Assessing Inbreeding Depression in Growth Traits and Efficiency of Feed Utilization of Moghani Sheep

The aim of the current study was to assessing the effect of inbreeding on growth-related traits including birth weight (BW), weaning weight (WW) and average daily gain (ADG) as well as efficiency-related traits such as Kleiber ratio (KR) and relative growth rate (RGR) of Moghani sheep. To this end, after editing data and preparing pedigree file, coefficients of inbreeding were estimated and according to them, lambs were grouped in three classes of non-inbred animals (F = 0), animals with inbreeding between 0 and 5% (0 5%), and then their growth and efficiency of feed utilization were compared using mean of traits in three mentioned groups. Instead of using raw inbreeding coefficients, inbreeding depression was studied by regressing traits on coefficients of individual increase in inbreeding ( ) in an animal model framework in which was fitted as auxiliary variable. The average inbreeding of the whole population was 0.3% and for the inbred animals was 1.99%. Inbreeding trend over years was non-significant (0.07 per year). Estimated value of the effective population size (Ne) was 107. Inbred animals had lower birth weight, weaning weight and average daily gain compared to non-inbred animals and also regarding efficiency of feed utilization which was measured by Kleiber ratio and relative growth rate were at the lower level, although the differences between inbred and non-inbred animals were non-significant (p>5%). Regression analysis showed that with 1% increase in inbreeding, BW, WW and ADG decreased by 18, 31 and 0.31 gr, respectively. This was 0.24 and 0.03 for KR and RGR. Low level of inbreeding in the population and higher than critical threshold estimate of Ne showed that genetic diversity in the population was at the acceptable level. However, it was suggested that applied strategies for avoiding inbreeding should be continued to prevent the increase in inbreeding rate in the future.