| Summary: | The purpose of the study was to analyze the microsatellite profile of sheep of different breeds and directions of productivity, to characterize them by reproductive abilities and to identify a possible relationship between the level of heterozygosity by microsatellite loci with some signs of fertility. Methodology. The object of the study were three groups of ewes: purebred Romanov breed (50R/50R, n = 31), two-breed crossbreeds of the Pechora semitonkorn with the Kuibyshev breed (50P/50K, n = 41) and three-breed crossbreeds obtained from crossing two-breed crossbreeds with the Romanov breed (25P25K/50R, n = 20). Each breed group of ewes, depending on the level of heterozygosity, was divided into three classes: modal – M0, with heterozygosity below the modal class – M– and above – M+. Results. The genetic distances between the 50P/50K and 50R/50R groups were established: FST = 0.390 ± 0.0062, DN = 0.242 ± 0.0479, 50P/50K and 25P/25K/50R: FST = 0.033 ± 0.0058, DN= 0.218 ± 0.0429, 50R/50R and 25P/25K/50R: FST = 0.022 ± 0.0058, DN = 0.127 ± 0.0292. According to all the analyzed reproductive characteristics, except for the survival rate of the offspring, Romanov sheep had a significant advantage over other groups. The 25P/25K/50R crossbreeds were characterized by an increased average observed heterozygosity by markers and a significantly higher average age of the beginning of reproduction, which was higher than the indicator characterizing the most late-maturing parent group. Inheritance of other reproductive traits in the 25P25K/50R group, excluding the age of onset and the rate of reproduction, was intermediate with some regression at 50P/50K. Scientific novelty. Scientific novelty. The possible influence of the level of average heterozygosity at 12 STR loci on the fertility of ewes was analyzed. Practical significance. In all groups of ewes, the rank of the reproductive characteristics of the modal class M0 was higher than that of M– and M+. The repeatability of the relationship of fertility indicators with ...
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