ABSTRACT
We aimed to estimate genetic parameters for growth traits of Polled Nellore beef cattle. Adjusted weights at 205 (W205), 365 (W365) and 450 (W450) days were used. The effects of contemporary groups (fixed), dam age at calving (covariate), and additive genetic, maternal genetic, maternal permanent environmental and residual (random) were fit under a multi-trait model. The additive genetic (98.80, 276.38 and 547.52 Kg2) and maternal genetic (61.77, 64.63 and 79.85 Kg2) variances estimates increased as the age of the animals increased. Unlikely, a decrease was observed from W205 to W365 for the maternal permanent environmental effect. Direct heritability estimates were, respectively, 0.21 ± 0.01; 0.38 ± 0.00 and 0.39 ± 0.00 for W205, W365 and W450. The maternal heritabilities were higher in lower ages (0.13 ± 0.01, 0.08 ± 0.00 and 0.05 ± 0.00). Genetic correlations were higher than 0.94 whereas phenotypic were between 0.50 and 0.87. Maternal correlations were higher than 0.91 for genetic and permanent environmental effects. Potential genetic gain might be expected by using any of these growth traits as selection criterion. The verified genetic variability may allow the selection of animals in lower ages (e.g., weaning), enabling higher genetic gain and generation interval reduction.
Keywords:
genetic correlation; genetic gain; heritability; variance components