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. 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.
Ulcers are often a man-made disease. Stall confinement alone can lead to the development of gastric ulcers. When horses are fed only two to three times a day, the stomach is subjected to a prolonged period without feed to neutralize the acid.

Stress can increase the likelihood of ulcers. Strenuous exercise can decrease both the emptying function of the stomach and blood flow to the stomach, thereby contributing to the problem. 

Also chronic administration of any non-steroidal anti-inflammatory drugs 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.

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.

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.