Dynamics of immune system indicators in pregnant cows with physiological gestation and with endotoxicosis

Particular attention in veterinary medicine is given to the study of the immune system status of pregnant cows, since this period is accompanied by significant physiological changes and increased sensitivity of the organism to stress factors and intoxications. One of such pathological conditions is endotoxicosis, which is associated with suppression of humoral, cellular, and nonspecific immunity, potentially leading to the development of secondary immunodeficiency. The aim of the study was to determine the dynamics of immune system indicators in pregnant cows with a physiological course of calving and in the presence of clinical signs of endotoxicosis. The work included analysis of humoral, cellular, and nonspecific immune components. It was established that the bactericidal activity of blood serum in the experimental group at the 8th and 9th months of pregnancy was lower by 11.3–18.7 % compared to the control, while lysozyme activity was reduced by 20.2–22.0 %. In addition, a significant decrease in neutrophil phagocytic activity and phagocytic index was observed, indicating suppression of nonspecific defense mechanisms. Cellular immunity studies showed that the number of T-lymphocytes in the blood of diseased cows was significantly lower by 23.2 % compared to the control group at the 9th month of pregnancy, and the number of B-lymphocytes decreased by 2.8–18.9 %. A decrease in serum immunoglobulin levels was also found: by 16.0 % at the 8th month and by 24.6 % at the 9th month of pregnancy. The most pronounced decline was observed in the concentration of immunoglobulins of class G, which decreased by 26.3 % compared to physiological pregnancy. The obtained results indicate that the development of endotoxicosis in pregnant cows causes systemic suppression of the main components of the immune system. This is manifested by a reduction in bactericidal and lysozyme activity of blood serum, numbers of T- and B-lymphocytes, neutrophil phagocytic activity, as well as decreased immunoglobulin levels. Such changes reflect the formation of secondary immunodeficiency, which has important practical significance for timely diagnosis, prevention, and therapy of endotoxicosis in cattle.