Estimation of (co) variance components and genetic parameters of some growth-related traits in Baluchi sheep considering the effect of sex-linked genes

Pedigree and weight trait records belonging to 13633 Baluchi lambs descendent from 308 ram and 3747 dam which were collected in North-east animal breeding center from years 1989 to 2021 were used. Six univariate animal models with fixed (birth year, month, type, sex of lamb and age of dam) and different random effects were fitted to data. Effects of non-genetic factors on weight traits were investigated by Proc GLM of SAS software, and to estimate the variance components the Wombat software was used. All fixed effects had significant effect on the studied traits (P<0.001). Model with additive autosomal, sex linked, and additive maternal random with covariance between direct additive genetic and maternal genetic effect had the lowest AIC and was used for genetic analysis. For birth, weaning, 6, 9 month and yearling weight respectively additive autosomal heritability were 0.16, 0.34, 0.41, 0.49 and 0.56, additive sex-linked heritability were 0.004, 0, 0, 0.007 and 0.005 and maternal heritability were 0.34, 0.38, 0.32, 0.32 and 0.36. Results showed that sex-linked genes possibly have negligible and close to zero additive genetic effects on body weights at initial ages and in comparison, more noticeable effects on body weights at higher ages. In general, it is recommended to use an animal model for genetic analysis of growth traits in sheep, which is able to separate the total genetic variance into three autosomal, sex-dependent and maternal components in order to be more effective in genetic selection.