancy shortens the time required to obtain satisfactory market finish. The back fat of the bred heifers was slightly softer than that of the open heifers. There was no difference in the firmness of the kidney fat. Pregnancy had no effect on the color of the lean. (For a brief statement of conclusions see next page) THE BREEDING OF YEARLING HEIFERS that are to be fed for about five months is sound practice, judging from the results of this investi- gation. Pregnant heifers take on a higher degree of finish during this time than do open heifers in the same period. The severe price discriminations practiced by market buyers against pregnant yearling heifers are not justified when such heifers are marketed by the end of the fifth month of gestation. Slaugh- ter tests and carcass studies show that at this stage of pregnancy neither the dressing percent- age nor the market grade of the dressed beef is lowered. 10,05012-4429103