Economic useful traits of first-calf cows of the simmental breed depending on the duration of their service period in organic dairy production

The results of studies of the influence of the service period's duration of first-calf cows of Simmental breed by their milk productivity, reproductive ability and mass-metric parameters have highlighted. The research material served as information on the breeding and productive using of 172 first-calf cows of the Simmental breed of private enterprise "Galex-Agro" of Zhytomyr region. It was founded that the increase in the duration of the service period leads to an increase in the level of milk production of cows - yield for 305 days of lactation of animals with an extended period of 1190 kg more compared with animals with a short service period. It has been proved that the duration of the service period directly affects the reproductive capacity of cows, but in contrast to the improvement of the quantitative indicators of dairy productivity, the reproduction rates are significantly reduced - the reproductive ability is reduced in the long service period to 0.77. Economically advantageous for the farm and physiological for the animals is breeding of animals, which will characterize length of the service period (an average of 125.3 days), and which the animals most effectively combine high dairy productivity with satisfactory reproductive performance. The best mass-metric parameters have characterized by animals with a longest service period. As the service period grows, the animals become taller, more massive, and narrower. As the service period grows, animals become taller, more massive, narrower-bodied, and better adapted externally to modern technology. Biggest weight, which is an important selection indicator, characterized animals with the longest duration of the service period of group III (624,6 kg). These cows were taller (135.6 and 142.2 cm high in the withers and sacrum) and longer (80.4 and 173.1 cm long, respectively, in the breast and trunk). In general, the overall effect of the duration of the service period on dairy productivity and reproductive performance was 0.207 and 0.333, respectively. That is a more significant effect has observed on the reproductive capacity, and this is quite natural, since the duration of the service period depends on all indicators of reproductive capacity, with the exception of the age of the first calving and the duration of dry period.