Direct and maternal genetic effects and their tendencies in weights at the weaning of Nellore Polled bovines, in the Goiás Brazil cattle area

Abstract

The objective of the present research was to estimate the genetic parameters of the
variation of the weaning weight of polled Nellore cattle been born in five mega regions of Goiás
Brazil, between 1977 and 2000. Estimates of genetic parameters were obtained through Animal
Model system. In the model fixed effects of contemporary groups, area, age of dam, and random
additive genetic effects of animal (direct, maternal and permanent environmental) were included.
Genetic trends for direct and maternal effects were estimated by the weighed regression of the
annual breeding value (direct and maternal) means on the year of birth of the animals. Heritability
estimates of the genetic direct and maternal effects were 0,17 and 0,14, respectively. The esteemed
genetic trends of the direct and maternal effects were 0,53 kg/year and 0,13 kg/year, respectively.
The results indicate the existence of enough genetic variability to promote the genetic earnings
through the selection.