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Gastric Ulcers

Signs and symptoms


Gastric ulcers are very common in horses. Their prevalence in racehorses has been estimated to be from 50% to 90%. 

The majority of horses with gastric ulcers do not show outward clinical signs. 

Clinical signs of ulcers are usually subtle and nonspecific. Some examples include:

  • Poor appetite;

  • A slight attitude change;

  • A decrease in performance;

  • Reluctance to train;

  • Dullness;

  • Poor body condition;

  • Poor hair coat;

  • Weight loss;

  • Excessive time spent lying down;

  • Low-grade colic; and

  • Loose faeces.


More serious cases will show abdominal pain (colic) and/or grinding of the teeth. Some horses are found on their backs (commonly seen in foals) to provide relief from severe gastric ulceration. Others will walk away from food for a period as if they experience discomfort when the food first hits the stomach, or preferentially eat hay rather than grain/pellets.

Note that horses that look completely healthy can also have gastric ulcers.


Causes and Risk Factors


Why are gastric ulcers so common in horses?


Horses have relatively small stomachs for their size and cannot handle large amounts of food. They are designed to graze and eat frequent, small portions of feed over extended periods of time. The horse’s stomach produces acid to digest food 24 hours a day, 7 days a week–up to 34 litres of acidic fluid per day, even when not eating. In a natural grazing situation, the acid is buffered by both feed and saliva on a continual basis.

When horses are stabled or restricted from free access to grazing, the stomach is subjected to a prolonged period without feed to neutralize the acid. Furthermore, high-grain diets produce volatile fatty acids that can also contribute to the development of ulcers.

Gastric ulcers also occur more frequently in horses that perform athletic activities. Research has shown that exercise increases gastric acid production and decreases blood flow to the gastrointestinal (GI) tract. When horses exercise, the acidic fluid in the stomach splashes and exposes the upper, more vulnerable portion of the stomach (squamous mucosa) to an acidic pH.

The highest incidences of ulcers are found in

  • Thoroughbred racehorses (80-90%)

  • Endurance horses (70%)

  • Show horses (60%)

When a horse with an empty stomach trots, canters, gallops or even simply tenses up its abdominal muscles the gastric fluids are splashed or squeezed up onto the unprotected upper section of the stomach. The acid simply starts to burn holes in the stomach wall lining. If you allow this to occur repeatedly the horse will eventually develop ulcers. This can happen in just a matter of days.

Other risk factors for developing gastric ulcers include physical and environmental stress such as transport stress and stall confinement (intermittent feeding and lack of exposure to other horses). Recent studies have demonstrated that a few hours of transport can induce gastric ulceration in horses that had none prior to departure.


Finally, long term use of non-steroidal anti-inflammatory drugs (NSAIDs)–such as phenylbutazone, flunixin meglumine or ketoprofen–can decrease the production of the stomach’s protective mucus layer, making it more susceptible to ulcers.

Gatric ulcers.PNG

Risk Factor Summary

  • Horses in work/training performing athletic activities

  • Restricted access to food and grazing eg. stabling

  • High grain diet, not enough roughage

  • Stress eg. confinement, transport, lack of company

  • Long term NSAID medication eg. Bute





Some practitioners will treat a horse for gastric ulcers based just on clinical symptoms and look for a change in clinical behaviour. This can be helpful but does not answer the question of when to discontinue treatment. Horses that improve with treatment should be scoped prior to discontinuing therapy.

At Illawarra Equine Centre, we can offer two alternative methods for diagnosis for gastric issues in horses. 


1. Faecal Blood Tests

Equine faecal blood tests detect blood loss from the gut that points to damage within the equine gastrointestinal tract. The test can be done in the field and is simple to use, affordable and non-invasive. It is an ideal first step to rule out the presence of digestive disease, such as gastric ulcers, colonic ulcers, colitis or other conditions. It is accurate and highly sensitive, particularly for detecting problems in the hindgut.

2. Gastroscopy

Illawarra Equine Centre is able to definitively diagnose gastric ulcers, as well as their severity, through gastroscopy. We run special Gastroscope Days every couple of months at which our clients can bring their horses to the clinic for a 30-minute procedure. This involves placing an endoscope into the stomach and looking at its surface. The procedure is easy to perform, minimally invasive, and allows us to evaluate the oesophagus, squamous and glandular regions of the stomach, and proximal segment of the small intestine in horses.

Gastroscope Day.jpg

Since feed material can prevent a complete evaluation of the stomach, horses are fasted for a minimum of 12 hours and water is withheld for four hours before examination.

To minimize stress, we sedate the horse slightly with a short-acting sedative. We then insert the endoscope through the nostril and down the oesophagus into the stomach. The light and camera on the end of the endoscope allow the veterinarian to observe the stomach lining via a monitor. The procedure is very safe, and a complete evaluation takes from 10 to 20 minutes.

Our next scheduled Gastroscope Day is on Thursday 18th June, 2020



Treatment for gastric ulcers is highly effective and easy to administer. The treatment of choice is a drug called Omeprazole which stops gastric acid secretion completely. It is delivered as a once daily oral paste for 28 days. Omeprazole can also be safely used for maintenance and prevention of gastric ulcers.

We recommend treating:

  1. horses with severe gastric ulceration,

  2. horses with clinical signs of gastric ulceration, and

  3. horses that are under stressful conditions and at risk of gastric ulceration.


Treatment should be given for a full month, followed by a recheck endoscopy to confirm complete healing.

A preventative dose of omeprazole is commercially available for use around transport or stressful events. Horses with a history of gastric ulceration may benefit from proactive treatment to decrease the chances of ulcer recurrence. At this dosage, the omeprazole is less costly and could serve as a good investment in your horse’s well-being.




As always, prevention is preferable to treatment. The following management techniques may assist in preventing ulcers:

  • Don’t exercise horses on an empty stomach – providing a small meal of lucerne hay prior to exercise will:

  1. Help to stop the acidic contents from the lower region of the stomach from splashing up onto the upper region where it can cause ulcers;

  2. Provide a buffering effect by causing the horse to produce saliva while it is chewing the hay and through the buffering effect of lucerne hay itself. If you don’t have lucerne hay then your horse’s regular hay will also work well.

  • Feed horses frequently or on a free-choice basis (pasture). This helps to buffer the acid in the stomach and stimulate saliva production, nature’s best antacid.

  • Reduce the amount of grain and concentrates and/or add lucerne hay to the diet. Lucerne hay appears to have a protective effect on the equine stomach, reducing the incidence of gastric ulcers in horses. Discuss any feed changes with your veterinarian.

  • Avoid or decrease the use of anti-inflammatory drugs such as Bute. If anti-inflammatory drugs must be given, consider newer ones such as firocoxib, if appropriate.

  • Limit stressful situations such as intense training, frequent transportation and social isolation.

  • If horses must be stabled, allow them to see and socialise with other horses as well as have access to hay.

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