Horses: How Heat Stress to Heat Stroke Can Be Fatal

Heat Stress vs. Heat Stroke
Heat stress, also known as heat exhaustion, is when fluids and electrolytes are lost from the body, typically during exercise that is exhausting. The surrounding temperature plays a critical role in heat stress. The air temperature, how sunny it is, and the humidity levels all contribute and can increase the chances of heat stress.

While both are dangerous, heat stroke is more severe. Heat stroke can occur following heat stress. Or heat stroke can occur simply from being in a hot trailer or poorly ventilated building for even just a short period of time. If not addressed immediately, heat stress which can lead to heat stroke, can be fatal.

What Happens to the Body?
When an animal is exercised, it needs to sweat. During exercise, horses especially, generate a lot of heat due to their large muscle mass. Heat, sun, and humidity make it challenging for the heat to escape from the horse’s body. This in conjunction with the sweat, causes a loss in fluids and electrolytes. This loss can lead to dehydration, which can then lead to heat stress. If not addressed, heat stress can very easily turn into heat stroke.

Signs of Heat Stress (Heat Exhaustion)
– rapid breath                 – not wanting to work          – sweat dripping on coat
– stiff mobility                 – abnormal mobility
– spasms of the diaphragm or flanks

Signs of Heat Stroke
– fatigue                                   – heavy breathing                – rapid pulse
– sweat dripping on coat      – increase salivation            – muscle spasms
– erratic heart beat                – stumbling                           – collapsing
– oral redness (esp. tongue)

How to Prevent Heat Stress and Heat Stroke
– Provide fresh, clean water (esp. during excessive heat)
– Provide a heat escape (shade, barn with fans, avoid hot trailers)
– Ride during cooler part of the day (early morning, late evening)
– Trim long coats
– Help your horse maintain a healthy weight

What to Do If Your Horses is Already Showing Signs of Heat Stress?
– Spray your horse down with cold, cold water
– Use a sweat scraper to scrape sweat and excess water from their coat
– Put horse in a shady, cool area
– Do NOT cover horse with a sheet

What to Do If Your Horse is Suffering from Heat Stroke?
– Apply ice packs to horse’s head and large muscle on the inside of legs
– If no improvement, call a veterinarian immediately (IV fluid may need to be administered, especially if horse is stumbling or falling)

Concerned about your horse’s overall health? Contact PetMedella at 612-812-9121 or email us at and ask about our hair and saliva testing!