Estimation of Genetic Parameters for Survival and Birth Weight in Moghani Sheep

Genetic parameters for birth weight and survival traits were estimated using data collected from 1995 to 2009 in Jafarabad Moghani Sheep Breeding Station. Number of observation for survival and birth weight were 7202 and 6585, respectively. Genetic parameters were estimated using restricted maximum likelihood (REML) procedure under 16 different models, including animal, threshold and sire models using ASReml software. The most appropriate model for each trait was determined based on Akaike’s Information Criterion (AIC) method. The appropriate model for birth weight was included direct additive genetic, maternal additive genetic and common litter effects. Also, the animal model for lamb survival were included direct additive genetic, maternal additive genetic, maternal permanent environmental, common litter effects and covariance between direct and maternal additive genetic effects. The appropriate sire model for lamb survival was included sire direct additive genetic and common litter effects. Estimated direct heritability for birth weight was 0.09±0.02. The direct heritabilities for survival with animal model and sire model was 0.070±0.002 and 0.05±0.02, which after correction was changed to 0.22 and 0.15, respectively. Also, the estimation of heritability for lamb survival from threshold model was 0.30±0.10. Genetic, environmental and phenotypic correlation between birth weight and lamb survival were 0.61±0.24, 0.08±0.02 and 0.07±0.01, respectively. Consideration of environmental factors, including common litter effects, is essential for unbiased estimation of genetic parameters.