The aim of the study was to study the allelic polymorphism of the growth hormone gene in a group of cows of the Montbeliard breed and to search for associations of its different genotypes with the parameters of the dynamics of milk yield during lactation. The research was conducted in the Department of Animal Genetics and Biotechnology of the Institute of Animal Breeding and Genetics of NAAS on a group of 30 cows of the Montbeliard cattle breed from PSP "Zhadkivske" of Chernihiv region. Genomic DNA was isolated from blood leukocytes by standard methods using the set "DNA-sorb-B" ("Ampli-Sense", Russia). Dairy productivity of first-born cows was determined monthly by control milkings. Types of lactation curves were studied according to the method of A. S. Emelyanov (1953). Polymorphism of the growth hormone (GH) gene in our first-born cows is represented by two alleles L I V, the frequency of which differs, and the frequencies of genotypes differ accordingly. In the studied group of animals, all possible genotypes of the growth hormone gene were identified: 25 animals (83%) have the GHLL genotype, 4 (13%) have the GHLV genotype, and only one cow has the GHVV genotype. The frequency of the L allele is 0.9, and the V allele is 0.1. The mean expectation for 305 days of the first lactation of a group of cows with the GHLL genotype was 352 kg higher than the expectations in the group of heterozygous cows with the GHLV genotype. In terms of milk fat and protein yield, cows with GHLL genotype were significantly dominated by cows with GHLV genotypes (74 kg fat and 36 kg protein, respectively, p < 0.001). Analysis of the dynamics of monthly milk yield of the studied cows for 305 days of the first lactation showed that the productivity of cows with GHLL genotype exceeds the average monthly milk yield of other groups of animals at the beginning (from 1 to 3 months), at the peak of lactation (4th month) and at the end of lactation (from 8 to 10 months). In general, during the 305 days of the first lactation, first-borns with the GHLL genotype had better milk yields compared to their peers with other growth hormone gene genotypes. Analysis of variance showed that the obtained share of variability in milking in animals with different genotypes of the GH gene is due to random factors. Analysis of lactation curves of primiparous women showed that milk yield of cows with all variants of genotypes in the GH gene gradually increased and reached its peak at 3–4 months of lactation, and then gradually decreased. This lactation curve, according to the classification of A. S. Emelyanov is characteristic of animals with high and stable lactation, and cows are able to digest food well and produce high hopes. \ Thus, a statistically significant difference in quantitative and qualitative characteristics of milk productivity of cows of Montbeliard breed with different variants of genotypes by GH gene on the example of a group of cows from "Zhadkivske" Chernihiv region suggests that the use of genetic markers, in particular the growth hormone GH selection of selection and further formation of the herd in the direction of increasing milk productivity.

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Genetic polymorphism of milk proteins, in particular kappa-casein, is of considerable research interest due to its possible associations with economically important traits of dairy cattle. The aim of the study was to determine the polymorphism of the kappa-casein gene and its association with signs of milk productivity in cows of different breeds. Polymorphism of the kappa-casein gene was studied in cows of Ukrainian red-spotted dairy (UCHERM), Ukrainian black-spotted dairy (UCHRM), Montbeliard (M) breeds and crossbred cows obtained by crossing cows of Ukrainian red-spotted dairy breed with Mongolians. DNA studies were performed in the Department of Animal Genetics and Biotechnology of the Institute of Animal Breeding and Genetics nd. a. M.V.Zubets NAAS using the PCR-RFLP method. As a result of research, three genotypes of the kappa-casein gene were identified: AA, AB, BB. Genotypes AA and AB were found in all studied groups of cows, genotype BB was found only in cows of Montbeliard breed with a frequency of 0.366. The highest hopes for 305 days of the first lactation among all studied cows were in crossbred cows with genotype AB (7029 kg), the lowest - in crossbred animals with genotype AA (6359 kg). According to the distribution of genotypes and alleles of the kappa-casein gene, domestic breeds of UCHRM and UCHERM are similar in genetic structure and have a low concentration of B-allelic variant, apparently due to the fact that these breeds were created by reproductive crossing with Holstein breed, in populations of which this allele quite low. The presence of such genotypes in the studied groups of first-borns is determined by the peculiarities of selection work in the herd of SE "DG" Niva "of the Institute of Animal Breeding and Genetics named after MV Tooth of NAAS ». Research results genotypes and alleles of the kappa-casein gene is an additional genetic characteristic of animals, which makes it possible to create herds with the desired characteristics of milk productivity