Stomach and duodenal ulcers are common in the adult horse, but they are seen more commonly in the foal. Racehorses are the population of horses most often affected by gastric ulcers with an ulcer prevalence between 63 and 90%. In contrast, a much lower prevalence (37%) of stomach ulcers is seen in pleasure horses and the degree of ulceration is less severe. Several endoscopic surveys have indicated that the frequency of gastric ulceration in Thoroughbreds in training is fairly high. Ulcers appear to be chronically progressive during training, but to regress during retirement. Large amounts of concentrated high-energy feeds, small rations of forage and a low feeding frequency per day as well as the use of spoiled food can contribute to the development of colics and ulcers. An extended period of diarrhea or treatment with NSAIDs also predisposes to gastrointestinal ulceration.
Acids also are the important causes - severe ulceration of the stomach, caused by excess acidity, can develop rapidly in horses deprived of feed or not consuming feed. Compared with being turned out to pasture, stall confinement alone appears to be an important factor in the development of gastric ulcers in horses. Current therapy targets the suppression of gastric hydrochloric acid (HCl) and creation of a suitable environment for ulcer healing. Diagnosis is based on history, clinical signs, gastroscopy, and response to treatment.
Clinical signs that typically are associated with gastric ulceration include recurrent colic for seven or more days, acute colic, poor bodily condition, and/or chronic diarrhea, poor appetite, and weight loss. Often symptoms are less obvious (such as poor performance), or not even noticeable. Foals with ulcers suck only half-hearted, grind their teeth and frequently chew on straw.
Of the products available, only GastroGard (FDA approved) and ranitidine have been shown to be efficacious in the treatment of EGUS. Ranitidine is often associated with treatment failure as a result of incorrect dosing and lack of owner compliance, because of the three times daily dosing required. Also, EGUS occurs in critically ill neonatal foals, but the underlying cause may be different than in adult horses and acid-suppressive therapy may not be as effective. Other studies demonstrated that omeprazole paste is highly effective in healing gastric ulcers in Thoroughbred racehorses and that the omeprazole paste effectively prevents the recurrence of EGUS. The study also indicates that gastric ulcers in untreated horses did not demonstrate a significant rate of spontaneous healing (contrary to an existing theory of self-healing equine ulcers).
Severe ulceration of the gastric squamous epithelial mucosa, caused by excess acidity, can develop rapidly in horses deprived of feed or not consuming feed. Suppression of gastric acidity with the histamine type-2 receptor antagonist ranitidine effectively minimized the area of ulceration caused by feed deprivation. Compared with being turned out to pasture, stall confinement alone appears to be an important factor in the development of gastric ulcers in horses, probably as a result of altered eating behavior.