Estimates of some environmental factors and genetic parameters on Lori-Bakhtiari lambs survival

Data and pedigree information for Lori-Bakhtiari sheep used in this study were 6241 records of lamb survival from 1721 dams and 246 sires collected from 1989 through 2007، from a Lori-Bakhtiari flock at Shooli station in Shahrekord. To estimate the effect of environmental factors on survival lambs used GLM procedure from SAS. The models included fixed factors that had significant effects and random direct genetic، maternal genetic and residual effects. Genetic parameters were estimated using restricted maximum likelihood procedure applying univariate animal models with and without maternal effects and repeatability model. Results showed that the overall mean of cumulative lambs’ survival were 0. 98، 0. 97، 0. 97، 0. 95، 0. 94، 0. 90، 0. 82، 0. 78، 0. 75، 0. 72، 0. 69، 0. 68، 0. 68، and 0. 68 from birth up to 7، 14، 21، 30، 60، 90، 120، 150، 180، 210، 240، 270، 300، 330 and 365 days of age، respectively. The age of dam، sex of lamb، year of birth and birth weight of lamb as covariate had a significant (p<0. 05) effect on lamb survival، but the type of birth was not significant. The least square means of lamb survival increased with age of dam and then decreased in dams with more than 5 years old. The least square means of lambs’ survival in females was higher than the male lambs from birth up to 12 months of age. The birth weight of lamb had a highly significant (P≤0. 01) effect on lamb survival at all ages as quadratic regression. Direct and maternal heritability estimates of lamb survival ranged from 0. 01 to 0. 22 and 0. 01 to 0. 04، respectively. Direct heritability increased with age of lamb، while maternal heritability decreased. The repeatability estimate of lamb’s survival from birth to 12 months of age was 0. 48.