The impact of Maternal Effects on Genetic Parameters of Performance Traits in a Commercial Broiler Dam Line

In this study, the effect of maternal additive genetic and environment on body weight at 6 weeks (BWT6W), breast width (HBRS), carcass weight (CARCWT), breast weight (BRSWT), blood hematocrit value (HEM), residual feed intake (RFI), daily feed intake (DFI) and average daily gain (ADG) were investigated in a commercial broiler dam line. With and without maternal effects, six different animal models were taken into account, and the most appropriate model chosen as based on likelihood ratio test. Data were analysed through animal model, DMU software. As for BWT6W, HBRS, RFI, DFI and ADG, direct and maternal additive genetic effects with direct-maternal additive genetic covariance and maternal environmental effects (model 8) were significant (P<0.01). Based on this model, direct and maternal heritabilities along with maternal environmental variance as a proportion of phenotypic variance were 0.328, 0.026, and 0.029 for BWT6W, 0.366, 0.039 and 0.029 for HBRS, 0.309, 0.018 and 0.023 for RFI, 0.319, 0.017 and 0.026 for DFI and 0.257, 0.026 and 0,025, for ADG, respectively. As for CARCWT and BRSWT, the important effects were direct additive genetic, maternal additive genetic and covariance between direct and maternal additive effects (model 4). Under this model, estimates of direct and maternal heritabilities were 0.326 and 0.073 for CARCWT vs. 0.485 and 0.036 for BRSWT, respectively. For HCT, none of the maternal effects were significant (P>0.05).The results indicated that ignoring maternal effects in the analysis tended to overestimate direct additive genetic variances as well as their corresponding heritabilities for all the traits.