Association of the leptin gene allelic variants with dairy productivity parameters in cows of Kostroma, Yaroslavl and Black-and-White breeds of the Kostroma region

The leptin gene is one of the most valuable genetic markers that determine milk productivity, technological features of milk production and productive longevity of cattle, which is of practical importance in breeding work. Conducting marker-associated breeding based on specific signs of productivity and functional longevity of animals using related leptin genotypes contributes to the preservation and multiplication of valuable breeding resources of local cattle breeds, as well as the creation of reference cattle herds. In this work, for the first time, data were obtained on the reliable association of the leptin gene LEP-A80V locus of with economically useful traits in Russian black-and-white cows in the Kostroma region, which proves the importance of these genotypes for characterizing the breeding and productive qualities of livestock in this area. The aim of the work was to study the associative relationships of various allelic variants of the leptin gene with signs of dairy productivity of cows from breeding farms in the Kostroma region. Kostroma, Russian black-and-white and Yaroslavl cows ( Bos taurus ) from breeding farms of the Kostroma region (2019-2021), a total of 141 cows, including 33, 47 and 61 animals of the corresponding breeds were tested. The data of breeding and zootechnical records were analyzed. Milk productivity was evaluated based on monthly control milking. Whole blood for DNA isolation was taken from the caudal vein into vacuum tubes with the anticoagulant EDTA. DNA was isolated using the DNeasy blood and tissue analysis kit (QIAGEN N.V, Germany). Polymorphic variants of the leptin LEP gene were determined by real-time polymerase chain reaction (RT-PCR) at three loci, the LEP-R25C (alleles R , C ; genotypes RR , RC , CC ), LEP-A80V (alleles A , V ; genotypes AA , AV , VV ), and LEP-Y7F (alleles Y , F , genotypes YY , YF , FF ) using a DTprime amplifier (DNA Technologies LLC, Russia) and HRM (high resolution melting) technology. It was found that the allele balance at the LEP-A80V locus in Russian black-and-white cows significantly shifts towards homozygous animals, mainly of the AA genotype (0.541±0.064). Homozygous carriers of the A allele have increased milk yield of 8856 kg (a confidence interval of 8819.2-9394 kg), while heterozygous animals had the highest milk fat content of 4.05 % (a confidence interval of 3.99-4.21 %). The allele balance at the LEP-Y7F locus in all the studied groups turned out to be significantly biased to YY homozygotes (0.936-0.970), however, effect of this polymorphism on dairy traits was not revealed. Nevertheless, for Y7F polymorphism, a tendency was revealed towards increased milk yield and fat content in the Russian black-and-white first-calf cows of the YY genotype, by 2275 kg and 0.075 %, respectively. For the LEP-R25C locus, a significant shift in the allele balance occurs only in Russian black-and-white cows towards homozygosity, but no statistically significant effect of this polymorphism on milk productivity was found, probably due to an insufficient number of genotyped animals, which indicates necessity of further research at a larger population.