Genetic and phenotypic trends for average daily weight gain from weaning to 550 days of age in a Angus Nellore population

Direct and maternal heritability coefficients were estimated and genetic and phenotypic trends were predicted for average weight gain from weaning to 550 days of age (AWG) from 33,267 animals of a multi-breed Angus-Nellore population, sired by 525 bulls and raised in 37 herds in several regions of Brazil, from 1987 to 2001. MTDFREML was used for estimating the (co)variance components utilized to estimate the genetic direct and maternal heritability coefficients and to predict the breeding values. The animal model included as fixed the genetic group of sire, dam and animal and the pos weaning year/station/herd contemporary group and the covariate weaning age, and as ramdom, the additive genetic, maternal and residual effects. The observed AWG was 384.22g, 1999 presented the highest (484.04g) and 1992 the lowest value (299.42g). The direct heritability was 0.30 +/- 0.11, the maternal h 2 was 0.29 +/- 40.07 and the average genetic value was -0.827g. The estimated genetic trend for AWG was -0.029g (P<0. 08) and the phenolyoic trend -was 5.68g (P<0.05). A phenotypic progressjbr average weight gain from weaning to 550 days of age occurred as a consequence of an environmental improvement, and the esthnatedgenetic progress was close to zero.