Estimation of genetic parameters of growth traits in Moghani sheep using random regression model

In order to estimate genetic parameters of body weight trait using random regression model 19388 test day records from 6013 Moghani sheep which were collected at Moghan Research Station located in Ardebil province, Iran, during 1995 to 2009 were used. In the model, year-season, birth year-season, sex of lamb, birth type and dam parity were classified as fixed effects and age of dam at parturition and age of animal were as covariates. Random effects of model were direct additive genetic effect, maternal additive genetic effect, direct permanent environmental effect and residual effect. Model 9 with 2nd order of fit for genetic effects and 4th order of fit for permanent environmental effect and 21 parameters was considered as the most appropriate model. Direct heritability estimated for weight at birth, 90, 180, 270 and 360 days were 0.069, 0.002, 0.005, 0.013 and 0.021, respectively. Results showed that direct heritability reduced after birth and reached to the lowest amount at 90 days of age, but after that increased as the age increased. Maternal heritability had considerable reduction after birth and then increased to 360 days. Weights at 270 and 360 days had the highest correlation. Commonly genetic and phenotypic correlations reduced as the age increased.