The main task of breeding in dairy cattle breeding is to raise dairy productivity of cows. Improvement of productive qualities of domestic dairy cattle with the use of Holstein breeders of high breeding value led to serious disadvantages, including impairment of animal health, reproductive capacity and quality of milk. Therefore, the purpose of our research was to examine the milk productivity of cows of different genotypes of the Ukrainian Black-and-White dairy breed and ascertain the relationship between quantitative and qualitative indicators of milk.
Research conducted at agricultural limited liability company "Lishche" Lutsk district of Volyn region on cows of different genotypes of the Ukrainian Black-and-White dairy breed. 5 groups of animals were formed: I − cows with a proportion of Holstein breed 75% or less, II − with a share Holstein heredity 75.1–81.25%, III − Holstein heredity share 81.26–87.50%, ІV − with a share of the heredity of the Holstein 87.51–93.75% and V − with a share of the heredity of the Holstein more than 93.75%. Evaluation of milk productivity was carried out by milk yield, fat content in milk and the amount of milk fat for the first, second, third and highest lactations according to the data of zootechnical accounting.
It was found that the largest number of animals under control (33.7%) was with the relative share of Holstein heredity of 81.26–87.50%, and the lowest (9.3%) was with relative share of the Holstein breed's heredity more than 93.75%. Analysis of the level of milk yield of cows of different genotypes showed that the increase of Holstein heredity increases milk yields, however, significantly reduces the fat content of milk. If the animals have a share of Holstein heredity up to 75% the milk yields was 5154, and the amount of milk fat − 199.7 kg, and cows with hereditary of 75.10–81.25% showed figures increased by 16.4 and 15.5%, with Holstein heredity 81.26–87.50% by 23.3 and 20.8%, Holstein heredity 87.51–93.75% for 26.1 and 23.2% and with Holstein heredity more than 93.75% for 34.8 and 31.4%, and fat content in milk, on the contrary, decreased, depending on the genotype of animals, by 1.6–2.3%. In all in the above cases, these changes were highly significant (P < 0.001).
The effectiveness of breeding on increasing the milk productivity of cows depends on the efficiency of selection and selection of animals, taking into account the phenotypic and genetic correlation between economically useful features. It was found that the studied cows of all genotypes had highest highly reliable (P < 0.001) positive values of correlation coefficients between milk yield and milk fat (Table 2). These features are the most predicted because strong relationship between them (r = 0.912–0.987). There was also observed direct positive ligament (r = 0.039–0.533, P < 0.05–0.001) between fat content in milk and milk fat content, and mostly weak, and only in some cases correlation coefficients had average values. The cows of the studied genotypes had the lowest and for the most part unreliable values of relative variability by the milk yields and fat content milk. The heifers with conditional share of Holstein heredity, more than 75% had negative and weak relationship features, and the older cows were diversified from weak to average values.
One of the reliable criteria for determining the level of heredity of features is the coefficient of frequency, which indicates their heredity stability in age. Coefficients of age-related frequency of milk yield, fat content of milk and the highest milk fat content of cows with a conditional share of Holstein heredity of up to 75% had indicating a higher degree of heredity of these features compared to high half-bred cows. With the increasing of heredity of the Holstein breed the genotype of controlled animals values were decreasing for the most part. The most significant and reliable (P < 0.001) genotype of animals affected milk yields (13.3–18.1% of the total variability of this feature), less – the fat content of milk (9.3–13.2% (P < 0.001) and the amount of milk fat (6.6–14.1% (P < 0.001), with the highest genotype influence on the studied features indicated in the first lactation.
Capa-casein gene polymorphism in cows of different breeds of dairy productivity
