A T 7 5, 1 2 5, 1 7 5, 225, AND 275 POUNOS. Dr. A. Pearson has worked with the p r i n c i p l e of determining volume i n a closed chamber.

Transcription

1 49 U l TRA'SONIC E V A 1 U A T I O N OF C O M P O S I T I O N I N HOGS ' S L A U G H T E R E D A T 7 5, 1 2 5, 1 7 5, 225, AND 2 POUNOS R I C H A R D L H I W E R and J W THORNTON Early research by Warner, Ellis and Howe (1934) and Hankins and Ellis (1934 j related both chemical determinations of etherextract t o physically separated f a t and carcass messuremnts of backfat thickness t o t o t a l f a t i n the hog carcass During the l a s t f i f t e e n years there has been a concerted e f f o r t made t o accurately determine t h e lean and f a t makeup of a l i v e hog One of t h e first attempts was that of i n j e c t i n g i n t o t h e blood stream a chemic a l, antipyrine Fatness was then calculated from the water content as determined by t h e water delusion technique Dr H F B a y b i l l reported this t o be an e f f e c t i v e and f a i r l y reliable rnethod for c a t t l e but not f o r hogs One of t h e troubles with hogs was that of being p o s i t i v e the s o l u t i o n was i n j e c t e d i n t o t h e c i r c u l a t o r y syskm Later D r Louis F e i c s t e i n used s l e e p t i m e as a method; a report of t h i s was given a t the Reciprocal Meat Conference i n 1955 He used the drugs Kkmithal and Thiopental The &as d i l u t i o n p r i n c i p l e has been reported by S i r i, i n which a change i n concentration of helium permitted a body volume calculation Dr A Pearson has worked with the p r i n c i p l e of determining volume i n a closed chamber The backfat probe reported by Hazel and Kline (1352) has beer, used as an objective method of measuring f a t n e s s i n l i v e hogs a t market weight Hazel and Kline (1959) indicated that t h e probe technique was not very e f f e c t i v e when used on pigs with less than 1 inch of backfat This lead t o t h e development of the l e a n m t e r a t Purdue Recently, u l t r a s o n i c equipment has provided another t o o l t a i n i n g an Objective measure of baclcfatthicla?ess on the l i v e hog a c o u s t i c a l properties of aniroal t i s s u e have been studied by Lu6wig S t o u f f e r (1959) and Price e t a l (196) These i n v e s t i g a t o r s have that the v e l o c i t y of ultl'gsonic aound through animal tissue v a r i e s and l e a n t i s s u e f o r ob The (195), indicated for fat Price et a l (196) reported a c o r r e l a t i o n of 74 between l i v e estimated and a c t u a l eye muscle area A c o r r e l a t i o n of 5 has been found

2 5 between an average u l t r a s o n i c reading and average backfat thickness by Meat Quality Laboratory personnel These were hogs of market weight (225 pound liveweight) Missouri workers have indicated reliable estimates of backfat thickness, eye muscle area and y i e l d of f a t and lean employing u l t r a s o n i c equipment T h i s study was undertaken by the Meat Quality Laboratory i n cooperation with t h e Agricultural Engineering Division, ARS, USDA, t o evaluate t h e usef'ulness of u l t r a s o n i c s i n detecting f a t and lean composition a t,, 1, 225 and 2 pounds A t o t a l of 97 crossbred pigs were used i n t h i s experiment These pigs were representative of "meat type" and f a t t e r and l e a n e r hogs The primary objective i n s e l e c t i n g these pigs was t o choose ones with a wide range of fatness The experimental procedure was designed t o obtain u l t r a s o n i c measures on a l l 97 pigs a t s p e c i f i c weight periods A t each of 5 weight periods a representative number of pigs were slaughtered Pigs slaughtered a t 2 pounds under t h i s system would have 5 recorded u l t r a s o n i c measures while pigs slaughtered a t pounds would have 1 u l t r a s o n i c measure The u l t r a s o n i c measure of f a t thickness was an average measure of f a t depth a t t h e f i r s t r i b, f i r s t and last lumbar vertebrae The a c t u a l carcass backfat thickness a t these 3 points was a l s o recorded and averaged Lean depth was obtained a t a point 2" off the midline on the r i g h t s i d e of t h e l o i n by f i r s t obtaining t h e measure of f a t and then measuring the distance t o the r i b a t t h i s point I n t e r p r e t a t i o n o f both l e a n and f a t depth requires some experience and t r a i n i n g i n reading t h e u l t r a s o n i c instrument A uniform c u t t i n g of the dressed c8rcasses by an appropriate standard method was employed throughout t h e experiment The method used was described by Hiner (1949) Each of the primal c u t s was physically separated i n t o lean, f a t, bone and s k i n To obtain t o t a l lean, the weight o f l e a n from each cut from the one animal were added fat was obtained i n t h e same manner T'nese data were prepared f o r a n a l y s i s i n two ways F i r s t, the u l t r a s o n i c measure of f a t f o r each pig a t the f i r s t rib, first lumbar and last lumbar vertebrae were recorded a t the time of slaughter and averaged Actual carcass backfat thickness a t these same points was a l s o recorded after slaughter and averaged For these data, multiple regressions of composition on weight and average of u l t r a s o n i c measures a t t h e f i r s t r i b, f i r s t lumbar and l a s t lumbar f o r each weight group were determined This involved only slaught e r e d animals from each weight group Significant (PCO1) p a r t i a l regressions of composition on slaughter weight were used t o a d j u s t each weight group t o its mean P a r t i a l c o r r e l a t i o n s (slaughter weight held constant) between composition and u l t r a s o n i c measures were then computed Using t h i s procedure, the usefulness of t h e u l t r a s o n i c instrument i n eva1ua t i n g both a c t u a l carcass backfat thickness and composition a t each weight group was determined

3 51 Next, f o r pigs slaughtered a t 1, 225, and 2 pounds there were 3, 4 and 5 sets of u l t r a s o n i c readings of f a t depth respectively For t h e 225 pound group, four sets were formed by reading 1, reading 1 + 2, reading and reading a t t h e first r i b, a t the f i r s t lumbar and a t the l a s t lumbar This same procedure was used f o r each weight group For the 1, 225, and 2 pound groups, the sets of readings were used t o determine i f ultrasonic readings a t an e a r l y weight were indicative of composition or a c t u a l backfat thickness a t time of slaughter The described sets evaluated the deposition of backfat thickness within pigs w i t h increasing weight The man6 and standard deviations of ultrasonic meausres, age, slaughter and carcass weight are shown i n Table 1 The differences i n standard deviations between slaughter and carcass weight is quite negligible i n the l i g h t e r weight groups As pigs become o l d e r evidently there i s g r e a t e r d i f f e r e n t i a t i o n between viscera and carcass components The preslaughter treatment b f a l l pigs was e s s e n t i a l l y the same V a r i a b i l i t y i n age increased as weight increased Some of these pigs were from dams selected f o r either high o r low f a t producing a b i l i t y and many account f o r some of the wide variance i n time required t o reach prescribed weights i n the heavier groups The u l t r a s o n i c measure of f a t thickness underestimated a c t u a l carcass backfat thickness i n a l l weight groups The v a r i a b i l i t y i n backfat t h i c h e s s was g r e a t e s t i n t h e heavier weight groups Lean thickness did not show a consistent pattern The standard deviations of three of the carcass components i n Table 2, t o t a l lean, f a t and skin, increased with increasing weight indicating more d i f f e r e n t i a t i o n i n these items a s pigs g e t heavier Standard deviations f o r t o t a l bone fluctuated from group t o group Eye muscle area was r e l a t i v e l y constant from t o 2 pounds Within weight groups, the trend was toward more d i f f e r e n t i a t i o n between pigs i n t h e heavier groups weight Table 3 shows the increasing fat t o lean r a t i o w i t h increasing It is apparent t h a t gains beyond 1 pounds a r e c h i e f l y f a t gains P a r t i a l correlations (slaughter weight held constant) betireen the recorded and averaged u l t r a s o n i c measures of f a t depth a t t h e shoulder, l o i n, and ham and composition and a c t u a l backfat thickness a t time of slaughter are shown i n Table 4 The u l t r a s o n i c measure of f a t depth was not s i g n i f i c a n t l y related t o a c t u a l backfat thickness u n t i l pigs reached the pound weight group lean was negatively related t o u l t r a sonic backfat thickness (increased backfat decreased lean) a t t h e, 225 and 2 pound weight groups These f a c t s indicate t h a t both l e a n and f a t between pigs can be detected a t either 225 o r 2 pounds when pigs are heavy enough t o allow d i f f e r e n t i a t i o n i n theae components Table 5 shows t h e m l t i p l e correlations among u l t r a s o n i c measures of fat depth a t t h e shoulder, l o i n and ham and composition i n pigs slaughtered a t 1, 225, and 2 pounds Actual carcass backfat t h i c h e s s a t these weights can be predicted from u l t r a s o n i c measures taken at poundson l i v e pigs i n t h e and 225 pound groups For pigs slaughtered a t 2 pounds, two u l t r a s o n i c measures were required, one a t and one a t pounds, t o predict carcass backfat thickness a t 2 pounds

4 52 These 3 groups of pigs exhibited v a r i a t i o n s within pigs i n backthe 1pound group was consistent i n depositing backfat i n a l i n e a r fashion For t h i s group, the most important s i n g l e point of measurement was over the l o i n for a l l u l t r a s o n i c readings The group slaughtered a t 225 pounds was q u i t e variable i n age They were a l s o q u i t e variable i n length I n f a c t, when these variables, age and carcass length were included with t h e u l t r a s o n i c l o i n measure, t h e u l t r a s o n i c measure taken a t, and 225 pounds adjusted f o r v a r i a b i l i t y i n age and carcass length was s t a t i s t i c a l l y s i g n i f i c a n t (R = 6,,65 and 68 respectively) f a t deposition Table 6 shows the most important points o f measurements f o r t h e three groups of pigs f o r each recorded u l t r a s o n i c measure As pigs increase i n f a t n e s s t h e shoulder measurement is more variable than measures a t the o t h e r two points These data i n d i c a t e that the use of the u l t r a s o n i c instrument i n hogs may be developed t o provide information on growth p a t t e r n s w i t h i n pigs not f i l l y known a t the present time This information would be very usef'ul t o animal breeders i f carcass backfat thickness can be determined i n young pigs of desired breeds of l i n e s For hogs of market weight (225 pounds), t h e u l t r a s o n i c instrument appears t o be as e f f e c t i v e as t h e probe

5 TAEZE 1 MEANS AND STANDARD DEVIATIONS OF ULTRASONIC MEASURES, AGE AND WEIGHT BY WEIGFD GROUPS aughter Number eight of roup pigs Age (days) Slaughter weight (lbs) 92,* Carcass Ultrasonic back Carcass back Ultrasonic l weight fat thickness a fat thickness b thickness (lbs) (inches) (inches) (inches) 51 & * , f f f a a 64 f * e9 * 33 An average ultrasonic measure of fat depth at the first rib, first lurribar and last lumbar An average ruler measure of carcass backfat thickness at the first rib, first lumbar and last lumbar C Ultrasonic measure of depth to bone minus ultrasonic measure of fat depth 2" off midline on right side of l o i n

6 TABLE 2 MEANS AMI m DEVIATIONS OF EYE MUSCLE AREA S AND CCMKISITION BY WEIGRI! GROUPS T o t a l sepsrable T o t a l separable separable T o t a l separable Carcass eye muscle lean fat bone skin weight (sq in) (lbs) (lbs) (lbs) (lbs) (lbs) laughter Area of weight p u p 2 ~ f t 228 1, ? 55 51, f t f f $ ,llf f 84; f ' 98 + '13 213? 76

7 TABU 3 GAINS IN COMPONEWS OF COMPOSITION B E X " laughter w e i g h t Period gains lean (lbs) (lbs) SUCCESSIVE WEIGET PEEUODS fat (lbs) bone (lbs) Fat t o lean ratio Lean t o bone ratio Fat to bone =ti t o LO6 4 1 t o to t o ;

8 TABLE 4 PARTIAL CORRELclTIONS E i W E E 3 J AVERAGE ULTRASONIC EWKFAT THICKNESS, AM3 COMEUSITION Slaughter NuItiber of weight pigs WUP By WEIGW GROWS* Backfat thickness fat 14 lean *78* 31 a # E* a 7 8 H 8* 62* Q ACTUAL BACKFAT TmCKNES bone Eye nruscle area b 624 w36 e 46 e PCOl a b S i g n i f i c a s t ( P C O ~ )weight gmup partial regessions of composition on slaue;hter weight used to adjust composition for variability in sl;lughter weight for x $ b Au, p u p s adjusted to means shown i n Table 1 Se correlation between ultrasonic lean thickness and eye m u s c l e area

9 TAl3LE 5 M'LEXCpLE CORRECATIONS Ml!G SUCCE;ssIVE ULWSONIC READINGS QF BACKFAT TMCKMGSS AT 'EB S K)W IOIN AND HAM, 2 POUNDS ACTUAL BACKFAT TKECKNESS AND COMPOSITION IN PIGS SLAUGHTERED AT 1, 225 AM) Weight group Ultrasonic readings a lean ** ** * 78* 1 (slaughtered) Weight group (slaughtered) Weight group (slaughtered) a P< b e64 72+* fat CarcassBackfat thickness 62* a= * 8992= bone * 66* 63H 73* = C 79* 86 1 = Fat depth a t shoulder, loin and ham recorded at lbs 2 = F a t depth at shoulder, loin and ham recorded a t and lbs 3 = Fat depth a t shoulder, l o i n and ham recorded a t,, and 1 lbs 4 = F a t depth a t shoulder, loin and ham recorded a t,, 1 and 225 lbs 5 Fat depth a t shoulder, l o i n and ham recorded a t,, 1, 225 and 2 l b s An vera e r u l e r measure of carcass backfat a t the f i r s t r i b (shoulder), f i r s t lumbar?loin$ and last lumbar (ham)

10 6 luk'iplj3 REx?rREsSIONS OF ACTUAL AVF3AGE CARCASS BACKFAT TBICKNESS ON ULTRASONIC BACKFAT THICKNESS AT DDFZBENT WIGETS AND LOCATIONS htered a t 1 lbs of Variation df sion due t o ultrasonic shoulder measure onal reduction due t o loin over shoulder measure onal reduction due t o bam over s b u l d e r and l o i n asure ual htered at 225 lbs df of Variation sion due t o ultrasonic shoulder measure onal reduction due to loin over shoulder neasure onal reduction due t o ham over shoulder end loin asure ual htered a t 2 lbs of Variation sion due t o ultrasonic s b u l d e r measure onaj reduction due t o l o i n over shoulder measure onal reduction due t o ban over shoulder and l o i n asure & * * P<1 P<5 a Mean squares lbs lbs 1 l b s MSOa MS MS w 18276* * 8966* IbS lbs 1 IbS 225 l b s MS MS MS MS l81* l lbs l b s 1 lbs 225 lbs2 dof MS MS MS MS MS * w 5539H ll81M

11 59 DR HIIJER The next part of our program, and one that has given me considerable concern, is this matter of fatness in relation to the palatability and the quality of pork We have a certain amount of evidence that fatness is one of the factors that must be kept in ruind when developing a lean or meat type hog To give us a report on that Dr Saffle, a menber of this Committee, has graciously consented to be the leader for this part of the program I believe he has had some experiences and a, head start on some of us It is my understanding that as a graduate student at Michigan State he worked on the problem of fatness Dr Saffle will now report on the third part of our program "Effects of Finish on the Palatability of Pork" DrSaffle