Medical procedure


Gastric Ulcers

An ulcer is an area of damaged and eroded tissue that leaves behind a painful loose of protective tissue. Gastric and duodenal (the first portion of the small intestine) ulcers, are very common. Veterinarians have adopted the term “equine gastric ulcer syndrome” (EGUS) to describe not only horses with overt ulcers but also horses with erosions in the superficial (surface) layers of the stomach or inflammation in the lining of the stomach or duodenum.

According to Tamzali, Y., Marguet, C., Priymenko, N, Lyazrhi, F. (2010) the prevalence of EGUS varies depending on a horse’s breed and use. Current estimates of EGUS in various horses are:

  • 90% in racing horses;
  • 37–66% in sport and leisure horses;
  • 66% in 50-80 km ride endurance horses;
  • 48% between the competitive season and 93% in 90-160 km ride endurance horses competitive season,
  • 70.9% in pastured broodmares
  • 50% in foals.

A horse’s stomach, like most of the horse’s gastrointestinal tract, is unique and specially designed for grazing animals. It is essentially divided into two portions. The top half has a skin like lining (squamous cells), whereas the bottom half has glandular cells that produce hydrochloric acid and mucus (to help protect the stomach lining the acidic pH). A horse’s stomach is quite small, and hydrochloric acid is produced continually rather than just when food reaches the stomach (as in humans). This design is perfect for the horse which is perpetual grazer. However this system is not beneficial for horses that are fed only a few times a day. Meritt (2003) and Jones, S.L. (2006) report that when horses are fed infrequently, the acid will splash up and damage the upper portion of the stomach. In addition to prolonged time between feedings or food deprivation, other factors thought to contribute to EGUS include feeding high-starch diets such as corn, barley, oats, and wheat that might increase the acid production in the stomach; strenuous training regimens; stall confinement; medications such as non-steroidal anti-inflammatory drugs (e.g., phenylbutazone, flunixin meglumine); stress due to lifestyle or transport; and severe illness.4,5

Most, if not all, of a horse’s outward signs reflect the pain stemming from the eroding patch(es) of the stomach. Classic signs include bruxism (clenching and grinding teeth), colic, salivation, decreased appetite or anorexia, decreased performance, changes in behavior (depression, unwillingness to train), weight loss, and poor hair coat. Some horses may even resent saddling. Foals might have diarrhea. In some cases, adult horses might not show any signs.


The Arizona Equine veterinarians best diagnose gastric ulcers by passing a video endoscope into the stomach and directly visualizing the inflammation/erosion of the stomach/duodenum wall. The horse’s stomach must be empty to visualize the ulcers, therefore the patient should be fasted for 24 hours. For foals on a milk diet, only a one- to two-hour fast is necessary. Our doctors record the degree of ulcer severity, location and ulcer numbers.


The two main goals when treating horses with ulcers are to maintain a pH level greater than 4 (to make the stomach less acidic and less damaging to the lining); and to coat the ulcer with an acid-resisting agent.

Controlling pH

Antacids (e.g., Maalox) effectively increase pH for at least two hours and are not expensive; however, these compounds must be administered on an empty stomach (which we try to avoid in horses with ulcers) at least four times a day. Some horses will eat the product mixed with grain, but your horse may need to be syringe-fed as many horses resent the taste.

Another option is to administer drugs (e.g., ranitidine and cimetidine) that decrease acid production by blocking histamine- 2 receptors. In contrast to antacids, the benefits of these drugs are enhanced when the horse’s stomach is full.

Finally, omeprazole (4 mg/kg once daily) – Gastrogard – is a proton pump inhibitor that stops the stomach’s hydrochloric acid secretion. Studies indicate that when administered before morning feed, omeprazole paste will have a maximum effect one to eight hours post-administration. This medication should be administered for one month to heal the ulcers. Preventative protocol requires the use of ulcer-gard, ulcergard is also ompeprazole.

Coating Ulcers

Oral sucralfate sticks to the ulcer, forming an acid-resistant barrier that enables the ulcerated tissue to heal. Again, this drug needs to be administered on an empty stomach, which is contraindicated for preventing additional ulcers.


Even severe ulcers in otherwise healthy adult horses are unlikely to perforate. In many cases, the horses will show clinical signs suggestive of gastric ulceration, allowing plenty of time to start treatment and institute management changes to prevent future ulcers from forming. In foals, EGUS is more serious and must be addressed aggressively in any neonatal foal that becomes ill to potentially avoid catastrophic rupture of the ulcerated stomach.

Prevention and Control

Management has a huge impact on EGUS development. Continuous pasture access is the best diet for all horses. When this is not an option, then at least 75% of the diet should be roughage, divided into four to six meals/day. Studies also show that forage type makes a difference for horses at risk for or diagnosed with EGUS. For example, horses fed alfalfa hay have lower ulcer scores than horses fed grass hay. Finally, make an effort to minimize the amount of stress in your horse’s lifestyle.


1. Merritt, A.M. Equine gastric ulcer syndrome (EGUS): clinical manifestations. 2003. Proceedings of the 8th Congress on Equine Medicine and Surgery.

2. Tamzali, Y., Marguet, C., Priymenko, N, Lyazrhi, F. Prevalence of gastric ulcer syndrome in high-level endurance horses. Equine Vet J. 2011;43:141-144.

3. Jones, S.L. Gastric ulcer disease. 2006. Proceedings of the North American Veterinary Conference.

4. Larson, E. Nutritional management of gastric ulcers.
5. Holland, J. Equine ulcers … for life?

6. Merritt, A.M. Equine gastric ulcer syndrome (EGUS): anti-ulcer therapy. 2003. Proceedings of the 8th Congress on Equine Medicine and Surgery.

7. Oke, S. Gastric ulcer supplements for horses evaluated.

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