Productive Traits and Reproductive Capacity of First-Calf Cows at Different Selection Options

Abstract

The research work is aimed at determining and establishing the degree of influence of various selection options on the productive and reproductive qualities of the first-calf cows of the black-and-white breed. The research results showed that according to the Parental Index of Cows (PIC), animals of the 5th experimental group surpass their mates in the 2 and 3 groups in milk yield by 746 kg, with p≤0.05 and 1746 kg, with p≤0.001 and the difference in fat content is 0.07 and 0.01%, respectively. The same advantage in milk yield over the 3 experimental groups is possessed by the 1st control and the 4th experimental groups 1827 and 1885 kg, with p≤0.001. In terms of protein, group 3 cows are inferior to first-calf heifers of groups 1, 2, and 5 by 0.03, 0.08, and 0.09%, with a significant difference p≥0.99. Groups 1, 2, and 5 have superiority over animals of the 4th -0.03%, with p≤0.05, as well as 0.05 and 0.06%, with p≤0.01. The Realization of the Genetic Potential (RGP) in milk yield for 305 days of lactation was higher in the 5th experimental group and amounted to 88.3%, which is 7.1% more than in the control, with p≤0.05. For milk fat, animals of groups 1 and 3 have a high potential of 99.5 and 99.9%. In terms of the mass fraction of protein, first-calf heifers of the 1st control and the 4th experimental groups surpass their mates from group 3 by 2.1 and 1.8%, with p≤0.05. The control group has the most optimal indicator of the calving period (406.5), while the tested ones exceed it by more than 40 days. The service period in all groups has been increased by almost 2 times. The highest calf crop (92.3%) and reproduction rate (0.92%) are observed in the control group.