Relationship between cow milk yield and milk quality indicators

Abstract In the Sverdlovsk region, purebred bull producers of the Holstein breed of German, Danish and Canadian selection and the breeding stock of the domestic black-and-white breed of the Ural offspring were used for improvement. The Ural offspring of the black-and-white breed was distinguished by high milk yield and fat mass fraction and protein mass fraction in milk. In 2002, the Ural type of the Holstein black-and-white cattle was officially registered in the Ural region. This type has significant differences from the original rocks. The purpose of the article is to study the relationship between milk yield and milk quality indicators in cows-daughters of the Holstein black-and-white cattle of the Ural type from different Holstein bulls. It is established that the relationship of indicators depends on the belonging of cows-daughters to a particular bull producer. However, it can be noted that there is a positive relationship with an average and high level of correlation between milk yield for the first lactation and fat mass fraction in milk, milk yield for lactation and protein mass fraction in milk, and between fat mass fraction and protein mass fraction in milk in the groups of bull daughters from producers Emen and Reverse. For the group of daughters of the bull Jesmen, a high negative correlation was found between milk yield per lactation and fat mass fraction in milk, an average negative correlation between milk yield and protein mass fraction in milk, and a low positive correlation between fat mass fraction and protein mass fraction in milk. Correlation coefficients change with age. For the second lactation, the correlation coefficients differed from those established for the first lactation. So, they went to negative between milk yield and fat mass fraction in milk in the daughters of all evaluated bulls, between milk yield and protein mass fraction in milk remained the same, but decreased. The correlation coefficient between the quality indicators of milk in bull’s daughters changed to negative. Selection of cows by milk yield for the first lactation will allow you to get an increase in milk yield for full-age lactation.