Random regression models for estimation of covariance functions growth traits in Iranian Kurdi sheep

Body weight (BW) records (n=۱۱,۶۵۹) of ۴۹۶۱ Kurdi sheep from ۲۱۵ sires and ۲۰۸۵ damswere used toestimate the additive genetic, direct and maternal permanent environmental effects on growth from ۱ to ۳۰۰ days of age. The data werecollectedfrom۱۹۹۳ to ۲۰۱۵at a breeding station in North Khorasanprovince; Iran.Genetic parameters for growthtraits were estimated using random regression test-day models. The model ۱۶ with a polynomial of ۳ order for fixed effect, ۶ order for direct genetic effect, ۶ order for direct permanent environmental and ۶ order for maternal permanent environmental effects with the lowest Bayesian information criterion (BIC) was considered to be the best model.Genetic correlations ranged from ۰.۰۳ to ۰.۹۸ for body weight between different days of age. The small value of genetic correlation (۰.۰۳) among early (day ۱) and late (۳۰۰ days) weights showed that early weights werenot under the same genetic control as weights at older ages.

Keywords:

Kurdi sheep , growth traits , Legendre polynomials