ss VALUE ON L i v f HOGS

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1 91. HECHANICAL cama MEASUREMENT OF FATNESS ss VALUE ON L i v f HOGS AND E f f o r t s t o improve carcass value i n hogs by genetic means have been handicapped f o r lack of a rapid and accurate method of measuring carcass value i n prospective breeding animals, Visual estimates and l i n e a r body measurements are not s u f f i c i e n t l y accurate ( P h i l l i p s, e t al,, 1939, and Hetzer, e t al.., 1950). They a l s o have an a d d i t i o n a l disadvantage i n t h a t t h e most accurate e x t e r n a l c r i t e r i a of high carcass value are narrow, shallow middles and long bodies and legs. D i r e c t carcass measurements which r e q u i r e slaughter of t h e individual can provide information f o r s e l e c t i o n between s i r e s o r families, b u t these are l i k e l y t o lengthen generation i n t e r v a l and are t o o laborious t o apply upon a l a r g e s c a l e. The purpose here i s t o describe a simple and rapid "probing" method of measuring backfat thickness on l i v e hogs. The method cause6 l i t t l e d i s comfort t o t h e pigs, and four measurements per pig can be taken i n one minute, Correlations between t h e measurements of backfat on l i v e hogs and carcass backfat measureaents, percentage of primal cuts, and cross-sectional area of lean in the loin and in t h e hem are given t o i n d i c a t e t h e accuracy of the method as a c r i t e r i o n of carcass value. W H O D S AM, DATA Measurements were taken on 96.pigs fed i n Record of Performance trials at t h e Iowa Agricultural Experiment S t a t i o n i n cooperation with the Regional. Swine Breeding Laboratory, during t h e f a l l and winter o f The pigs were s i n g l e crosses and three-breed crosses of inbred l i n e s of Poland, Landrace, Duroc, and Chester White. Four pigs of each l i t t e r were fed as a group i n a small concrete pen from weaning t o a weight of about 215 pounds, Forty-eight l i t t e r s were s e l f - f e d a r a t i o n of shelled corn and p r o t e i n supplement free choice. The first and t h i r d pigs of each l i t t e r t o reach a weight of 215 pounds were slaughtered, The pigs were taken o f f feed b u t had access t o water 24 hours p r i o r t o slaughter. Live Animal Measurexents The pigs were r e s t r a i n e d by looping one end of a s m a l l rope around t h e upper mandible md t h e other end around a post o r o t h e r s t a t i o n a r y object. I n c i s i o n s about 1/4 inch deep and 1/2 inch long were made w i t h a s c a l p e l or l a n c e t through t h e skin. A narrow metal r u l e r w i t h a b l u n t end was pressed through t h e soft f a t t o t h e firm t i s s u e underneath. S u f f i c i e n t r e s i s t a n c e i s encountered when t h e r u l e r reaches t h e juncture of t h e fat ard f i r & t i s s u e to izzdicate that t h e r u l e r has passed through t h e f a t, Pressure on t h e ruler i s relaxed f o r an instarit and t h e reading masked at s k i n l e v e l w i t h t h e thumb n a i l o r a s l i d i n g m e t a l c l i p on t h e r u l e r, There i s p r a c t i c a l l y no danger of penetrating t h e well-defined muscles of t h e body which are covered w i t h a d e f i n i t e l a y e r of connective tissue, such as t h e longissimus d o r s i o r muscles of t h e shoulder o r ham, p a r t i c u l a r l y i f t h e incisions i n the s k i n are made t r a n s v e r s e l y t o t h e underl y i n g muscle f i b e r s. Penetration may occur between t h e longissimus d o r s i and t h e scapula i f i n c i s i o n s are m a d e d i r e c t l y over t h e shoulder.

2 92. I n preliminary t r i a l s, an i n j e c t i o n of l o c a l anesthetic at t h e s i t e of t h e proposed i n c i s i o n caused g r e a t e r discomfort t o t h e pigs than an i n c i s i o n made without anesthesia. Shaving the hair a t the s i t e of the i n c i s i o n and applying a n t i s e p t i c proved t o be unnecessary i n preventing infection; no noticeable Ill e f f e c t s have occurred among t h e many animals retained under observation a f t e r they were measured. Hence the technique i n use at the time the present data were collected was a r e l a t i v e l y simple one involving four steps; (1)Restraining t h e pig; (2) making incisions at the chosen sits; (3) measuring the fat from t h e s k i n t o the underlying firm t i s s u e, and (4) recording t h e measurements, The actual sites of the measurements i n t h i s study were chosen more o r l e s s a r b i t r a r i l y a f t e r some preliminary experimentatfon, Three of t h e s i t e s were about l* inches off t h e midline of thebcdy above the longissimus d o r s i. The f i r s t of these w a s immediately behind t h e shoulder; t h e second w a s t h e middle of t h e back, while t h e t h i r d w a s t h e middle of the l o i n. The f o u r t h s i t e w a s the middle of t h e l o i n over t h e exact midline of the body. Carcass Measurements The carcasses were s p l i t immediately af"ter slaughter and were c h i l l e d f o r 72 hours at a temperature of approximately 34' F. Thickness Of backfat w a s measured t o the nearest one-tenth inch at t h e first, seventh and last thoracic vertebrae, and at the last lumbar vertebra, The r i g h t half of each carcass was cut as described by Hankins and Hiner (1937). M a x i m u m length and maximum width of the longissimus dorsi were measured from t h e trimmed l o i n cut at t h e last thoracic vertebra. Maximum length and maximum width of t h e lean a r e a of t h e face of t h e untrimmed ham were measured. About 1/4 Inch of f a t w a s l e f t on both l o i n and ham a f t e r trimming. The b e l l y was trimmed above t h e teat l i n e and squared at t h e shoulder and flank ends. The shoulder was removed at the t h i r d thoracic v e r t e b r a and divided i n t o t h e picnic h a and Boston b u t t. Weights were taken on all c u t s t o t h e TABLE 1, MEANS AND STANDARD DEVIATIONS OF VARIABLES Variable Age at slaughter ( d a y s ) Shrunk l i v e weight at slaughter (pounds) Average of 4 C B T C B ~ S backfat measurements Individual l i v e hog backfat measurements Behind shoulder (Inches) Middle of back (inches) Middle of l o i n over longissimus d o r s i Middle of l o i n over v e r t e b r a (inches) Average of 4 l i v e hog backfat measurements Lean l o i n area (square inches) Lean ham area (square inches) Primal c u t s (percent of shrunk l i v e weight) mare e t one-tenth pound. Averagle Standard devi a t ion

3 93. The p a r t i c u l a r carcass measurements studied were as follows: (A) average of t h e four backfat measurements; (B) l c i n area a6 measured by t h e product of m a x i m u m length and maximum width; (C) l e a n ham area a8 measured by t h e product of maximum width and maximum length, and ( D ) percentage primal c u t s as measured by t h e combined weights of f i v e cuts, l o i n, ham, bacon, p i c n i c shoulder and Boston b u t t, divided by t h e shrunk l i v e weight taken immediately before slaughter. RESULTS AND DISCUSSION The pigs grew rapidly, reaching slaughter weight at s l i g h t l y less than f i v e months of age ( t a b l e 1). The average depth af backfat on t h e carcasses was 1.61 inches at t h e four s i t e s measured, Although t h i s i s near t h e accepted optimum f o r fatness, there was considerable v a r i a t i o n between individuals p a r t i c u l a r l y with reference t o breed-group d i f f e r e n c e s, The comput a t i o n s were m a d e on an intrabreed-group b a s i s to eliminate breed d i f f e r e n c e s i n fatness and conformation, The primary e f f e c t of t h i s was t o decrease s l i g h t l y t h e c o r r e l a t i o n s between any two measures of SatEess and t o increase s l i g h t l y those between measures of f a t n e s s and leanness, Seventeen of t h e 96 pigs were g i l t s, most of which were i n two of t h e breed-groups. Hence t h e intrabreed-group analysis eliminated most of t h e sex difference., Depth of fat w a s g r e a t e r at t h e carcass l o c a t i o n s than at t h e l i v e hog l o c a t i o n s most nearly corresponding t o them. The hverage of the four carcass measurements was inches while t h e average of t h e four live-hog l o c a t i o n s was 1.43 inches ( t a b l e 1). The c a x a s s measurements were made from TABU 2, CORRELATIONS BETWEEN BACKFA!P THICKNESS AND LOIN AREA, HAM AREA find Le an loin are a Variable -,414 Average of 4 carcass backfat measurements Average of 4 l i v e hog backfat measurements Individual. l i v e hog backfat measurements Behind shoulder.483 Middle of back.321 Middle of l o i n over longissimus d o r s i.412 Middle of l o i n over v e r t e b r a Lean ham area ,538 -,468, Percentage primal cuts --, ,468 -, ,449 t h e s k i n t o t h e t o p of t h e v e r t e b r a while t h r e e of t h e live-hog measurements were made from t h e s k i n t o t h e t o p of t h e longissimus dorse. The c o r r e l a t i o n s between t h e a v e r w e backfat thickness on t h e carcafis and t h e individual live-hog measurements at t h e four sites were as follows: Behind shoulder,.79; middle of back,.59; middle of l o i n over longissimus d o r s i,.67; middle of l o i n over vertebra, '73; and average of t h e four live-hog measurements,.81. The l o c a t i o n behind t h e 6houlder was t h e most accurate single i n d i c a t o r of carcass f a t n e s s, That c o r r e l a t i o n i s s i g n i f i c a n t l y g r e a t e r than those involving t h e midlle of t h e back and t h e middle of t h e l o i n over t h e langiss-hus dotsi. Eeccuse t h e average of t h e four carcass measurements i s common t o all of t h e c o r r e l a t i o n s, t h e value /2 ( IT,, ) (1-R ') which i s d i s t r i b u t e d approximately as t, was ( ry1-r, 2 ) (1143) used as suggested by Hotelling (1940) i n making t h e t e s t s of significance.

4 94.. All of t h e c o r r e l a t i o n s involving backfat measurements and the measures of carcass value are negative (table 2 ). Surprisingly, the average of the live-hog measurements appears t o be a more accurate i n d i c a t o r of leanness and carcass value than does t h a average of the carcass backfat measurements. The d i f f e r e n c e between the two c o r r e l a t i o n s involving l e a n ham area (-.427 and i n t a b l e 2) is s t a t i s t i c a l l y s i g n i f i c a n t and the smaller differences between the c o r r e l a t i o n s involving lean l o i n m e a and percentage primal c u t s point i n the sane d i r e c t i o n. The only l o g i c a l reason f o r t h i s seems t o be t h a t three of the live-hog measurements are made from t h e s k i n t o t h e muscle instead of from t h e s k i n t o t h e vertebra. The middle of t h e back i s d e f i n i t e l y t h e poorer location f o r measuring backfat on l i v e hogs. Correlations involving t h a t l o c a t i o n are lowest f o r the t h r e e measures of carca6s value as well as f o r carcass backfat. The locations behind t h e shoulder and at t h e middle of t h e l o i n over the longissimus d o r s i are most accurate if the measurements are t o be used as i n d i c a t o r s of carcass leanness. The former i s s i g n i f i c a n t l y more accurate as a measure of lean l o i n area while the l a t t e r i s s i g n i f i c a n t l y more accurate 88 a measure of l e a n hem area. This seems t o b e l o g i c a l, since t h e l a t t e r location I s much c l o s e r t o t h e ham. Considerably g r e a t e r accuracy i n measuring carcam value i s POSSib l e than is indicated by t h e foregoing c o r r e l a t i o n s. Chemical methods, as i l l u s t r a t e d by t h e s o l u b i l i t y of antipyrine i n body water (ICraybill e t al., 1951), may have greater accuracy than the probing technique described herein. Hwever, t h e l a t t e r has considerably g r e a t e r usefulness i n being more rapid and e a s i e r t o apply as well 88 i n t h e fact t h a t t h e r e s u l t s are immediately available. The l a t t e r consideration i s of considerable p r a c t i c a l importance because the animals should b e measured at approximately market weight so those not selected f o r breeding can be s e n t immediately t o market. There i s a l s o considerable likelihood t h a t g r e a t e r accuracy can be a t t a i n e d by refining and extending t h e probing technique. For example, t h e r e seems t o b e no reason w h y the fat covering of t h e shoulder and ham cannot b e measured as e a s i l y as that over t h e back. As far as t h e r e s u l t s of t h i s study go, t h e preferred l o c a t i o n s are over t h e longissimus d o r s i about 13 inches o f f t h e midline of the body j u s t behind t h e shoulder and at t h e middle of t h e l o i n. Since l i t t l e addit i o n a l labor i s required i n m a k i n g additional measurements, both sides of t h e body could be sampled at these l o c a t i o n s, I n t h i s event, each l o c a t i o n should be chosen a8 independently as possible of t h e others. SUMMARY A probing technique f o r measuring f a t covering on l i v e hogs i s described. The method is very quick and easy t o apply and cause6 l i t t l e d i s comfort t o t h e pigs, The c o r r e l a t i o n between t h e average of four backfat measurements taken on carcasses and on l i v e hogs was.81. Measurements made on 96 l i v e hogs were s l i g h t l y more accurate as i n d i c a t o r s of leanness and percentage primal c u t s than were cazcass measurements of backfat thickness. The most accurate locations were j u s t behind t h e shoulder and at t h e middle of t h e l o i n about l* inches o f f t h e midline of t h e body,

5 95. LITERATUREc r m Hankins, 0. G., and R. L. Hiner, A progress report on t h e meat y i e l d s of Danish Landrace hogs i n comparison with c e r t a i n American breeds. Am. SOC. An. Prod. Proc. (1937) Hetzer, E. O., 0. G. Hankins, J. K. King, and 3. H. Z e n e r, Relationship between c e r t a i n body measurements and carcass c h a r a c t e r i s t i c s i n swine. Journal of Anima Science 9:37. Hotelling, Harold Selection of' v a r i a t e s f o r use i n prediction with some comments on t h e problem of nuisance parameters. Ann. Math. S t a t. 11:2 71. graybill, H. F., 0. G. Hankins, and H. I,. B i t t e r Body composition of c a t t l e. I. Estimation of body fat from measurement i n Vivo of body water by use of antipyrine. Jour. Applied Physiol. 3:681. P h i l l i p s, R. W., H. 0. Hetzer, and R. L. Hiner, Relation of scores of swine t o carcass y i e l d s and c e r t a i n camass measurements, Reg. Swine B r. Lab. Res. Item No. 15 (Mimeo.) MR. PEARSON: Are t h e locations q u i t e exact o r do you have q u i t e a degree of l a t i t u d e? MR. KLINE: W e have t e s t e d r e p e a t a b i l i t y between individuals and within t h e same individual, taking these l i v e animals, measuring on one s i d e and on t h e o t h e r side, md we have found t h a t they are q u i t e repeatable and q u i t e accurate, We come j u s t behind the shoulder and go r i g h t over t h e s m a l l of t h e l o i n about an inch and a half t o one side, so t h a t we don't g e t r i g h t down over t h e back. MR. HANKfNS: Have you probed and held t h e animals for some time and then slaughtered some of them, o r are the ones t h a t you have held now i n the breeding herd? MR. KLINE: We have held them and put them back i n t o the breeding herd. These animals m a y be probed t w o o r t h r e e days before they come e generally probe them 24 hours before they come i n t o the laboratory. W i n. We can see j u s t a f a i n t red l i n e through t h e f a t where the probe has made a mark. W e haven't had any trouble y e t. MR, HANKINS: A t B e l t s v i l l e we have used t h i s technique on q u i t e a number of pigs s e v e r a l measurements spaced over a period of time on individual p i g s, and on ultimate slaughter we have run i n t o a l o t of abscesses, -- MR. BRATZLER: How long does it take t h e abscess t o develop? MR. HANKfNs: I cannot answer t h a t question because these pigs where we found abscesses have continued on feed, for s e v e r a l months perhaps MR. KLINE: MR, WKINS: J u s t s m a l l localized abscesses? Yes.

6 96. MR. BIUIER: Mr. Whatley i s n ' t here, b u t he probes a l l of the females he i s putting back i n our swine breeding herd, actually all t h e animals he i s considering f o r t h i s purpoee. He has done t h a t f o r two se88ons. As far as I know he has not had an abscess t o d a t e, He examined 8 good many of t h e m before they went t o t h e laboratory. Some of them were not slaughtered f o r a few days and there were no 8bscesses. Do you have the r u l e r at r i g h t angles t o the back o r i s it p a r a l l e l with t h e back? MR. KLINE: through t h e skin. It i s at right angles t o the back as you go MR. HEIUEX: I n other words, it comes acros8 t h e muscle instead of p a r a l l e l w i t h the muscle. MR. MINE: Yes. MR, HILLIER: I t h i n k t h a t this is t h e importaslt f a c t o r, you go down p a r a l l e l t o t h e muscle fibers you stand some chance of separating them. If ME?. PIEFEE: What correlation d i d you get on your back f a t thickness w i t h your probe? MR. =NE: It i s above.8. It seems t o me it i s.8 o r.82. MR. PIERCE: The reason I ask i s because Pat and I probed 66 last f a l l i n our breeding program and we came up w i t h a t e r r i f i c a l l y high correlation, something above.95. MR. BWMER: IP you were compaxing t h e back f a t probe w i t h t h e back fat measurement, t h a t correlation w i l l be higher. e compared t h e probes w i t h t h e back f a t measuremr. WILDER: W ments, f o r instance, the shoulder probe w i t h t h e seventh r i b and the l o i n probe with t h e last rib. Then we d i d some r e p e a t a b i l i t i e s on P i e r c e ' s and my work, and that is t h e reason we were so high. We were very high, higher than some others. We usually probed i n t h e morning and slaughtered i n the afternoon. Some hogs probed as 8 demonstration were slaughtered t h r e e weeks later. We had no abscesses whatsoever. MR. BFWZLEZ: Have the animd breeding men used these probes as a reason f o r discarding o r continuing animals i n t h e i r herds? MR. HILLIER: For the last two seasons, a t Oklahoma, it has been incorporated i n t h e index or the bases f o r keeping or discarding them. M R. BRATZLER: A t what weight do they probe? MR. HILLIER: They are a l l probed between 210 and 215 pounds. I f you l e t them go over 10 pounds more o r l e s s t h e probe does not mean ao much.

7 97. MR. BRATZLER: The l i t t l e marks we s a w yesterday should be cross-wise shouldn't they? MR. HILLIER: Yes, It i s a f i n e w a y t o teach the boys i n swine judging which ones have t h e t h i c k back fats. I use t h a t indentif i c a t i o n a good d e a l. We had one old hog last year w i t h a broad back and they were a l i t t l e surprised when they measured it. MR, WILDER: We s t a r t e d some dam and daughter c o r r e l a t i o n s i n our breeding work and we are s t a r t i n g t o probe a l l the g i l t s t h i s year, We wanted t o check last year on our technique and t h i s y e a r we have s t a r t e d t o probe every g i l t we have. #######