Inbreeding and Inbreeding Depression on Body Weight in Iranian Shal Sheep

The aim of this study was to estimate amount of inbreeding coefficient in Shal sheep and its impact on growth performance. Pedigree information and body weight at different ages (birth weight, 3 month weight, 6 month weight, 9 month weight and 12 month weight) were used from 6692 lambs from 90 rams and 1007 ewes. Data were collected on Ghazvin sheep breeding station during 1997-2013. Estimation of inbreeding coefficient was done by CFC program and quantifying the individual inbreeding regression of traits was run by wombat software. Number of inbred animals at pedigree was 1616 lambs, equal to 24.15% of total population. The average of inbreeding coefficient on whole population and inbred population were 1.51% and 6.28%, respectively. Regression coefficients per 1% inbreeding for birth weight, 3 month weight, 6 month weight, 9 month weight and 12 months weight were estimated as -0.001, -0.017, -0.005, -0.019 and -0.019 kg, respectively. The highest inbreeding coefficient was 31.25% and most of inbred animals had inbreeding coefficients lower than 5%. These results confirmed the low level of inbreeding in the population. Annual trend of inbreeding coefficient on population average was 0.07 and non significant statistically. Applying a designed mating system like cross-breeding could be a suitable method to avoid inbreeding depression.