Influence of increasing milking capacity level in black-and-white first-calf heifers on their subsequent milk productivity under the conditions of the Vologda region

In the research the dependence of milk productivity of Holsteinized Black-and-White cows on the intensity of their milking during the first lactation was studied. The experiment was conducted under the conditions of the Vologda Region. The sample included 583 animals, where there were included the cows that were dropped out of the herd in the period from 2020 to 2021. The selected animals were divided into three groups according to the milk yield for the first lactation. In the groups the average milk yield for the first, second, third and best lactations, as well as the total milk yield for all three lactations, were calculated. All three groups of cows were kept under the same feeding and keeping conditions. As a result it was found that the first-calf heifers with a lower milk yield level were also able to realize their genetic potential of high productivity in the following lactations - 7,745.4 kg (±752.6) for the 3rd lactation and 8,412.8 kg (± 809.1) for the best one in comparison with the average for the herd. According to the effect of the increased milk yield level on the mass fraction of fat, the animals of the first group take precedence. During all three lactation periods, their mass fraction of fat remained at a high level and was inferior to the animals of the second group by 0.003% for the best lactation. With an increase in milk yield, the mass fraction of protein decreases. Cows of the first group had the highest rate of 3.38% after the first lactation.