PARÂMETROS GENÉTICOS PARA CARACTERÍSTICAS PRODUTIVAS DE ANIMAIS DA RAÇA NELORE

This study aimed to estimate the genetics parameters for weight traits at 120 (W120), 240 (W240) and 420 (W420) days of age for Nellore cattle raised in Brazil. The genetic parameters and correlations were obtained using univariate and bivariate animal model analyzes. The fixed effects of the model were contemporary group [sex and farm] and covariate age of dam (linear and quadratic) and error. As random effects, we used direct and maternal genetic effects, and the uncorrelated maternal permanent environmental effect. Estimates on direct heritabilities were, respectively, 0.18; 0.18 and 0.23 for W120, W240 and W420. Genetic correlations between weights were 0.55 (W120-W240), 0.60 (W240-W420) e 0.76 (W120- W420). The values of direct heritability estimates indicate the possibility of selection, but with slow progress. Correlations between weight performance characteristics suggest that selection for weight at younger ages may lead to satisfactory correlated response to future ages.