Abstract: The aims of this study were to investigate the importance of maternal effects and to determine the most appropriate model of analyses for early growth traits of Arabi lambs. Records of 2445 lambs from 139 rams and 804 ewes for Birth Weight (BWT) on 2237 lambs from 127 rams and 784 ewes for Weaning Weight (WWT) and on 2098 lambs from 115 rams and 739 ewes for Average Daily Gain from birth to weaning (ADG) were used in this research. The data collected from Animal Science Research Station of Agricultural and Natural Resources Ramin (Khuzestan) University during 2001-2008. Genetic parameters were estimated by derivative free restricted maximum likelihood method. Six different animal models were fitted by including or excluding maternal genetic effect, maternal permanent environmental effect and covariance between direct-maternal genetic effects. On the basis of log likelihood ratio test results, Model 3 which included direct genetic and maternal genetic effects was determined to be the most appropriate model for all traits. The maternal genetic effects contributed about 74, 69 and 64% to the direct genetic effects and 15, 11 and 10% to the phenotypic variance for BWT, WWT and ADG, respectively. Depending on the model, the estimates of maternal heritability ranged from 0.074-0.146 for early growth traits of Arabi lambs. Results showed that maternal genetic effects were important for pre-weaning growth traits and should not be neglected from the model; therefore inclusion of maternal effects into the model for mentioned traits is necessary.
K. Mohammadi, A. Aghaei, M. Bojarpour, Kh. Mirzadeh and Gh. Motaghinia, 2010. Investigation of Maternal Effects on Early Growth Traits in Arabi Lambs, Using Single-Trait Animal Models. Journal of Animal and Veterinary Advances, 9: 1712-1716.