Ulcers: why are they occurring?

Are your horsekeeping practices contributing to this common equine problem?

Several years ago, a University of Florida study made an important discovery. It revealed that any exercise above a walk could force gastric acid up into sensitive areas of a horse’s stomach. This may be one reason why 80% or more of performance horses have ulcers.

Horses have areas in their stomachs that are more like regular hairless skin than the glandular mucosa found in human stomachs. “The lining of the human stomach consists entirely of a glandular tissue that secretes acid, digestive enzymes, hormones and mucus that protects it from damage from the acid,” writes Thomas R. Lenz, DVM, MS.2 “In contrast, only about 40% of the horse’s stomach is lined by glandular tissue. The remaining 60% is lined by non-glandular tissue that is structurally similar to hairless skin. In horses, ulcers occur primarily in the non-glandular portion of the stomach, which is extremely sensitive to elevated gastric acid levels.”

In nature, horses eat almost constantly, don’t eat grain, and don’t exert themselves for more than a few minutes at a time unless under extreme duress. When we ride or work horses at faster gaits and for longer than they would play by themselves, the tightened muscles of the abdominal wall force stomach contents and acid upwards, splashing the squamous cell portion of the stomach.

Not just performance horses

Dr. Lenz adds that two-year-old Thoroughbreds just starting training had few or no gastric ulcers. After two or three months of intense training, however, 90% had ulcers. By contrast, only 37% of horses used for light riding or lessons had ulcers.

Ulcers are not just found in high performance athletes; even the occasional weekend show or trail ride can cause problems. A recent Iowa State University study involved 20 horses that had been trained and used for recreational riding, and showed no sign of ulcers prior to the study. Ten were hauled four hours to an unfamiliar barn where they were stabled, ridden and longed for three days, then shipped home. The other ten horses served as controls by remaining at home, where they were longed and ridden. Seven of the transported horses developed ulcers, compared to only two who were ridden and longed at home. Ulcers in the traveling group were also more severe.3

In a separate study, Dr. Sarah S. le Jeune, a staff veterinarian at UC Davis, found that 44 of 62 pastured Thoroughbred broodmares had ulcers. Training, showing, stall confinement and travel have been proven to increase ulcer incidence, but most people believe that a pastured, relatively idle horse would not have these issues. The mares in Dr. le Jeune’s study had not been shipped recently, and all were similarly managed. Yet they had the same ulcer rates found in race horses in active training, although the mares’ ulcers tended to be less severe. One hypothesis is that crowding of the fetus caused stomach acid to be squeezed into the squamous cell section of the stomach, yet mares scoped after foaling showed no change in stomach health.4

Other causes

Severe illness and the use of NSAIDs (like bute) are also well known causes of gastric ulcers in foals and adult horses. The most likely cause of non-glandular ulcers is the introduction of more grain into the ration, because grain increases gastric acid production. Dr. Lenz cites a 1988 study which found that stomach acidity was 60 times greater in grain fed horses than in those fed only hay.

Clay’s the thing

Consuming clays for digestive upsets is as old as recorded history – and as new as taking Kaopectate, which contains kaolin clay. In the wild, animals instintively search out clay deposits to soothe digestion and as a natural acid buffer and detoxifier. Clay is a paramagnetic substance with a very high pH.

For horses, one ounce of bentonite clay (about two heaping tablespoons dry measure) can be made into a thin paste by adding four to five tablespoons of water. The mixture is orally syringed into the horse, and this simple practice has worked wonders on performance horses. Give it to your equine partner after walking him out and preferably at least an hour before feeding. The more intense or lengthy the exercise, the more important this practice becomes. In fact, many top competitors also give a syringe of clay before a class or event, and endurance riders may give several doses over the course of a ride. Give it before hauling, too – tightened abdominal muscles and trailer motion can have the same negative effects as exercise.

More solutions for ulcers

Free choice grass hay is another great way to prevent ulcers – if horses are nibbling all the time the stomach is more protected. Split grain meals into smaller portions (the stomach becomes more acidic with a grain meal) and feed the grain after the horse has eaten some hay. Less acid is needed to digest hay, and the hay in the stomach will “buffer” the effects of grain feeding. You may even want to add a little wet activated clay to grain meals. Besides helping to prevent ulcers, clay helps horses cope with the residues of chemical dewormers, feed preservatives and other toxins in the diet and environment. Some people have found it beneficial to add some aloe vera gel to the diet, and a good probiotic or prebiotic is also essential to digestive health. A happy gut is a happy horse!

1The Horse, April 2003 2Quarter Horse Journal, February 1995 3Journal of the American Veterinary Medical Association, (McClure, SR, Caruthers, DS, Gross, SJ, Murray, MJ, “Gastric Ulcer Development in Horses in a Simulated Show or Training Environment”) 4The Horse, AAEP Convention Wrap Up, March 2007