Effective Factors on Genetic Parameters of Day-Old Chicken Body Weight in a Commercial Broiler Line

Genetic and non-genetic factors on day-old chicken body weights (BWT1) were investigated in a commercial broiler line with restricted maximum likelihood (REML) procedures. Ten different animal models were used to estimate the genetic parameters. All models consisted of the direct additive genetic effect but differed in combinations of maternal additive genetic, maternal environmental, generation-hatch-sire interaction (GHS) and covariance between direct and maternal genetic effects (covam). When covam was considered in the models, higher estimations of direct and maternal genetic variances were obtained that could be because of negative covariance between these effects. Also adding GHS factor in analysis reduced the covam. Although GHS variance represented only 5% of the phenotypic variance, but ignoring it in the models made up 70% of negative covariance between direct and maternal genetic effects. Based on the full model, direct heritability (h2a), maternal heritability (h2J, maternal environmental variance as a proportion of the phonotypic variance (c2), GHS variance as a proportion of the phonotypic variance (s2) and direct-maternal additive genetic correlation (ram) were estimated 0.02, 0.411, 0.107, 0.046 and -0.168, respectively.