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Estimation of the genetic parameters for ultrasonic backfat measurements, growth and carcass traits in… Jeffries, Duncan Charles 1978

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ESTIHA1T0N OF THE GENETIC PABAHETEBS FOB ULTBASONIC BACKFAT MEASUBEMENTS, GBOWTH AND CABCASS TBAITS IN SHINE by DUNCAN CHABIES JEFFRIES B.Sc.(Agr), University of B r i t i s h Columbia, 1975 A THESIS SUB8ITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOB THE DEGBEE OF HASTES OF SCIENCE in THE FACU LT Y OF GRADUATE STUDIES {Department of Animal Science) He accept th i s thesis as conforming to the reguired standard. THE UNIVERSITY OF BBITISH COLOMBIA September, 1978 (c) Duncan Charles J e f f r i e s , 1S78 In presenting th i s thes is in p a r t i a l fu l f i lment of the requirements f o r an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I a g r e e that the L ibrary shal l make it f ree l y ava i lab le for reference and s t u d y . I fur ther agree that permission for extensive copying of th i s thes is for scho lar l y purposes may be granted by the Head of my Department o r by h is representat ives . It is understood that copying o r pub l i ca t ion o f th is thes is fo r f i n a n c i a l gain sha l l not be allowed without my wri t ten permission. Department of AA> <VM^1 S^;C~C<. The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i i ABSTRACT Genetic parameters were estimated f o r 2403 purebred Landrace pigs ever a two year p e r i o d , r e p r e s e n t i n g 21 s i r e s . The t r a i t s s t u d i e d i n c l u d e d average d a i l y g a i n , age a d j u s t e d to 91 kg, u l t r a s o n i c measurements o f backfat a t the midback and l o i n p o s i t i o n s , t o t a l and a d j u s t e d t o t a l u l t r a s o n i c b a c k f a t and corresponding c a r c a s s b a c k f a t measurements. Least squares analyses were used to estimate and a d j u s t f o r the e f f e c t s of sex, season and sex by season i n t e r a c t i o n . H e r i t a b i l i t i e s and g e n e t i c c o r r e l a t i o n s were c a l c u l a t e d f o r a l l t r a i t s u s i n g both h a l f and f u l l - s i b estimates. Adjusted age and adjusted t o t a l u l t r a s o n i c b a c k f a t measurements were found to be the nest a p p r o p r i a t e p r e d i c t o r s of c a r c a s s v a l u e . Estimates o f h e r i t a b i l i t y f o r adjusted age and adjusted t o t a l u l t r a s o n i c b a c k f a t were 0.24±0.10 and 0. 26±0. 10 based on h a l f - s i b and 0.56±0.07 and 0.4110.06 from f u l l - s i b a n a l y s e s . Genetic c o r r e l a t i o n s between these two t r a i t s were -0.07±0.28 and -0.01±0.10 based on the two r e s p e c t i v e methods. -the t o t a l phenotypic c o r r e l a t i o n was -0.01±0.02. A s e l e c t i o n index example was developed from h a l f - s i b e stimates of the g e n e t i c parameters and economic f a c t o r s were estimated from f i x e d and v a r i a b l e c o s t s f o r a d j u s t e d age and the Canadian market index system. i i i T A B L E OF CONTENTS PAGE INTRODUCTION . . . . . . . . . , 1 L I T E R A T U R E REVIEW. . . . . . , 5 M A T E R I A L S AND M E T H O D S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • , 1 1 E x p e r i m e n t a l A n i m a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . » 11 C o l l e c t i o n o f D a t a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 E s t i m a t i o n o f G e n e t i c P a r a m e t e r s . . . . . . . . . . . . . . . . . . . . . . . . . 17 a . S t a t i s t i c a l m o d e l s . 17 b . E s t i m a t i o n o f v a r i a n c e c o m p o n e n t s . . . . . . . . . . . . . . . . . . 18 c . S t a n d a r d e r r o r o f v a r i a n c e c o m p o n e n t s . . . . . . . . . . . . . . 20 d . H e r i t a b i l i t y e s t i m a t e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 e . C o r r e l a t i o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . * V* * * « . . . . . . 21 P r e d i c t i o n o f C a r c a s s F a t M e a s u r e m e n t s . . . . . . . . . . . . . . . . . . . 24 S e l e c t i o n I n d e x . . . . . . . . • . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . . . . 26 R E S U L T S AND D I S C U S S I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 I , E s t i m a t i o n o f G e n e t i c P a r a m e t e r s . . . . . . . . . . . . . • . • . • . . 27 a . V a r i a n c e c o m p o n e n t s . . . . . . . . . . . . . . . . . . . . . . . . . . . • •'••*• 27 b . H e r i t a b i l i t y e s t i m a t e s . . . . . . . . . . , > • • ; . . . . . . . . . . . . . . . ,31 c . G e n e t i c a n d e n v i r o n m e n t a l c o r r e l a t i o n s . . . . . . . . . . . . • 39 I I . R e l a t i o n s h i p B e t w e e n L i v e a n d C a r c a s s M e a s u r e m e n t s . . . . 50 I I I . S e l e c t i o n I n d e x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 a . E c o n o m i c w e i g h t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 b . S e l e c t i o n i n d e x e x a m p l e . . . * . . . . . . . . . . . . . . . . . . . . . • . . 63 S U M M A R Y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i . . . . . . . . . . • • . . 64 L I T E R A T U R E C I T E D . . . . . . . . . . . . . . . . . . . . . . . 67 LIST OF TABLES TABLE PAGE I. Analysis of variance for the estimation of variance components. ,19 I I . Values of c o e f f i c i e n t s for the calculation cf variances of co r r e l a t i o n s . ......... 23 I I I . Proportion of the t o t a l variance (R2) accounted for by the factors time, sex and time by sex i n t e r a c t i o n . . . 2 8 IV. Least square means and standard errors f o r l i v e animal measurements from Data Set I I . . . . . . . . . . . . . . . . . . . 29 V. Least square means and standard errors for carcass measurements from Data Set II 30 VI. Degrees of freedom and K values for the estimation of components of variance from Data Set I I . . . . . . . . . . . . . 32 VII. Estimates of components of variance f o r l i v e and carcass t r a i t s from Data Set I I . . . . . . . . . . . . . . 33 VIII. Estimates of h e r i t a b i l i t y for l i v e and carcass t r a i t s from Data Set II 34 IX. Genetic correlations (below the diagonal) and genetic covariance (above the diagonal) f o r l i v e and carcass t r a i t s from Data Set I I . . . . . . . . . . . . . . . . . . . . . . . . 40 X. Environmental correlations (below the diagonal) and phenotypic correlations (above the diagonal) f o r l i v e and carcass t r a i t s from Data Set II. 44 XI. Means and standard deviations of l i v e and carcass t r a i ts f o r Cat a S et I............•.....•.....•......... 51 XII. Simple correlations among l i v e and carcass t r a i t s f o r Data Set I. 52 XIII. Stepwise regression analyses f o r prediction of carcass f a t and Grade Index for Data Set I............. 54 V PAGE XIV, Heans and s t a n d a r d d e v i a t i o n s o f l i v e and c a r c a s s t r a i t s f o r D a t a S e t I w i t h 0-17 d a y s between probe and s l a u g h t e r . . . . . . . . . . . . . . . . . . . . . . * 56 XV. S i m p l e c o r r e l a t i o n s among l i v e and c a r c a s s t r a i t s f o r Data S e t I w i t h 0-17 days between p r o b e and s l a u g h t e r . . . , . . . . . . . . . vv 57 XVI. S i m p l e l i n e a r r e g r e s s i o n e q u a t i o n s f o r c a r c a s s t r a i t s f o r D a t a S e t I w i t h 0-17 d a y s between p r o b e and s l a u g h t e r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 v i ACKNOWLEDGMENTS Considerable assistance was given by personnel of the Production and Marketing Branch, Agriculture Canada, Vancouver, i n the c o l l e c t i o n of ultrasonic and carcass data, and also by the s t a f f of Colony Farm swine unit by providing the pigs used i n t h i s project. Their contribution to thi s study i s g r a t e f u l l y acknowledged. Appreciation i s extended to the author's thesis committee, Drs,, E.M. Beames, G.H. Eaton, and B.D. Owen, for the i r helpful suggestions and c r i t i c i s m s i n the writing cf the thesis., I also thank my research supervisor Dr. E.G. Peterson for his keen inter e s t and advice on t h i s project. / This research was supported by an Agriculture Canada research grant.„• 1 I N T R O D U C T I O N U n t i l r e c e n t l y , the most common method o f e v a l u a t i o n c f backfat on the l i v e p i g was by r u l e r probe., With t h i s method, a s c a l p e l i s used to make a s m a l l i n c i s i o n i n the s k i n and a t h i n metal r u l e r i s eased through the f a t l a y e r s t o gi v e a d i r e c t measurement. The accuracy o f t h i s procedure can vary c o n s i d e r a b l y as i t i s hard to determine the bottom of the f a t l a y e r , A common source of e r r o r i s f a i l u r e t c penetrate the f u l l depth of bac k f a t due t o i n s u f f i c i e n t pressure on the r u l e r . Too much pressure s i l l f o r c e the r u l e r i n t o the l e a n and exaggerate the f a t measurement, a d d i t i o n a l v a r i a t i o n i s caused by a l a c k of u n i f o r m i t y of f a t cover which would a f f e c t any s i n g l e estimate of f a t depth. The more r e c e n t method c f e v a l u a t i n g b a c k f a t t h i c k n e s s i n v o l v e s the use of u l t r a s o n i c measurement eguipment. High freguency sound i s d i r e c t e d downward from the s k i n s u r f a c e by means of a small transducer held l i g h t l y a g a i n s t the a i i m a l . When the u l t r a s o n i c sound s t r i k e s the i n t e r f a c e between f a t and muscle, a p o r t i o n o f the sound i s r e f l e c t e d back t o the t r a n s d u c e r . T h i s echo i s transformed by the machine t o give a d i r e c t measurement o f t i s s u e t h i c k n e s s . L i t t l e time i s r e g u i r e d t o o b t a i n a f a t depth r e a d i n g , and repeated measurements may be taken at a number of p o s i t i o n s without harming the animal. T h i s g i v e s a t e t t e r i n d i c a t i o n of the f a t cover on the animal as w e l l 2 as increased accuracy at each s i t e . This technigue i s also painless and the stress involved i s associated only with r e s t r a i n t of the animal. A disadvantage of the ultrasonic technique i s that the equipment i s expensive and requires an experienced operator to obtain accurate r e s u l t s . Only large commercial farms would f i n d i t p r a c t i c a l to employ a testing program with their own machine and operator. In most areas of Canada ultrasonic probing i s available to farmers enrolled on the Record of Performance (E.O.P.) swine testing program. For each animal probed the breeder obtains a record of s i r e , dam, age, and weight as well as ultrasonic f a t measurements. The breeder has several options f o r using t h i s information i n a selection program. I f the herd i s below average i n only one t r a i t , he may f e e l i t i s most important to improve t h i s t r a i t as rapidly as possible. This can be accomplished by selecting on the basis of the single t r a i t . Generally i t i s desirable to improve more than one t r a i t at a time. The method of independent c u l l i n g l e v e l s , or a se l e c t i o n index can be used for t h i s purpose. With the method of independent c u l l i n g l e v e l s , a miniiium or maximum acceptable value i s chosen for each t r a i t and animals that do not meet these c r i t e r i a are c u l l e d . A disadvantage with 3 t h i s method i s that an animal w i l l be culled on the basis of one t r a i t regardless of any su p e r i o r i t y i n the other t r a i t s . , The selection index has been found to be the most e f f i c i e n t method for selecting two or more t r a i t s simultaneously. , The conventional selection index takes into consideration the h e r i t a b i l i t y and r e l a t i v e economic value of each t r a i t along with the correlations between the t r a i t s to give a measure of the r e l a t i v e genetic merit of each animal in terms of economic value. For a s e l e c t i o n index to be of value, accurate estimates of economic value, h e r i t a b i l i t y of each t r a i t and the genetic and phenotypic c o r r e l a t i o n s between the t r a i t s must be available. Since i t i s only recently that ultrasonic measurements have been available to a large number of breeders, few studies have been conducted to estimate the genetic parameters associated with these measurements. The main objectives of t h i s study were: 1. To determine the rel a t i o n s h i p between ultrasonic and carcass fat measurements, 2. To estimate genetic parameters of the t r a i t s measured by the Canadian Becord of Performance heme test program with ultrasonic backfat t e s t i n g . These parameters are reguired to u t i l i z e some or a l l of the t r a i t s i n a selection index, and To propose a s e l e c t i o n index based on Record of Performance measurements to o p t i m i z e economic gain i n order to demonstrate the use of the estimated paramaters. 5 LITERATOBE REVIEW The ultrasonic technique has been deaonstrated to be quite sa t i s f a c t o r y for the estimation of f a t depth i n swine by a number of researchers. High correlations ranging from 0.70 to 0.93 were reported i n several studies to determine the relationship between ultrasonic backfat measurements and corresponding carcass measurements (Hazel and Kline 1959, Price et a l . 1960, Stouffer 1961, Horst 1969, Combs 1970, G i l l i s et a l . 1972). Lower c o r r e l a t i o n s (0.24-0.69) were found i n s i m i l a r studies by I s l e r and Swiger (1968) and Anderson and Whalstrcm {1969). Blendl (1968) investigated the p r a c t i c a l i t y of the ultrasonic technigue under f i e l d conditions and reported comparable r e s u l t s with c o r r e l a t i o n s of 0. 53-0. 56. In preliminary work with the swine herd used i n t h i s study, J e f f r i e s (1975) found both midfcack and l o i n ultrasonic f a t measurements to have high correlations (0.92) with the corresponding carcass measurements made under te s t conditions with 98 pigs. In t h i s same study, correlations between the ultrasonic measurements taken 5 cm from the spine and carcass measurements taken at the spine were reported for a group of 1904 pigs measured under f i e l d conditions. These c o r r e l a t i o n s ranged from 0.49 to 0.5-2., I s l e r and Swiger (1S66) evaluated the use of ultrasonic 6 measurements of f a t depth taken on 379 l i v e pigs i n predicting carcass composition as measured by percent lean cuts. A multiple regression eguation for the prediction of percent lean cuts incorporated the variables; ultrasonic fat at twelfth r i b , ultrasonic f a t at l o i n , and l i v e weight, and accounted for 52 percent of the t o t a l variance (B 2). Similar work by Anderson and Wahlstrcm (196 9) investigated the value of ultrasonic measurements taken at the tenth r i b i n predicting percent lean cuts for a group of 78 animals., The proportion of the t o t a l v ariation accounted for in 14 prediction equations ranged from 61 percent with 17 variables to as low as 37 percent with only 2 variables, age at slaughter and fat probe at the tenth r i b . In a study with 59 Yorkshire Becord of Performance test pigs, i t was found that the average of three ultrasonic f a t measurements, shoulder, midback, and l o i n accounted for 45 percent of the variation i n percent trimmed lean cuts ( G i l l i s et a l . 1S72). This same study reports H 2 values for separate ultrasonic measurements of shoulder midback and l o i n with corresponding carcass measurements of 0.52, 0.69 and 0.76 respectively. , Early reports on the h e r i t a b i l i t y of backfat for swine were based on carcass rather than l i v e measurements. In a studv with 357 pigs from 41 s i r e s , h e r i t a b i l i t y values of 0.12 f o r carcass backfat and 0.18 for average daily gain were reported (Blum and 7 Baker 1947), The genetic and phenotypic correlations were also reported with respective values of 0.33 and 0.29 for carcass backfat with average daily gain. In a study by King et a l . (1957) with 3648 pigs, the h e r i t a b i l i t y of carcass backfat adjusted to 91 kg was calculated as 0.42 from a paternal h a l f - s i b c o r r e l a t i o n . The same h e r i t a b i l i t y value (0.42) was reported by Whatley and E n f i e l d (1957) for carcass backfat also calculated from paternal h a l f - s i b c o r r e l a t i o n . , fi maternal h a l f - s i b estimate was reported with a value of 0.84. The h e r i t a b i l i t y cf carcass backfat has been calculated by regression of offspring on midparent with 256 degrees of freedom (Beddy et a l . 1959). Estimates of 0.16-0.18 were l i s t e d for spring, f a l l and combined seasons. The h e r i t a b i l i t y range for average daily gain was reported to be 0.20-0.31. Enfield and Hhatley (1961) reported estimates for t h i s t r a i t from paternal h a l f - s i b , maternal h a l f - s i b and f u l l - s i b c o r r e l a t i o n s to be 0.42, 0.84 and 0.63, with 531 pigs and 57 degrees of freedom for s i r e s . In a larger study with 2296 Landrace pigs from 250 boars, a high value of 0.74 was reported for the h e r i t a b i l i t y of carcass backfat estimated from a paternal h a l f - s i b c o r r e l a t i o n (Smith and Boss 1S65). In t h i s same study the h e r i t a b i l i t y of average d a i l y gain was l i s t e d as 0.41 with genetic and phenotypic correlations of -0.26*0.18 and -0.08+0.02 between the two 8 t r a i t s , A correspondingly high value of G,69±0.17 for the h e r i t a b i l i t y of carcass backfat thickness has also been reported (Jensen et a l , 1967), A paternal h a l f - s i b correlation was used to obtain t h i s estimate from 116 sir e s of mixed breeds. Data were coll e c t e d from a swine breed development project over a seven year period, and h e r i t a b i l i t i e s estimated from a paternal h a l f - s i b c o r r e l a t i o n with 85 degrees of freedom for s i r e s were reported as 0.33±0.14 for average d a i l y gain and 0.35±0.12 fo r carcass backfat adjusted to 67,3 kg hot carcass weight (Hoy et a l . 1968). Values of genetic and phenotypic correlations f o r these same t r a i t s were reported as Q.23±0.25 and 0,24 respectively, An average of shoulder, midback and l o i n measurements was also included i n calculations of genetic and phenotypic correlations. Genetic and phenotypic correlations for t h i s t r a i t were -0,24 and 0.07 with d a i l y gain and 0,46 and 0,48 with carcass backfat. Results of f i v e generations of sel e c t i o n for low backfat thickness i n swine have also been reported (Gray et a l . 1S68). A t o t a l of 1828 pigs from 67 s i r e groups and 270 dams were used to estimate h e r i t a b i l i t y from i n t r a - s i r e regression of mean of offspring on dam. Backfat was measured with a rul e r probe on the l i v e animals at the shoulder, l o i n and ham positions and a l l measurements were adjusted to 79.4 kg l i v e weight. Respective h e r i t a b i l i t y estimates of 0,3610.0 9, 0.51±0.09 and 0.44±0.C7 as 9 well as an estimate of 0.56±0.09 for the average of these three backfat measurements were reported. H e r i t a b i l i t y estimates of 0.62±0.19 for l i v e backfat probe and 0.53±0.16 for carcass backfat, both a t o t a l of shoulder and l o i n measurements, were reported by Arganosa et a l . {1969), These estimates were calculated from the s i r e components of variance and covariance with 650 pigs of various breeds fxon 89 s i r e s . A somewhat lower estimate of 0.38*0.02 for the h e r i t a b i l i t y of ruler probe backfat measurement adjusted tc 63.6 kg l i v e weight has been reported (Berruecus et a l . , 1970). Live weight at 130 days was reported to have a h e r i t a b i l i t y c-f 0.23±0.03. These values were obtained from 483 pigs and are weighted averages of several h e r i t a b i l i t y estimates. Fahmy and Bernard (1970) reported the h e r i t a b i l i t y of average daily gain as O.T6±0.27 when estimated from the s i r e component of variance and -0.02±0.09 frcm regression of offspring on midparent. This study included 4428 pigs from 161 s i r e s and 780 dams. A higher estimate of h e r i t a b i l i t y for average d a i l y gain was reported as 0.33±0.04 by Hetzer and K i l l e r (1S72) i n a study with 1835 pigs. The h e r i t a b i l i t y of l i v e backfat probe was also l i s t e d with a value of 0.50±0.05. These h e r i t a b i l i t i e s were estimated from regression of offspring on mean of parents. Genetic and phenotypic correlations between these t r a i t s were reported as -0.12 and 0.04 respectively. 10 a study by Batra et a l . (1972) using B.0.P. swine data from i n d i v i d u a l s i r e progeny appraisal reports on 1849 Yorkshire pigs l i s t e d f u l l - s i b h e r i t a b i l i t y estimates. The reported values were 0.31 for average da i l y gain and 0.44 for the t o t a l of shoulder, midback and l o i n carcass f a t measurements. The correlations between these t r a i t s were l i s t e d as -0.21 for genetic and 0.18 for phenotypic, Siers and Thomson (1972) also estimated the h e r i t a b i l i t y of carcass backfat and reported a value of 0 , 2 3 ± 0 , 0 9 . This value was estimated from the s i r e component calculated from 3,439 pigs out of 216 s i r e s . 11 MATERIALS AND METHODS Experimental Animals A l l of the data used in t h i s study were c o l l e c t e d from the swine herd at the Province of B.C. Farm, Essondale, between October, 1974 and December, 1976. , This herd consisted of approximately 144 purebred Yorkshire sows, 12 Hampshire, Landrace and crossbred sows, and 12 purebred Yorkshire boars. The method of independent c u l l i n g l e v e l s was used for herd improvement throughout the 2 year study period. Eith t h i s method a minimum or maximum acceptable value i s chosen for each t r a i t and animals that do not meet these c r i t e r i a are c u l l e d . The two t r a i t s and the respective c u l l i n g l e v e l s used i n t h i s s e l e c t i o n program were, age adjusted to 91 kg with a maximum value of 175 days and probe fat adjusted to 91 kg with a maximum of 20 mm. Potential replacement breeding stock were evaluated in r e l a t i o n to these standards and any animal f a i l i n g to meet one or both of these l i m i t s was c u l l e d . This was a normal farrow to f i n i s h operation with group feeding of approximately 18 animals of the same sex to a pen. There was a tendency for pigs of the same sex from a l i t t e r to remain together i n the same pen throughout the growing period. The farm was under a normal management system si m i l a r to that of a commercial unit with t*o exceptions: 12 1. The f i r s t p r i o r i t y for marketing was tc provide Esscndale hospital with a steady supply of fresh pork., In some cases t h i s resulted in a delay i n slaughtering the animals for three weeks or more from probe date. 2. The diet of these animals consisted of between 20 and 30 percent cooked garbage (dry matter basis). C o l l e c t i o n of Data A l l animals i n the herd were u l t r a s o n i c a l l y backfat probed at between 82 and 100 kg l i v e weight by trained B.0.E. s t a f f . A l l ultrasonic measurements were taken with a Krautkramer Ultrasonic Flaw Detector 0SM2, Design F. This model i s designed especially for the determination of fat and lean meat thickness cn livestock. I t operates i n accordance with the pulse echo pr i n c i p l e i n which very short e l e c t r i c a l impulses are converted into ultrasound pulses which are transmitted into the medium to be tested. These pulses t r a v e l through tissue in a straight l i n e and at a high speed (1500-6000 m/sec) . When the ultrasound s t r i k e s a layer of d i f f e r e n t sound attenuation (density x acoustic velocity) than that of the basic medium, the ultrasound waves are r e f l e c t e d . When s t r i k i n g at right angles to the r e f l e c t i n g layers, the ultrasound waves are returned to the transmitting probe and are reconverted into e l e c t r i c a l pulses. The transmitting to receiving time i n t e r v a l of the ultrasound pulse 13 i s r epresented OB a Cathode Bay fube (CRT) as a d i a g r a m - l i k e d i s p l a y . I f the a c c o u s t i c v e l o c i t y of the t i s s u e remains constant over the f u l l depth range, then the sound t r a v e l time corresponds to the t r a v e l d i s t a n c e of the p u l s e . This means t h a t the base l i n e o f the CBT s c r e e n can be d i r e c t l y c a l i b r a t e d as t i s s u e depth. The use of t h i s p r i n c i p l e on l i v e s t o c k i s f a c i l i t a t e d by the f a c t t h a t the t i s s u e l a y e r s i n the animal body such as muscular membranes, f a t t o l e a n meat t r a n s i e n t zones, and f a t i n c l u s i o n s i n the d o r s a l muscle are p a r t i a l l y permeable. This means t h a t a p o r t i o n of the u l t r a s o u n d wave i s r e f l e c t e d while the r e s t t r a v e l s to the next l a y e r . ,• These r e f l e c t e d s i g n a l s produce a p a t t e r n cn the CRT screen which can be i d e n t i f i e d as separate t i s s u e l a y e r s . Each animal was r e s t r a i n e d e i t h e r i n the s c a l e s used f o r weighing or i n a c r a t e designed f o r t h i s purpose, both o f which allowed the animal to stand n a t u r a l l y . P i g s were probed on each s i d e 5 cm v e n t r a l t o the spine a t the l a s t r i b (midback) r e g i o n , and 15 cm p o s t e r i o r to the l a s t r i b i n the l o i n r e g i o n , t o g i v e a t o t a l of 4 f a t depth measurements, ( l e f t and r i g h t midback p l u s l e f t and r i g h t l o i n ) . L i v e weight, sex, and ear t a t t o o i d e n t i f i c a t i o n were recorded at the time of probe, while date of b i r t h and s i r e and dam i d e n t i f i c a t i o n were added a f t e r probing was completed. 14 Measurements of maximum shoulder and maximum l o i n backfat, taken at the the spine cn the s p l i t carcass, along with carcass weight. Grade Index, ear tattoo i d e n t i f i c a t i o n and date of slaughter were recorded by agriculture Canada grading s t a f f f o r each carcass with c l e a r i d e n t i f i c a t i o n . , The additional measurement of minimum carcass midback f a t was also recorded for animals slaughtered after December 1974. Additional variables were calculated a f t e r compiling and matching l i v e and slaughter information., These variables were, age i n days, l i v e weight per day of age, average midback fat average l o i n f a t , and t o t a l for the ultrasonic fat measurements, as well as carcass weight per day of age., 8.O.E. swine adjustment values e f f e c t i v e June 1977 were used to calculate age, and average probe fat adjusted to 91 kg l i v e weight. The t r a i t s used i n t h i s study were: 1. Average daily gain, b i r t h to probe date (kg/day) 2. Age adjusted to 91 kg l i v e weight (days) 3. Average of l e f t and ri g h t midback probe fat (mm) 4. Average of l e f t and ri g h t l o i n probe fat (mm) 5. Total of 2 midback plus 2 l o i n probe measurements (mm) 6. Average midback plus average l o i n probe fat measurements adjusted to 91 kg l i v e weight (mm) 7. Carcass weight per day of age (kg/day) 8. Maximum carcass shoulder fat (mm) 9. Minimum carcass midback f a t (mm) 15 10. Maximum carcass l o i n fat (mm) 11. Total of 9 and 10 above 12. Total cf 8 and 10 above 13. Carcass Grade Index A l l barrows and females in the herd with ultrasonic probe information were used i n t h i s study. Boars were not included due to i n s u f f i c i e n t numbers,, I t was also noted that boars which were early candidates f o r selection as breeding animals but not actually selected were castrated much l a t e r than normal. This resulted i n an extended period of time between probe and slaughter dates which was inconsistant with the other animals in the herd. The animals used i n t h i s study were divided i n t o two groups. The f i r s t group (Data Set I) included a l l animals i n the study., This set of data was used i n stepwise multiple regression analyses to determine the relationship between carcass measurements and various sets of l i v e animal measurements. These analyses were also used to determine which combinations of the l i v e animal measurements would give the best estimates of the carcass measurements. These equations show the maximum proportion of the t o t a l variation in each of the carcass t r a i t s that can be accounted for by combinations of the available independent variables. These maximum values can be used for comparison with the proportion of the t o t a l variation 16 accounted for by each of the simple l i n e a r regressions with the same dependent variables. This gives an i n d i c a t i o n of the value of each of the simple l i n e a r regression equations. The second group of animals (Eata Set I I ) , a subset of the f i r s t , including only purebred Yorkshire pigs, was used for the estimation of genetic parameters. The animals i n t h i s group with carcass information were slaughtered within 17 days of probe date and were within the Grade Index range of 92 - 112. As p i g s sere slaughtered only once a week, the 17 day period was selected as i t included a majority of the animals but excluded the extreme values. In order to r e t a i n the maximum number of observations for the estimation of genetic parameters, the second group of animals (Data Set I I ) , was further divided into three subgroups, each a subset of the preceeding subgroup. The f i r s t subgroup contained a l l animals with l i v e probe information. The second contained those with observations f o r a l l variables except carcass midback f a t and the t o t a l of carcass midback plus carcass l o i n f a t . No observations were missing i n the t h i r d subgroup. These three subgroups are referred to in t h i s study as analyses groups I, II and III respectively. Each of the three subgroups was treated as a separate set of data f c r a l l adjustments and analyses. 17 A l l i n d i v i d u a l s in Data Set II were c l a s s i f i e d by the quarter of the year in which the animal was probed. , Each year was divided into four three-month periods beginning with the period January - March to give four categories i n each year analagous to seasons. This was done to enable adjustment of data for possible effects due to the seasons i n each year, and any change i n management practices with time. Estimation of Genetic Parameters a. S t a t i s t i c a l models. The following s t a t i s t i c a l model was assumed to describe the data: a) Yijk = U + Ai * Bj * ABij • Eijk where: Yijk = the k-th i n d i v i d u a l of sex j within the i - t h season 0 = the common mean Ai = the e f f e c t of the i - t h season Bj = the e f f e c t of the j-th sex ABij = the e f f e c t of the interaction between the i - t h season and the j-th sex Ei j k = the uncontrolled environmental and genetic deviations attributed to indivi d u a l s A l l e f f e c ts were assumed to be fix e d . A second s t a t i s t i c a l model was assumed to describe the data adjusted by model (a): b) Y*ijk = 0 + S i + Dj/Si • Ik/Dj/Si 18 where; Y'ijk = the k-th progeny of the j-th dam mated to the i - t h s i r e adjusted for the effects of sex, season and the interaction between sex and season from model (a) 0 = the common mean Si = the e f f e c t of the i - t h s i r e Dj/Si = the e f f e c t of the j-th dam mated to the k-th s i r e Ik/Dj/Si = the uncontrolled environmental and genetic deviations attributed to the k-th i n d i v i d u a l of the j - t h dam mated to the i - t h s i r e A l l effects were assumed to be random, normal, and independent with expectations egual to zero. b. Estimation of variance components. The data were f i r s t adjusted for the ef f e c t s of season, sex, and season by sex inter a c t i o n by the method of le a s t squares constants. The analysis of variance and expected mean sguares used to ca l c u l a t e the variance components are given i n Table I , with the following d e f i n i t i o n s of terms as given by Becker (1967): 6e 2 = the within family variance component associated with in d i v i d u a l s from a single s i r e dam mating. This component contains 1/2 the additive genetic variance (VA), 3/4 of the dominant genetic variance (VD) , 3/4 of the additive by additive genetic variance (VAA), 7/8 of the additive by dominance genetic variance |VAD), 15/16 of the additive by additive by additive genetic variance (VAAA) and a l l of the environmental variance (VE). 19 fable I Analysis of variance for the estimation of variance components. Source of Variation Degrees of Freedom Expected Mean Squares Sires Dams/Sires Ind/D/S 2 Ni~1 i £ < » j - 1 > 2{Nk-1) 0' Oe 2 * K2ed 2 * K30s 2 Ge 2 • KlOd 2 e e 2 K1 = (N.. - ]£{ ^  Nij 2/Ni.) )/d.f. , dams K2 = t(£Nij 2/Ni.) ~ ( j N i j 2 / N . . ) ) / a . f . s i r e s K3 = ( N . 2 »i.?/H«.) )/d.f. s i r e s 20 ed 2 •= the variance among dams caused by factors common to pigs by the same dam, but varied from dam tc dam within a s i r e . This component contains 1/4 VA, 1/4 VD, 3/16 VAA, 1/8 VAD, 1/16 VDD, 7/64 VAAA and a l l of the variance associated with maternal e f f e c t s . 6 s 2 = the variance among s i r e s caused by factors common to pigs by the same s i r e , but variable from s i r e to s i r e . This component contains 1/4 VA, 1/16 VAA, 1/64 VAAA, The K values were calculated by the method given by Bcberts (1975) where: K1 = the weighted average number of progeny per dam, K2 = the weighted average number of progeny per dam within a s i r e K3 = the weighted average number of progeny per s i r e . c.Standard error of variance components. The general formula as given by Becker (1967), was used for the ca l c u l a t i o n of the standard error of variance components: var(6g 2) = 2/K2 £ (MSg2/Fg+2) S. E. (6g 2) = (var (6g 2)) where: K •= the c o e f f i c i e n t of the variance component being tested. BSg = the g-th mean square used to estimate the variance component. Fg •= the degrees of freedom of the g-th mean sguare. 21 d. H e r i t a b i l i t y estimates. The h e r i t a b i l i t y analysis followed the method described by Falconer (1960) for a sib analysis. Half-sib estimates were obtained from both the s i r e and dam components of variance and both components were used for a f u l l - s i b estimate., An approximation of the standard error of h e r i t a b i l i t y was calculated as described by Becker (1967): S.E.(h 2s) = 4S6s 2 / (6s 2 * Cd2 • 6w2) S.E.(h2d) = 4S6d 2 / (fis 2 + ed 2 • Gw2) S.E.(h2s+d) = 2(S 26s 2 • S 2Od 2 • 2SGsd) W 2/(Gs 2 • Cd 2 + 6e 2) where: S6s 2 = [2/K3 2( (SSs 2/S-1) + (MSdz/d.f dams) ) S6d 2 = [2/K1 2 ((HSd 2/d. f. dams) • (HSe2/n..-D) ) ]** SCds = -K2/K3(S 26d 2 - (2HSw2/(n. .-D) K 12) ) e. Correlations. The genetic, environmental and phenotypic i n t r a c l a s s c orrelations between each pair of t r a i t s were estimated by the general formula as given by Falconer (1976): Bi = cov(xy) / (ex 26y 2) Where Bi i s the i - t h c o r r e l a t i o n estimate., The covariance between a pair of t r a i t s was obtained from the analysis of variance of the sum of the two t r a i t s and the solution to the eguation: VAB(x+y) = VABx • VABy • 2COVxy The variance of the correlation c o e f f i c i e n t was estimated by the method given by Hammond and Nicholas (1972): 22 Est. Var (Bi) = 2F 2Bi{[ ( ( a 2 (UxUy+Oxy2) /u) • (b 2 (VxVy«-Vxy2)/v) +(c 2(axwy+8xy 2)/w)) / 2cov 2xy] +[((a 2Ox 2/u) • (b 2Vx 2/v) * (c2Wx2/w)) / «ivarx2J *l < (a 2Oy 2/u) + (b 2Vy 2/v) * (c 28y 2/w)) / <*vary2] ~r((a 2UxUxy/u) + (b2VxVxy/v) • (c2»xHxy/w) ) / varxcovxy] -[((a 20yUxy/u) • (b2VyVxy/v) + (c2WyWxy/w)) / varycovxy] *l ( (a 2Dxy 2/u) + (b 2V 2xy/v) • (c2Wxy2/w)) / 2varxvary ] ) I 2 where: u,v,w = the degrees of freedom for the corresponding mean sguare and mean cross product., 0 = the mean sguare associated with the s i r e component for a pa r t i c u l a r t r a i t . V = the mean sguare associated with the dam component for a p a r t i c u l a r t r a i t . W = the mean sguare associated with the within component for a p a r t i c u l a r t r a i t . Oxy = the mean cross product associated with the s i r e component for t r a i t s x and y, Vxy = the mean cross product associated with the dam component for t r a i t s x and y. wxy = the mean cross product associated with the within component for t r a i t s x and y. Values for the c o e f f i c i e n t s F^L,a,b and c for the estimates of variance f o r the genetic, environmental and phenotypic correlations are l i s t e d i n Table I I . , Table I I Values of c o e f f i c i e n t s fox the c a l c u l a t i o n of v a r i a n c e s of c o r r e l a t i o n s . C o r r e l a t i o n C o e f f i c i e n t s P L a b c Genetic S i r e s 4 K3 -1 -K2/K1 (K2-KD/K1 Dams 4 K1 0 1 -1 S + D 2 K1K3 K1 K3K2 (K2-K1-K3) Environmental W-2S 1 K3 -2 2K2/K1 (<K1~K2)/K1) +K3 B-2D 1 K1 0 -2 K1 + 2 W-S-D 1 K1K3 -K1 K2-K3 K1-K2+K3 (K1 + 1) Phenotypic 1 K1K3 K1 K3-K2 K2-K1+K3 (K1-1) 24 Predict ion of Carcass Fat Measurements Multiple regression analyses were performed t o investigate the relationships between carcass measurements and l i v e animal measurements for Data Set I. Step-up stepwise multiple regression was used to incorporate the largest number of s i g n i f i c a n t l y important independent variables i n the model. The dependent variables i n these analyses were: 1. Minimum carcass midback fat plus maximum carcass l o i n f a t 2. Maximum carcass shoulder f a t plus maximum carcass l o i n fat 3. Grade Index These dependent variables were selected for their importance in the Canadian swine grading system. The maximum carcass shoulder f a t plus maximum carcass l o i n f a t measurements are used i n conjunction with hot carcass weight to determine the carcass index for swine graded i n Canada. This index i s subseguently used to determine the market value of the carcass. The minimum midback plus maximum l o i n carcass f a t measurements have been proposed as alternatives to the current grade measurements, and have been included in t h i s study for comparison. Dependent variable three i s the Grade Index based cn the hot carcass weight and the carcass f a t measurelents, maximum shoulder plus maximum l o i n . Due to the high c o r r e l a t i o n between the various ultrasonic backfat measurements, three separate regression analyses, each 25 with a dif f e r e n t set cf potential independent variables were performed for each dependent variable. The following sets of potential independent variables were used: Set I 1. age adjusted to 91 kg l i v e weight 2. Average midback probe fat 3. Average l o i n probe fat 4. Time between probe date and slaughter date Set II 1. Age adjusted to 91 kg l i v e weight 2. Total probe backfat (midback plus loin) 3. Time between probe date and slaughter date Set I I I 1. Age adjusted to 91 kg l i v e weight 2. Average probe backfat adjusted to 91 kg l i v e weight 3. Time between probe date and slaughter date The l i n e a r model assumed for each of these analyses was: Yj = A • B i X i j where: Yj = the observed value of the dependent variable for the j-th animal, (j= 1... n) A = the Y intercept Bi = the i - t h regression c o e f f i c i e n t associated with the i - t h independent variable, (i=1...number of independent variables selected) 2 6 X i j = the i - t h independent v a r i a b l e f o r the j - t h animal., (j=1...n and i-1...number of independent v a r i a b l e s s e l e c t e d ) a d d i t i o n a l analyses were performed to determine the simple l i n e a r r e l a t i o n s h i p between each of the s i n g l e independent v a r i a b l e s and the dependent v a r i a b l e s used i n the m u l t i p l e r e g r e s s i o n a n a l y ses. The data used i n t h i s a n a l y s i s were s e l e c t e d from Data Set I with a maximum of 17 days between probe date and s l a u g h t e r date. T h i s subset of data was used to minimize the e f f e c t of time such t h a t the data would be comparable t o t h a t o f other commercial o p e r a t i o n s . S e l e c t i c n index ft s e l e c t i o n Index was c a l c u l a t e d by the method d e s c r i b e d by Peterson (1974). The eguation f o r t h i s index i s : I = £ E i G i where: E i = the r e l a t i v e economic weight of t r a i t i Gi = the breeding value of t r a i t i (based on s e l e c t i o n f o r a l l t r a i t s i n the index eguation) T r a i t s were s e l e c t e d to be i n c o r p o r a t e d i n t o the s e l e c t i o n index on the b a s i s of economic and g e n e t i c value. 27 RESULTS AND DISCUSSION 1 • E s t i m a t i o n o f Genetic Parameters a. Variance components. Table I I I gives a summary c f the p r o p o r t i o n of the t o t a l variance accounted f o r by the f a c t o r s sex, time and sex by time i n t e r a c t i o n . , T h i s t a b l e shows t h a t o n l y a s m a l l p r o p o r t i o n o f the t o t a l v a r i a n c e was accounted f o r by these t h r e e f a c t o r s f o r a l l t r a i t s i n t h i s study. The i n t e r a c t i o n between time and sex was used to t e s t f o r a dependence of time on e i t h e r sex. The s m a l l R 2 values f o r a l l t r a i t s i n d i c a t e the e f f e c t of t i n e on each sex does not account f o r a s u b s t a n t i a l p r o p o r t i o n o f the t o t a l v a r i a n c e . The a n a l y s i s f o r the e s t i m a t i o n of the v a r i a n c e compcnents was s i m p l i f i e d t o t h a t c f a completely h i e r a r c h i c a l d e s i g n , by f i r s t a d j u s t i n g the data f o r the e f f e c t s o f time, sex, and the i n t e r a c t i o n between these f a c t o r s . The l e a s t - s g u a r e s means and standard e r r o r s f o r the f a c t o r s a s s o c i a t e d with each t r a i t are l i s t e d i n Ta b l e s IV and V f o r the three subgroups of animals used i n the e s t i m a t i o n o f g e n e t i c parameters. To o b t a i n h e r i t a b i l i t y e stimates by the s i b c o r r e l a t i o n method, the compcnents of v a r i a n c e were separated i n t o p o r t i o n s a t t r i b u t e d to t h r e e main sources; (1) S i r e , the d i f f e r e n c e among s i r e s , (2) Dam, the d i f f e r e n c e among l i t t e r s by the same s i r e , and (3) W i t h i r , the d i f f e r e n c e among l i t t e r mates. 28 Table I I I P r o p o r t i o n of the t o t a l v a r i a n c e 1 (R 2) accounted f o r by the f a c t o r s time, sex and time by sex i n t e r a c t i o n from Data Set I I T r a i t Time 3 Sex Time * Sex Average d a i l y g a i n Adjusted age 2 Probe f a t midback l o i n t o t a l a d justed t o t a l 2 Carcass wt/age Carcass f a t : shoulder midback l o i n midback + l o i n shoulder • l o i n Index 0. 060 0. 092 0.038 0.112 0.07 3 0.112 0.084 0.065 0.03 9 0. 041 0.045 0.048 0. 064 0.000 NS 0.000 NS 0. 062 0.052 0.060 0.076 0.002 NS 0.023 0.017 0.007 0.013 0.023 0.054 0. 013 0.011 0.007 0.005 0.006 0.008 0. 008 0.007 0.0C8 0.012 0.011 0.007 0.009 *A11 values s i g n i f i c a n t (P<0.05) except as noted by NS 2 A d j u s t e d to 91 kg l i v e weight 3 N i n e three-month i n t e r v a l s , Oct. 1974 t o Dec. 1976 Table IV Least square means and standard errors for liva animal measurements from Data Set IX Probe Proba Probe Probe Factor Ave. Daily Gain Ad-justed Aqe» Midback Fat Loin Fat Total Fat Adlusted Fat 4 (Icq/day) (days) (mm) (mo) (mm) (am) Sumber Overall Time*: S e x : Hale Female 2403 0.520±0.001 0.505i0.004 0.51410.002 0.529±0.003 0.531t0.002 0.535±0.002 0.530±0.003 0.523l0.003 0.515±0.0C3 0.50 1±0.003 0.519±0.005 0.52U0.005 240 3 170.50±0.28 174. 171. 168. 165. 165. 167. 170. 173. 177. 62i 1.15 99±0.63 0310.98 72±0.74 14±0.72 1010.79 93+0.79 3810.75 6510.74 169. 641 1.42 171.3811.37 2403 17.9810.05 18.6810.22 18.4110.12 17.9410.19 18.7110.15 18.25l0.14 17.2610.15 17.2510.15 17.56 + 0. 15 17.48l0.14 1S.5010.27 16.4610.27 2403 22.2410.06 24.3810.27 23.75+0.15 22.8510. 23 22.4710.17 21.8710.17 21.0410. 13 21.0810.13 21.3910. 17 21.2610.17 24. 3410. 33 20.1310.32 2403 80.46t0.23 86.1510.95 84.35±0.52 81.7310.81 82.3410.62 80.2810.59 77. 22 + 0. 66 76.67+0.65 77. 90±?0.62 77.4910.61 87.7011.17 73. 22i1. 13 2403 21.0310.06 22.7310.24 22.16±0. 13 21.1610.20 21.9 1i0. 15 21.2010.15 20.2310.16 19.6910.16 20.0910.15 20.0610.15 23.2310.29 18.82±0.28 Sex * Time: 11 12 21 22 31 32 41 42 51 52 61 62 71 72 81 82 91 92 0.51310.009 0.498tO.C07 0.52710.0C8 0.50110.007 0.53810.008 0.52110.007 0.50410.026 0.557i0.026 0.53110.004 0.53910.003 0.52510.004 0.53510.003 0.52810.004 0.51810.004 0.507t0.004 0.52310.003 0.501l0.004 0.50110.004 170. 178. 165. 178. 162. 173. 173. 158. 166. 164. 168. 166. 169. 172. 174. 172. 176. 178. 3312.48 90i2.07 3812.24 61i2. 17 8312.34 23i2.15 2717.65 16i7.63 1611.09 12+0.94 14i 1.24 061 1.00 08i1.21 7811.01 64H. 1 1 131 1.00 9011.04 3911.07 21.2510.48 16.1010.40 20.8310.43 15.99i0.42 20.6410.45 15.2510.42 21.49l1.48 15. 92H. 47 16.79i0.21 17.7010.18 17.74+0.24 17.3810.19 18.0910.23 16.4110.19 18.3410.22 16.7810.19 18.3410.20 16.6210.20 28.1210.57 20.65i0.48 27. 3010. 52 20.2010.50 26. 7610. 54 18.9410.50 26.8211.77 18. 13H. 76 22.5010.25 21.2210.22 21.2910.29 20.79i0.23 22.0710.28 20.0910.23 22.0810. 26 20.69i0.23 22.0810.24 20.45i0.25 98.8012.04 73.5011.71 96.29+1.85 72.4211.78 94.96±1.93 68. 49H.77 96.4816.30 68.2016.39 82.6610.90 77.9010.77 78.08H.02 76.3510.83 80.33+1.00 73.0110.83 80.3310.92 74.9610.83 80.8410.86 74. 1410.88 26.5310.51 18.9310.42 25.8510.46 18.47+0.44 25.23+0.48 17.10+0.44 26.0111. 56 17.81±1.56 21.9310.22 20.4610.19 20.5810.25 19.8810.20 20.6310.25 18.7510.21 21. 1610.23 19.0310.20 21.16i0.21 18.9610.22 to *Ad-justed to 91 kq live weight *Three-month intervals from Oct. 1974 to Dec. 1976 Table V Least square means and standard e r r o r s f o r carcass measurements from Data Set II Carcass Carcass Carcass Carcass Carcass Carcass Grade f a c t o r Seiqht/Age Shoulder Fat Bidback Fat Loin Fat flidback • Loin Shoulder • Loin Index (Icq/day) (mm) (BID) (mm) (mm) (Dm) (percent) Number O v e r a l l Time 2: 1383 0.394t0.001 0.399±0.005 0. 392±0.003 0.399t0.004 0. 407t0. 003 0.402i0.002 0. 398±0.002 0.391±0.002 0.389±0.003 0.371i0.003 1115 40.55±0.22 NA> NA 44.75i0.98 4C.92i0.45 39.87i0.44 40.55i0.45 39.41l0.45 40.08t0.55 38.29i0.47 1115 23.80±0.19 NA NA 23.4Kt0.85 23.97±0.39 24.0410.38 24.54l0.39 23.5510.39 24.8210.47 22.27l0.41 1115 31.«2t0. 19 NA NA 32.2710.88 31.9810.41 31.4610.40 32.0910.41 30.6610.41 31.9610.49 29.5610.43 1115 55. 4210.29 NA NA 55.8611.34 56.0410.62 55.59i0.60 56.69i0.62 54.8410.62 56.9010.74 51.9910.64 1383 71.8410.22 74.2211.01 70.8310.55 73.7510.82 72.9010.53 71.3410.52 72.5810.53 71.2510.53 71.7810.63 67.8910.55 1383 103.3910.07 103.0410.33 104.2010.18 103.1310.27 102.6110.17 103.0710.17 102.80l0.17 103.5210.17 103.6410.20 104.5010. 18 Sex: Hale Female 0.39710.006 0.39010.006 41.2810.30 39.8210.31 24.3010.26 23.3110.27 31.7710.27 31.0810.28 56.31l0.41 54.5210.43 72.7111.19 70.9611.19 102.87±0.39 103.9010.39 Sex * Time: 11 12 21 22 31 32 41 42 51 52 61 62 71 72 81 82 91 92 0.41410.010 0.38510.009 0.40410.009 0.38010.009 0.41110.009 ,386+0.0C8 39610.031 , 417i0.031 ,40210.003 , 40110. 004 0.397i0.004 0. 400l0.003 0.397±0.003 0.38410.004 0.38510.004 0.392l0.004 0.374i0.003 0.367i0.004 .35 .42 NA NA NA NA 45. 19i1, 44.32+1 41.6810.66 40. 17l0.62 40.11l0.57 39.6310.68 41 . 1910.65 39.91+0.63 39.7410.63 39 .0810.65 41.7010.77 38.4610.77 39.3910.59 37. 19t0.74 NA NA NA NA 23.7111. 17 23. 1611.23 24.5410.57 23.4110.54 24.5010.49 23.5710.58 24.51l0.57 24.56i0.54 23.9010.55 23. 1910.56 25.6410.67 24.0010.67 23.26l0.51 21.2710.64 NA NA NA N A 32. 86H.22 31.6811.28 32.3510.59 31.6010.56 31. 8710.51 31.0510.61 31.47i0.59 32.7010.56 30.7610.57 30.5610.59 32.7010.70 31.2210.69 30.3810.53 28.7410.67 NA NA NA NA 56.67t1.84 55. 0511. 94 57.0010.91 55.08t0.84 56.4610.78 54.7U0.92 56. 1010.89 57.29l0.85 55.7910.86 53.3810.89 53.39i1.06 55.42l1.05 53.7510.79 50.2311.00 76.7212.04 71.7211.83 73. 30H.89 68.37t1.81 75. 8011. 93 71.70t1.76 67.4U6.58 78.40i6.56 72.0310.66 70.6410.79 72.6210.76 72.5410.73 72.8410.73 69.6710.75 73.95t0.89 69.61t0.90 69.75t0.68 66.0210.86 101. 104. 102. 105. 101. 104. 105. 99. 102. 103. 102. 103. 102. 104. 102. 104. 103. 105. 6610.66 4210.59 6310.61 77±0.59 60i0.62 6610.57 7212.13 4812.12 6410.22 50t0.26 5410.25 05t0.24 5810.24 47l0. 24 7110.29 5610.29 6910.22 3110.28 Co o *Data not c o l l e c t e d at s t a r t of pr o j e c t 31 The degrees of freedom and K values used i n the computation of these estimates are l i s t e d i n Table VI and the compcnents of variance are given i n Table VII. The mean sguares i n the analysis of variance from which these components were extracted were found to be s i g n i f i c a n t (P<0.05) i n a l l cases. This indicates that s e l e c t i o n pressure has not been intense for any one t r a i t . I f for example intense selection had been exerted on a pa r t i c u l a r t r a i t , selected sires would tend to become more homogeneous phenotypically f o r this t r a i t . . These selected animals would then be s i a i l a r genotypically and non-significant differences between s i r e groups would be expected for t h i s t r a i t . Other factors could r e s u l t i n non-significant differences however, including lack of degrees of freedom i n the model, l i t t l e or no genetic variation in the population, and large environmental v a r i a t i o n s between and within l i t t e r s . b. H e r a t a b i l i t y estimates. Table VIII l i s t s the estimates of h e r i t a b i l i t y calculated i n t h i s study. The three estimates l i s t e d for each t r a i t correspond to the s i r e h a l f - s i b estimate, the dam h a l f - s i b estimate and the f u l l - s i b estimate. In a l l cases, the h e r i t a b i l i t y estimate calculated from the dam component was found to be considerably higher than that calculated from the s i r e component., This i s possibly due to maternal e f f e c t s , since t h i s component contains variation due to environment common to l i t t e r mates. Table VI Degrees of freedom and K values for the estimation of components of variance from Data Set II Analyses d.f. , d. f. Group N Sires Dams K1 K2 K3 I 2403 20 317 7.03 8.19 111.22 II 1383 20 291 4.36 5.42 64.07 III 1115 16 227 4.50 5.66 63. 99 K1 = weighted number of progeny per dam K2 = weighted number of progeny for dams within s i r e s K3 = weighted number cf progeny per s i r e Table VII Estimates of components of variance for l i v e and carcass t r a i t s f r o i i Data Set I I Analyses Group S i r e Dan Within Ave. daily qain I 0. 1201i0.0411E* 0. 3782±0.0502E 1.379U0.4044E Adjusted aqe1 I 9.5C83i3.95113 34.4624*4.0519 114.563113.5636 Prcbe f a t : midback I 0.2719±0.1133 0.8105±0.1205 4.8283±0.1502 loin I 0.4516i0.1772 0.9729±0.1595 7.048410.2192 total I 5.6918i2.2656 13.8326i2.1219 87.933212.7353 adjusted t o t a l 1 I 0.429210.1643 0.9149±0.1339 5.274910.1641 Carcass wt/age II 0.0243i0.0018E 0.2231±0.0397E 0.907610.0443E Carcass fat: shoulder III 1.0380±0.5371 3.594910.6849 15.941410.7630 ssid tack III 1.0483i0.4528 1.202310.3999 12.888910.6169 loin III 0.584210.3233 1.9074t0.4785 13.568810.6469 nidtack «• Icin III 2.7483*1.3C67 5.6551H. 4639 42.230612.0213 shoulder • loin II 3. 256611.3837 8.214311. 4925 40.084211.7305 Grade Index II 0.361310.1485 0.741810.14S4 4.321110.1865 »Adjusted to 91 kg l i v e weight *E = x10~3 for component and S.E. 'Standard error 34 Table VIII Estimates of h e r i t a b i l i t y f or l i v e and carcass t r a i t s from Data Set II H e r i t a b i l i t y T r a i t Analyses Group j Sire Dam ~~ -I F u l l - s i b Ave. daily gain I 0,22±0.092 0.8110. 11 0.5210.07 Adjusted age 1 I 0.24±0.10 0.8710.10 0.5610.07 Probe f a t : midback I 0.18±0.08 0.5510. 08 0.3710.05 l o i n I 0.2110.08 0.46i0.08 0.3410.06 t o t a l I 0.2110.08 0.5210.08 0.3610.06 Adjusted t o t a l 1 I 0.2610.10 0.5510.08 0.4110.06 Carcass wt/age II 0.0810.07 0.7710.14 0.4310.07 Carcass f a t : shoulder III 0.2010.10 0.7010.13 0.4510.08 midback III 0.2810.12 0.3210.11 0.3010.08 l o i n III 0.1510.08 0.4810,12 0.3110.07 midback + l o i n I I I 0.2210.10 0.4510.12 0.3310.08 shoulder • l o i n II 0.2510.11 0.6410.12 0.4510.08 Grade Index II 0.2710.11 0.5510.11 0.41+0.08 1 Adjusted to 91 kg l i v e weight. 2Standard error 35 The f u l l - s i b e s t i m a t e s a l s o c o n t a i n v a r i a t i o n due t o maternal e f f e c t s as w e l l as dominance and e p i s t a t i c v a r i a n c e , but only one h a l f t h a t of the dam component, H e r i t a b i l i t y estimated from t h i s component i s t h e r e f o r e o n l y s u i t a b l e f o r those t r a i t s f o r which o n l y a d d i t i v e gene e f f e c t s are expected to be important. C o n t r a s t i n g these estimates with the s i r e component estimate g i v e s an est i m a t e of the v a r i a n c e due to the common environment of l i t t e r s . The s i r e component i s f r e e o f the e f f e c t of dominance and common environmental d e v i a t i o n s and i s g e n e r a l l y c o n s i d e r e d the best estimate o f a d d i t i v e g e n e t i c v a r i a n c e . Estimates of h e r i t a b i l i t y from the s i r e component f o r average d a i l y gain (0,22) and age adjusted t c 91 kg (0.24) are i n general agreement with l i t e r a t u r e v a l u e s r e p o r t e d f o r average d a i l y g a i n , , Blunn and Baker (1947), Berruecus e t aJL. (1970) and Fahmy and Bernard (1970) reported values of 0.18, 0.23, and 0.16 f o r the h e r i t a b i l i t y o f t h i s t r a i t c a l c u l a t e d from the s i r e component of variance. Reports on the h e r i t a b i l i t y o f l i v e b a c k f a t probe were g e n e r a l l y higher than the values of 0.18 t o 0.26 c a l c u l a t e d i n t h i s study. I t should be noted t h a t a l l e s t i m a t e s r e p o r t e d i n the l i t e r a t u r e were f o r the r u l e r probe method r a t h e r than the u l t r a s o n i c probe used i n t h i s work. The h e r i t a b i l i t y value c l o s e s t t o esti m a t e s of t h i s study was 0.38 r e p o r t e d by 36 Berruecus et a l . {1970) for r u l e r backfat probe adjusted to 63.6 kg l i v e weight. Similar studies by Gray et a l . (1968) and Arganosa et a l , (1969) found the h e r i t a b i l i t y of t h i s t r a i t to be considerably higher with values of 0.44 to 0.62 reported. The h e r i t a b i l i t y estimates from the s i r e component for age adjusted to 91 kg (0.24) and adjusted average probe fat (0.26) were s l i g h t l y higher than estimates for the related t r a i t s average dai l y gain (0.22) and t o t a l probe fat (0.21). This i s possibly due to reduced environmental variation obtained by adjusting the values to a common weight. This reduced environmental variation would tend to reduce the si z e c f the denominators of the h e r i t a b i l i t y estimates, thus re s u l t i n g i n a larger percentage of the t o t a l variance being accounted for by additive gene action. The low h e r i t a b i l i t y estimate of 0.08 f o r carcass weight per day of age i s most l i k e l y due i n part to the delay i n slaughtering the animals as discussed e a r l i e r . In t h i s s i t u a t i o n the oldest and heaviest pigs would be slaughtered ahead of younger animals ready for slaughter* This would tend to make the population more homogeneous f o r t h i s t r a i t than i t would be i f animals were slaughtered on the basis of l i v e weight independent of age. I f animals were sent to slaughter on the basis of l i v e weight alone, carcass weight per day of age would be expected to have a h e r i t a b i l i t y value s i m i l a r to that of l i v e 37 weight per day of age. In t h i s study the h e r i t a b i l i t y value for carcass weight per day cf age (0.C8) was much lower than the h e r i t a b i l i t y value of 0.22 calculated for average d a i l y gain. Reports on the h e r i t a b i l i t y of carcass backfat vary considerably i n the l i t e r a t u r e . Estimates range from 0.12 by Blunn and Baker (1947) to a high of 0.74 by Smith and Ross (1965)., The estimates for the measurements of carcass backfat do, however, compare with the lower estimates reported i n the l i t e r a t u r e . , Estimates obtained by the paternal h a l f - s i b method ranged from 0.15 to 0.28 for the f i v e measurements of carcass backfat in t h i s study. These estimates compare to the value of 0.23 that Siers and Thomson (1972) reported as a paternal h a l f - s i b estimate. They also compare to estimates by Eeddy et a l . (1959) when they reported values of 0.16 t c 0.18 obtained by regression of o f f s p r i n g on midparent., A s l i g h t l y higher estimate of 0,35 calculated from the s i r e component was reported by Roy et a l (1968) from a swine breed development project. Of the three carcass backfat measurements, shoulder, micback and l o i n , the paternal h a l f - s i b h e r i t a b i l i t y estimate was highest for the midback position (0.28). The higher h e r i t a b i l i t y estimate for t h i s t r a i t may be due to less chance for measurement error at the midback position. The shoulder measurement i s often hampered by a ragged or angled cut from the 38 carcass s p l i t t i n g process. The l o i n position measurement may be affected by the exaggeration of fat depth by lean i n f i l t r a t i o n in t h i s region. Measurements taken too close to t h i s area w i l l over estimate the fat depth thus increasing the measurement variation associated with t h i s t r a i t . This could explain the r e l a t i v e l y low h e r i t a b i l i t y estimate (0.15) for t h i s t r a i t . In contrast with these measurements, the f a t depth at the midback region tends to stay constant over a larger area, consequently, any error associated with a measurement s l i g h t l y out of position wculd be small.... It i s also noted that the paternal and maternal h a l f - s i b and the f u l l - s i b estimates for the h e r i t a b i l i t y of carcass midback f a t are a l l si m i l a r in magnitude with respective values of 0.28, 0.23 and 0.30. This i s not the case f o r the other carcass fat measurements, due to a high estimate from the dam component r e l a t i v e to the s i r e component estimate. This indicates that the midback fat measurement was not affected appreciably by the common environment of a l i t t e r . , A l l of the estimates of h e r i t a b i l i t y i n th i s study were accompanied by r e l a t i v e l y small standard errors ranging from 0.05 to 0.14. This i s due mainly to the large sample s i z e , and ensures a certain degree of precision i n the estimates. In comparing ultrasonic probe fat to carcass fat measurements, si m i l a r h e r i t a b i l i t y estimates are evident. , A large difference 39 in the magnitude of the h e r i t a b i l i t y estimates for these two methods would indicate a larger measurement error for the method with the lower estimate. The s i m i l a r i t y of the h e r i t a b i l i t y estimates i n t h i s study indicates that any error i n measuring backfat by use of the ultrasonic probe did not contribute to increased environmental variance as compared with backfat measured on the carcass. c. gfiDgtic and environmental correlations. The genetic, environmental and phenotypic correlations calculated i n t h i s study are l i s t e d i n Tables IX and X. The genetic covariances used to calculate these correlations are also given i n Table IX. Genetic co r r e l a t i o n s are caused mostly by pleiotropy, which res u l t s when one gene a f f e c t s more than one t r a i t . The degree of genetic c o r r e l a t i o n i s thus a measure of the extent to which the t r a i t s are influenced by the same genes. This i s important in selection as i t indicates how a change in one t r a i t w i l l a f f e c t other t r a i t s . The environmental c o r r e l a t i o n i s a measure of the degree to which two t r a i t s are affected by t h e i r common environment. These two c o r r e l a t i o n s together constitute the phenotypic c o r r e l a t i o n . The genetic correlations for average daily gain with l i v e probe measurements of midback (0.22), l o i n (0.12) and t o t a l Table IX Genetic correlations (below the diagonal) and genetic covariance (above the diagonal) for live and carcass traits from Data Set II Ave. Daily gain Adjusted age1 Probe Midback fat Probe Loin Fat Probe Total Fat Probe Adjusted Fat* Average Daily Gain Adjusted Age1 Probe Hidback Fat Prote Loin Fat Probe Tctal Fat Frobe Adjusted Fat1 Sire Das S+D Sire Dam S + D Sire Dam S + E Sire Dam S + D Sire Dam S + D Sire Dam S+D -3. 1630H.3011E* -0. 1047i0.0133=» -0.3787±0.0188 -1.02l0.02 -0.92±0.01 -0.9410.01 0.2210.30 0. 13±0.C9 0.15±0.09 0.12i0.29 0.19±0.09 0.17±0.10 0.17±0.29 0.18±0.09 0.18+.0.09 0.05±0.29 -0.03±0.09 -0.01±0.10 -0.27±0.28 -0. lOiO. C9 -0.14i0.09 -0.16i0.28 -0.15±0.10 -0.15±0.10 -0.21±0.28 -0.12±0.09 -0.14i0.10 -0.07±0.28 0.02±0.09 -0.01±0.10 0. 1150i0.0504E 0.2315i0.0436E 1.8217i0.0566E -0.430510.1506 -0.512410.0811 •3.418710.1063 0.9810.03 0.9510.02 0.9510.01 0.9910.01 0.9910.01 0.9910.01 0.9910.02 0.9410.02 C.9510.01 0.081210.0437E 0.4651l0.1761E 0.376510.0547E 1.37 15l0.183 1E 2.236410.0695E 8.1287i0.2529E -0.333610. 1324 -1. 576U0.5744 -0.882610.1215 -2.535410.3834 -4.391910.1366 -15.5872t0.4849 0.34 1710.1357 1.234210.4999 0.842710.1255 3.304210.4914 5.046010.1570 19.730410.6137 1.595910.6281 3.6207t0.5687 24.167010.7517 1.0010.01 0.9910.01 0.99t0.01 1.0010.02 0.9210.02 0.9510.01 0.030110.0121E -0.048510.0144E -0.072510.0211E -0.148210.04 27 0.136410.0065 -0.344710.0107 0.336610.1315 0.808010.1150 4.387610.1365 0.440110.1670 0.872010.1324 5.430610.1689 1.561610.59 97 3.368U0.4955 19.660410.6116 1.0010.01 0.9510.01 0.96+0.01 *Adjusted to 91 kg live weight 2E = x10 - 2 fcr covariance and S.E. 3 S t a n d a r d e r r o r Table IX Genetic correlations continued Probe Probe Probe Probe Are. Daily Gain Adjusted Age* Midback Fat Loin Fat Total Fat Adjusted Fat* Slauqhter Sire 1 o. 96±0. 122 -0. 9910. 13 C.7810.27 0.7010.27 0.7410.27 0.7110.27 Ht./aqe I Dam 1 c 90±0.C2 -0. 8910. 02 0.3210.13 0.3810.13 0.3510.13 0.2010.12 S + D 1 o. 9U0.02 -0. 90l0. 02 0.3910. 10 0.4210.10 0.4010.10 0.2910.09 Carcass Sire 1 o. 34±0.31 -0. 4210. 33 0.5310.27 0.5010.27 0.5310.27 0.5410.27 Shoulder Fat 1 Da o 1 o. 37±0.11 -0. 35l0. 12 0.5310.12 6.57i0. 13 0.5510.12 0.4610.13 S + D 1 o. 36±0.10 -0. 3610. 11 0.5310.10 0.5410. 11 0.5410.11 0.4810.11 Carcass Sire 1 o. 12±0.30 -0. 19l0. 34 0.8410.13 0.7210. 17 0.7910.15 0.8510.12 Midback Fat 1 Dan 1 o. 32±0. 15 -0. 2710. 16 0.6510.13 0.7210.13 0.6810.13 0.5710. 15 S + D 1 o. 25±0.13 -0. 2410. 13 0.7110.09 0.7110. 10 0.7110.09 0.67i0.10 Carcass Sire 1 o. 18±0.37 -0. 1910. 38 0.5710.26 0. 45l0. 28 0.5110.27 0.5510.26 Loin fat 1 Dan 1 o. 28±0.13 -0. 26l0. 13 0.65i0.12 0.7610.11 0.71i0.11 0.6210.12 S + D 1 o. 26±0.12 -0. 25l0. 12 0.6310.10 0.67l0. 10 0.66i0.10 0.6010.11 Carcass Sire 1 o. 16±0.33 -0. 2010. 35 0.7810.16 0.6510.25 0.7210.18 0.7810.16 Midrack • Lcin 1 Das 1 c. 32±0.13 -0. 2eio. 14 0.6810.1 1 0.7710.11 0.7310.10 0.6310.12 S + D f o. 27+0.12 -0. 26l0. 12 0.7110.09 0.7310.10 0.7210.08 0.67i0.09 Carcass Sire 1 o. 42±0.28 -0. 4 310. 28 0.75l0.15 0.68t0.17 0.7110.16 C.7410.16 Shoulder • loin J Da n 1 o. 3810. 11 -0. 3 6l0. 11 0.5610.11 0.5610. 11 0.5710.11 0.4810.11 S + D 1 o. 38l0.10 -0. 37i0. 10 0.6210.09 0.6010.09 0.6110.09 0.5610.09 Grade Index Sire I - c . 48l0.28 0. 47l0. 28 -0.7510.16 -0.6910.17 -0.7210.16 -0.71i0.16 Cam i - o . 18+0.13 0. 19l0. 12 -0.5210.13 -0.48 + 0. 14 -0.5110.13 -0.5010. 12 S + D I - o . 2510.12 0. 2 5l0. 11 -0.6010.10 -0.55l0. 11 -0.58t0.10 -0.5810.09 1 :„•„•,.-••. ... - _ _ ____ Table IX Genetic covariance continued Carcass Carcass Carcass Carcass Carcass Carcass Grade Height/Age Shoulder Fat Hidback Fat loin Fat Hidback + Loin Shoulder + Loin Index Average Sire | .004151.00227E2 0.3449±0.1722E 0. 1399±0.0862E 0. 134 9±0.0818E 0.2699±0.1715E 0. 631510.2617E -0.238510.C736E Daily Gain Dan | .025611.00437E 1.421 1l0.1738E 0.6761±0.1342E 0.761U0.1551E 1.4911±0.2722E 1.905U0.2528E -0.2713i0.0125E S + D I .093551.004C4E 1.7393±0.0541E 2.8C19iO.0872E 3.2713±0.1018E 6.0742t0.2321E 4. 815210.2088E 0.937510.0405E Adj usted Age1 Sire 1-1. 261U0. 6912E -1.1352±0.51823 -0.5100t0.2600 -0.3824±0.2369 -0.8930±0.4969 -1.983510.8013 0.719510.2318 Dam I-7. 4626+1.1532E -3.99C9±0.4595 -1. 795 1±0. 3208 -2.1723±0.3894 -3.9720±0.7103 -5. 735710.7070 0.914910.0449 S + D I -o. 2641±0.0114 -4. 0582±0. 1543 -6.934210.2636 -8.4410±0.3209 - 15.3755±0.5845 -11. 782110. 4479 -1.8180t0.0785 Prote Sire I o. 2291±0.0978E 0.2870±0.1345 0. 4549±0. 1901 0.2307l0.1198 0.6852±0.3099 0. 798010. 3036 -0.266510. 0957 Hidback Fat Dan t o. 3853±0.0723E 0.85S7±0.1355 0.6032±0.1446 0.7602±0.1567 1.3630±0. 3012 1. 307510.2339 -0. 360810. 0556 S + D I 1. 8849l0.0814E 2.5184i0.0957 3.9337±0.1495 3.8438±0.1461 7.777410.2957 6.204810.2359 -1.283U0. 0554 Probe Sire I o. 259U0. 1014E 0. 3494 + 0. 1624 C.5C72±0.2152 0.2365±0. 1327 0.7435±0.3478 0. 813010.3468 -0.3085+0. 1093 Lcin Fat Dam 1 o. 5C52±0.0910E 1.035510.1597 C.758210.1716 1.0 144±0.1941 1.7725±0.3657 1. 401610.2680 -0.363710. 0599 S + D 1 2. 4636±0.1065E 2.876810.1094 4.5064±0.1713 4.4755±0.1701 8.9819*0.3414 7. 200110.2737 -1.4787i0. 0638 Probe Sire 1 o. 9791±0.3804E 1.273310.5934 1.9147±0.8072 0.9325±0.5044 2.8465±1.3113 0. 912210.3561 -1.165010.4148 Total Fat Dan 1 1. 7353±0.3211E 3.7707±0.5896 2.7094±0.6315 3.5497i0.7015 6.2592±1.3327 1. 428110.2984 -1.461310.2316 S + D | 8.6975±0.3755E 10.8325±0.4586 16.8931±0.7151 16,6410±0.7045 33. 534011. 2748 7. 402810.2814 -5.501910.2375 Probe Sire t o. 2413±0.0811E 0.3400±0.1493 0.5417±0.2169 0.2625±0.1304 0.803910.3472 0. 919710.3367 -0.297310. 0015 Adjusted Fat» Dam I o. 2798±C.0434E 0.8077±0.1191 0.5756±0. 1304 0.7964±0.1491 1.3727i0.2855 1. 236410.2208 -0.388310. 0195 S+D I 0. 8010±0.0331E 2.274U0.0963 3. 6878±0. 1561 3.6388±0.1540 7.325610.2785 5. 847910.2223 -1.822610. 0787 to 'Adjusted to 91 kg live weight *E = x10~2 for covariance and S.E. 'Standard error Table IX Genetic correlations (belcs the diagonal) and genetic covariance (above the diagonal) continued Slauqhter Ht./4ge Carcass Shoulder Fat Carcass flidtack Fat Carcass Loin Fat Carcass aidfcack • Loin Fat Carcass Shoulder • Loin Fat Grade Index Sire Dan S + D Sire Daa S + D Sire Daa S + D Sire Dan S + D Sire Dan S+D Sire Daa S*D Sire Cam S + D Carcass Beight/Age 0.29i0.42» 0.45i0.11 0.42i0.10 0. 15±0. 43 0.46±C. 14 0.35l0.12 0.17±0.63 0.36±0.12 0. 32+.0. 12 0. 16±0.49 0.42+.0. 13 0.36±0.12 0.53±C.32 0.46±0.10 0.46l0.09 -0.63±C.34 -0.14±0.13 Carcass Shoulder Fat Carcass Midback Fat Carcass Loin Fat Carcass Hidback *• Loin Carcass Shoulder • Loin Grade Index 0.1685±0.1112E* 1.47CC1C.1821E 2.1808±0.0678E 0. 76l0. 16 0.8510. 12 0.8010.08 0.67i0.23 0.7010. 11 0.7010,09 0.7910.16 0.6010.C9 0.7910.08 0. 94t0.07 0.9510.02 0.9410.02 -0. ?4i0.08 -0.7810.07 -0.8210.05 0. 088510.C8C2E 0. 889010. 1646E 3. 345 1i0. 1041E 0.812910.3547 1.768310.2965 5.955510.2521 I-0.2210.11 i 'Standard error 2 F = r i d - ? f n r r n v a r i a n r o a n ^ ^ _ F . 0.7110.18 0.8410.10 0.77i0.08 0.9510.05 C.9510.C3 0. 94i0.03 0. 82i0. 13 0. 9210.03 0.85l0.C6 -0.8910. 11 -C.6610. 14 -0.73+0.09 0.068510. 0. 86OO1O. 3.6114i0. 0.523110. 1.837810. 5.481010. 0.558310. 1.272710. 7.886310. 0739E 1611E 1124E 2579 2920 2320 2654 2956 3339 0.9010.08 0.9710.02 0.9510.03 0.89t0. 10 0.90i0.04 0.8910.04 -0.95i0.10 -0.7710.09 -0.31i0.07 0. 158510.1485E 1.7400i0.3213E 6.957810.2631E 1.335810.6125 3.606610.5881 11.436310.4347 1.606510.7182 2.475210.7003 20.775010.7897 1. 142210. 5886 0.931310.7451 3. 180110. 1209 0.9210.08 0.9410.04 0.93t0.03 -0.99t0.08 -0.75t0. 10 -0.8210.07 0.463210.2212E 1.949610.2828E 5.689110.2219E 1.561210.7949 5.4327t0.S812 21.422710.9069 1.371U0. 6201 3.041U0. 5914 13.842010.5860 1.107310.5811 3.745310.7742 19.049810.8064 2.480411.2011 6.786211.3656 32.891611.2503 -1.0010.03 -0.85i0.05 -0.9110.03 -0.186310. 0555E -0. 175310.0132E 1.023410. 0442E -0.5371t0.2467 -1.320110.2427 -5.3879t0.2281 -0.508210.2027 -0.647510.1201 -2.686810.1137 -0.404610.1831 -0.9507t0.1730 •3.804110.1610 •0. 913010. 3858 •1.598410. 2931 -6. 492710. 2468 •1. 135110. 4402 •2.084410.3619 •9.354610.3556 Table X Environmental correlations (below the diagonal) and phenotypic correlations (above the diagonal) for live and carcass traits from Data Set II Ave. Probe Probe Daily Gain Adjusted Age1 Hidback Fat Loin Fat Probe Total Fat Probe Adjusted Fat* Average Daily Gain Adjusted Age* Sire | -0.92l0.01* Dam | -0.95±0.01 S + D | -C.92±0.01 Probe Sire | 0.23±0.05 Hidback Fat 1 Dam | 0.30±0.09 S+D | 0.25±0.05 Probe Sire | 0.24+0.05 loin Fat 1 Da m | C.26i0.08 S + D | 0.25±0.05 Probe Sire I 0.24i0.05 Total Fat I Dam | 0.27t0.08 S + D | 0.25+0.05 Probe Sire | -0.02l0.06 Adjusted Fat1 Dam | 0. 0UC.09 S + C | -0.01±0.06 i Adjusted to 9 1 kq liv *Standa rd error -0.9510.006 -0.1310.05 -0.2010.10 -0.1510.05 -0.15l0.05 -0. 17l0.09 -0.1610.05 -0.15i0.05 -0.2010.09 -0.17t0.05 -0.0C2+0.06 -0.05i0.10 -0.02+0.06 0.2010.02 -0. 15l0.02 0.8510.01 C. 8310.02 C.8410.01 C.9510.004 0.9410.01 C.S510.004 C.85+0.01 0. 8310.02 0. 85l0.0 1 0.2110. 02 0.87t0.01 0.97i0.003 0.9710.004 0.97+0.003 0.88+0.01 0.87i0.01 0.881O.01 0.2210.02 -0.1310. 02 -0. 1510.02 0.9610.005 0.9710.001 0.9010.01 0.9010.01 0.9010.01 -0.0110.02 -0.01l0.02 0.8910.01 0.9110.01 0.9310.01 Table X Environmental correlations continued Ave. Daily Gain Adjusted Age1 Frobe Hidback Fat Probe Loin Fat Probe Total Fat Probe Adjusted Fa Slaughter r— Sire | 0.83±0.01* -0.8310.01 C.2410.05 0.2710.05 0.27t0.05 0.0UO.O5 Height/age 1 Dam | 0.7210.05 -0.7610.05 0.2710.10 0. 28i0.09 0.2910.09 0.01±0.10 S + D ! 0.7910.02 -0.8110.02 C.2510.06 0.27i0.05 0.2810.06 0.0110.06 Carcass Sire | 0.09i0.07 -0.0510.07 0.2510.06 0.2410.06 0.2510.06 0.2010.07 Shoulder 1 Dam | -0.1610.19 0.2010.20 0.1510.11 0.1210.11 0.1410.11 0.1210. 12 S + D | 0.0110.07 0.0410.09 0.2110.07 0.19l0.07 0.2110.07 0.1710.07 Carcass Sire | 0.2310.07 -0.18l0.C7 C.4410.05 0.4410.05 0.4510.05 0. 3810.06 Hidback Fat 1 Dam | 0.2010. 12 -0.1610.13 C.46l0.07 0.41i0.07 0.4510.07 0. 4210.07 S + D | 0.2210.07 -0.17t0.07 0.45l0.05 0.4210.05 0.4510.05 0.3910.05 Carcass Sire | 0.2610.06 -0.2210.06 0.46i0.04 0.4710.05 0.4810.04 0.42l0.05 Lcin fat 1 Dam | 0.2510.14 -0.2010. 14 0.40+0.08 0.3510.08 0.3910.08 0.3510.09 S + D | 0.25i0.07 -0.2110.07 C.4410.05 0.41l0.05 0.4410.05 0.3910.05 Carcass Sire | 0.2810.06 -0.2310.06 0.5110.04 0.5110.04 0.5210.04 0.4510.05 Hidtack • Loin 1 Fat Dam | C.2510.13 -0.2 U0. 14 0.4910.07 0.4310.07 0.4810.07 0.4410.08 S + D | 0.2610.07 -0.2210.07 0.5010.05 0.47i0.05 0.5U0.05 0.44t0.05 Carcass Sire | 0.1810.C6 -0.14l0.06 0.3910.05 0.4010.05 0.4110.05 0.3410.06 Shoulder • Loin 1 0.37+0.09 Fat Dam | 0.0810.12 -0.0 1l0. 15 0.4010.08 0.40l0.08 0.4210.08 S + D | 0. 14i0.07 -0.09i0.07 0.3910.05 0.4010.05 0.4210.05 0.3510.06 Grade Index Sire | 0.2210.07 -0.18iO.C7 -C.2010.06 -0. 1910.07 -0.2010.07 -0.3210.06 Cam | C.3410. 12 -0.3210. 14 -C. 1810.09 -0. 19i0.08 -0.1910.09 -0.33+0.08 S + D | C.2710.C7 -0.23l0,C8 -C.19+0.06 -0. 1910.06 -0.1910.06 -0.3210.06 * Ad -justed tc 91 kg live weiqht -' "4"' *•>"'• Table X Phenotypic correlations continued : — ~ ———^ — — Carcass Height/Age Carcass Shculder.Fat Carcass Hidback Fat Ca rcass Loin Fat Carcass Carcass Midback • Loin Shoulder +Loin Grade Index Averaqe Daily Gain Adjusted Age> Probe Hidback Fat Probe Loin Fat Probe Total Fat Probe Adj usted Total Fat» 0.87*0.01* 0.18±0.03 0.22±0.03 0.24*0.03 0.26±0.03 0.25±0.03 -0.06±0.03 -0.87±0.01 -0. 1610.03 -0.19*0.03 -0.22l0.03 -0. 23±0. 03 -0.23±0.03 -0.01l0.03 0. 3110. 03 0. 27i0. 03 0.52*0. 03 0.51±0.03 0.57*0.02 0.48*0.02 -0.3Ut0.03 0.33*0.03 0.3210.03 0.50*0.03 0.50*0.03 0.55*0.03 0.47*0.02 -0.32l0.03 0.34*0.03 0.3410.03 0.54*0.03 0.51*0.03 0.57*0.02 0.50i0.02 -0.35l0.03 0.04*0.03 0.3010.03 0.4710.03 0.47*0.03 0.52*0.03 0.45*0.02 -0.43*0.02 »Adjusted to 91 kg live weight 'Standard error Table X Environmental correlations (below the diagonal) and phenotypic correlations (above the diagonal) continued == —= — = =— = = ===—== ==—============== ================ ============== ============== ================= ================= ============ Carcass Weight/Age Carcass Shoulder Fat Carcass Hidback Fat Carcass Loin Fat Carcass Midback » Loin Carcass Shoulder • Loin Grade Index Slauqhter Wt./Age ! 0.23t0.03* 0.3110.03 0.3110.03 0.3510.03 0.34i0.03 O.O81O.04 Carcass Shoulder Sire 1 0.1710.06 0.4910.03 0.4510.03 0.5210.03 0.8810.01 -0. 70t0.02 Fat Cam S + E I -0.1310.20 I 0.0710.08 Carcass Hidback Sire I 0.3310.06 0.3510.06 0.6210.02 0.9010.01 0.6610.02 -0.4210.02 Fat Cam S + D ( 0.27i0. 12 | 0.3010.06 0.2510.10 0.21t0.06 Carcass Loin Sire 1 0.3410.05 0.3410. 05 0.5910.C4 0.9 110.01 0.83+0.02 -0.5710.02 Fat Dam S+E. 1 0.3310. 13 I 0.3310.06 0.2010.11 0.2810.06 0.5310.06 0.5610.04 Carcass Hidback + Sire I 0.3710.05 0.3910.05 0.881O.01 0.9010.01 0.8210.02 -0.5610.02 Loin Fat Dam 1 0.3410.11 0.26+0.10 O.881O.02 0.87t0.02 S + D I 0.35i0.06 0.33i0.06 O.881O.01 0.89i0.01 Carcass Shoulder • Sire | 0.2810.06 0. 83lO. 02 0.5710.C4 0.8110.02 0.7810.02 -0.7610.02 Loin Fat Dam I 0. 1610. 12 0.7610.05 0.5 1 + 0.07 0.79t0.04 0.74+0.05 S + C ! 0.23+0.06 0.80l0.02 0.5410.05 0.8010.02 0.7610.03 Grade Index Sire | 0.25l0.06 -O.6O1O.04 -0.26i0.07 -0.4410.05 -0.4010.05 -0.65±0.04 Dam I 0.37t0.11 -0.56+0.08 -0.26i0.C9 -0.37i0.09 -0.36+0.09 -0. 63i0.06 S + D I 0.30 + 0.07 -0.58i0.05 -0.2610.06 -0.41i0.05 -0.38±0.06 -0. 6 410.04 S t a n d a r d e r r o r 48 (0.17) were a l l low and p o s i t i v e . This would indicate that, genetically, as backfat i s reduced average daily gain w i l l also decrease somewhat, and that these two t r a i t s are influenced by some of the same genes., Similar r e s u l t s were obtained f o r the genetic correlations between average d a i l y gain and the corresponding carcass fat measurements. The correlations obtained for these t r a i t s were 0.12 f o r midback, 0.18 for l o i n and 0.16 f o r t o t a l . These r e s u l t s are somewhat lower than the genetic c o r r e l a t i o n of 0.33 found by Blunn and Baker (1347) and that cf 0.23 by Roy et a l . (1968) for average d a i l y gain with carcass backfat. „ Relatively high p o s i t i v e genetic correlations between corresponding carcass and probe f a t measurements of 0.84 for midback, 0.45 for l o i n and 0.72 for t o t a l of midback plus l o i n were found i n t h i s study. .,• & s l i g h t l y higher genetic c o r r e l a t i o n of 0.78 was obtained between probe f a t adjusted to 91 kg and t o t a l of midback plus l o i n carcass f a t . This indicates that selection on the basis of low adjusted t o t a l probe f a t measurement should also be guite e f f e c t i v e i n decreasing carcass fat measurement. With a high negative c o r r e l a t i o n of -0.71 between Grade Index and adjusted t o t a l probe f a t , s i m i l a r desirable r e s u l t s could be expected. Selection tc decrease adjusted t o t a l probe f a t would have the e f f e c t of increasing the Grade Index or economic value of the carcass. 49 Age adjusted to 91 kg shows a genetic c o r r e l a t i o n with probe f a t si m i l a r i n magnitude but opposite in sign to that of average d a i l y gain with probe f a t . This i s a similar response as i t indicates that faster gaining animals tend to have thicker backfat. With the effects of weight removed by adjusting to a common l i v e weight of 91 kg for both adjusted age and adjusted probe f a t , the genetic c o r r e l a t i o n between the two t r a i t s i s es s e n t i a l l y zero (-0.07). This suggests that the genetic c o r r e l a t i o n between age and fat i s due mainly to the common relati o n s h i p of both t r a i t s with l i v e weight. With t h i s low co r r e l a t i o n , a decrease in days to 91 kg should have l i t t l e e f f ect on probe fat adjusted to 91 kg. The environmental co r r e l a t i o n s between average d a i l y gain and probe f a t measurements were low with a value of 0. 23 f o r midback and 0.24 for both l o i n and t o t a l f a t . Values obtained for the environmental c o r r e l a t i o n between age adjusted to 91 kg and these same probe f a t measurements were -0.13 for midback and -0.15 for both l o i n and t o t a l . , Average d a i l y gain and age adjusted to 91 kg both show essentially no environ mental cor r e l a t i o n with probe f a t adjusted to 91 kg. The respective values for these t r a i t s were -0.02 and -0.002. These indicate that the t r a i t s are not influenced by s i m i l a r environmental conditions. 50 A comparison of g e n e t i c parameters estimated f o r both l i v e and c a r c a s s measurements shows t h a t both s e t s of measurements produce s i m i l a r r e s u l t s . T h i s g i v e s confidence i n the g e n e t i c parameters estimated from t h e l i v e animal measurements.„ H » B e l a t i o n s h i p Between L i v e and Caycass Measurements Table XI l i s t s the number of o b s e r v a t i o n s , means and standard d e v i a t i o n s f o r a l l animals i n Group I. Slaughter i n f o r m a t i o n was not a v a i l a b l e f o r a l l animals and the separate measurements of shoulder, midback and l o i n f a t were not taken u n t i l p art way through the study. T h i s r e s u l t e d i n d i f f e r e n c e s i n the number of o b s e r v a t i o n s f o r the v a r i o u s c a r c a s s t r a i t s . The product moment c o r r e l a t i o n s between l i v e and c a r c a s s t r a i t s are l i s t e d i n Table XII. A l l values i n t h i s t a b l e were found t o be s i g n i f i c a n t (P<0.05) except f o r the c o r r e l a t i o n between average d a i l y gain and probe f a t adju s t e d to 91 kg. The c o r r e l a t i o n s between l i v e and c a r c a s s backfat measurements compare f a v o r a b l y with s e v e r a l e s t i m a t e s i n the l i t e r a t u r e . , The c o r r e l a t i o n s c a l c u l a t e d i n t h i s study range from 0.35-0.61. These estimates compare t c those of 0.53-0.56 t h a t B l e n d l (1956) r e p o r t e d i n a study c f the p r a c t i c a l i t y of the u l t r a s o n i c technigue under f i e l d c o n d i t i o n s . They a l s o compare to values of 0.24-0.69 found i n s i m i l a r s t u d i e s by I s l e r and Swiger (1968) and by Anderson and Whalstrom (1969). S i m i l a r values of 0.49-0.52 were r e p o r t e d by J e f f r i e s (1975) i n e a r l i e r 51 Table XI Means and standard deviations of l i v e and carcass t r a i t s for Data Set I T r a i t Number of Observations Mean Standard Deviation Average daily gain (kg/day) 3265 0.52 0.05 Adjusted age* (days) 3265 169.09 13. 39 Probe fat (nm): midback 3265 18.24 2.78 l o i n 3265 22 . 56 3.39 t o t a l 3265 81.65 12.00 adjusted t o t a l 1 3265 21.37 3.09 Carcass wt./age (kg/day) 2344 0.40 0.04 Carcass fat (mm): shoulder 1856 40.64 4,97 midback 17S7 24.55 4. 12 l o i n 1856 32.42 4.50 midback + l o i n 1797 56.95 7.86 shoulder+loin 2344 72.89 7.90 Grade Index (percent) 2344 102.69 3. 81 Time 2 (days) 2344 11.84 10.27 1 Adjusted to 91 kg l i v e weight 2Days from probe to slaughter Table XII Simple c o r r e l a t i o n s 1 among l i v e and carcass t r a i t s f o r Data Set I Probe Fat Carcass Fat •| Carcass )• A. D.G. Adj. Age HB LN Total Adj. Tot Ht./Age SH HB LN UB+LN SH+LN Index adjusted age* 1 " " - ' " 1 -1 -0.96 • I II _. Probe Fat: 1 i midback I 0.20 -0. 16 ! loin I 0.19 -0. 16 0.88 total I 0.20 -0. 16 C. 96 0.97 ! adjusted total 2 | NS -0.07 0.90 0.92 C.94 ! Carcass Ut./age I 0.81 -0.83 0.32 0.33 0.33 0.21 1 Carcass Fat; 1 ! shoulder I 0.27 -0. 24 0.40 0.39 0.41 0.35 0.34 I midback I 0.29 -0.25 0.55 0.53 0. 55 0.49 0.39 0. 53 I loin 1 0.33 -0.31 0.53 0.54 0.55 C.50 0.44 0. 50 0.66 I midback • loin I 0.34 -0.31 0.59 0.59 0.61 0.54 0.46 0. 57 0.90 0. 85 ! shoulder • loin i 0.33 -0.31 0.52 0.50 0.53 0.46 0.43 0.88 0.68 0.92 0. 84 1 Grade Index 1 -0.22 0.20 -0.32 -0.29 -0.32 -0.28 -0.25 -0. 55 -0. 43 -0. 53 -0.54 -0.63 1 Time3 1 0.20 -0.23 -0.09 -0.04 -0.06 -0.07 0.12 0. 17 0.14 0.17 0. 17 0.18 -0.201 _ _ _ _ = = . = _ _ _ _ _ _ _ _ _ _ _ - = _ _ _ = = _ _ __ _ _ _ _ _ _ — — — — _ _ _ _ _ _ , __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Ul 1 A l l values significantly different from 0 (P<0.05) except as indicated 2Adjusted to 91 kq live weight 'Days from probe to slaughter 53 work with the same swine herd but a different set of data than that used in t h i s study. Stepwise a u l t i p l e regression analyses were performed in order to determine the rel a t i o n s h i p between the dependent variables carcass midback plus l o i n f a t , carcass shoulder plus l o i n f a t and Grade Index with the l i v e animal measurements. The res u l t s of these analyses are l i s t e d i n Table XIII, The absolute value of the standardized p a r t i a l regression c o e f f i c i e n t s i n t h i s table indicate the r e l a t i v e importance cf each of the independent variables i n the eguation. The E 2 values show the proportion of the t o t a l variance accounted for by the independent variables included in the eguation. Three groups of potential independent variables were used in the stepwise regression analyses. This was done because of the high co r r e l a t i o n between the variables average d a i l y gain and age adjusted to 91 kg, and also between the probe f a t measurements. These three groups are referred t c as A, B and C with the potential independent variables as l i s t e d i n Table XIII. l i t t l e difference was found i n the B 2 values between analyses A and B f o r each of the dependent variables. This indicates that there i s l i t t l e advantage i n using the separate measurements of midback and l o i n fat i n any of the prediction 54 Table XIII Stepwise r e g r e s s i o n a n a l y s e s f o r p r e d i c t i o n o f c a r c a s s f a t and Grade Index fo r Data Set I P o t e n t i a l Ind. , V a r i a b l e s Carcass Midback + L o i n f a t Carcass Shoulder + L c i n f a t Grade Index A n a l y s i s A Adjusted a g e 2 Midback probe f a t Lo i n probe f a t Time 3 B 2 f o r t o t a l model •0.176* 0.342 0.269 0.166 0.445 -0. 180 0. 378 0. 145 0. 179 0. 356 0.094 •0.328 NS •0.211 0.167 A n a l y s i s B Adjusted a g e 2 T o t a l probe f a t Time B 2 f o r t o t a l model C 180 0.588 0.161 0.440 •0. 184 0.505 0. 170 0.352 0. 100 0.313 •0. 199 0.159 A n a l y s i s C Adjusted age 2 Adjusted probe f a t 2 Time B 2 f o r t o t a l model •0.244 0.537 0.145 0.392 •0.240 0.455 0. 155 0.310 0. 134 •0.283 •0.190 0.144 1 Standardized p a r t i a l r e g r e s s i o n c o e f f i c i a n t 2 A d j u s t e d t o 91 kg l i v e weight 3Days from probe to s l a u g h t e r 55 equations. Analysis C accounted for a noticeably lower proportion of the t o t a l variance i n each of the dependent variables than with analyses A and B. This i s possibly due to the adjustment of probe backfat to a constant weight of 91 kg while the dependent variables were not adjusted. Simple l i n e a r regression analyses were performed i n order to determine the relationship between each of the dependent variables and the single independent variables used i n the previous analyses. A l l individuals in data set I with more than 17 days between probe and slaughter were removed for these analyses. This reduces the e f f e c t of time and gives a set c f data comparable to that of other commercial operations. The number of observations, means and standard deviations for t h i s set of data are l i s t e d i n Table XIV. The simple co r r e l a t i o n s among the l i v e and carcass t r a i t s l i s t e d i n Table XV are larger but show the same trends as those i n the o r i g i n a l data set. These higher correlations would be due to the s e l e c t i o n of data from animals with seventeen days or less between probe and slaughter. The simple linear regression equations for the prediction of carcass midback plus l o i n f a t , carcass shoulder plus l o i n fat and index are presented in Table XVI. The proportion of the t o t a l v a r i a t i o n accounted for (B2) by the separate independent variables, average d a i l y gain and age adjusted to 91 kg was 56 Table XIV Means and standard deviations of l i v e and carcass t r a i t s for Data Set I with 0-17 days between probe and slaughter Number of Standard T r a i t Observations Mean Deviation Average daily gain (kg/day) 1892 0.52 0.05 Adjusted age* 1892 171.23 13.62 Probe fat (mm): midback 1892 18.47 2.67 l o i n 1892 22.71 3.25 t o t a l 1892 82.41 11.51 adjusted t o t a l * 1892 21.59 2.91 carcass wt./age (kg/day) 1892 0.41 0.04 Carcass fat (mm): shoulder 1551 40.34 4.92 midback 1526 24.39 4.10 l o i n 1551 32.13 4.46 midback • l o i n 1526 56.54 7.79 shoulder + l o i n 1892 72.37 7.84 Grade Index (percent) 1892 102.99 3.02 Time 2 (days) 1892 7.96 5.51 * Adjusted to 91 kg l i v e weight 2Days from probe to slaughter Table XV Siaple correlations 1 among live and carcass traits for Data Set I with 0-17 days between probe and slaughter Probe Fat Carcass Fat A. E. G. Adj. Age HB LN Total Adj. Tot 1 Carcass| Wt./Age SH HB LH HB+LN Adjusted Age* r I -0.96 Prcbe Fat: 1 midback 1 0.32 -0.28 lcin I 0.30 -0.26 0.88 total 1 0. 32 -0.28 0.96 0.97 adjusted total 2 | 0.13 -0. 18 0.89 0.91 0. 93 Carcass Ht./age I 0. 88 -0. 86 0.35 0.37 0. 37 0.23 Carcass Fat: ! shoulder | 0.26 -0.23 0.4 1 0.40 0. 42 0. 36 0.33 midback . | 0. 30 -0.26 0.56 0.55 0.57 0. 50 0. 39 0.53 loin I 0.34 -0.31 0.56 0.57 0. 58 0.52 0.43 0.49 0.65 midback • loin I 0.35 -0. 32 0.62 0.62 0.63 0.56 0.45 0.55 0.90 0. 92 shoulder • loin 1 0. 33 -0.33 0.54 0.53 0.55 0. 48 0.42 0.87 0.68 0. 84 0.84 Grade Index | -0.17 0.17 -0.42 -0.38 -0. 41 -0. 40 -0.18 -0.64 -0.47 -0.59 -0.59 = = = = = = = = = = = = = = = = = = = = = = = = = „ _ _ _ . — E =  _ _ _ _ _ _ _ _ = = = = = = = = = _ _ _ _ _ _ - 0 . 7 2 »A11 values significantly different from 0 (P<C.05) 'Adjusted tc 91 kg live weight 58 Table x v i Simple li n e a r regression eguations for carcass t r a i t s for Data Set I with 0-17 days between probe and slaughter Average Dependent Daily Adjusted Probe Probe Probe Adj. Variable Gain Age 1 Midback Loin Total T o t a l 1 Carcass Midback Plus Loin Fat Intercept 26.05 86.69 23.94 23.25 22.00 24.54 Slope 58.44 -0. 18 1.77 1.49 0.42 1.50 B 2 0. 12 0. 10 0.38 0.38 0.40 0.32 Carcass Shoulder Plus Loin Fat Intercept 43.02 101.90 42.89 43.66 41.47 44.60 Slope 56.69 -0.17 1.60 1.26 0.38 1.29 B 2 0.11 0.09 0.30 0.28 0.30 0.23 Grade Index Intercept 108.90 96.67 111.70 110.90 111,80 111.90 Slope -11.38 0.04 -0.47 -0.35 -0. 11 -0.41 B 2 0.03 0.03 0. 18 0.14 0. 17 0. 16 1 Adjusted to 91 kg l i v e weight 59 found to be low (0.03-0.11) for each of the dependent variables. This was also the case for the prediction of Grade Index from each of the probe f a t measurements with B 2 values of 0.14 to 0.18 obtained. As i n the multiple regression analyses, the eguations for the prediction of carcass fat from the ultrasonic probe f a t measurements gave the highest B 2 values. These values ranged between 23 and 40 percent of the t o t a l variation accounted for. These analyses show that a large proportion of the t o t a l variation in the carcass f a t measurements i s explained by the separate ultrasonic f a t measurements, The importance of the variables time and adjusted age, indicated by the standardized p a r t i a l regression c o e f f i c i e n t s , was also generally much lower in r e l a t i o n tc the probe f a t measurements., This indicates that any of the probe backfat measurements could be used alcne to simplify the prediction of any of the carcass backfat measurements with minimal loss i n predictive value. III.Selection Index Two of the l i v e t r a i t s considered in th i s study were chosen to be incorporated i n t o the selection index. These t r a i t s are age adjusted to 91 kg and t o t a l probe backfat adjusted to 91 kg. These t r a i t s were chosen on the basis of h e r i t a b i l i t y , genetic c o r r e l a t i o n and economic value. 60 The h e r i n a b i l i t i e s of adjusted age (0*24) and adjusted t o t a l fat (0.26) were the highest of a l l estimates for the l i v e t r a i t s measured i n t h i s study. The high c o r r e l a t i o n between adjusted age and average d a i l y gain indicates that these t r a i t s measure the same thing and the addition of t h i s t h i r d t r a i t to the selection index would be of l i t t l e genetic or economic value. This was also the case with the other probe backfat measurements., The value of using one or more addit i o n a l backfat measurements would be small compared to that of adjusted t o t a l backfat alone. The low genetic c o r r e l a t i o n of -0.07 between adjusted age and adjusted t o t a l f a t i s desirable for a selection index., This low c o r r e l a t i o n indicates that the two t r a i t s are nearly independent and that improvement i n one t r a i t w i l l not cause a deterioration i n the other. This low c o r r e l a t i o n also helps to simplify the selection index to es s e n t i a l l y the sum cf the products of h e r i t a b i l i t y and economic weights of the two t r a i t s . Both of these t r a i t s have considerable economic importance. Adjusted age indicates the production cost for an animal raised to 91 kg. A reduction i n days to 9 1 kg on a herd basis would r e s u l t i n reduced production costs along with potential for increased throughput of market animals. Backfat i s also an important t r a i t as i t i s used to establish the grade of a carcass. By estimating the carcass backfat with the l i v e 61 ultrasonic probe before the animals have reached market weight, a producer can select breeding stock on the basis of i n d i v i d u a l performance. a» Economic weights Assuming an increased throughput of pigs by decreasing days adjusted to 91 kg, the fixed costs per pig marketed would be reduced. Using the average of values for feed and other operating costs from Ontario, Manitoba, and Alberta reported by Fredeen (1977) f o r a 65 sow farrow to f i n i s h operation, the economic value of reducing days adjusted to 91 kg by 1 day would be as follows: t o t a l feed cost per pig marketed = $53.24 other operating costs (cash and non-cash) = $38.30 Assuming the average for days adjusted to 91 kg to be 170 days, a reduction of 1 day would reduce the cost per pig marketed by: feed cost 53.24 - (169/170 * 53.24) = $0.31 other operating costs 38.30 - (169/170 * 38.30) = $0.23 The ef f e c t that a change i n days adjusted to 91 kg would have on feed e f f i c i e n c y should also be taken into account in the cal c u l a t i o n of economic value of th i s t r a i t . Based on the high 62 negative phenotypic correlation (-0.95) between age adjusted to 91 kg and average d a i l y gain, we can assume that a percentage reduction i n adjusted age w i l l r e s u l t i n a s i m i l a r percent increase i n average daily gain. In order to estimate the economic value of any associated change i n feed e f f i c i e n c y , i t was assumed that an average pig at 91 kg l i v e weight would have an actual gain of 0.82 kg per day. From a report by Beames (1978) which tabulates the relationship between feed intake and feed e f f i c i e n c y , and based cn the preceding assumptions, a 10 percent increase i n t o t a l gain per day could r e s u l t i n an increase of 0.1 kg feed reguired per kg gain. With the average feed price of $0.20 per kg reported by Fredeen (1977), the t o t a l increased cost for a 91 kg pig would be $1.82. In terms of a 1 day reduction i n days to 91 kg the value would be $0.11 per day. This changes the o r i g i n a l feed cost saving from $0.31 to $0.20 per day. The t o t a l economic value of decreasing days to 91 kg i n t h i s example would be $0.43 per day. The economic weight for backfat thickness was calculated from the Agriculture Canada Grade Index table. The carcass backfat values i n the table were f i r s t converted to t o t a l u ltrasonic backfat adjusted to 91 kg with the appropriate eguation from Table XVI. The economic value cf the adjusted t o t a l backfat was obtained by regressing the carcass value for a 63 70 kg carcass on adjusted t o t a l backfat thickness. For a 70 kg carcass valued at $1.26 per kg, Grade Index 100, a 1 mm decrease in adjusted t o t a l ultrasonic backfat would be worth $0.44. It was considered unnecessary to adjust t h i s economic value for the e f f e c t that a reduction in t h i s t r a i t would have ct the economic value cf other t r a i t s . , Bith the low phenotypic correlation between f a t adjusted to 91 kg and age adjusted to 91 kg found in t h i s study, a change i n one t r a i t would not resu l t i n any predictable change i n the other. In other words, only a very small portion of the t o t a l v a r i a t i o n in adjusted age can be accounted f o r by adjusted f a t . A reduction i n adjusted f a t would therefore res u l t i n a minimal change i n adjusted age. b» _ _ i _ _ t i o f i index example The following selection index example was calculated from the parameters estimated in this study. The parameters used in the cal c u l a t i o n of this index were as follows; I = Adjusted Age + 4.51 Adjusted Fat Adjusted backfat H e r i t a b i l i t y 0.24 0.26 Phenotypic variance 152.60 6.99 Additive genetic variance 38.03 1.7 2 Economic value $0.43 /day $0.44 /mm Genetic co r r e l a t i o n -0.07 64 sum as y This study made use of data collected frcm a l l market pigs raised i n the Province of B.C. swine herd at Colony Farm during the period October, 1974 to December, 1976., Live animal measurements of average daily gain, age adjusted to 91 kg l i v e weight, ultrasonic measurements of midback and l o i n f a t , t o t a l ultrasonic backfat and t o t a l ultrasonic backfat adjusted to 91 kg l i v e weight were used i n t h i s study., Carcass measurements were used for comparison with the l i v e measurements. The carcass measurements were; carcass weight per day of age, maximum shoulder f a t , minimum midback fat, maximum l o i n f a t , t o t a l shoulder plus l o i n f a t , t o t a l midback plus l o i n f a t and Grade Index. The genetic parameters of the l i v e animal measurements used in t h i s study were estimated from 2403 i n d i v i d u a l s with 20 degrees of freedom for s i r e s and 317 degrees cf freedom for dams. A l l of the data were adjusted for the e f f e c t s of time (season), sex and the time by sex interaction by the method of least-squares. H e r i t a b i l i t y estimates were obtained from paternal h a l f - s i b , maternal h a l f - s i b and f u l l - s i b c o r relations for each of the l i v e and carcass t r a i t s . The paternal h a l f - s i b estimates of h e r i t a b i l i t y for the l i v e animal measurements were; 0.22 and 65 0.24 for average daily gain and age adjusted to 91 kg l i v e weight, with estimates of 0.18, 0.21# 0.21 and 0.26 for the ultrasonic backfat measurements of midback, l o i n , t o t a l and t o t a l adjusted to 91 kg l i v e weight respectively. These values were comparable to those obtained for the carcass measurements. Estimates of h e r i t a b i l i t y frcm the si r e components are in general agreement with l i t e r a t u r e values for average daily gain but somewhat lower than values reported f o r l i v e backfat measurements. The higher values reported for l i v e backfat probe were based on the r u l e r probe rather than the ultrasonic method of measurement. The genetic c o r r e l a t i o n s for average daily gain with l i v e probe measurements of midback (0.22), l o i n (0.12) and t o t a l (0.17) were a l l low and p o s i t i v e . This indicates that, ge n e t i c a l l y , as backfat i s reduced average daily gain w i l l also decrease, and the two t r a i t s are influenced by some of the same genes. Age adjusted to 91 kg shows a genetic c o r r e l a t i o n s s i m i l a r i n magnitude but opposite in sign to that of average d a i l y gain with probe f a t . The genetic c o r r e l a t i o n between adjusted age and adjusted probe f a t , both adjusted tc a common l i v e weight of 91 kg, was found to be close to zero (-0.07). This suggests that the genetic correlation between age and f a t i s due mainly to the 66 common relationship of both t r a i t s with l i v e weight. A comparison of genetic parameters estimated for both l i v e and carcass measurements shows that both sets of measurements produce s i m i l a r results, This gives confidence i n the genetic parameters estimated from the l i v e animal measurements, Eegressson analyses were performed i n order to determine the relationship between the dependent variables carcass midback plus l o i n f a t , carcass shoulder plus l o i n f a t and Grade Index, with several l i v e animal measurements. I t was concluded that simple li n e a r regressions with ultrasonic probe f a t as the independent variable had s i m i l a r value f o r predicting the dependent variables as compared to multiple regression eguations incorporating up to 4 independent variables. A selection index was proposed, based on l i v e animal measurements i n order to demonstrate the use of the estimated parameters. Two of the l i v e t r a i t s considered i n t h i s study were chosen to be incorporated into the selection index. These t r a i t s were age adjusted to 91 kg and t o t a l probe backfat adjusted to 91 kg. These t r a i t s were chosen on the basis of h e r i t a b i l i t y , genetic co r r e l a t i o n and economic value. The proposed selection index, based on parameters estimated i n t h i s study was: I = adjusted age (days) + 4.51 adjusted f a t (mm). 67 LITEBATURE CITED Anderson, L.M. and B.C. Wahlstrom, 1969. Ultrasonic prediction of swine carcass composition., J. Anim. S c i . , 28:593-600. Arganosa, V.G.,1.T. Omtvedt and L.E. Walters, 1969. Phenotypic and genotypic parameters c f some carcass t r a i t s i n swine. J. Anim. S c i . , 28: 168-174., Batra, T.B., G.H. Bowman and M.G. Freeman, 1972. Genetic parameters of Canadian swine. Paper presented at C.S.A.S., P.E.I. June 1972. Beanies, D., 1978. Relationship between feed intake and feed e f f i c i e n c y . 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