DYNAMICS OF CORTISOL AND TESTOTERON IN THE BLOOD OF HEIFERS OF DIFFERENT BREEDS

The paper presents the results of a study of the dynamics of testosterone and cortisol in 40 heifers of different breeds (Holstein black-and-white breed, Simmental breed, Aberdeen-Angus breed, crossbred animals. 10 heads from each breed.All experimental groups of heifers were analogous in age and term of pregnancy. The conditions for raising animals were the same and corresponded to their zootechnical feeding standards. The hormones cortisol and testosterone were determined by the enzyme immunoassay. The results of the conducted studies showed that before insemination, a slightly higher concentration of testosterone was observed in crossbred animals (Aberdeen-Angus x Simmental) and was 4.7±0.4 nmol/l. This indicator was relatively lower in black – and-white heifers and was 3.6±0.4 nmol/l. Significant changes in it were observed at 5 months of pregnancy.By the 5th month of pregnancy, the concentration of testosterone in all experimental groups increased approximately 2 times. There is a significant difference between crossbreeds, Simmental and black-and-white breeds at 5 months of pregnancy (р<0.05). More pronounced interbreeding differences were observed from the 6th month of pregnancy to the last month of pregnancy. At 6, 7, 8, 9 months of pregnancy between black – and-white heifers and crossbred animals, the testosterone level was statistically significant (р<0.05). Interbreed differences in the level of testosterone in the blood of experimental animals indicate the features of the testosterone-synthesizing system of different breeds, which is probably determined at the gene level. An increase in the concentration of testosterone in the blood of heifers indicates its participation in the processes of fetal formation and the reaction of the testosterone-synthesizing system of the mother’s body to the course of pregnancy. Differences in the level of testosterone in the blood of Black-and-white, Simmental, Aberdeen-Angus breeds and crossbreeds indicate the breed characteristics of the testosterone-synthesizing system, which is possibly determined at the gene level. Changes in cortisol concentration were similar to changes in testosterone. It should be noted that the highest levels of cortisol in the second half of pregnancy were consistently maintained in cross-bred heifers in relation to the black-and-white and Simmental breeds. At the 9th month of pregnancy, local weeks were statistically significantly higher than black-and-white and Simmental weeks (р<0.05). During pregnancy, the level of cortisol in the blood of heifers had ambiguous indicators and depended on the month of pregnancy and the breed affiliation of the animals. The increase in cortisol in the blood during pregnancy is obviously due to the effect of estrogens on the female body. Thus, we believe that as a result of pregnancy, the synthesis of α-glycoprotein increases, which binds to cortisol, contributing to an increase in its life in the blood and contributing to an increase in the concentration of total cortisol.