Help your horse stay cool on the trailer and know what to do if he overheats

For many horse owners, warmer weather means more off-property trips to shows, clinics, trail rides, and other activities—some minutes away and others requiring several hours, or even days, of travel. As the temperatures rise, so does your horse’s risk of heat stress during trailering.

Heat stress can cause a horse to become unsteady on the trailer and, if left untreated, can lead to heat exhaustion or collapse. Learning to recognize the signs of heat stress in your horse before they become severe and understanding how to cool him if he experiences heat stress can help reduce the risk of severe complications.

Heat Stress in Horses

Heat stress is the horse’s response to dehydration—characterized by sustained skin “tenting” after a pinch test, pale and tacky mucous membranes, sunken eyes, dry feces, lack of appetite, and lethargy—along with extreme heat and electrolyte loss. Keep in mind, horses can become dehydrated due to loss of fluids through sweat in both dry and humid climates.

Horses with mild heat stress typically have a body temperature above 103 F and increased capillary refill time—the color of the gums takes more than two seconds to return after pressing them with your finger. Those suffering from severe heat stress can have a temperature of 106 F or more, elevated heart rate, thready pulse, and a lack of thirst despite being dehydrated.

If you believe your horse is experiencing heat stress, contact your veterinarian and formulate a plan to cool the animal as quickly as possible. Move him out of direct sunlight into an area with good airflow, continuously hose him, and offer a few sips of water multiple times (avoid him guzzling the entire bucket) to help him rehydrate.

Dangers of Hot Weather Trailering

“When horses suffer from heat stress they may become dehydrated, develop low blood pressure, can colic, or suffer from kidney compromise or failure,” says Ragan Adams, MA, DVM, veterinary extension specialist in the Department of Clinical Sciences at Colorado State University College of Veterinary Medicine and Biomedical Sciences, in Fort Collins. This is what might cause the horse to become unsteady on the trailer.

Check horses often enough that you recognize dehydration before they become unsteady and/or fall in the trailer, says Adams. Each horse that goes down in the trailer must be evaluated on an individual basis—some might get up easily with encouragement while others are unable to stand.

Another important issue to consider is horses with anhidrosis—the inability to sweat. Bob Coleman, PhD, associate professor at the University of Kentucky, in Lexington, recommends carefully monitoring affected animals during travel; watering them frequently; maximizing trailer ventilation (consider a more open-sided trailer); hauling during the coolest times and planning routes carefully to avoid traffic; and avoiding parking in the direct sun