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In the article, the authors presented information on the effect of heat stress on cows in the dry and postpartum periods. The study aims to study clinical and metabolic manifestations of heat stress in dry and fresh cows. The object of the study is cows of the early and late dry periods and new calves. The authors assessed the parameters of the microclimate of livestock premises, clinical examination of cattle, and blood sampling for hematological and biochemical studies. The authors also calculated the leukocyte index of intoxication, the shift index of blood leukocytes, and the lymphocytic index. Animals were found to have worsened general conditions, weakness, and reduced feed intake during the medical examination. An increase in body temperature (39.42±0.55 °C), tachypnea (86.45±8.04 resp.), and tachycardia (127.65±3.66 bpm) were also revealed. A hematological study revealed a decrease in the absolute number of lymphocytes and a shift in the indicators of the leukocyte formula. According to the results of the assessment of the lymphocytic index in cows during the dry period, the ratio of humoral and cellular immunity was balanced, and in new calves, an imbalance was observed. Biochemical screening of the blood serum of cows under conditions of heat stress showed significant changes in the metabolic profile against the background of a general decrease in feed intake. The content of total protein and globulins in the blood serum in the first days after calving was 68.36±3.48 (p≤0.01) and 35.36±3.89 g/l (p≤0.01), which is 16 .0 and 33.0% lower than in cows of the early dry period. Glucose and cholesterol levels progressively decreased after starting, reaching a minimum in the postpartum period (glucose - 3.14±0.59, total cholesterol - 2.18±0.55 mmol/l (p≤0.01)). The content of urea in the blood of animals increased significantly, reaching a maximum in the first days after calving - 7.44±1.48 mmol/l (p≤0.01). The authors also found an increase in the content of total bilirubin, aspartate aminotransferase, and creatine phosphokinase. Thus, heat stress leads to changes in the clinical and metabolic status of highly productive cows.

Modern diagnostic laboratory methods and application of biochemical parameters of blood will allow to determine the pathological process, determine its cause, degree of development, and prognosis. The introduction of these principles can be useful in the development and correction of health measures. The aim of this work is to identify pathognomonic metabolic signs of mycotoxicosis in cattle. In the work, highly productive cows, with clinical signs of intoxication syndrome were examined, and laboratory studies of feed confirmed the availability of metabolites of fungi.Metabolic parameters of the examined group of cows were studied in a comparative aspect with clinically healthy animals in this agricultural enterprise that were examined a year earlier.Conducted investigations have established that the use of feed, contaminated by toxic fungal metabolites leads to the development of symptoms in animals chronic toxemia.Clinical signs are the development of diarrhea and dehydration, and there is a decrease in milk production.The pathological changes that occur in toxemia lead to metabolic disturbances, which can be identified by laboratory diagnostic methods.The pathological process is accompanied by the appearance of severe form of acidosis, including renal tubular acidosis (a decrease in bicarbonate blood capacity, hyperchloremia, hyperphosphatemia, globulinemia, hypokalemia, hypercreatininaemia).Metabolic acidosis predetermines the violation of many types of metabolism, including protein, carbohydrate, mineral and lipid.The pathology of the hepato-biliary system of predominantly toxic etiology is a high percentage in the structure of diseases.Other important metabolic symptoms include the development of the inflammatory process (leukocytosis, an increase in the number of segmented neutrophils and circulating immune complexes), an increase in signs of allergization (eosinophilia, monocytophilia), as well as general intoxication (predominance of abnormal forms of erythrocytes, hypoglycemia).

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The creation of new drugs and feed additives is an urgent task that contributes to the growth of the efficiency of the livestock and poultry industries of agriculture, especially during the period of import substitution in the Russian Federation. An experimental study of possible changes in the body of laboratory animals after single or multiple uses of new feed additives is necessary for the toxicological assessment of newly created products. Single intragastric administration of feed additive Endoforce Multi containing live vegetative cells and spores of cultures: Bacillus subtilis B-5449, Bacillus subtilis B-1323, Bacillus subtilis B-3679 - 5.0 109 CFU / ml, at a dose many times higher than recommended, did not lead to the death of laboratory animals, which confirmed the absence of its acute toxicity. Over the entire observation period, the authors did not note any disturbances in the rats’ behavioural reactions and physiological states. Determination of chronic toxicity was carried out for 30 days. The studied suspension of the feed additive was given with water to rats of the experimental groups at doses: 1st - 100 mg, 2nd - 150 mg and 3rd - 200 mg per head. At the end of the empirical study, an increase in the number of erythrocytes by 2.68–3.72 1012/l, haemoglobin - by 41.50–61.58 g/l in laboratory animals of the experimental groups compared with the control ones was revealed, which indicated an increase in blood oxygenation and the organism as a whole. In addition, in the rats of the experimental groups, a decrease in the content of urea in the blood to 3.14 ± 0.53 - 4.68 ± 0.41 mmol / l and creatinine to 32.26 ± 5.18 - 48.13 ± 6.23 µmol/l. The opposite trend was observed when determining the serum activity of alkaline phosphatase, which increased by 39.0–52.6% in intact individuals, which indicated dynamic processes of growth, formation and development of the skeleton. According to the results of the autopsy of the rats of the studied groups, regardless of the dose of the introduction of the feed additive Endoforce Multi, no pathological changes in the colour, consistency and size of the internal organs were registered.