Productivity of fi rst-calf cows of different sire lines

The results of the study of milk productivity and lactation rates of rst-calf cows are presented. The research into rst-calf cows of black-andwhite Holstein breed, belonging to sire lines of Wis Ideal 1013415 and Re ection Sovereign 198998 was conducted in 2018 in Novosibirsk region. The number of cows under study was 64, the period of the study covered 305 days of lactation. Monitoring of milk production, milk ow intensity, fat and protein content was carried out monthly. The research materials were analyzed for groups of cows depending on their sire line and productivity for single and daily milk yield, fat and protein content, and dynamics of milk ejection for the rst 3 minutes of milking. The highest daily milk yield in both lines was observed in the second month of lactation. In the fourth and fth months of lactation, the average daily milk yield of Re ection Sovereign cows was signi cantly higher (р < 0.001) than that of their peers of the Vis Ideal line, by 1.3 kg. During the lactation period, the productivity of the Vis Ideal and Re ection Sovereign cows was almost the same: milk yield – 8296 and 8220 kg, fat content – 4.02 and 4.06%, protein – 3.36 and 3.35% and milk ow intensity – 2.70 and 2.78 kg/min, respectively. In the second and third months of lactation, cows of both lines had a decrease in the content of fat, protein and intensity of milk ow with a gradual increase in these indices in the fourth and fth months of lactation. First-calf cows of the black-and-white breed of Canadian selection of different sire lines showed a high level of milk productivity and proved to be suitable for further breeding work.