Relationship of biochemical parameters of blood with milk protein content in black-and-white cows with linear selection

Among the indicators characterizing the biological, breeding and productive qualities of the breed, the composition of milk is an important feature. The mass fraction of fat and protein is determined by the peculiarity of the breed and is considered a breed trait. The number of dairy cattle in the Moscow subregion has a high genetic potential, the growth of which is due to the widespread use of Holstein bulls in the reproduction of livestock. It is generally accepted that the most pronounced changes in the composition of milk are observed at the beginning and at the end of lactation, but the composition of normal milk is also subject to changes with certain selection measures. The direction of selection associated with protein content is caused by the need to improve the quality of dairy products and it must be said that the greatest effect is achieved with direct selection for only one trait - the protein content in milk. In the breeding farm "Povadino" selection work begins with the fact that the genotypes of the cows of the breeding group are determined, while assessing the origin. Further, cows and sires with desirable genotypes are identified, their selection is carried out, however, the study of the relationship between milk protein content and blood biochemical parameters in cows with different selection options remains a little-studied issue, which was the basis for our research.