THE ROLE OF CORTISOL AND PROGESTERONE IN THE FORMATION OF RESPIRATORY BLOOD PROPERTIES IN HOLSTAN HEIFERS
A quantitative assessment of erythrocyte homeostasis in the body of Holstein heifers and its relationship with the amount of steroid hormones - cortisol and progesterone is given. Blood was taken from heifers of the experimental group (n=10) at 3, 6, 9, 12, 15 months of age. The number of erythrocytes, hemoglobin and hematocrit by the age of 15 months increases by 36.33; 12.93 and 40.18%. At the same time, the volumetric characteristics of erythrocytes (average erythrocyte volume, erythrocyte distribution index by volume) practically do not depend on age, but their saturation with hemoglobin (average hemoglobin content in an erythrocyte, average hemoglobin concentration in an erythrocyte) decreases. The level of steroid hormones - progesterone and cortisol in the blood of heifers increases with age by 46.06 and 8.24 times (p≤0.05). At the same time, the concentration of cortisol statistically significantly correlates with the number of erythrocytes (r=0.71 - 0.95), the value of the index of distribution of erythrocytes by volume (r=0.74 - 0.98). The level of progesterone, starting from the age of 9 months, as well as erythrocytes (r=0.82 - 0.93) and hemoglobin (r=0.63 - 0.73). The results obtained allow us to judge the close relationship between the cellular composition of the blood and steoid hormones. Therefore, further study of this issue is relevant.