Impact of maternal components on fitting of animal models in genetic parameters estimation for body weight traits in Rahmani lambs

The present research was undertaken to determine the effect of application animal six models including or ignoring maternal genetic and/or maternal permanent environmental effects based on single and multi-trait animal model analyses and choose the most efficient method of selection to improve body weight traits in Rahmani lambs on genetic base. Current findings pointed to increase phenotypic variances of weight traits by increasing lamb’s age. Maternal environmental effects shared approximately 13% (ranged from 11% to 20%) of the whole phenotypic variation for body weight traits in multi-trait analysis and thereafter declined significantly for all the traits especially in single- trait analysis. The results show the significance of including at least one maternal component with covariance between direct and maternal effect for genetic evaluation body weight traits and high direct heritability estimates denoted possibility to use weight traits as selection criteria due to their direct response to genetic improvement through direct selection method and their economic importance in mutton production.