Stomach ulcers are often associated with stress, but they can also be caused by a variety of factors, including diet and medications. For horses, Equine Gastric Ulcer Syndrome (EGUS) is a common condition that is often diagnosed without its true cause ever being known.

Between 50-90 percent of horses will experience this condition at some point in their lifetime, according to Dr. Amanda Trimble, a clinical assistant professor of equine internal medicine at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

“The prevalence of EGUS varies with breed and activity level, with gastric ulcers most commonly seen in high-level performance horses and racehorses, as well as individuals and breeds that tend to be a bit more high-strung, such as Thoroughbreds or young fillies,” Trimble said. “However, gastric ulcers can occur in any horse, even those living out on pasture full-time and not being ridden.”

While gastric ulcers can occur in both parts of a horse’s stomach, they are more common in the squamous (top) portion than in the glandular (bottom) portion.

Although veterinarians still do not know exactly why many horses develop EGUS, risk factors include the use of non-steroidal anti-inflammatory drugs, stressful events, eating a diet high in starches or concentrate feeds, and not eating often enough.

“Horses’ stomachs continuously produce acid, so grazing and small, frequent meals are important for neutralizing this acid and preventing it from splashing up in the stomach and causing ulcers,” Trimble said. “Fasting should be avoided, and horses should always have access to fresh, clean water.”

If a horse develops EGUS, the most common sign is that it will prefer to eat hay rather than grain.

“Other signs we may see are a lack of appetite, weight loss, behavior changes such as grinding teeth, or mild signs of low-grade colic (abdominal pain), particularly right after eating,” Trimble said. “Many horses show no clinical signs at all, and the ulcers may be an incidental finding.”

A veterinarian who suspects EGUS in a horse will perform a gastroscopy to look at the stomach lining and the beginning of the small intestine with a small camera. Horses will need to be briefly fasted before this procedure to ensure the stomach is empty and clean, and sedation is often required.

If EGUS is confirmed, the most common treatment is giving one dose of omeprazole each day for a month to buffer the stomach acid and give the stomach lining time to heal.

Trimble cautions horse owners to only use omeprazole formulations approved for horses by the U.S. Food and Drug Administration and to avoid specialty omeprazole products that may contain lower, less-effective doses of the drug.

“We also recommend dietary changes when managing gastric ulcers,” she said. “Small, frequent meals are ideal, as well as having hay or grass available throughout the day, possibly in a slow feeder or a toy, if the horse’s metabolic status allows for that. Fresh green grass and pasture grazing is great for decreasing stress and helping gastric ulcers heal.”

After a month of treatment, another gastroscopy can help determine if the ulcers are resolved or if treatment needs to be continued.

For horses prone to ulcers, some precautions can help reduce the risk of EGUS, including giving a low dose of omeprazole before a stressful event, feeding a low-starch diet, offering alfalfa hay, and adding a small amount of vegetable oil to the horse’s food.

“Being aware of your horse’s behavior deviating from normal and working with your veterinarian to develop a proper nutrition and management plan can help to prevent gastric ulcers from forming in the first place,” Trimble said.

Because the lack of specific clinical signs means that many horses with EGUS go undiagnosed, the condition is most likely even more prevalent than believed. Fortunately, ulcers often resolve on their own with time and cause no lasting issues.