Equine gastric ulcer syndrome is a common condition, both in performance horses, such as racehorses, and in foals. Pamela Wilkins, DVM, PhD, Dipl. ACVIM, ACVECC, an equine veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana, says more than 90% of performance horses have gastric ulcers, as do between 25 and 50% of foals.

“Ulcers are sores in the lining of the stomach,” explains Wilkins, who is boarded both in equine internal medicine and in equine emergency and critical care.

In horses, the top portion of the stomach is lined with flat non-glandular cells and the lower portion has glandular cells.

Wilkins says approximately 80% of equine gastric ulcers occur in the non-glandular upper portion, which is less resistant to injury from stomach acid. The glandular tissue is more resistant to damage because it secretes mucus.

“Ulcers in the upper portion of the stomach are caused by stomach acid, whereas glandular ulcers occur when the mucosal protection and blood flow are impaired, which may be related to the use of non-steroidal anti-inflammatory drugs,” says Wilkins.

There are multiple risk factors for equine gastric ulcer syndrome. During intensive exercise, such as training or racing, the body concentrates the flow of blood to the horse’s heart and muscles, and a reduced amount of blood flows to the gastric mucosa of the stomach, which can result in ulcers.

Intense exercise also increases the intra-abdominal pressure, causing compression of the stomach, which in turn could force acid that is normally in the lower portion of the stomach into the upper, non-glandular portion. As a result, ulcers could arise since the upper region has no mucosal secretions to protect it from acid.

Horses fed a high-carbohydrate diet are also at increased risk for ulcers.

“Excessive amounts of carbohydrates and sugars will ferment in the stomach,” Wilkins says. “The byproducts of this fermentation are thought to synergize with the stomach acid and may lead to non-glandular ulcers.”

Clinical signs of gastric ulcers in adult horses include poor appetite and body condition, attitude changes, mild to moderate colic, decrease in performance, and a poor hair coat.

In foals, clinical signs include poor appetite or intermittent nursing, colic, poor body condition, frequently lying on their back (which indicates gastrointestinal pain, but not necessarily an ulcer), teeth grinding, excessive salivation, and diarrhea.

However, these clinical signs are only suggestive of an ulcer. For a definitive diagnosis, a veterinarian must examine the horse via endoscopy, a nonsurgical procedure in which a light and camera attached to the end of a flexible tube are inserted down the throat and into the stomach. Images from inside the stomach are displayed on a monitor, enabling the veterinarian to determine definitively whether there are ulcers.

Equine gastric ulcer syndrome can be treated using management modifications or medical therapy or a combination of these approaches.

“Management modifications may include reducing the level of exercise, limiting periods of fasting, and changing the diet, such as by increasing the amount of roughage and reducing grain concentrate in the diet,” says Wilkins. “Horses kept on pasture are less likely to develop gastric ulcers.”

In horses as in people, stress can play a role in ulcer development. Thus, Wilkins recommends that owners limit stressful events for horses, such as trailering, overcrowding, and long-term stall confinement.

Medical treatment of gastric ulcers includes either antacid therapy (to neutralize the acid) or anti-secretory agents. Wilkins says veterinarians most commonly use anti-secretory medications and more specifically use what are called “proton pump inhibitors.” These medications work at the level of the parietal cell, where the acid is being produced, to inhibit acid formation.

“The most effective treatment of for equine gastric ulcers combines management and medical interventions,” advises Wilkins.

Speak with your equine veterinarian if you believe your horse could have gastric ulcers.