Effect of hyperthermia on hematological parameters and productivity of laying hens

Abstract

Studies were conducted in the period 2020-2021 based on the department of ecology and noncontagious pathology of animals of the Ural Veterinary Research Institute - a structural subdivision of FSBSI “UFARC UB RAS” (Federal State Budgetary Scientific Institution “Ural Federal Agrarian Research Center of the Ural Branch of the Russian Academy of Sciences”). Significant increases in ambient temperature in industrial poultry farming have natural and incidental effects on all processes in the living organism of birds, affecting their direction and intensity. We studied the use of feed additives containing dried live yeast of different variants and concentrations before and after heat stress on changes in the live body weight of laying hens, the importance of laid eggs, and quantitative and qualitative characteristics of the blood leukocyte formula. The authors registered a significant increase in the concentration of erythrocytes and hemoglobin in birds of the control group - 18.1 and 25.5% during the period of heat stress, which indicated the beginning of a long adaptation process.Furthermore, the authors noted a significant increase in the ratio of the number of heterophils to lymphocytes (g/l) and in individuals of the control group by 44.2% (0.62 units), which confirmed the intensity of all processes in the body. During the study, the authors note that the total number of leukocytes increased against the background of a stress factor in the blood of laying hens of the control, 1st, and 2nd experimental groups - 1.4, 1.2, and 1.3 times, respectively. This increase occurs due to the release of immature heterophils into the bloodstream and the outflow of lymphocytes into peripheral tissues. The authors note the best stress resistance to 48-hour hyperthermia when using feed additives of hepatoprotective action in chickens of the 1st and 2nd groups reported the best stress resistance to 48-hour hyperthermia. This stress resistance is confirmed by regular physiological changes in the level of heterophils, basophils, monocytes, and G/L, characteristic of the period of urgent adaptation and maintenance of immune homeostasis.