section_path: Interaction with humans/Climate change
section_name: Climate change
paragraph_text: Climate change
  
  As of 2019, there are around 17 million horses in the world. Healthy body temperature for adult horses is in the range between 37.5 and 38.5 °C (99.5 and 101.3 °F), which they can maintain while ambient temperatures are between 5 and 25 °C (41 and 77 °F). However, strenuous exercise increases core body temperature by 1 °C (1.8 °F)/minute, as 80% of the energy used by equine muscles is released as heat. Along with bovines and primates, equines are the only animal group which use sweating as their primary method of thermoregulation: in fact, it can account for up to 70% of their heat loss, and horses sweat three times more than humans while undergoing comparably strenuous physical activity. Unlike humans, this sweat is created not by eccrine glands but by apocrine glands. In hot conditions, horses during three hours of moderate-intersity exercise can lose 30 to 35 L of water and 100g of sodium, 198 g of choloride and 45 g of potassium. In another difference from humans, their sweat is hypertonic, and contains a protein called latherin, which enables it to spread across their body easier, and to foam, rather than to drip off. These adaptations are partly to compensate for their lower body surface-to-mass ratio, which makes it more difficult for horses to passively radiate heat. Yet, prolonged exposure to very hot and/or humid conditions will lead to consequences such as anhidrosis, heat stroke, or brain damage, potentially culminating in death if not addressed with measures like cold water applications. Additionally, around 10% of incidents associated with horse transport have been attributed to heat stress. These issues are expected to worsen in the future.