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