INFLUENCE OF VARIOUS FACTORS ON THE LEVEL OF CORTISOL IN THE BLOOD OF DAIRY BREEDS OF CALVES

The studies were conducted in the dairy herds of the State Enterprises of Research Farms "Shevchenkivske" and "Khrystinivske". The object of the study was calves of the Ukrainian Black-and-White and Red-and-White dairy breeds. It was found that the level of cortisol in the blood serum of calves aged 2 to 10 months ranged from 0.1 to 68.3 ng/ml. On average, this indicator in the experimental animals was 26.7 ± 0.82 ng/ml. The difference in the level of cortisol in the blood serum of calves of different sexes was statistically significant (P < 0.001) for all age groups of the experimental groups. The average cortisol level in the blood of bulls was 12.1 ± 1.3 ng/ml, and in heifers – 35.2 ± 1.9, which is significantly higher by 23.1 ng/ml (P < 0.01). One-way analysis of variance showed that the factors “sex” (effect strength at the level of 30%), “age” (effect strength of 16%) have a statistically significant effect on the level of cortisol in the blood serum. The breed of animals does not affect the level of cortisol in the blood serum of calves.