Variance component estimates for weight and visual scores of slaughter conformation in Nellore cattle

The aim of this study was to estimate variance components, heritability and genetic correlation for slaughter conformation at weaning (SCW), slaughter conformation at yearling age (SCY), weaning weight (WW) and yearling age weight (YW) of Nellore cattle. A total of 6,397 records of all traits measured at weaning and at yearling age were used in the analysis. A multiple trait animal model which included the direct genetic additive, maternal genetic additive, maternal permanent environmental and residual random effects, as well as the fixed effect of contemporary group and the covariates age at calving (for weight and slaughter conformation at weaning and yearling age) and age at the evaluation time (slaughter conformation at weaning and yearling age) was proposed. The heritability estimates for SCW, SCY, WW and YW were, respectively, 0.13, 0.25, 0.22 and 0.29. Positive and high genetic correlations between body weight traits and visual evaluation traits suggested that direct selection for one trait results in positive indirect response in the remaining trait. Slaughter conformation trait can be selected at earlier age due to the high and positive genetic correlation between conformation scores at different age.