THE GROWTH AND REPRODUCTIVE ABILITY OF HEIFERS AND FIRST-CALF COWS UKRAINIAN RED AND BLACK-SPOTTED DAIRY BREEDS IN THE CONDITIONS OF THE CENTRAL REGION OF UKRAINE
Authors: Ilyashenko G. D. 
Published: July 2021

Introduction. The significant and long-term increasing of milk yield is possible only with proper organization of heifer breeding. Therefore, now is important to study the ontogenetic patterns of living mass formation. It is known, that between the growth rate of heifers and their future milk productivity exists correlation. The young age’s animals, which have a high growth energy, in the first lactation give 5000–6000 kg of milk. The force of influence of the live weight the heifers on variability of milk productivity, in depending on the age and lactation, is concluded 8.21–42.87%.
The aim of our research was to study the dynamics of live weight, reproductive capacity and the level of their interconnection of heifers and first-born cows of Ukrainian Red and Black-and-White dairy breeds.
Materials and methods of research. The research was carried out on first-born, heifers of Ukrainian Red (UR) and Black-and-White dairy breeds (UBS) in SE «SH «Elitne» ISА NAAS». Groups of animals (n = 15) were formed for research by the method of analog pairs. Growth indicators were studied: live weight at 3-, 6-, 9-, 12- and 15-month-old age, at the first insemination. Reproductive ability was studied: age of the first insemination and calving, duration of pregnancy of heifers and first-born, duration of service and intercorporeal periods. Along with the main studied indicators, auxiliary indicators were calculated: reproductive capacity, fertility index and possible yield of calves per 100 cows. The biometric processing of the obtained data was carried out according to the method of N. A. Plokhinsky, using Microsoft Excel software.
Research results. The studies of ontogenetic patterns in formation the live weight of repair heifers in controlled herds demonstrated a fairly high level of their cultivation. However, it was found that the growth rate of live weight of heifers in the studied breeds at different ages was different. Thus, at the age of six months, the animals of the Ukrainian Black-and-White dairy breed significantly outnumbered the analogues of the Ukrainian Red dairy breed. The interbreed difference in this period by live weight was 5.0 ± 1.70 kg (P < 0.01). At 9, 12, and 15 months their weight gaining was 15.0 ± 3.42 kg, respectively; 26.0 ± 4.08 kg; and 29.0 ± 6.48 kg, at P < 0.001.
In general, during the growing period, the absolute increasing in live weight of UBS heifers by 7.0% exceeded that of UR heifers. At the same time, heifers of the Ukrainian Black-and-White dairy breed were more precocious and had the age of the first insemination, which was 14.5 months at a live weight of 400 kg, while the peers of the Ukrainian Red dairy breed were 15.4 months and 402 kg.
Characterizing the coefficient of variation of live weight of heifers, we should note the tendency to decrease with age in both breeds. Thus, the level in the for Ukrainian Red reached 11.6% in three months, for Ukrainian Black-and-White – 15.0%, at the age of 15 months respectively 8.9% and 8.4%.
It was established the significant coefficients of recurrence of live weight of heifers during the year with such at 9, 12 and 15 months of age with high degrees of probability. This indicates the possibility of effective early selection.
The studies of the reproductive capacity of heifers and first-born demonstrated, that the age of first insemination and calving were significantly lower in heifers of the Ukrainian Black-and-White dairy breed. The difference was 26.0 ± 9.8 days (td = 2.65, at P < 0.05) and 22.0 ± 9.5 days (td = 2.31, at P < 0.05), respectively. However, in terms of duration of pregnancy and service period of first-born cows, Ukrainian Red animals had positively lower values in compare to the analogues of Ukrainian Black-and-White dairy breed, which provided a higher reproductive capacity at the level of (0.90 vs. 0.88) and estimated possibility yield of calves per 100 cows (90.3 vs. 87.7 heads). However, the fertility index for both breeds was at the same level 48.7–48.8.
The interconnection of live weight of animals at different ages with the indicators of reproductive capacity was mostly the opposite in direction at an unreliable level in most cases. However, both breeds show a positive interconnection between live weight at 6 months of age and fertility index, between live weight at 1st insemination and age of 1st insemination, and between live weight at 1st insemination and coefficient of reproducibility
Conclusions. It was found, that at different ages the heifers of the Ukrainian Black-and-White dairy breed significantly (p < 0.01) outnumbered the analogues of the Ukrainian Red dairy breed, and the coefficient of variation with age on this basis decreased for both breeds.
The coefficients of recurrence of live weight of the studied heifers, which are quite significant at high degrees of probability, were revealed, which indicates the possibility of effective early selection. Thus, the live weight of Ukrainian Black-and-White heifers at 9, 12 and 15 months of age can be reliably predicted by its size at the age of three months after birth - heifers of Ukrainian Red dairy breed a little later.
There was a positive interconnection between live weight at 6 months age and fertility index, between live weight at the first insemination and age of the first insemination and between live weight at the first insemination and кcoefficient of reproducibility.