Estimates of (co)variance components for production and reproduction traits with different models in Fars native fowls

Abstract

The estimates of direct and maternal genetic, in addition to maternal common environmental effects were considered for body weight at 1 day of age (BW1), body weight at 8 weeks of age (BW8), body weight at 12 weeks of age (BW12), egg weight at first day of laying (EW1), egg number (EN), mean egg weight at 28th, 30th, 32nd weeks (MEW), age at sexual maturity (ASM) and weight at sexual maturity (WSM) records on 44,390 Fars native fowls. Data were analysed with a series of 6 different single-trait animal models which included or excluded the maternal effects for all traits, using an AI-REML algorithm. For each trait, the most appropriate model was chosen based on likelihood ratio tests (LRT). Based on the most appropriate fitted models, direct heritability (h2) estimates ranged from 0.14 (BW1) to 0.64 (MEW). Both maternal genetic and common environmental effects were statistically significant for all of the studied traits except for EN. The estimates of maternal heritability (m2) ranged from 0.02 (MEW) to 0.32 (BW1), and the estimates of maternal common environmental variance as a proportion of phenotypic variance (c2) ranged from 0.02 (BW8, BW12, WSM, EW1 and MEW) to 0.25 (BW1) based on the fitted models. Correlation between direct and maternal additive genetic effects (ram) was significant for WSM, ASM, EW1 and MEW, and was negative for all of the studied traits. Overall, it was concluded that for more precise designing selection programs and increased efficiency of selection for production and reproduction traits of fowls, inclusion of maternal effects and direct genetic effect into the model is necessary.