Genetic analysis of longevity and lamb survival from birth to yearling in Moghani sheep

The objective of this study was to estimate genetic parameters for longevity and survival traits from birth to yearling in Moghani breed of sheep. The data set comprised of 4580 lamb survival records collected during 1994 to 2012 in the breeding station of Moghani sheep. Traits studied were cumulative lamb survival from birth up to 3 (S1), 6 (S2), 9 (S3) and 12 (S4) months of age, and corresponding longevity of lambs (L1, L2, L3 and L4, respectively). The linear and threshold animal model analyses were run using a restricted maximum likelihood method and average information algorithm (AIREML) of the WOMBAT software and MATVEC program, respectively. Also, cumulative survival traits were analysed using the sire model through the Weibull proportional hazard function of the MATVEC program. Direct heritability estimates obtained from different linear models varied from 0.004-0.021, 0.014-0.023, 0.058-0.069 and 0.006-0.061 for L1, L2, L3 and L4, respectively. Also, heritability estimates on the logarithmic scale for S1, S2, S3 and S4 obtained from the Weibull sire model were 0.57, 0.40, 0.08 and 0.03, respectively. Medium to high estimates of heritability for survival traits, employing proportional hazard models, suggest that lamb survival could be improved through direct selection within the flock.