Realization of the potential of milk productivity of cows depending on some factors

The implementation of the genetic potential of dairy productivity of cows can be infl uenced by many different factors, so the purpose of our research was to study some of them. The experiments were carried out in a herd of dairy cows of Holstein breed. The following factors were studied such as age at the first eff ective insemination (groups: 1st – 11–13 months, 2nd – 14–16 months, 3rd – 17–19 months and 4th – 20 months and older); live weight at the fi rst effective insemination (groups: 1st – 250–350 kg, 2nd – 351–450 kg, 3rd – 451–550 kg) and the calving season of the cows (winter, spring, summer, autumn). The analysis of the ratio of animals in the herd of CJSC Konstantinovo depending on the studied factors showed that the largest number of heifers are inseminated at the age of 14–16 months. Thus, the live weight of heifers at the fi rst insemination is within 351–400 kg, the largest number of calving occurs in the winter and autumn periods. According to the results of the studies, it was established that the highest milk productivity for 305 days of lactation of 8513 kg (p < 0.001), the yield of milk fat 313 kg (p < 0.001) and protein 270 kg (p < 0.001) were obtained in the group of animals inseminated at the age of 12.5 months. The maximum milk productivity for 305 days of lactation of 7558 kg (p < 0.05), milk fat yield of 279 kg (p < 0.001) and protein yield of 230 kg (p < 0.001) were obtained in the group of animals with a live weight of 376 kg. The highest milk productivity for 305 days of lactation of 10339 kg (p<0.01), milk fat yield of 374 kg (p < 0.001) and protein yield of 342 kg (p < 0.01) were noted in the group of animals of the autumn calving period. Based on the relationship between the studied traits we found that with increasing age at the fi rst insemination, milk yield for 305 days of lactation as well as the yield of milk fat and protein decreased while the correlation was high (r=0.89–0.99). With an increase in live weight at the fi rst insemination, the milk yield for 305 days of lactation decreased as well as the yield of milk fat and protein while the relationship between the correlated traits was strong (r = 0.86–0.87). According to the analysis of all periods of the calving season and the traits of milk productivity, it was noted that a positive relationship close to one was observed. Therefore, to increase the milk productivity of cows it is necessary to take into account the totality of all factors aff ecting the productivity of animals as well as the relationships between them.