The Ayrshire breed is a highly specialized breed of dairy cattle, characterized by high milk production,
resistance to infectious diseases, productive longevity, good fi tness, reproduction and
feed conversion and has plasticity of the gene pool. The modern gene pool of the Ayrshire cattle
may contain the blood of red breeds: Swedish Red, Norwegian Red, Ayrshire of American
origin, often derived from admixture of the blood of the Red-and-White Holstein and Brown
Swiss breeds. In the breed, there is a tendency toward decreasing the fertility of cows and calves,
caused by LOF-mutations that lead to embryonic losses or that are manifested postnatally as
genetic defects. PIRM syndrome of the Ayrshire cattle, manifested in the violation of development
and early death of young animals in Ayrshire herds, is due to the homozygous state of
the gene UBE3B for the mutant allele and is an autosomal and recessive defect leading to the
appearance of AH1 fertility haplotype in the Ayrshire cattle. The goal of our work was to study
the prevalence of AH1 fertility haplotype in the Russian population of the Ayrshire cattle in the Central and Northwestern regions of Russia; the work was carried out by solving a number of
problems (theoretical modeling and practical testing of allele-specifi c polymerase chain reaction,
experimental testing of animals of the Ayrshire breed, and subsequent monitoring of the
distribution of AH1 haplotype in the population of the Ayrshire cattle in four regions of Russia).
The study of 259 cows and 28 seed bulls bred in four regions of the Central and Northwestern
regions of Russia revealed the presence of 47 hidden carriers of AH1, including 37 cows and 10
bulls, which corresponds to the frequency of occurrence equal to 14.3 and 35.7%, respectively,
and on average in the breed – 16.4%. Seed bulls of fi ve stud farms, carriers of AH1 haplotype,
belong generally to the line of O.R. Lichting (Lightning) 120135, code 19. The results of the study
of UBE3B gene polymorphism and the frequency of occurrence of AH1 haplotype carriers in
breeding herds of the Ayrshire dairy cattle in Russia will be used in breeding work with the breed
Keywords
ayrshire breed, lof mutations, ube3b gene, ah1 fertility haplotype