Endocrine and metabolic profile of Sychev breed cows under heat stress

The article presents data on the hormonal and biochemical profile of cows of the Sychev breed under optimal and stressful temperature conditions. Reference values of the concentration of gestagens hormones (progesterone, estradiol, DHEA), the main thyroid hormone (tT4) and the main glucocorticoid – cortisol in the organism of cows of the Sychev breed have been determined. The main features of the endocrine system reaction of cows of this breed during the development of heat stress have been established. The part of Sychev breed cattle population demonstrated resistance to the development of heat stress. The main changes in the metabolic profile of cows of the studied breed induced by high-temperature stress are also demonstrated. The data presented in the study allow us to draw conclusions about the significant adaptive potential of this breed. The study showed that 41.8% of animals demonstrated high tolerance to heat stress, which was reflected in the absence of imbalance of key hormonal systems. In addition, a significant number of animals utilized a variety of strategies to counteract heat stress, including balancing some of hormones and a relatively small number of individuals that utilized the full hormonal potential examined. Metabolic manifestations of the effects of heat stress did not vary. However, a significant part of the population of the Sychev breed did not need to activate or depress regulatory systems to maintain homeostasis and compensate for the negative effects of heat stress. Some part of the population used a certain amount of hormones of steroidal nature to regulate homeostatic metabolic mechanisms.