Genotyping of the leptin gene locus (LEP) (SNP: R25C, Y7F, and A80V) has been conducted in cows from two cattle droves (n = 106 and n = 34) and in bulls of Ayrshire cattle (n = 9) that are intensively used at present for artificial insemination in cows in Krasnodar krai. The absence of A80V polymorphism (C→T at position 95691973 bp of leptin gene) has been established in the genotypes of Ayrshire cattle as com pared to Holstein cattle; however, the F allele (Y7F site A→T at position 95689996 bp of LEP gene), which is rare in Holstein cattle, was shown to be frequent in Ayrshire cows and producer bulls (with a frequency of 0.22-0.79). The heterozygosity did not exceed 0.11 in adult animals, which might be evidence of a decreased vitality in animals bearing the FF genotype. Moreover, the CC genotype (R25C site T→C at position 95690050 bp of LEP gene) was revealed to be linked to the YY genotype (Y7F site) in 97% of cases from pos sible combinations of the CCYY, CCYF, and CCFF genotypes, while the FF genotype (Y7F site) was observed to be linked to the RR genotype (R25C site) in 100% of cases of possible combinations of FFCC, FFRC, and FFRR genotypes.

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