Estimation Of Genetic Parameters For Hair Shedding Score And Relationship To Performance In Angus Charolais And Hereford Dams

Author : Robert B. Church
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (143 download)

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Download or read book Inheritance and Interrelations of Live Performance and Carcass Characteristics in Beef Cattle written by Robert B. Church and published by . This book was released on 1963 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was undertaken to evaluate live performance, carcass characteristics and meat quality traits of 183 progeny test steers sired by 10 Hereford, 3 Charolais, 1 Holstein and 1 Angus sires and from grade Hereford dams. An additional group of 10 steers were Hereford sired, from Holstein X Hereford dams. Disproportionate data necessitated an analysis of variance using a nested or hierarchial classification. Components of variance were estimated for groups (feeding method, ranch and breed), sires within groups and progeny within sires. Heritabilities were calculated from paternal half sib correlations. Intercorrelations among 42 performance and carcass traits were calculated. Sire variance and heritability estimates were high for feedlot average daily gain (ADG) for the calves which were fed to market condition rapidly (fed-calf program) but were low for those carried on a lower plane of nutrition for 174 days followed by full feeding to market condition (fed-yearling program). High heritabilities were obtained for lifetime average daily gain (LADG) under both programs and would therefore seem to be a more useful measure of gainability than feedlot ADG. Dressing per cent and per cent kidney fat showed significant sire differences with heritability estimates of 78 per cent and 45 per cent respectively. Measures of fat cover over the rib-eye had low heritabilities which were probably influenced by marketing at an appraised constant finish. Fat cover per cwt. had a higher heritability at 46 per cent and would therefore be a preferred measure for progeny testing purposes. With a heritability of 89 per cent, rib-eye area per cwt. was superior to rib-eye area, rib-eye depth and per cent separable lean in a rib core, for detecting sire progeny differences in leanness. Rib-eye depth proved to be of no value in this regard. No significant group or sire within group differences were obtained for retail yield although the heritability estimate was 29 per cent for this trait. Marketing at an appraised constant finish may have masked sire differences for this measure. Sire progeny groups did not differ in ether extract of longissimus dorsi muscle, a measure of marbling. Sire progeny group differences were easily detected for tenderness of the longissimus dorsi muscle. A similar result was obtained for muscle fiber diameter. Average fat cover was the best individual predictor of retail yield accounting for 29 per cent of its variation. Estimating yield by the U.S.D.A. formula of Murphey et al. (1960) was no more accurate as a predictor than fat cover alone. Other possible predictors of retail yield along with their coefficients of determination were; per cent trimmed chuck (17 per cent), per cent trimmed round (15 per cent), per cent separable lean in a rib core (11 per cent) and rib-eye area per cwt. (6 per cent). No significant relationships were found between measures of gain and retail yield or measures of quality and retail yield.