Genetic diversity and effect of inbreeding on litter size of the Romanov sheep

The objective of the present study was to describe the population structure and quantify the effect of inbreeding on litter size in Romanov sheep in the Czech Republic. The analysis was based on the pedigree information of 26,447 animals. The numbers of generations were 19, with average equivalent known generations of 6.41. The effective numbers of founders and ancestors contributing to the current genetic pool were, respectively, 92.96 and 47.41 respectively. The average inbreeding coefficients were 5.5% and the average inbreeding rate was 1%. The corresponding estimates of effective population size were 48.28 and 45.64, based on an individual increase in inbreeding or coancestry, respectively. Classical inbreeding coefficient and two kinds of new inbreeding coefficient were used to quantify the effect of inbreeding. The effect of all tested kind of inbreeding on litter size was statistically significant, but very small (around −0.05 lambs per change of 1% in inbreeding). Statistical difference measured by ΔAICc was not-significant. These statistics suggest that the genetic variability has decreased and inbreeding depression is occurred, and without changes in breeding strategy the genetic variability might continue to decline.