The role of cortisol and progesterone in the formation of the cellular com-position of blood in Holstein heifers

Abstract

Purpose: quantitative assessment of the cell composition of the blood of the heifers of the Holstein breed and the study of the relationship between it and the level of steroid hormones - cortisol and progesterone.Materials and methods. The work was carried out in 2020-2021 on the basis of Belagash LLP (Republic of Kazakhstan), which specializes in the production of milk by using the productive potential of the Golstein breed. The diets of animal feeding were in accordance with the norms of VIZH. Heifers born in the spring of 2020 were included in the experimental group (n = 10). In its formation, the principle of close analogues was used. In the heifers of an experimental group of 3, 6, 9, 12, 15 months, blood samples were obtained by a vacuum method for conducting morphological and biochemical studies. The level of progesterone and cortisol was determined in the blood serum by the immunofortment method.Results. The total number of leukocytes in the blood of animals changed in the interval of 9.57-12.00 109/l, corresponding to the boundaries of the norm; The level of monocytes and lymphocytes fluctuated in the range of 3.33-7.80 and 58.93-75.01 %, amounting to 0.40-0.81 and 5.64-9.00 109/l. The number of red blood cells, hemoglobin and hematocrit by 15 months increased by 36.33; 12.93 and 40.18 %. At the same time, the volumetric characteristics of red blood cells (the average volume of red blood cells, the red blood cell distribution index almost did not depend on age, but their saturation with hemoglobin (the average hemoglobin content in red blood cells, the average concentration of hemoglobin in red blood cells) decreased. The level of steroid hormones – progesterone and cortisol in the blood of heifers increased with age in 46.06 and 8.24 times (p≤0.05). At the sametime, the concentration of cortisol statistically significantly correlated with the amount of red blood cells (r=0.71 - 0.95), the size of the red blood cell distribution index in volume (r = 0.74 - 0.98) and the absolute number of lymphocytes (Rr= 0.71 - 0.99). The level of progesterone, starting from 9 months of age, was interconnected with the total number of leukocytes (r = -0.63 --0.88), an absolute number of monocytes (r = 0.69 -0.89) and lymphocytes (r = -0.65 – -0.87), as well as red blood cells (r= 0.82 -0.93) and hemoglobin (r = 0.63 -0.73).