CHALLENGES OF EQUINE FARMING IN THE AMAZON: EFFECTS OF CLIMATE ON EQUINE PHYSIOLOGY

The Amazonian climate, characterized by high temperatures, elevated relative humidity, intense solar radiation, and substantial rainfall, represents an important challenge to equine thermoregulation and performance. This review discusses the effects of these environmental conditions on the physiological responses, health, welfare, and sustainability of equine production in the Amazon. The interaction between high temperature and humidity reduces the efficiency of evaporative heat dissipation, particularly during exercise, when metabolic heat production increases substantially. Under thermal stress, horses may exhibit increased heart and respiratory rates, peripheral vasodilation, excessive sweating, dehydration, hemoconcentration, electrolyte imbalance, increased cortisol concentrations, metabolic alterations, and reduced exercise performance. Prolonged or recurrent exposure to heat may also affect immune and reproductive functions, increasing the risk of health disorders and compromising animal welfare. Environmental indicators such as the Temperature-Humidity Index (THI) and Heat Load Index (HLI), combined with physiological parameters including rectal temperature, heart rate, respiratory rate, hydration status, and recovery time, can improve the assessment of thermal load. Adaptive management strategies, including shade provision, adequate ventilation, continuous access to water, scheduling exercise during cooler periods, and post-exercise cooling, are essential to reduce thermal stress. Considering the intensification of climate change, the development of region-specific management and monitoring protocols is necessary to improve the adaptation, health, performance, and sustainability of Amazonian equine production.