By Jorge Nieto, DVM, PhD, Dipl. ACVS–Reprinted from The Horse Report with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis (UC Davis).


A common case of heartburn can bring intense discomfort, even pain, to a person. Imagine your horse trying to perform with a stomach ulcer. Did you know that the clinical signs of ulcers in horses are subtle and nonspecific and might be reflected in a slight attitude change, a decrease in performance, or a reluctance to train?

Gastric ulcers are common in horses. Their prevalence has been estimated to be from 50% to 90%, depending on populations surveyed and type of athletic activity horses are engaged in.

Gastric ulcers can affect any horse at any age. Foals are particularly susceptible because they secrete gastric acid as early as 2 days of age and the acidity of the gastric fluid is high. Foals that have infrequent or interrupted feeding, or are recumbent for long periods have been found to have lower gastric fluid pH (aqueous solutions with a pH less than 7 are acidic), suggesting that milk has a protective effect against ulcers and that recumbency increases exposure of the stomach to acid.

In adult horses, gastric ulcers occur more frequently in horses that perform athletic activities, with the highest frequency found in Thoroughbred racehorses (80-90%), followed by endurance horses (70%), and show horses (60%). Researchers have found that exercise increases gastric acid production and decreases blood flow to the gastroin