Influence of the degree of homozygosity of STR-loci on the fertility of thoroughbred horses

Abstract

Purpose: to study the effect of the level of homozygosity and inbreeding on the fecundity of thoroughbred mares.Materials and methods. A total of 3662 heads of breeding sows from leading stud farms of the Russian Federation were selected for the analysis. The influence of the homozygosity level on 17 microsatellite DNA loci on the main indices of reproduction of thoroughbred mares, such as the safe yield of foals and the number of fetal years, was analyzed in the article. All mares in the experimental sample had at least three years of breeding use. Individual fecundity rates and the number of homozygous loci in the STR profile were calculated for each horse.Results. The highest live foal yields (75.92%) had sows with homozygosity levels of 62.78-69.02%, and the lowest foal yields (45.73%) were recorded in mares with the highest homozygosity levels (75.28-76.92%). The maximum foal yield (65.85%) was determined in sows with an inbreeding rate of 4.1% or more, with a productive longevity of 6.26 fetal years on average. Analysis of the data showed that the level of inbreeding had almost no effect on the yield of live foals (R=0.010 at P>0.05), but had a negative correlation with the number of fruiting years (R=-0.092 at P<0.005).Conclusion. Estimation of homozygosity level of thoroughbred horses is especially relevant, as this breed has been perfected by purebred breeding method only for more than thirty years. In the thoroughbred horse breed, it is necessary to create a system of maintaining heterozygosity as well as the diversity of genotypes through the organization of breeding work.