FEATURES OF LACTATION ACTIVITY OF COWS OF THE REFLECTION SOVERING LINE AND THEIR REPRODUCTIVE QUALITIES
The main livestock of dairy cattle in the country belongs to the black-mottled and Holstein breeds, and the second one has been used everywhere for a long time and continues to be used in improving the breeding stock of the domestic black-mottled breed. In some herds, the blood content of the Holstein breed is more than 94%, which corresponds to the generally accepted concept of these animals belonging to the Holstein breed, and the breeding of animals is carried out along Holstein lines. As a result of the conducted studies, it was found that, depending on the period of lactation activity of the cow and age, there is a significant change in milk yield. Thus, an increase in the duration of lactation (the indicator for the entire lactation) leads to an increase in milk yield for the first lactation by 846 kg or by 13.2%, for the third lactation by 732 kg (9.6%). The difference in both cases was significant at P<0.05. There is also an increase in milk yieldfor full-age lactation relative to the first by 1149 kg or by 17.9% (P < 01). The highest milk yield for lactation was established for 3 full-age lactation - 8834 kg with a lactation duration of365 days. Starting from the 4th lactation, there is a decrease in milk yield for lactation to the 7th with a simultaneous decrease in the number of milking days in the 4th and 5th lactation. In the sixth lactation, we observed a decrease in milk yield with an increase in the duration of lactation activity, which led to a surge in productivity for the 7th lactation, which is explained by its duration. The seventh lactation was the longest and amounted to 369 days, which is 4-84 days more than in other periods of lactation activity. The coefficient of reproductive ability corresponding to a high level of reproduction was established only after the 8th lactation, but at the same time all animals dropped out of the herd after calving. During the rest of lactation, reproduction problems are observed, which is most likely due to gynecological reasons.