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Gastric ulcers are erosions of the stomach lining due to prolonged exposure to the normal acid in the stomach. Ulcers may also occur in the duodenum (small intestine just beyond the stomach) and the large colon. In nature the horse sleeps little, grazes constantly and eats small volumes of roughage. Their stomach secretes acid at a nearly constant rate throughout the day. If the horse is not eating regularly, there is no roughage to neutralize the acid. Ulcers are a man-made disease with an incidence that approaches zero in horses in “natural” environments.


  • Elite Western Performance horses: 40% of all those evaluated, but 88% of those with owner-reported complaints
  • Thoroughbred Brood Mares: 70% had ulcers (pregnant or not)
  • Thoroughbreds in Race Training: 90% had ulcers
  • Horses used for Recreational Showing/Light Activities: 37% had ulcers
  • Hunter/Jumper: 58% had ulcers.
  • Horses evaluated for poor performance: 63% had ulcers.


  • Stall confinement
  • Horses fed grain twice a day
  • Horses fed more than 5 pounds of grain at a single feeding or closer than 5 hour intervals (increasing volatile fatty acids).
  • Stabling next to horses which they aren’t well-socialized with.
  • Transport
  • Strenuous exercise/training
  • Chronic administration of NSAIDs such as Bute or Banamine

A majority of horses do not show obvious outward signs.  Subtle signs may include:

  • Poor appetite
  • Decreased performance
  • Poor hair coat
  • More serious cases will suffer from recurrent colic.
  • Other possible symptoms include:
  • Stretching unusually often to urinate
  • Loss of attention in competition
  • Frequent pawing
  • Bruxism (grinding of teeth)
  • Head tossing
  • Flank biting
  • Cribbing
  • Pulling rear leg up into flank
  • Girthiness


  • Clinical signs and history
  • Presence of occult blood in manure
  • Laboratory values for bloodwork indicating low platelets, protein, WBC, RBC, hemoglobin
  • Response to therapy (GastroGard).
  • The only definitive diagnosis is by use of a 3 meter gastroscope— this allows for direct visualization of a horse’s (empty) stomach.


  • Feed more frequently and in smaller amounts
  • More roughage
  • More free-choice access to roughage
  • Higher fat and lower carbohydrate feeding
  • Reduced stress
  • Increased turnout
  • Socialization
  • Stall Toys
  • Careful observation and avoidance (where feasible) of stressful situations
  • Medication
  • Omeprazole/GastroGard for treatment
  • UlcerGard or buffers for prevention
  • Misoprostol, Cimetadine, Ranitidine and Sucralfate have limited usefulness.