By Scott R. McClure, DVM, PhD, Diplomate ACVS, Diplomate ACVSMR
Why Do Horses Get Ulcers?
Equine gastric ulcers can affect any horse at any age. Up to 90 percent of racehorses and 60 percent of show horses, as well as non-performance horses and even foals are affected by equine gastric ulcers. These are the result of the erosion of the lining of the stomach due to a prolonged exposure to the normal acid in the stomach. Unlike ulcers in humans, bacteria do not appear to cause equine gastric ulcers. Horses are designed to be grazers with regular intake of roughage. Since the horse’s stomach continually secretes acid, gastric ulcers can result when the horse is not eating regularly due to there being less feed to neutralize the acid.
The horse’s stomach is divided into two parts. The bottom part is glandular and secretes acid and has a protective coating to keep it from being damaged by acid. Ulcers do occur in the glandular portion of the stomach, but this is less common. The top portion of the stomach is designed for mixing of the contents of the stomach and does not have as much protection from the acid. This is the most common place to find gastric ulcers.
Ulcers are often a man-made disease. Stall confinement alone can lead to the development of gastric ulcers. Horses maintained without direct contact to other horses and horses kept and trained in urban areas are more likely to develop squamous gastric ulcers. When horses are fed two times per day, the stomach is subjected to a prolonged period without feed to neutralize the acid. Furthermore, high-grain diets produce volatile fatty acids that can contribute to the development of ulcers.
Stress (both environmental and physical) can also increase the likelihood of ulcers. Even typical training and recreational showing have been shown to induce ulcers within a five to seven day period. Hauling and mixing groups of horses as well as horses in training, can lead to ulcers. Strenuous exercise can decrease both the emptying function of the stomach and blood flow to the stomach, thereby contributing to the problem.
Many foals being hospitalized for routine or critical care, or foals in any stressful environment, are commonly and prophylatically placed on medication to help prevent gastric ulceration.
Finally, chronic administration of any non-steroidal anti-inflammatory drugs such as phenylbutazone, flunixin meglumine or ketoprofen, can decrease the production of the stomach’s protective mucus layer, making it more susceptible to the formation of ulcers in the glandular portion of the stomach.
The majority of horses with gastric ulcers do not show outward symptoms. They have more subtle symptoms, such as a poor appetite, and poor hair coat. The effect on performance is not well understood. Thoroughbred and Standardbred racehorses with poor performance have a higher incidence of squamous gastric ulcers. More serious cases will show abdominal pain (colic) and/or bruxism (grinding the teeth).
Some horses are found on their backs or continually “cast” in their stalls since this position seems to provide some relief from severe gastric ulceration.
The only way to definitively diagnose ulcers is through gastroscopy, which involves placing an endoscope into the stomach and looking at its surface. To allow this, the stomach must be empty, so most horses are held off feed for 12 to 24 hours and not allowed to drink water for two to three hours. With light sedation and possibly a twitch, the endoscope is passed through the nostril and down the esophagus into the stomach. The light and camera on the end of the endoscope allow the veterinarian to observe the stomach lining.
Treatment of ulcers is aimed at removing the predisposing factors and decreasing acid production. When possible, horses should be allowed free-choice access to grass or hay. Environmental factors also need to be addressed, which may include relationships with other horses or the horse’s job description. Horses that must be stalled should be arranged so they can see and socialize with other horses as well as having constant access to forage. Some horses appear to enjoy having a ball or other object in the stall to occupy their time.
More frequent feedings help to buffer the acid in the stomach. Decreasing types of grain that form the volatile fatty acids may help some horses. The energy from the grain can be replaced by using a feed higher in fat. In horses with lower caloric needs, free-choice grass hay with the appropriate vitamin and mineral supplements will help.
Medication to decrease acid production is only necessary in horses showing clinical disease or when the predisposing factors cannot be removed, such as with some horses in race training or aggressive show campaigning. While antacids sound like a good idea, to be effective they would need to be administered six to 12 times a day. Antacids in feeds are relatively ineffective because they are ingested at the same time as the feed, which will buffer the acid. Although many options are available to you and your veterinarian for treating gastric ulcers, only very few are actually labeled for this purpose. Be sure to check with your equine veterinarian and use a product that is labeled specifically to prevent and/or treat equine gastric ulcers and approved by the FDA. Omeprazole is currently the only approved drug for treatment of gastric ulcers. Studies have shown a lack active ingredient or lack of effectiveness when using some compounded medications.
Prevention of ulcers is key. Limiting stressful situations, frequent feedings and free-choice access to grass or hay is imperative. This provides a constant supply of feed to neutralize the acid and stimulate saliva production, which is nature’s best antacid. There are many supplements on the market that claim to prevent squamous gastric ulcers. Many are ineffective and lack validation. Horse owners should utilize products for prevention of squamous gastric ulcers that have been validated in competent scientific studies. When this is not adequate or possible, horses at greatest risk will benefit from medication (omeprazole) to decrease acid production.
In any case of suspected gastric ulcers, a qualified equine veterinarian should be consulted to determine the best course of action and treatment for the individual horse.
Reviewed and updated by original author in 2016.