Relevance. Many scientists reasonably believe that disturbances in microclimatic parameters are the basis for reduced adaptation of the animal organism to environmental conditions, to aggressive stress factors affecting the immune system of animals. This leads to a violation of the barrier function of the lungs, the rapid multiplication of microflora in the mucous membrane of the upper and lower respiratory tract, the development of exudative processes and a bright leukocyte reaction.Methods. To conduct the experiment in the winter stall period of 2021–2022, calves of the Holstein breed aged 15.0± 5.0 days were selected, from which two groups were formed according to the principle of pairs of analogues of 15 heads each.Results. The authors found that the use of a «Biological inactivator of toxic gases in the litter» for animals makes it possible to achieve a significant reduction in the amount of ammonia in the air inhaled by calves of the over-lining layer. At the same time, the respiratory function of the animal organism is activated (normalization of the body's homeostasis, improvement of erythropoiesis, reduction of erythrocyte sedimentation rate, increase in the level of alkaline blood reserve, etc.).