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The research presents the findings of DNA testing of allelic polymorphism by the PCR-RFLP method of the SCD1 gene and the relationship of genotypes with the milk fatty acid composition of Holstein cows of Tatarstan population. The research was conducted among 172 Holstein cows at the Integrated Agricultural Production Centre “Stud farm named after Lenin” in Atninsky district of the Republic of Tatarstan in 2017–2018. All genotypes of the SCD1 gene were identified through the research. The milk yield test showed that the maximum content of the mass fraction of fat was in animals with the TT genotype. The significant difference between the content of the mass fraction of fat in milk in individuals by the locus of the SCD1-Fsp4H I gene was: TT to CC – 0.32 % (p < 0.05) and TT to TC – 0.40 % (p < 0.01). The results of chromatography indicate the balance of the milk fatty acid composition of cows with the TT genotype and, as a consequence, its positive effect on the human body. Cows with a homozygous TT genotype are characterized by the optimum ratio of fatty acids in milk fat. The maximum value of the oxygen desaturation index is also observed in animals with the TT genotype by the SCD1 gene.

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The study presents the results obtained in the course of DNA testing of allelic polymorphism by PCR-RFLP on CSN3 and LGB genes and the associations of their complex genotypes to the indicators of milk productivity of Holstein cow-heifers.Genetic polymorphism was detected by digestion with the endonucleases Hinf I (CSN3) and Hae III (LGB). All integrated CSN3/LGB genotypes were identified during the work. The maximum frequency of occurrence is observed in a combination of heterozygous AB/AB genotypes – 120 animals (25.5%), which is the fourth part of the studied cattle population. The group of animals with homozygous BB/BB genotypes of CSN3/LGB genes is the smallest one – 10 animals (2.1%). Milk productivity test, based on the complex CSN3 and LGB genotypes is observed in heifers with an integrated combination of CSN3BBLGBAAshowed that a significantly high level of productivity for 305 days of lactation – 7239.8 kg, and a minimum level of productivity (6222.9 kg) is observed in heifers with the complex CSN3BBLGBAB genotype, compared with indicators of milk yield of cow-heifers with other integrated genotypes. According to the content of the mass fraction of fat, the best indicators were established in the subpopulation of animals with the complex AA/AB genotype – 3.90%, and the worst result was recorded in the group of animals with the complex AB/AA genotype, which amounted to 3.44%. The high content of the mass fraction of protein was observed in individuals by the complexof the CSN3 and LGB genes BB/AA – 3.43%, and a reduced level of protein was observed in heifers with a combination of homozygous AA/AA and BB/BB genotypes by the genes under study – 3.18%. Thus, individuals carrying the homozygous A allele of the kappa-casein (CSN3) gene and the homozygous B allele of the beta-lactoglobulin (LGB) gene in the integrated genotype favorably differed on the main indicators of milk productivity.

МОНИТОРИНГ ВАРИАБЕЛЬНОСТИ АЛЛЕЛЕЙ ГЕНА ЛЕПТИНА (LEP) КРУПНОГО РОГАТОГО СКОТА В ЗАВИСИМОСТИ ОТ НАПРАВЛЕНИЯ ПРОДУКТИВНОСТИСафина Н.Ю.Реферат. Для управления биоразнообразием сельскохозяйственных животных и распределе-ния хозяйственно-полезных признаков продуктивности среди популяций крупного рогатого ско-та необходимо использовать достижения молекулярной генетики, основанной на отборе создания ДНК-маркеров. Ген лептина, играющий главную роль в метаболизме и накоплении жира, являет-ся одним из потенциальных маркеров молочной продуктивности крупного рогатого скота. Для исследования были генотипированы 301 корова-первотелка голштинской породы СХПК «ПЗ им. Ленина» Атнинского района РТ. Проведен мониторинг вариабельности аллелей гена лептина крупного рогатого скота в зависимости от направления продуктивности у разных авторов. В ходе работы были идентифицированы следующие аллельные варианты и генотипы: C -0,58 и T -0,42; CC -29,9% (90 гол.), TC -55,5% (167 гол.), TT -14,6% (44 гол.). Тестирование методом хи-квадрат между наблюдаемым и ожидаемым распределением генотипов свидетельствует о генети-ческом равновесии в исследуемой популяции. Анализ ранжирования аллелей C и T у других ав-торов показало преобладание благоприятного для оценки молочной и мясной продуктивности аллеля LEP C , что может быть результатом направленной селекции по желаемому хозяйственно-полезному признаку среди молочных и мясных пород крупного рогатого скота. Полученные в ходе работы данные предполагают возможность использования генно-маркерной селекции при составлении планов животноводческих мероприятий.Ключевые слова: лептин, аллель, генотип, полиморфизм, ПЦР-ПДРФ, продуктивность, се-лекция, крупный рогатый скот.

The efficiency of selection and breeding work in animal husbandry depends largely on the accuracy of the evaluation of the breeding value of animals. The integration of molecular genetics into applied science made it possible to assess the genetic potential of animal productivity not only on the basis of phenotype data but also directly at the DNA level. The study was conducted on the basis of Tatar Scientific Research Institute of Agriculture, FRC Kazan Scientific Center, Russian Academy of Sciences. The object of the study was DNA samples obtained from the blood of Holstein cows belonging to the stud farm “named after Lenin” of Atninsky district of the Republic of Tatarstan. Animal blood was taken from the tail vein using vacutainer tubes with 100mM EDTA. DNA was isolated from the blood in the amount of 100 µl using a set of reagents for DNA extraction from the “Ampliprime DNA-sorb-B” clinical material (NextBio, Russia), according to the method presented by the producer. DNA fragment amplification was performed in T100 Thermal Cycler (Bio-Rad, USA) and on MyCycler programmable Thermal Cycler (Bio-Rad, USA). After amplification, each DNA fragment obtained by us in the study of TG5, CSN3, LGB genes, was subjected to cleavage by a restriction endonuclease. Hydrolysis was conducted at 37°C for 12 hours. The analysis of polymorphism of candidate genes of dairy productivity of leptin, thyroglobulin, kappa casein and beta-lactoglobulin with the use of PCR-RFLP was carried out. The most common were homozygous TG5CC, CSN3AA and heterozygous LEPCT, LGBAB genotypes. The study of the effect of polymorphism of these genes on milk production showed that animal carriers of LEPCT, TG5TT, CSN3AB, LGBBB genotypes have the best indicators of dairy productivity.

The study examined the effect of polymorphism of the fibroblast growth factor 21 gene (Bos taurus FGF21 g.940 C/T) on the level of FGF21 and biochemical metabolic parameters in blood serum of highproducing cows. DNA genotyping of 148 animals of Holstein cows was performed by a PCR-RFLP method. As a result of genotyping, two FGFC – 0.642 and FGFT – 0.358 alleles as well as two FGFCC – 28.4% (42 animals) and FGFTC – 71.6% (106 animals) genotypes were identified. Individuals with the FGFTT genotype were not identified. The obtained data show that the seroen zyme FGF21 level is statistically significantly higher in cows with the FGF21CC genotype than in cows of the heterozygous genotype by 165.5 pg/ml (28.2%; p < 0.001). Analysis of the association between the polymorphism of the FGF21 gene and the level of fibroblast growth factor 21 suggests that the activity of this enzyme changes depending on the genotype, as a result of which there is a variation in serum biochemical parameters of Holstein cattle.

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