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Influence of heat stress on cows during the dry and postpartum period

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.