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item Riley, David
item Chase, Chadwick - Chad
item Hammond, Andrew - Andy
item OLSON, T
item Coleman, Samuel

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2004
Publication Date: 6/1/2004
Citation: Riley, D.G., Chase, C.C., Hammond, A.C., Olson, T.A., Coleman, S.W. 2004. Genetic and nongenetic influences on vigor at birth and preweaning mortality of purebred and high percentage Brahman calves. Journal of Animal Science Vol. 82; pp. 1581-1588.

Interpretive Summary: Brahman crossbreds are an important part of cow-calf production in the Gulf Coast region of the United States. However, relatively large numbers of straightbred Brahman cattle are required to generate crossbred cows for various types of crossbreeding production systems. The production difficulties associated with straightbred Brahman cattle include poor calf viability, and frequent negative market perception of the body conformation, body condition, and meat quality as compared with Bos taurus beef cattle. This study was conducted to determine the heritabilities of calf birth vigor (scored subjectively), calf body condition score at weaning, and calf survival from birth to weaning. Though the heritabilities of calf birth weight, weaning weight, and hip height at weaning are widely known, these traits were included in order to estimate genetic correlations between the different traits. We found that sires could be selected to effectively increase calf body condition score at weaning without substantially increasing birth weight. Although selection progress based on calf vigor or calf survival performance would be limited, we found a strong positive genetic correlation between these two traits, indicating that parents with high values for calf vigor score would also tend to have high calf survival values. Breeding programs for Brahman herds could be developed using the information of this study for improvement of calf preweaning performance.

Technical Abstract: Genetic parameters for birth (n = 689) and weaning (n = 581) characters of straightbred Brahman calves (sired by 22 bulls) in Florida were estimated using animal and sire models. Estimated direct (and maternal) heritabilities from animal models for birth weight, calf birth vigor, weaning weight, weaning height, body condition score at weaning, and calf survival to weaning were 0.62 (0.21), 0.11 (0.12), 0.57 (0.31), 0.57 (0.18), 0.42 (0.01), and 0.05 (0.14). Estimated heritabilities from sire models for these characters were 0.55 +/- 0.05, 0.11 +/- 0.02, 0.63 +/- 0. 0.49 +/- 0.04, 0.46 +/- 0.03, and 0.04 +/- 0.02, respectively. Though most the estimated genetic correlations (from sire models) for pairs of characters were low to moderate, the genetic correlation of calf birth vigor with calf survival to weaning was 0.77 +/- 0.04 (P < 0.001). Though animal models are generally preferred for genetic parameter estimation, the esire models used provided estimates and rankings of sires for these traits that were reasonably similar to those of the animal model.