Six Different Models for Estimation of Genetic Parameters and Breeding Values for Pre-weaning and Post-weaning Weights in Suckler Cattle


Abstract: Estimates of (co)variance components and breeding values for pre-weaning (100-day) and post-weaning (300-day) weights were obtained for a commercial herd of Welsh Black cattle recorded from 1976 to 1996. Estimates were obtained from six animal models ranging from a model with only an additive direct effect to a model that also included an additive maternal effect, a maternal permanent environmental effect and a covariance between additive direct and additive maternal effects. The most appropriate model for 100-day weight, based on a likelihood ratio test, was a model with additive direct and additive maternal effects with no covariance between them, yielding estimates of 0.25 (0.053) and 0.07 (0.025) for h^2 and m^2 respectively. For 300-day weight, the model with only an additive direct effect was the most appropriate with an h^2 of 0.27 (0.050). Trends in additive direct breeding values for 100-day and 300-day weights were 0.39 (0.029) and 0.96 (0.077) kg per annum respectively. Additive maternal breeding values for 100-day weight increased by 0.08 (0.008) kg/annum. A correlation of 0.77 (0.066) was estimated between additive direct effects for 100- and 300-day weight.

Keywords: Welsh Black cattle, genetic parameters, maternal effects, genetic trend.

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