Bob Judd, DVM, DABVP (Equine Medicine), DABVP (Canine and Feline Practice)
With the upcoming heat and humidity, horse owners with performance horses need to be familiar with exhausted horse syndrome. The University of Kentucky shows in the publication The Horse that exhausted horse syndrome refers to multiple conditions of horses becoming fatigued. Affected horses appear stiff or weak, and some show decreased energy or appetite.
In serious cases, irregular heartbeat, shock, muscle damage, colic, and diarrhea can develop. Under-conditioned horses performing in heat and humidity are more likely to experience the condition.
Exhaustion has multiple causes that include heat, electrolyte imbalance, and energy stores. Your horse removes body heat by sweating and with air movement. If these do not occur, core body temperature increases.
The primary energy source for muscles is stored sugar, or glycogen, and when this is used up with exercise, your horse will slow down or stop exercising.
If you are riding and think your horse may have exhausted horse syndrome, stop at once and do not move your horse. Call your veterinarian.
Cool your horse by running large amounts of water over the entire body. Intravenous fluids may be needed to help cool your horse. If the digestive tract is functioning, giving fluids with a tube through the nose can also help, as long as your horse is not having colic symptoms. If colic symptoms are present with abnormal gut sounds, the stomach should remain empty.
Exhaustion can be prevented with proper training, nutrition, electrolyte supplements, and allowing time for your horse to become acclimated to new environments.