ON FAT. a t the Colorado s t a t i o n since t h e project revision i n 1960.

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1 173. G E N E T I C AND E N V I R O N M E N T A L E F F E C T S C O M P O S I T I O N OF l A M B S 0. A. ON FAT CRAHER Ebny people were informally asked if they l i k e d lamb and if not, why. The main objections voiced by people who do not l i k e lamb were that the odor of cooking lamb is undesirable and that they would taste t h e f a t f o r a long period of time after eating. &en people who do l i k e lamb admitted that the f a t tends t o coat the inside of the m u t h and leaves an undesirable after t a s t e. Eating quality of lamb was discussed with sheep carcass salesmen f o r the major packing companies and it was t h e i r opinion that t h e p a l a t a b i l i t y of lamb and mutton f a t is a major problem i n merchandizing. A survey of the literature substantiated these conjectures. The tallowy e f f e c t of mutton f a t is apparently due to the high degree of saturation of t h e f a t t y acids which increases the melting point. Mutton f a t contains a l a r g e r amount of s t e a r i c acid and l e s s o l e i c acid than beef tallow and lard. A greater degree of saturation i n mutton f a t is also indicated by iodine values of 3546 as compared t o iodine values f o r beef tallow and lard, respectively, of 4048 and The melting point of mutton f a t ranges f r o m 445loC, whereas, beef f a t melts f r o m 4048OC and lard melts from 3346OC. (AMIF, 1960). The above findings resulted i n a revision of t h e Colorado cont r i b u t i n g project t o W61 (Development of selection c r i t e r i a f o r the genetic ttmprovement of carcass merit i n sheep) t o research on lamb flavor and f a t composition. Elnvironmental e f f e c t s on f a t composition a r e being studied and fat samgles f r o m inbred l i n e s of sheep are being analyzed t o determine if enough genetic variation exists to make selection f o r a more desirable fat possible. While feeding d i f f e r e n t types and amounts of f a t t o sheep have l i t t l e e f f e c t on subcutaneous fat (Shorland, 1955) other environmental factors have rather profound effects. Callow (1958) has observed that such conditions a s temperature, rate of f a t deposition, l e v e l of fatness and stage of maturity can e f f e c t the iodine numbers of sheep f a t. P r e l i m i n a r y studies at the Colorado s t a t i o n indicate that alterat i o n of rumen fermentation patterns by feeding a n t i b i o t i c s w i l l change f a t composition. Shaw, e t al. (1960) reported that feeding steamed corn and pelleted hay increased iodine numbers of f a t f r o m Holstein s t e e r s. Feeding o r implanting stilbestrol also appears t o a l t e r t h e characteristics of depot f a t. The following presentation is a summary of t h e results obtained a t the Colorado s t a t i o n since t h e project revision i n 1960.

2 174. Tlie f i r s t problem encountered was s e l e c t i o n of a s i t e on t h e lamb carcass f o r collection of f a t samples. The area arcund tile dock i s a desirable location because c u t t i n g f a t o f f the dock does not damage t h e appearance of t h e carcass and it i s a r e l a t i v e l y convecient s i t e f o r biopsy. To determine t h e usefulness of sampling from a s i n g l e location, f a t was collected from e i g h t d i f f e r e n t areas of 82 lamb carcasses and analyzed f o r iodine numbers, saponification numbers and melting points. Freliminary r e s u l t s obtained froa 23 of t h e carcasses are l i s t e d i n Table 1. The differences i n composition of f a t between areas i s highly s i g n i f i c a n t. However, the correlations f o r iodine numbers between dock fat and t h e o t h e r seven areas are high enough t o sanple from t h e dock and p r e d i c t t h e composition of t h e o t h e r areas. Prediction of f a t composition from one area t o another i s possible because, although iodine nwo'oers d i f f e r, there i s a d e f i n i t e p a t t e r n i n all lambs with the perinephric f a t having the lowest and l e g f a t t h e highest iodine numbers. Table 1. Average values by area of carcafis and dock x o t h e r area c o r r e l a t i o n s of iodine numbers. Skponification Melting CorPelations Area Numbe r PcJint r dock cod kidney % loin neck G 92 rzck 43.O shoulder average In another study t e n lambs (Lot I) were fed outdoors i n the coldest part of the winter Eznd t e n lambs (Lot 11) were kept i n a heated room t o deteimiue the effect of ambient temperature on f a t composition. Onehalf of each group of lambs were shorn. As reported i n Table 2, f a t f r o m lambs kept w a r m had s i g n i f i c a n t l y lower iodl'ne numbers and higher melting points than t h e lambs kept outside (P<G.Cl). These results indicate tbat feeding lambs i n t h e winter i o cold c l i m t e s might produce a mre desirable product. Analysis of Fat from LarnXTed a t Temperature Extremes Saponification Melting Fo i n t Treatment Lot shorn unshorn Table 2. Lot I1 shorn unshorn zoo

3 175. The e f f e c t s of p e l l e t i n g feed and feeding an a n t i b i o t i c on f a t composition were studied using 40 lambs i n a 2 x 2 f a c t o r i a l design. There were no s i g n i f i c a n t differences i n any of the c h a r a c t e r i s t i c s of t h e f a t between the p e l l e t e d and unpelleted feed treatments. The a n t i b i o t i c used was zinc b a c i t r a c i n added t o the feed a t such a r a t e t h a t approximately 40 mg. were consumed d a i l y per head. The melting points of f a t from lambs supplemented with b a c i t r a c i n were not s i g n i f i c a n t l y d i f f e r e n t from the f a t from the untreated lambs, but t h e iodine numbers were s i g n i f i c a n t l y higher (P< 0.C1) Apparently, a l t e r a t i o n s took place i n t h e m n which suppressed hydrogenation of u n d t u r a t e d f a t t y acids. The r e s u l t s of t h i s study a r e reported i n Tables 3 and 4. The treatments by l o t are a8 follows: Lot I p e l l e t e d feed with bacitracin, Lot I1 pelleted feed without bacitracin, Lot I11 mal with bacitracin, and Lot IV meal without bacitracin. bt I l t i n g Points Melting Point, OC * ht I bt Lot N *Lots I & I11 s i g n i f i c a n t l y higher than Lots I1 and IV, (P<O.Ol) There a r e no s i g n i f i c a n t differences between treatments f o r the various f a t t y a c i d percentages l i s t e d i n Table 4, although b a c i t r a c i n supplementation resulted i n higher iodine numbem. Apparently the slight increase i n most of the unsaturated f a t t y acids and decrease i n t h e various saturated f a t t y acids was a u f f i c i e n t t o produce s f g n i f i c a n t differences in iodine numbers, Table 4. Average Percentages Acids by carbon chain length and number of double bonds Lot I < "l AB =1 0.5 Ea C" l '2 18' o cjf Fatty Acids i n Lamb Fat Lot I Lot I o Lot Iv 3.O t k a t u r a t ion W e s e acids have not y e t been i d e n t i f i e d and have a r b i t r a r i l y been assigned these designations.

4 176. Fat samples were collected f m m around the dock o f 165 r a m lamb carcasses from the U. S. Sheep Experiment Station a t k b o i s, Idaho t o a t tempt t o determine s i r e differences i n f a t composition. The l a b s were progeny f r o m inbred ram top cross matings and represent three breeds on the sire side and two years' data. The progeny were f r o m a t o t a l of 79 ram w i t h d i f f e r e n t ram each year. Although the numbers of progeny f r o m each ram were l i m i t e d (range of one t o f i v e ) t h e t e n t a t i v e r e s u l t s were quite i n t e r e s t i n g. The data a r e not completely analyzed a t t h i s t i m, but a preliminary analysis of variance revealed highly s i g n i f i c a n t differences between s i r e s f o r iodine numbers of progeny fa,t and a h e r i t a b i l i t y estimate f o r iodine number of 1.5. Rernoval of t h e year and breed e f f e c t will pmbably lower t h e h e r i t a b i l i t y estimate t o a more r e a l i s t i c figure. Average iodine values by sire ranged from a low of 41.6 t o a high of which is a great deal of variation f o r a n i m l s reared under t h e sane environmental conditions. There was also considerable variation i n t h e melting points of t h e which suggests the possif a t by s i r e. The overall range was 39.6 t o 46.4'C b i l i t y of improvement of lamb f a t p a l a t a b i l i t y through selection. Samples of f a t have been obtained from over 206 lamb carcasses of known genetic background through the cooperation o f New Yixico State Univ e r s i t y t o further explore t h e h e r i t a b i l i t y of f a t composition. The lambs were from t h e various l i n e s of sheep a t t h e U. S. Sheep Experiment Station a t Fort Wingate, New Mexico and were processed through the New Elexico State University Meats Laboratories. If t l e genetic variation i n f a t com2osition f y o m the Fort Wingate sheep substantiates tht found i n the Dubois sheep a breeding flock will be established a t the Colorado Agricultural Fxperiment Station and the selection program w i l l be based on f a t composition. Lamb f l a v o r studies being conducted a t the Colorado Station a r e not reported i n t h i s paper but will be i n c o q o r a t e d i n t o t h e selection index i f a breeding flock is s e t up a t t h e Station livestock farm. LITEZATURE CITED American Meat I n s t i t u t e Foundation The science of meat and meat products. W. H. Freeman and Company, San Francisco. Callow, E. E Comparative s t u d i e s of meat. Part V I. Factors a f f e c t i n g the iodine number of f a t f r o m the f a t t y and muscular t i s s u e s of lambs. J. Agr. S c i. 51:361. Shaw, J. C., W. L. Ensor, H. F. Tellechea and S. D. Lee Relationship of d i e t t o rumen v o l a t i l e f a t t y acids, d i g e s t i b i l i t y, efficiency of gain and degree of unsaturation of body f a t i n s t e e r s. J. Nutr. 71:203. Shorland, F. B Effect of the rumen on d i e t a r y f a t. Mature

5 177. DR. WALTERS: Thank you, Dave, f o r a most i n t e r e s t i n g report, undoubtedly the forerunner of some mrk t h a t w e t 1 1 hear more and more about as time goes on. No doubt t h i s r e p r t has s t i w l a t e d a great deal of curiosity, and will you Please make note of t h e questions which come t o your minds? We hope w e ' l l have s u f f i c i e n t time f o r questions and discussion after all t h e speakers have given t h e i r reports, The next speaker on our program, I believe, is with us for the first time t h i s year. It came t o the a t t e n t i o n of t h e committee t h a t a t the University of California, a great d e a l of work has been done i n t h e area of biopsy technics, p a r t i c u l a r l y with reference t o mrk with lambs. Our first contaci; with Professor Spurlock indicated that he wasn't sure &.ether o r no% he'd be able t o attend t h i s meeting. Later on it developed t h a t circume are very g r a t e f u l f o r your stances were suck t h a t he could be with us. W coming t h i s distance, Dr. Spurlock, t o give us your very i n t e r e s t i n g peport on "The Biopsy Technique f o r Estimation of Meat Quality i n LEun13s." Prof e s s o r Spurlock f r o m California. ######Pi#####