Gastric Ulcers in Performance Horses

By Wendy Mallot, DVM, DACVIM; Hospital Director & Large Animal Internist, Pilchuck Veterinary Hospital

Gastric (stomach) ulcers can wreak havoc on your show horse, turning your star competitor into an underweight, dull coated, poorly behaved citizen. Think it can’t happen to your lovingly cared-for equine? Think again: research studies have estimated that 60 to 90 percent of performance horses have gastric ulcers.

So, what are the signs that your horse is one of them? Fact is, horses with gastric ulcers can display a variety of symptoms. In addition to problems with weight, coat, and behavior, an afflicted horse can also exhibit low-grade colic, diarrhea, or poor appetite. Any of these symptoms—and especially a combination of some—should trigger concern and a consultation with your equine veterinarian.

Gastric Ulcers

Why ulcers develop

Horses develop gastric ulcers when excess digestive acid damages the lining of the stomach. A little knowledge of horse anatomy helps explain the underlying mechanisms. The equine stomach has two distinct regions: an upper, non-glandular (or squamous) region and a lower, glandular (acid-producing) region. Food enters the squamous region, which comprises roughly a third of the stomach, and from there descends into the glandular region,

where digestive acids and enzymes break it down into nutrients. Ulcers can form in either region, but most occur in the non-glandular tissue, which lacks certain protective features that characterize the lining of the glandular region.

Having evolved as grazers that eat throughout the day, horses continuously secrete stomach acid. In the wild (or in the pasture), the potentially damaging effects of this acid are buffered by the nearly continuous intake of grass and the ongoing production of acid- neutralizing saliva. But modern-day equine management often results in horses only eating just two to three meals a day, putting our equine companions at significant risk for the development of gastric ulcers.

Moreover, the stress of prolonged travel increases the production of stomach acid, ratcheting up the incidence of gastric ulcers. So, too, does the intense training and exercise of show horses. Research has shown that the size of the equine stomach decreases during exercise, which results in the delicate non-glandular portion of the stomach being in contact with acid for a prolonged period. Finally, the use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as Banamine (Flunixin) and Bute (Phenylbutazone) can also cause gastric ulcers.

Diagnosis and treatment

Currently, the only reliable method for diagnosing equine gastric ulcers is gastric endoscopy; that is, passing a tube with a small camera through the esophagus and into the stomach. This procedure, which is performed in a veterinary clinic, allows the veterinarian to directly visualize the stomach for the presence of ulcers or other abnormalities. Since food contents can interfere the examination, the horse should not eat for 12 hours nor drink for four hours preceding gastric endoscopy. Once diagnosed, most gastric ulcers are very effectively treated with GastroGard (omeprazole), an orally administered paste that inhibits the production of acid in the stomach.