Immunobiological aspects of cow lactation

Lactation of cows is a high-energy metabolic process. It is regulated in the body by the complex physiological mechanisms of the nervous, endocrine and immune systems. The purpose of to study changes in the immunobiological reactivity of the body of cows during lactation. Clinical and experimental studies were accomplished at the veterinary clinic and in the specialized laboratory of reproductive animal immunology. For the study, four groups of analogues of experimental animals were formed in which the immunological methods determined the immune status: cows (n = 17) during the early lactation (secretion of colostrum, 3–5th day); second (n = 32) – cows (n = 32) in the mid (3–5th month) lactation; the third (n = 28) – during the late lactation (5–7th day) and the fourth group (n = 28) – during the dry period (12–20th day). Our research has shown that during lactation in the body of cows fluctuations of the studied indicators of cellular and humoral immunity occur. Experimental data that showed that the percentage of T-lymphocytes in the blood of cows of Ukrainian dairy black-billed breed during the initial (3–5 days) period of lactogenesis is the lowest (37.88 ± 1.53%). However, the lowest expression of B-immune cells (16.05 ± 0.74%) was also detected during colostrum secretion. These changes occurred against the background of the decrease in CD3+/СD22+ (2.36 ± 0.11). In particular, at the 3–5th month of lactation, peripheral blood flow contained 53.40 ± 0.83% CD3+, ie 1.40 times more. The number of CD22+ mononuclear cells increased by only 1.14 times (up to 18.31 ± 0.69%). The beginning late lactation and dry period in the number of immunocompetent cells was observed: CD3+ – up to 42.11 ± 1.03%, and CD22+ – up to 22.92 ± 0.89%. All this was accompanied by a corresponding redistribution of the balance (CD3+/СD22+). We have identified certain patterns in the blast transformation ability of T-lymphocytes, which was manifested in the change in the activity of activated immune cells of blood. At the beginning of lactation, the functional capacity of T cells was the lowest (42.47 ± 0.62%). But subsequently with the increase of the lactation curve there was a certain activation of their transformation into blasts (51.11 ± 1.05%). At the beginning of late lactation cows underwent a gradual decrease in the blasttransformation capacity of immunocompetent cells (43.11 ± 0.89%). And which continued to decline gradually during the dry period. Thus, during lactation in the body of cows there are dynamic permanent changes in the system of cellular and humoral immunity. From the beginning of lactogenesis, there is a gradual increase in the increase in the functioning of the mammary gland of cows, and further decrease in the population composition of CD3+ and СD22+, which was also accompanied by changes in the functional activity of immunocompetent cells.