ESTIMATION OF VARIANCES DUE TO DIRECT AND MATERNAL EFFECTS FOR GROWTHTRAITS OF NELORE CATTLE

Estimates of(co)variance components and genetic parameters were obtain ed for birth, 205-d, and 365-d weight for Nelore cattle in Brazil, usi ng single and multiple-trait animal models. Data were from the Brazili an Zebu Breeders Association (ABCZ). Records of 27,549 calves sired by 587 bulls and raised on pasture in 57 herds were analyzed by restrict ed maximum Likelihood fitting an animal model including direct and mat ernal genetic and permanent environmental effects. Single and multiple -trait analyses were carried out. Heritability estimates for direct ef fects were lower than previous values reported for the Nelore breed. T he estimates for maternal genetic effects showed that the contribution of this component to the phenotypic variance of birth and weaning wei ght is not very high but is still present at yearling weight. Correlat ions between direct and maternal additive genetic effects were negativ e for all traits analyzed except for yearling weight in the single-tra it analysis where the sign was positive but the magnitude was small ( .09). Genetic correlations between weaning and yearling weights were .74 (direct effect) and .84 (maternal effect). Permanent environmental and residual correlations among traits were-also obtained.