Influence of intensity of milking of simmental breed first lactation cows on their lifelong productivity and duration of productive use

According to the results of the research, the influence of milking intensity of first-calf heifers on the duration of productive use of Simmental cows was established. In first-calf cows with average milk yield for 1 lactation – 4000–5000 kg of milk life expectancy was higher by 177, 29; 181,31 and 209,74 days than in coevals with productivity class 5001–6000; 6001–7000 and 7001 and more kg of milk. Group I animals also had longer productive period of 1670.51 days, which was higher by: 165.74; 151.86 and 154.63 days than cows of groups II, III and IV, respectively. With the increase in milk yield for the first lactation, there was a decrease in the number of lactations used from 3.89 to 3.16. A statistically significant difference of 0.73 lactations (P ≥ 0.95) in productive longevity was found between animals with productivity class 4000–5000 kg and 700 1 and more kg. A higher lifetime milk yield of 20316.73 kg was obtained from animals with productivity class of 7001 kg of milk and more for 3.16 lactations, the difference in this indicator compared to group I, II and III was 87.42, 620.38 and 2267.44 kg (P ≤ 0.95). The average milk yield for all lactations in group IV was 6636.21 kg, which was significantly higher than the average of cows of groups I, II and III by 29.55; 22.28 and 23.11 % (P ≥ 0.999), and the difference in milk yield per 1 day of life and per 1 day of productive use, respectively, was 8.52 % (P ≥ 0.95); 4.44 % (P ≤ 0.95); 13.76 % (P ≥ 0.999) and 10.65 % (P ≥ 0.95); 2.37 % (P ≤ 0.95); 13.56 % (P ≥ 0.99). Comparative evaluation of milk productivity dynamics between the groups revealed superiority in milk yield from 1 to 6 lactation in first heifers of group IV, compared to I, II and III by 1491.47; 1191.29 and 1388.62 kg, respectively.