Parâmetros genéticos para características de crescimento e reprodutivas em bovinos nelore no Brasil

Abstract

To know the genetic and phenotypic progress of a population is important to evaluate the outcome of the adopted selection programmes and as guiding elements of future actions. The objective was to estimate genetic parameters, genetic and phenotypic trends of weights at 205 (W205) 365 (W365) 550 (W550) days of age, age at first calving (AFC), scrotal circumference (SC) and calving interval (CI) of 175.231 Nellore, born in the period 1967-2011 in the Northeast region of Brazil. The components of (co) variance and breeding values were obtained by restricted maximum likelihood methodology. Estimates of heritability coefficients for growth traits were of a low to moderate magnitude. Direct selection will provide greater genetic gains for W550. For reproductive traits, the heritability estimate was low for ACF and close to zero for CI. However, for the SC heritability was moderate, indicating its use as selection criteria. Direct genetic trends for W205, W365, W550 and ACF indicate small genetic gains over the years. Phenotypic progress shows that the features are improving with the years, mainly because of environmental improvements.