REVIEW: ENVIRONMENTAL AND ANIMAL INDICATORS FOR HEAT STRESS ASSESSMENT IN DAIRY CATTLE

Climate change, the increase in global surface temperature and extreme changes in weather patterns, presents substantial difficulties for farm animals. A main issue is heat stress, which happens when environmental conditions go beyond the thermoneutral zone, hindering animals' ability to release extra body heat. Dairy cattle are seen as highly vulnerable to heat stress because of their elevated metabolic heat production. Under heat stress, dairy cattle encounter alterations in their welfare and health that affect their reproductive and reproductive performances. Hence, climate change has enormous impact on dairy cattle farming as a major source of global food production. To maintain the isothermal condition, animals employ several physiological and behavioral mechanisms in order to dissipate heat. The pathophysiology of heat stress and its impact on various organs and organic systems has been studied extensively in dairy cattle in recent years. Understanding the effects of heat stress on animals, including environmental factors, physiological and behavioral responses, and pathophysiology, is crucial for creating successful strategies to safeguard them. The goal of this paper was to provide an overview of the most recent information on the Temperature-Humidity Index (THI) as a commonly used indicator of environmental heat stress, and on physiological and behavioral responses as indicators of heat stress in animals. The complexity of these two indicators was an incentive to compile and summarize the most recent papers comprehensively, and provide them as a resource for future research in various fields.