EFFICIENCY OF REARING REPAIR HEIFERS OF DAIRY BREEDS IN CORRELATION WITH MILK PRODUCTIVITY

The article presents analytical data on the assessment of Holstein, Ukrainian Black-and-White dairy and Ukrainian Red-and-White dairy heifers for the development of live weight in the dynamics of rearing from birth to 18 months of age. The study was conducted in the same conditions of the herd of LLC “Kamyshevatsky dairy complex” of the Kharkiv region. The assessment of heifers by absolute and relative indicators of live weight gain showed a high level of heifers rearing on the farm. In terms of live weight of heifers in the studied age periods of 6, 9, 12, 15 and 18 months, they exceeded the target standards of the Holstein breed by 7.8; 12.5; 42.7; 43.1 and 40.4 kg, respectively, the Ukrainian Black-and-White dairy – by 5.7; 11.2; 37.8; 39.3 and 37.1 kg, and the Ukrainian Red-and-White by 8.6; 13.4; 35.7; 37.9 and 35.9 kg. According to the indicators of absolute and relative growth of live weight of repair heifers of controlled breeds in the three-month dynamics of postnatal ontogenesis, interbreed differentiation was established with a significant advantage of Holstein heifers during the entire growing period. Holstein heifers in the three-month Age periods of 3-6, 6-9 and 9-12 with a high and statistically significant difference were better than the peers of Ukrainian Black-and-White and Red-and-White dairy in terms of average daily live weight gain by 32.9 and 47.5, respectively; 15.6 and 61.7 and 25.9 and 56.4 g (p<0.001). However, the greatest difference in average daily growth in Holstein heifers was found in the age period of 15-18 months and amounted to 69.1 and 115.7 g (p<0.001) in their favor. Holstein heifers took a priority position in terms of relative live weight gain during the entire rearing period. Thus, in the 0-3-month age period, at the highest growth rate (93.7%), Holstein heifers were dominated by the peers of the Ukrainian Black-and-White dairy by 1.7 % (p<0.001) and the Ukrainian Red-and-White by 2.1 % (p<0.001). A similar excess of Holstein heifers of the same age as Ukrainian Black-and-White and Red-and-White dairy breeds in relative development was observed during all three-month growing periods and in the last 15-18 month period it was 1.4 % (p<0.001) and 2.4 % (p<0.001), respectively. A direct correlation was established between the live weight of heifers and the average daily weight gain with signs of milk productivity of first calving cow for 305 days of lactation, regardless of breed.