The aim of this study was to apply Simple Repeatability Model (SRM) and Random Regression Models (RRMs) to describe growth curve of Afshari lambs. Results revealed the inadequacy of SRM to model variation in growth curve of Afshari lambs. A RRM with orders 3, 2, 3, and 2 for direct genetic, direct permanent environment, maternal genetic and maternal permanent environmental effects was selected as the parsimonious model. Direct heritability (h2) and maternal permanent environmental effect (c2) were maximal at 98 days of age, and decreased with age until the end of growth trajectory. Direct permanent environmental effect (p2) and maternal heritability (m2) were minimal at 98 days of age, but increased thereafter to a peak at 525 days of age. In conclusion, results revealed substantial genetic potential for selection responses in early growth of Afshari lambs and that this genetic potential can be exploited by breeders to improve growth performance of Afshari lambs.
