estimation of genetic parameters for lamb survival in zandi sheep breeds using animal, sire and threshold models.

in this research, 6517 records, collected by khojir sheep breeding station (tehran, iran), during 1991 to 2011 were used to estimate genetic parameters of lamb survival in zandi sheep. genetic parameters were estimated using 16 different models of animal model, sire and threshold models using reml procedures. the aic criterion was used to evaluate the models. the effects in the most suitable animal model were included direct additive genetic, maternal additive genetic and permanent environmental effects. the effects in the most suitable sire model were included sire additive genetic effects and maternal common litter effects. the effects in the most suitable threshold model were included only sire additive genetic effect. the estimated heritability of lamb survival based on animal, sire, and threshold models were 0.09 ± 0.001 and 0.13 ± 0.02, and 0.19 ± 0.06, respectively.