Bayesian analysis of direct and maternal effects for birthweight in Iranian buffaloes using Gibbs sampling

Abstract

Calving records from April 1994 to March 2010 comprising 8570 calving events from the first three parities of 734 buffalo herds of Iran were analysed using a linear animal model to estimate variance components and heritability for birthweight. A linear animal model including direct and maternal genetic effects with covariance between them and maternal permanent environmental effect was implemented by Gibbs sampling methodology. A single Gibbs sampling chain with 500 000 rounds was generated by the Threshold Model program. Posterior means of direct and maternal heritabilities and repeatability for birthweight were 0.21, 0.15 and 0.23, respectively. Estimate of correlation between direct and maternal genetic effects for birthweight was –0.71. Also, the ratio of permanent environmental variance to phenotypic variance was 0.02. Along with the direct genetic effects, the contribution of maternal effects to the phenotypic variance of birthweight may provide producers with information to optimally use the reported estimates when making selection decisions. The results of this study indicated that exploitable genetic variation observed for birthweight could be considered in designing future selection programs for Iranian buffaloes and improvement in birthweight could be attained by genetic selection.