How your horse’s stomach works.

Horse Stomach Callouts

Stomach — The stomach of the horse contains about 10% of the capacity of the small intestine (compared with 70% for cows). Therefore, horses cannot handle large amounts of feed and must eat frequent, small portions of feed.

Esophagus — A muscular tube that carries food from the mouth to the stomach. In the horse, food only moves one way down this tube; horses cannot throw up.

Squamous mucosa — Covers approximately one-third of the equine stomach and is void of glands. The texture of the healthy cells in this area feel like the skin on the back of your hand. Ulcers most regularly occur in this region near the margo plicatus curvature.

Margo plicatus — The folded ridge of the mucous membrane between the stomach’s nonglandular portion and the glandular portion.

Glandular mucosa — Covers the remaining two-thirds of the stomach and contains the acid-producing glands. Ulcers are less prevalent here (but still possible) due to having more protective factors.

Pylorus — Lower portion of the stomach that leads into the small intestine.

Duodenum — Uppermost part of the small intestine that plays an important role in the digestive function. Carries partially digested food out from the stomach.

Acid-stimulating receptors — Trigger an “acid pump” to secrete acid. Sensitive to diet and stress.

Stomach acid is needed for digestion.

  • In a natural grazing situation, the horse requires a steady flow of acid for digestion. For that purpose, a horse’s stomach produces acid 24 hours a day, seven days a week (up to 16 gallons of acidic fluid per day).1
  • In this natural, high-roughage diet, the acid is buffered by feed and saliva. But higher intake of grain can increase acid levels.2

Excess stomach acid can lead to stomach ulcers.1,2,3

The stomach lining contains acid-stimulating receptors that are sensitive to diet and stress.

  • When activated, they trigger an “acid pump” to secrete acid into the stomach.
  • If the acid level builds up in the area of the squamous mucosa, it can eat through the lining.
  • The resulting stomach ulceration often suppresses appetite and thirst, so the horse may receive even less benefit from buffering roughage and water.
  • This creates a vicious cycle of increased acidity, causing decreased roughage consumption, resulting in damaging stomach ulcers.

The horse you love is probably not constantly grazing. Therefore, with high-protein diets and the added stresses of your horse’s busy lifestyle, excess acid can easily build up and cause painful stomach ulcers.

 

1Kitchen DL, Merritt AM, Burrow JA. Histamine-induced gastric acid secretion in horses. AJVR 1998;59(10):1303-1306.
2Murray MJ. Overview of equine gastroduodenal ulceration. AAEP Proccedings 1997;43:382-387.
3Murray MJ, Schusser GF, Pipers FS, Gross SJ. Factors associated with gastric lesions in Thoroughbred racehorses. Equine Vet J 1996;28:368-374.

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