VARIABILITY AND INTERRELATION OF THE CONTENT OF THE MASS FRACTION OF PROTEIN AND THE MASS FRACTION OF FAT WITH AGE IN COWS OF DIFFERENT GENERATIONS

Intrabreed mating is the main method of improving breeds. This method of selection is based on the patterns of variability,heredity and the relationship of economically useful traits [1]. The determination of correlations of individual traits allows forbreeding with the goal of improving dairy breeds [6]. In dairy cattle breeding, it is important to study the variability of the massfraction of protein in aged cows. The variability of the milk yield, the content of the mass fraction of fat and protein depend onmany factors, genetically determined heritability is not an exception [2], [3], [4], [5]. The study of variability and interrelationof the content of the mass fraction of protein is especially relevant in cows of different generations [2], [3], [4].Studies show that with a high level of dairy herd, the possibilities of breeding highly productive first-born heifers frommothers of different ages are not the same. The intensification of dairy cattle breeding is impossible without the creation ofhighly productive animals capable of not only showing high productivity indicators for the first lactation but also to increase itwith age realizing the genetic potential of dairy productivity characteristic of the Holstein breed. By improving the technologyof feeding and maintenance and providing a differentiated approach to the first heifers it is possible to significantly increase thedairy productivity of livestock.One of the goals of researchers and stockbreeders is to use a selection methodology that can lead to an increase in milkproduction. Statistical processing via computer technology made it possible to use more advanced methods in obtaining a moreaccurate assessment of the productive qualities of cows. Consequently, the result of this assessment can be fundamental indecision-making in selection programs, as well as in management decisions. The total milk yield correlates with the productionat different stages of lactation [8], [10].