REPRODUCTIVE ABILITY OF FIRST-CALF COWS OF SIMMENTAL BREED IN ORGANIC AND CONVENTIONAL MILK PRODUCTION
Authors: Kochuk-Yashchenko O. , Kucher D. , Ustimovich O. , Mosiychuk M. , Bystranivskyi Yu. 
Published: January 2022

The aim of the work was to study the influence of biological periods of reproduction of first-born cows of Simmental breed on their productive features of organic and conventional milk production.
Research materials and methods. The research was carried out in the herds of Simmental breed PС "Halex-Agro" (organic milk production, n = 272) and LLC "Myroslavel-Agro" (conventional milk production, n = 120) Novograd-Volyn district of Zhytomyr region according to conventional methods.
Research results. The article presents the results of research on the influence of the age of the first fertile insemination, age of first calving, the duration of service and dry periods of Simmental cows in their productive traits in organic and conventional milk production.
The best indicators, regardless of the technology of milk production, were characterized by animals of the middle group, the age of the first fertile insemination of these animals in PE "Galex-Agro" ranged from 526 to 678 days, and in STOV "Miroslavel-Agro" – from 505 to 648 days. The value of this indicator within farms was 462.5 and 458.0 kg, respectively. Therefore, both early insemination and late insemination were not desirable for this herd, because with early insemination farmers don’t get enough milk and there is a high probability of giving birth to calves with lower live weight, while with late insemination there is an irrational overuse of investments in uncovered heifers. their future milk productivity.
In the conditions of both farms there is a clear pattern that animals with an earlier age of the first fertile insemination are characterized by more intensive formation of live weight. Animals of the first and second experimental groups were statistically significantly superior to peers of the third experimental group in live weight at the age of 3 to 18 months in PE "Galex-Agro", and from 6 to 18 months in STOV "Myroslavel-Agro" (P < 0.05–0.01). There is almost the same live weight of heifers at different ages in both farms, due to the common origin of the breeding stock imported from the Czech Republic.
It has been established that with increasing age of the first calving milk productivity of cows increases. The highest yield for 305 days (6117.2 and 5937.6 kg) and all lactation (6920.9 and 6953.4 kg) were observed in cows whose age of first calving was 995 and older and 917 and older days in the conditions of PE "Galeks-Agro” and STOV “Myroslavel-Agro” respectively. The lowest yield for 305 days (5733.9 and 5863.0 kg) and all lactation (6528.2 and 6424.6 kg) were in cows with the age of the first calving 835 and less and 778 and less days in both farms, respectively.
There was a statistically significant effect (P < 0.01–0.001) of the duration of the service period in both farms on the duration of lactation of cows (58.6 and 63.9%), hopes (22.8 and 34.2%), as well as on the fat content in milk (2.2%) only in the conditions of PE "Galex-Agro". In the conditions of intensive management of the dairy industry in organic and conventional production, it is necessary to take into account the rate of reproduction of the herd, which is largely determined by the length of the service period. The service period is one of the key indicators that determines not only the reproduction of animals, but also their future milk productivity.
Conclusions. According to the results of our own research, it was found that the extension of the service period leads to an increase in the duration of biological periods of reproduction and to a decrease in the coefficient of reproducibility (from 1.06 to 0.68; from 1.05 to 0.72), which is predictable. Statistically significant effect (P < 0.001) of the value of the service period was found in the conditions of PE "Galex-Agro" and LLC "Miroslavel-Agro" on the duration of the interbody period (74.2 and 68.8%), the coefficient of reproducibility and 78.2), as well as the duration of the dry period (2.6%) and the age of the first calving (2.7%) only in the conditions of PE "Galex-Agro".
When comparing animals with a shortened and optimal duration of the dry period, a statistically significant difference was found in the conditions of organic production in the duration of lactation (25.3 days), milk yield during lactation (673 kg) and 305 days (359 kg), milk fat (13.7), milk protein (13.4 kg), total milk fat and protein production (26.2 kg). In terms of conventional production, animals with a shorter dry period are characterized by longer lactation and higher milk yield.