Equine Gastric Ulcer Disease 

 Dr. Frank Andrews is a Professor and Section Chief of Large Animal Medicine, University of Tennessee College of Veterinary Medicine. His research focus is gastric physiology and gastric ulcer disease in horses. He is well published and considered an international expert on this subject.

Dr. Andrews reviewed the anatomy and physiology of the equine stomach. The equine stomach is separated into two portions. The upper portion of the stomach is lined by squamous epithelium. The lower portion is lined by glandular epithelium. Gastric ulcers in adult horses are most commonly found in the squamous portion of the equine stomach. The squamous portion is more sensitive to acid than the glandular portion because the glandular portion is able to secrete a protective layer of mucus. Clinical signs of gastric ulcers in horses are variable and may include mild signs of abdominal discomfort (colic), poor appetite, weight loss, and poor performance. A definitive diagnosis can only be made by gastric endoscopy, which requires a 3 meter endoscope. The horse must be fasted at least 12 hours prior to the procedure. The stomach is insufflated with air and the contents are aspirated. Most horses are mildly sedated for this procedure.

Dr. Andrew’s research has shown that the pH of the gastric fluid is dependent on the diet of the horse. The horse’s digestive tract is best suited to continuous grazing, not intermittent feeding of large meals. Domestication of the horse has imposed our eating habits upon the horse, some of which may have deleterious effects. For example, it has been shown that large concentrate grain meals result in more acidic gastric contents. The consumption of hay, especially alfalfa hay, has the ability to buffer some of the acid that is produced. Studies have shown that subjecting a horse to a strenuous exercise program (race training) may induce ulcers. Modifying the feeding schedule and environment of a horse may allow for management of gastric ulcers. Smaller grain concentrate meals should be fed along with better quality and continuously accessible hay. Ideally horses should be housed outdoors and have continuous grazing. Once again the demands of a performance horse may make this type of management difficult and pharmacologic agents should be considered.

A visit to the anti-ulcer section of your local pharmacy reveals the variety of over-the-counter medications available to humans suffering from gastric ulcers. In contrast, the first gastric ulcer medication (GastroGard/omeprazole) was developed by Merial LLC and FDA approved in 1998. Omeprazole acts by irreversibly binding to the enzyme responsible for the production of acid from the parietal cells in the stomach. It is approved for human prescription use as Prilosec. GastroGard is available as an oral paste and is to be administered once-a-day for a period of 28 days, after which the dose is halved and administered for at least four more weeks. Dr. Andrews conducted clinical trials with omeprazole and demonstrated by gastric endoscopy that omeprazole was 77 percent effective in healing ulcers after a period of 28 days and that in 84 percent of horses, recurrence of ulcers could be prevented by continued administration of omeprazole for an additional four weeks of treatment. Other medications for the treatment of gastric ulcer disease such as cimetidine (Tagamet), ranitidine (Zantac) and sucralfate (Carafate) are not approved for use in the horse and have not been subjected to the well-controlled studies necessary to confidently predict effectiveness. Following the lecture, Dr. Andrews showed videotapes of gastric examinations conducted during the studies. The videotapes clearly showed the ulcers prior to treatment and the resolution of ulcers following treatment.

 Credits: US Food and Drug Administration