Maternal Effects on Production and Reproduction Traits in Mazandaran Native Fowl

Maternal effects on body weight at 8 weeks of age (BW8W), egg weight (EW), egg number (EN) and age at sexual maturity (ASM) from 13 generations of Mazandaran native fowl were investigated. The data were analyzed using restricted maximum likelihood procedures and animal model with DFREML software. With or without using maternal effects, six different animal models were fitted. Likelihood ratio test wase employed to determine the most appropriate model. For all traits, maternal additive genetic and environmental effects together with the covariance between direct and maternal additive genetic effects were important. Direct heritability (h2a) ranged from 0.130 (for EN) to 0.506 (for EW). These estimates for maternal heritability (h2m) and maternal environmental variance as a proportion of the phenotypic variance (c2) varied from 0.008 (for EW) to 0.034 (for ASM), and 0.020 (for EN) to 0.047 (for BW8W), respectively. Also for all traits c2 was higher than h2m. The correlation between direct and maternal additive genetic effects (ram) were all negative and -0.737, -0.692, -0.590 and -0.396 for EN, EW, ASM and BW8W, respectively. The results indicated that ignoring maternal effects in the analysis of BW8W tended to overestimate direct additive genetic variance and heritability, but for EW, EN and ASM ignoring the covariance between direct and maternal additive genetic effects caused a decreased in those estimates.