The relevance of the search for markers and indicators of thermal tolerance in cattle (review)

The efficiency of livestock farming, especially dairy farming, in the context of global warming is determined by a complex of factors: climatic conditions (heat stress), feed base, physiological state of animals and their genetic adaptability. Elevated temperatures provoke complex disorders in cattle, including metabolic disorders and decreased productivity. Against the background of climate change, the impact of heat stress on cattle is a serious problem for animal husbandry. The objective of the review: to consider the signs of adaptive qualities and thermotolerance of cattle. In the context of climate change, heat stress in cattle is becoming a major concern for the livestock industry. Studies of domestic and foreign authors show that when the temperature-humidity index (THI) exceeds the threshold value (> 66), animals experience physiological disorders (increase in rectal temperature, increased respiration, etc.), behavioral changes (decreased activity, reduced feed intake, etc.), biochemical shifts (increased cortisol, increased ketone bodies, etc.), and biochemical changes (increased cortisol, increased ketone bodies, etc.). ), biochemical shifts (increase in cortisol, increase in ketone bodies, etc.), decrease in productivity (decrease in milk yield, decrease in fat and protein mass fraction, change in fatty acid composition, decrease in live weight gain), deterioration of reproductive functions (decrease in fertilizability, and deterioration in sperm motility). Genetic studies have identified key markers of thermotolerance, including genes for heat shock proteins and factors (HSP and HSF), antioxidant enzymes, immunity and metabolism genes. However, selection is complicated by antagonism between productivity and stress tolerance. To minimize the consequences of negative effects of heat stress, it is recommended to control microclimate (ventilation, cooling) in livestock buildings, optimize feeding (introduction of antioxidant and vitamin supplements) and apply, along with traditional breeding methods, genetic selection using GWAS-analysis.