(Co) variance component for birth weight and mortality and evaluation of inbreeding effects on it at Zandi sheep

In this research 5633 records, which collected by Khojir Sheep Breeding Station of Tehran, during the 1994 to 2011 were used for estimate of (co)variance component and evaluation of inbreeding effects on birth weight (BW) and pre weaning mortality (PMW) in Zandi lamb. Genetic parameters were estimated using REML procedures. AIC criterion test were used to choose the most suitable model. The most suitable animal model for BW included direct additive genetic, maternal additive genetic, maternal permanent environmental and common litter effects, and suitable model for PMW were included direct additive genetic, maternal additive genetic and common litter effects. Also suitable threshold model was included sire additive genetic effects and litter effects, but the most appropriate sire model only including sire additive genetic effect. Direct and maternal heritability for BW was 0.11 and 0.08, respectively. Also, logit heritability and heritability obtained from threshold, animal and sire models were 0.14, 0.20 and 0.18, respectively. Genetic, environmental and phenotypic correlation between BW and PMW was -0.27, -0.23 and -0.28, respectively (p<0.05). The 27 percent of all animals in population were inbred. The mean of inbreeding coefficients in population and inbreed animals were 3.5 and 0.9 percent, respectively. The estimates of inbreeding depression were -3.5 g for BW and 0.1 percent for mortality, respectively (p<0.05).