MILK PRODUCTIVITY AND REPRODUCTIVE ABILITY OF COWS, DEPENDING ON THE GENETIC AND PARATYPIC FACTORS

Abstract

Research has been carried out to study of milk productivity traits and reproductive ability of animals of the Holstein and Ukrainian Black-and-White dairy breeds in the conditions of the industrial enterprise "Globinskyi meat and dairy complex" of the Pol-tava region. The interbreed variability was determined in milk yield by which the leading cows of Holstein breed with a yield of 7334 kg according to the first lactation data with an excess of Ukrainian Black-and-White peers by 609 kg (P <0.001). According to the data of the second, third and best lactations, the milk yield advantage was 1542 and 2531, 1678 and 2581, 2179 and 3237 kg, re-spectively, with a high and reliable difference in all comparisons. A comparative analysis of the reproductive ability indicators of cows testified that the Holsteins were more early maturing, since they first inseminated at the age of 461.6 days, which was on 42.4 days earlier than peers of Ukrainian Black-and-White dairy breed. The duration of cow's service period of Holstein breed was 109 days, which was less than that in peers of the Ukrainian Black-and-White dairy cows at the same age, the difference of 14 days was highly reliable (P <0.001). The difference in live weight of repair heifers of the Holstein breed in 19 kg compared to peers of Ukrainian Black-and-White was reliable at the level of the last threshold (P <0.001), as well as the body weight at the first calving by 35 kg. A reliable influence of the first fruitful insemination age of heifers and calving on the milk productivity indicators has been determined. High rates of the first lactation and lifelong milk yield in cows of Ukrainian Black-and-White dairy breed were at their insemination at 16-17 months and calving at 25-26 months with milk yield in the first lactation and life - 6952 and 37674 kg, and in cows Holstein breed, these indicators were 7412 and 44274 kg., respectively. The reliable variability of reproductive ability indicators of the daugh-ter offspring of sires of the evaluated lines was revealed within the experimental breeds. The correlation coefficients were estab-lished between age at first calving and milk yield, which ranged from low (r = 0.087) to moderate (r = 0.214) and depended on lacta-tion. The highest correlation obtained at the age of best lactation (r = 0.274) indicated that selection by age at first calving can be to a certain extent effective. In terms of fat content in milk, negative correlations (r = -0.032 ... -0.085) indicated the lack of effective selec-tion for this trait. Whereas selection for milk fat yield will also be effective (r = 0.095-0.303), especially for better lactation. The effec-tiveness of cows selection, taking into account age at the first calving, was evidenced by the power of influence indicators for all milk productivity traits, which were the highest in terms of milk yield, especially for better lactation (31.4%) and the total yield of milk fat (28.5%).