COMPARATIVE CHARACTERISTICS OF GROWTH OF CALVES WITH DIFFERENT SENSITIVITIES TO STRESS

The studies were conducted in the herd of the Khrystynivske Research Farm of the M.V. Zubets Institute of Animal Breeding and Genetics of the National Academy of Sciences of Ukraine on calves of the Ukrainian Red-and-White dairy breed. The growth indicators of heifers were analyzed taking into account individual assessment of stress sensitivity. The analysis of the differentiation of young animals by the sign of resistance to stress factors at an early age indicates its connection with growth indicators. Heifers classified as stress-sensitive exceeded their peers, which are resistant to stress, by 3.7 kg in live weight with a statistically significant difference (P < 0.05). At the age of three months and older, the advantage of stress-resistant heifers over their peers in live weight was observed. At the age of three and six months, this difference was statistically insignificant; in the period from 9 to 15 months, the live weight of stress-resistant heifers was significantly greater than that of stress-sensitive heifers (P < 0.01 and P < 0.001). A statistically significant (P < 0.05 and P < 0.01) intergroup difference was established in sensitive and stress-resistant heifers in terms of absolute live weight gain within 7.8–12.5% ​​depending on the age period. In terms of average daily live weight gain, stress-resistant heifers exceeded their peers by 8.8–15.4%, with the exception of the period of 3–6 months, the intergroup difference in this indicator was statistically significant. The influence of stress status on the live weight of heifers tends to gradually increase with age. At the age of 15 months, the influence of stress status on the live weight of heifers is 17% (P < 0.05).