The dissertation work presents the results of the research conducted at the industrial dairy complex for milk production during the first-fourth lactations of cows, which are characterized by high productive properties: milk yield per 305 days of lactation is 10382–10740 kg with mass content of fat – 3.75–3.88 % and of protein – 3.18–3.23 %; insemination index is 4.5–4.8 and adaptation index is 4.9–9.6.
It has been proved that the level of milk yield of Holstein cows is genetically determined to be quite high and during economic use depends practically on the duration of the lactation period. The highest milk yield was found in daughter cows from the III (control) and IV groups, as the lactation duration there is the longest – 1783 and 18264 days, respectively. Lifetime milk yield of daughter cows from the I and II groups is 45316 and 48498 kg, respectively; milk fat production is 1732 and 1860 kg, respectively. At the same time, the highest milk yield during one day of lactation of daughter cows from the II group is 36.2 kg. The dynamics of the realization of the milk productivity of animals from the II group during the economic use looks like a growing curve from the first to the fourth lactation. Stimulation of lactogenic function in cows does not disturb metabolic homeostasis: the level of lipoproteins is on average 546.8–700.7 mg%; total protein – 73.0–76.6 g/l; protein index – 0.70–0.96; de Ritis Ratio – 1.94–2.38.
It was found that under the same operating conditions in the industrial complex, daughter cows from the II group from mother cows of the second lactation have the best reproductive qualities: the insemination index does not exceed 2.46, the service period and calving interval – 88 and 369 days, respectively. In these animals, the loss of offspring from infertility does not exceed 0.48 head, which is less than in groups I, II and IV by 1.88 (P <0.001), 4.1 (P <0.001) and 4.46 times (P < 0.001), respectively.
The adaptation index in the “genotype - environment” system of cows from the II group does not exceed 3.1 units, while for their peers this indicator is from ˗8.1 to ˗22.4 and ˗25.8. It was discovered that, regardless of the age of mothers, the main reasons for leaving the herd of daughter cows are metabolic disorders – 46.4–55.6 %, operational risks – 35.7–37.0 % and udder diseases – 3.7–14.3 %.
Keywords: cows, live weight, lactation, milk yield, fat and protein mass content, metabolism, insemination index, adaptation index, herd replacement.
