Study of genetic relationship between longevity and body weights in Guilan province native sheep

The aim of this study was to estimate genetic parameters associated with longevity and body weights and analysis of longevity in the Guilan province native sheep. The data set included full information of pedigree, sex, year, month and day of culling, dam age, year, month and day of birth, type of birth, and birth weight, 3 and 6-month weight. In order to study genetic relationship between longevity and body weights at different ages, bivariate linear-linear models and AIREML algorithm of WOMBAT software were used. The models included the fixed effects of year and month of birth, sex, type of birth, dam age and linear effect of birth weight as covariate. Direct heritability of longevity was low and equal to 0.03. Althogh direct heritability of birth weight 3 and 6-month weight were equal to 0.13, 0.022 and 0.097 respectively. Also, direct genetic correlation between longevity-birth weight, longevity-three month weight and longevity-six month weight were estimated to be -0.081, 0.91 and -0.90, respectively. Negative correlations indicated that lambs with high birth weight and lambs with high weight in 6 month due to culling from flock don’t have high longevity. Because of the low heritability of longevity, for improving the longevity of lambs from birth to yearling age, environmental and management conditions should be improved and indirect selection should be conducted using the correlated traits to increase the survival rate of Guilan province native lambs.