THE STATE OF THE IMMUNE SYSTEM OF HORSES IN CONDITIONS OF STRESS

Abstract

The study assessed the impact of adverse conditions of feeding and keeping horses on the state of their non-specific resistance. Morphological indicators of blood (hemoglobin content, number of erythrocytes and leukocytes), as well as indicators of humoral (BASC, LASC) and cellular link of innate immunity (phagocytic activity of leukocytes) were used. During the experiment, the horses had a satisfactory general clinical condition, and the main physiological indicators (body temperature, arterial pulse frequency, number of respiratory movements) were within the age norm. It is important to note that there was no significant difference between these parameters in animals at different time periods, which indicated a stable physiological state of the horses at the beginning and at the end of the experiment. The results of the study showed that long-term stress can cause changes in the hematological and biochemical parameters of horses. For example, the level of hemoglobin in clinically healthy horses was 136±2.2 g/l, but after exposure to stress factors it decreased to 110±1.8 g/l (р<0.001). At the stage of adaptation, the hemoglobin level increased to 124±2.6 g/l (р<0.01) and almost reached the values of clinically healthy horses (132±3.2 g/l) at rest. The number of erythrocytes in clinically healthy horses was 8.8±0.1 T/l. Under stress, this indicator increased to 9.8±0.2 T/l (р<0.01), but decreased to 9.6±0.2 T/l (р<0.05) at the stage of adaptation and reached the lowest level at rest — 8.6±0.1 T/l. A decrease in the number of leukocytes under the influence of stress has been confirmed by our research. In clinically healthy horses, the number of leukocytes was 6.7±0.3 G/l, while under stress this indicator decreased to 5.3±0.2 g/l (p<0.001). At the stage of adaptation, the number of leukocytes increased to 5.5±0.3 g/l (р<0.01) and was 6.2±0.3 G/l at rest. Stress also affected the indicators of non-specific resistance. In clinically healthy horses, the level of BASC was 85±1.8%, but under stress this indicator decreased to 70±2.1% (р<0.001). At the stage of adaptation, BASK increased to 75±1.1% (р<0.01), and at rest it was 82±1.7%. The level of LASK in clinically healthy horses was 35±0.2%, but under stress this indicator decreased to 28±0.4% (р<0.001). At the stage of adaptation, LASK increased to 30±0.2% (p<0.001) and reached 36±0.5% at rest. The phagocytic activity of leukocytes in clinically healthy horses was 60±1.5%, but under stress this indicator decreased up to 50±1.1% (р<0.001). At the stage of adaptation, phagocytic activity increased to 55±0.5% (р<0.01) and was 63±0.9% (р<0.05) at rest. Thus, the results of our study confirm that stress negatively affects the hematological and biochemical parameters of horses, as well as their non-specific resistance.