INFLUENCE OF LIVE WEIGHT OF FIRST-CALF COWS FROM INSEMINATION TO THE FIRST 100 DAYS OF LACTATION ON SUBSEQUENT MILK PRODUCTION

The article presents the results of determining the influence of the live weight of primiparous cows from fertilization to the first 100 days of lactation on subsequent milk productivity. The study was conducted on primiparous cows of the Ukrainian black-and-white dairy breed, which are kept at the breeding plant of the State Enterprise “Hontarivka” of the Chuguyiv district of the Kharkiv region. During the experiment, the influence of various technological regimes on changes in live body weight during the first 100 days of lactation was studied. The main parameters studied were the live weight of primiparous cows at the stages of fertilization, after calving and in the first 100 days of lactation, as well as their milk productivity for 305 days of the lactation period. The determination of milk productivity included accounting for the gross milk yield of natural fat content on the 100th, 200th and 305th days, as well as an estimate of the mass fraction of fat and protein in milk for the entire lactation period. For the analysis, a retrospective study of cow productivity over the past decade was conducted. For the study, four groups of primiparous cows were formed depending on their live weight at the time of fertile insemination: Group I – up to 380 kg, Group II – 380–399 kg, Group III – 400–419 kg, Group IV – over 420 kg. The average live weight at insemination was: in Group I – 358.8 ± 1.51 kg, Group II – 387.7 ± 0.49 kg, Group III – 406.3 ± 0.65 kg, Group IV – 445.5 ± 3.66 kg. Animals of Group IV exceeded their peers from other groups by 39.2–86.7 kg, which corresponded to an increase in weight by 8.8–19.5%. The live weight of cows after calving was: in group I – 573.9 ± 3.56 kg, II – 583.4 ± 3.58 kg, III – 590.3 ± 6.01 kg, IV – 591.1 ± 5.51 kg. However, after calving, the difference between the groups began to decrease: cows of group IV outweighed animals of group I by only 17.2 kg (2.9%), group II – by 7.7 kg (1.3%), group III – by 0.8 kg (0.1%). On the 100th day after calving, the difference in live weight between group IV and other groups increased again. The average weight in group IV was 561.7 ± 4.54 kg, which exceeded the indicators of group I by 5.5% (530.6 ± 3.00 kg), group II by 3.1% (544.1 ± 2.95 kg), group III by 1.6% (552.8 ± 4.90 kg). Live weight losses from the moment of calving to the 100th day of lactation were: in group I – 43.2 ± 8.6 kg (7.5%), in group II – 39.3 ± 8.3 kg (6.7%), in group III – 37.6 ± 11.2 kg (6.4%), in group IV – 29.3 ± 9.2 kg (5.0%). Analysis of the obtained data showed that the first-born cows of group III had better adaptation to further productive use. The implementation of these results in production will help optimize the feeding of heifers and cows in the post-calving period, which will increase the efficiency of herd management.