Genetic parameters for milk production of Australian beef cows and weaning weight of their calves

Abstract

Estimates of covariance components were obtained for milk production of beef cows, measured by the weigh-suckle-weigh method, and weaning weight and preweaning growth of their calves for a herd of Polled Herefords and a herd of a multibreed synthetics, so-called Wokalups. Analyses were carried out by restricted maximum likelihood fitting an animal model incorporating both direct and maternal genetic and permanent environmental effects and allowing for the direct-maternal covariances. Average 14-h milk yield was 3.6 kg for Herefords and 4.9 kg for Wokalups and heritabilities were .12 and .08, respectively. Treating preweaning gain of the calf as a trait of the cow, estimates of the additive genetic and permanent environmental correlations between preweaning gain and milk yield were higher for Herefords (.73 and 1.00, respectively) than for Wokalups (.53 and .77). Bivariate analyses of milk production (treated as a trait of the cow) and weaning weight (treated as a trait of the calf) showed virtually no direct additive genetic, direct permanent environmental, or phenotypic association between the two traits but identified strong correlations between direct effects for milk yield and maternal effects for weaning weight. The estimate of the direct-maternal genetic correlation between milk yield and weaning weight was .80 for both breeds, and the estimated correlation between direct, permanent environmental effects for milk yield and maternal, permanent environmental effects on weaning weight was unity for Herefords and .89 for Wokalups. Results indicate that milk production is the main determinant of maternal effects on the growth of beef calves with breed differences in the importance of maternal effects largely attributable to differences in milk production.

Inclusão da covariância genética direta-materna no modelo para estimar parâmetros e predizer valores genéticos para ganho de peso em bovinos da raça Angus

“…Comportamento semelhante foi relatado por Meyer et al (1994), para as raças Hereford e Wokalup na Austrália, e por Albuquerque et al (1998), para a raça Caracu no Brasil. Coeficientes de herdabilidade para o efeito direto, não considerando a covariância entre os efeitos direto e materno, inferiores aos obtidos neste estudo foram relatados por Cardellino & Cardellino (1984), para a raça Hereford no Rio Grande do Sul (0,012 ± 0,07), e por Sarmento et al (2003), para a raça Nelore na Paraíba (0,12 ± 0,04).…”

“…Por outro lado, Willham (1972) afirmou que a habilidade materna, em bovinos de corte, estaria relacionada diretamente à produção de leite da vaca, o que traria reflexos no desempenho do bezerro, principalmente à desmama, embora tenha registrado contribuição do efeito materno também para o peso ao nascer, indicando que outros fatores são importantes na determinação do efeito materno. Similarmente, Meyer et al (1994) afirmaram que a produção de leite é o principal determinante dos efeitos maternos no crescimento de bezerros das raças de corte.…”

“…Entretanto, relatos sobre o antagonismo entre os efeitos genéticos aditivos diretos e maternos foram feitos por Meyer et al (1994) e Lee & Pollak (1997), o que, segundo Eler et al (1989), comprometeria a resposta positiva para potencial de crescimento, sujeito à influência materna. Se a seleção fosse feita com base no valor fenotípico dos animais, uma resposta positiva para potencial de crescimento estaria associada à redução na habilidade materna.…”

The nature of nurture in a wild mammal's fitness

“…For example, much of the variation in growth rates in beef cattle (Bos taurus taurus and B. t. indicus) can be explained by the identity of their mother; some cows raise faster-growing calves than others [13]. One reason for this is that some females produce more milk than others, which affects how quickly their calves grow [14]. Since variation in milk production is heritable, maternal genes for milk production affect the growth rates of a cow's calves [14], which therefore represent a MGE.…”

“…One reason for this is that some females produce more milk than others, which affects how quickly their calves grow [14]. Since variation in milk production is heritable, maternal genes for milk production affect the growth rates of a cow's calves [14], which therefore represent a MGE. Since MGEs represent an additional source of genetic variation, they have the potential to affect the rate of evolution [11], which has long been appreciated by animal breeders [15,16].…”