Comparison different models for estimation genetics parameter of growth traits with the likelihood ratio test in Kermani sheep breed

Data of Kermani sheep which collected during 2003-2009 were used in this study. The data included birth weight (BW)، weaning weight (WW)، six month weight (6MW)، nine month weight (9MW) and yearling weight (YW) traits. Estimate of (CO) variance component with the DFREML program and animal model with unitrait and multitrait analysis. In this study، fitting six different animal models and significant effects on the models were tested by likelihood ratio. In this breed، direct additive genetic analysis without other random effects result in overestimated direct heritability. underestimate the maternal effect especially، maternal additive effects، with and without genetic covariance effect، showed that a significant portion of phenotypic variance of body weight at different ages، especially before weaning due to maternal genetic effect. Estimate direct Heritability of the traits by univariate analysis was 0. 003، 0. 1، 0. 08، 0. 0006 and 0. 06، respectively. Direct heritability results by multitrait analysis was 0. 42، 0. 17، 0. 09، 0. 02 and 0. 11، respectively. Genetic correlation between BW with WW and 6MW were 0. 33 and 0. 15 and the correlation for BW and YW was 0. 09. phenotypic correlations between yearling weight، BW and WW were 0. 01 and 0. 09 respectively، and the other traits were negative correlation. This result indicate sever weight changes controlled by environmental conditions.