Comparison of different models for estimation of genetic parameters of early growth traits in the Mehraban sheep.

Genetic parameters for birth weight (BW), weaning weight (WW) and pre-weaning daily gain (PWDG) in Iranian Mehraban sheep were estimated using restricted maximum likelihood (REML) procedure. Six different animal models were fitted, differentiated by including or excluding maternal effects, with and without covariance between maternal and direct genetic effects. The estimates for direct heritability ranged from 0.26 to 0.53, 0.18 to 0.32 and 0.15 to 0.33 for BW, WW and PWDG respectively. The estimates were substantially higher when maternal effects, either genetic or environmental, were ignored in the model. The results of this study show that full models with maternal genetic and environmental effects gave the most accurate estimates for early growth traits.