Download vigor1581-GENETIC AND NONGENETIC INFLUENCES ON VIGOR AT BIRTH AND PREWEANING MORTALITY OF PUREBRED AND HIGH PERCENTAGE BRAHMAN CALVES.pdf

Contents : Genetic and nongenetic in uences on vigor at birth and preweaning mortality of purebred and high percentage Brahman calves1 2 3 D. G. Riley*4 C. C. Chase Jr.* T. A. Olson S. W. Coleman* and A. C. Hammond* *ARS USDA Subtropical Agricultural Research Station Brooksville FL 34601 and University of Florida Gainesville 32611 ABSTRACT: The objectives of this study were to assess the risk associated with proportion Brahman inheritance cow age dystocia and birth date weather conditions on calf vigor at birth (n 3 253) and preweaning mortality (n 3 631) and to estimate heritabilities for these traits. Calves that had poor vigor at birth and calves that died before weaning were coded 1 and those that had adequate birth vigor or survived to weaning were coded 0. Traits were analyzed using GLM. Year (1951 to 2002) cow age calf gender minimum temperature on date of birth (two levels: 5.6 C or 5.6 C) and occurrence of dystocia were main effects in models. The proportion of Brahman inheritance in calves was modeled as a covariate. Males had greater odds of poor birth vigor (odds ratio 1.44 95% con dence interval 1.14 to 1.82). The odds of death before weaning for steers relative to heifers approached signi cance (P 0.07 odds ratio 1.41 95% con dence interval 0.97 to 2.04). Calves born to young (3-yr-old) or very old (13 yr or older) cows had greater (P 0.05) odds of poor vigor and death before weaning than calves of 5-yr-old cows. Calves with dif cult births had 2.59 times greater odds of poor birth vigor (95% con dence interval 1.40 to 4.79) and 12.9 times greater odds of death before weaning (95% con dence interval 8.14 to 20.39) than calves born with no dystocia. Calves born on days with minimum temperatures of 5.6 C or less had greater odds of poor vigor (odds ratio 1.97 95% con dence interval 1.50 to 2.59) and of death before weaning (odds ratio 1.64 95% con dence interval 1.27 to 2.13) than did calves born on days with higher minimums. The occurrence of rainfall on date of birth did not in uence calf vigor at birth or preweaning mortality (P 0.85). Purebred Brahman calves had 24.7 times greater odds (95% con dence interval 8.23 to 73.97) of poor vigor than Brahman calves. The regression coef cient estimate for fraction of Brahman inheritance approached signi cance (P 0.07) for preweaning mortality. Estimates of direct and maternal heritability were 0.09 0.05 and 0.10 0.04 for birth vigor and 0.06 0.05 and 0.09 0.04 respectively for preweaning mortality. Some exploitable genetic variation exists for these traits but management of other factors may yield more immediate improvement than selection. Key Words: Brahman Calves Genetic Parameters Mortality Vigor 2004 American Society of Animal Science. All rights reserved. Introduction Adaptation of Brahman cattle to hot harsh environments (Turner 1980) and the high heterosis for reproductive and maternal traits expressed by Brahman-Bos 1 This research was supported by the Florida Agric. Exp. Stn. and approved for publication as Journal Series No. R-07951. 2 Names are necessary to report factually on available data however the USDA neither guarantees nor warrants the standard of the product to the exclusion of others that may also be suitable. 3 Appreciation is extended to M. L. Rooks E. J. Bowers V. E. Rooks E. L. Adams and the STARS staff for technical assistance and animal care. 4 Correspondence: 22271 Chinsegut Hill Rd. (phone: 352-796-3385 fax: 352-796-2930 e-mail dgriley@mail.ifas.u .edu). Received August 8 2003. Accepted February 16 2004. J. Anim. Sci. 2004. 82:1581 1588 taurus cows (Cartwright et al. 1964) account for the widespread use of the breed in cow-calf production in the Gulf Coast region of the United States. Straightbred herds are necessary in order to generate these highly productive crossbreds (Gregory and Cundiff 1980) formidable dif culties associated with straightbred Brahman production include poor neonatal performance and low calf survival rates (Cartwright 1980). In order to obtain valuable colostrum a newborn calf must be vigorous enough to stand nd its dam s udder and nurse. Extremely weak calves have been frequently observed among Bos indicus newborns (Bauer 1973 Olcott et al. 1987). Calf mortality before weaning accounts for almost a third of calf crop losses (Cundiff et al. 1982) and is higher in subtropical and tropical regions (Plasse 1973) where Bos indicus cattle are the predominant type of cattle. Preweaning mortality is negatively 1581 1582 Riley et al. in uenced by a variety of environmental in uences including occurrence of dystocia (Laster and Gregory 1973) and hypothermia (Rowan 1992 Wittum et al. 1993). There may be a genetic cause for weak calf syndrome (Ogata et al. 1999) but there have been no reported estimates of genetic parameters for traits related to vi

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