estimation of genetic parameters for pre weaning growth traits and lamb survival in iran black sheep

the aims of this research were to estimate of genetic parameters for pre-weaning traits and lamb survival in iran-black sheep. for this purpose 6344 records for birth weight (bw) and lamb survival (ls) and 5264 records for weaning weight (ww), average daily gain (adg) and kleiber ratio (kr) were available, which collected by abbasabad animal breeding and rearing station, over the period from 1984 to 2010. for pre weaning traits only animal model, and for lamb survival animal, sire and threshold model were fitted. direct heritability for bw, ww, adg and kr were 0.05±0.01, 0.12±0.03, 0.11±0.03 and 0.10±0.03, respectively. genetic parameters were estimated by using of reml procedures. akaike’s information criterion (aic) test was used to choose of the most suitable model. heritability estimate for lamb survival with animal and sire model was 0.09±0.01 and 0.07±0.01, which after correction was increased to 0.22 and 0.17. also, the estimation of heritability from threshold model was 0.21±0.08. therefore, underlying heritability obtained from animal and sire models are not deviated from the heritability estimate from the threshold model. the genetic correlation between bw-ww, bw-adg, bw-kr, bw-sl, ww-adg, ww-kr and adg-kr were 0.98, 0.99, 0.64, 0.96, 0.99, 0.31 and 0.92 respectively.