Equine Gastric Ulcer Syndrome (EGUS) courtesy of NORBROOK

Horses have evolved over thousands of years and have had many adaptations to their changing environments; however modern day activities have tested their bodies to the maximum. But with ever evolving technology and modern techniques many conditions can be resolved more effectively.

According to recent research in the western world, approximately 80-90% of racehorses, over 60% of competition horses, up to 50% of leisure horses and 50% of foals have been shown to have gastric ulcers with a range of severity1.

What Causes EGUS

The development of Equine Gastric ulcers may be perpetuated by excessive exposure of the mucosal liningof the stomach to acidic gastric juice. This causes erosion of the lining resulting inulceration and even bleeding. Ulcers are commonly seen in the upper squamous lining of the stomach as this has limited protection against acid injury.

The cause of EGUS is still not fully understood but certain risk factors have been identified. These include anatomy of the stomach, diet, restricted grazing, restricted feed intake and periods of starvation, high grain diets, high speed exercise and stress 2. During exercise, increased pressure in the abdomen compress the stomach, pushing acid contents up into the squamous region of the stomach. On-going exposure leads to erosion of the delicate mucosa creating ulceration. Causes in foals can include physiological stress, bowel diseases including diarrhoea, prolonged time between feeding, use of NSAIDs and other illnesses e.g. pneumonia .


It is important to note horses can display no clinical signs yet be diagnosed with potentially severe gastric ulcers when examined with a gastroscope3. Also clinical signs of stomach ulceration may be vague and can often be mistaken for other conditions or behavioural problems4.

Adult Horses

  • Poor performance
  • Dull appearance
  • Picky appetite
  • Grumpy temperament
  • Resistance to riding aids
  • Resistance to girthing
  • Mild colic
  • Weight loss


Foals can show clinical signs of ulcers from two days of age. Ulcers can often occur secondary to other diseases particularly bowel problems such as diarrhoea and obstructive colic.

Foals showing the following clinical signs will often have severe gastric lesions.

  • Salivation
  • Teeth grinding
  • Restlessness
  • Diarrhoea
  • Signs of colic including rolling
  • Poor appetite
  • Intermittent nursing

 Types of Gastric ulcers

Two types of gastric ulcers have been identified. Glandular ulcers affect the glandular mucosa in the lower region of the stomach, while squamous ulcers affect the squamous mucosa of the stomach. Squamous mucosa ulcers are found in the proximal (top) half of the stomach and 80% of ulcers occur in this region2. The Squamous mucosa  have a higher occurrence of ulcers due to the decreased physical barrier to acid as compared to that of the distal (bottom) half of the stomach where the glandular mucosa is present, these accounts for only 20% of gastric ulcers.


If equine gastric ulcers are considered the cause of symptoms, then the best diagnosis is achieved by performing a gastroscopy. The vet will ask you to starve your horse overnight in preparation; this allows greater visual clarity when using the endoscope. At the time of the gastroscopy the vet will give sedation in order to perform the examination, the examination will last approximately 20 minutes. The gastroscopy involves the use of a three metre long endoscope being passed into the nose and then down the oesophagus and into the stomach. This is often recorded in order for the horse owner to view afterwards. During the gastroscopy, the vet will score and describe the stomach ulcers for severity. Gastric ulcer grading and descriptive benchmarking allows the vet to monitor healing and evaluate the efficacy of the treatment3. Once the gastroscopy is over, the vet will advise aftercare regarding food and water. Water can be given directly after the treatment, but food will need to be delayed in order for the horse to become fully alert from the sedation.

 Gastric ulcer grades and descriptions

Squamous ulcers can be graded on severity, the grades are from 0-4, and it is recommended that the best method for identification and grading of gastric ulcers is gastroscopy, performed by a vet1.


Glandular ulcers are more accurately benchmarked using descriptive terminology as opposed to grading them.


If gastric ulcers are identified in adult horses, treatment is available; the recommended treatment is oral treatment with medication over a period of weeks, depending on the severity of the EGUS. The vet will then monitor the treatment progress with regular visits and gastroscopy and also suggest management and feeding changes.

In foals, treatment is recommended from four weeks of age, depending on the clinical severity. Ensure you know the correct weight of your horse or foal before dosing withoral treatment.

Oral Medications Available and What They Do


Omeprazole is taken orally. Omeprazole has an indirect effect on the stomach, this means that it does not coat the stomach the way a human indigestion product might. It initially passes straight through the stomach without having any effect and continues on into the small intestine where it is absorbed into the blood stream. It makes its way back, via the blood stream, to the stomach walls of the horse where it has its effect on the cells in the stomach wall that are responsible for producing the acid. These secretory cells are called the parietal cells and are mostly present in the lower glandular region, the ‘parietal cells’ of the stomach.

Once within these cells the omeprazole works by blocking special pumps on the cells’ surface known as proton pumps. It is these pumps that are responsible for the release of acid into the stomach. Once the omeprazole exerts its effect,  the parietal cells s lining the stomach can no longer release acid to maintain its highly acidic environment and the pH starts to rise towards a more neutral level, essentially giving the whole inside of the stomach a break from acid exposure and time for the ulcers to heal.

The parietal cells start to naturally make more proton pumps every 24 hours5, therefore a once daily dose of omeprazole is required to maintain the lowered acid secretion.

It is good to note that omeprazole will not affect the natural digestion of the horse.

Whilst omeprazole is the only licensed treatment for gastric ulcers in horses, vets may prescribe certain human medicines where deemed necessary. Your vet will discuss these options with you if required.

Management and Feeding changes

Rule 1: Enable your horse to be in the field as much as possible each day.

Maintaining a horse in pasture can enable easier management of EGUS4. This willaid the overall wellbeing of your horse, reducing stress and allowing for naturalgrazing. Grazing will also help buffer (reduce) the acid levels in the stomach.

Rule 2: Feed horses little and often

Feeding little and often will allow the horse to buffer the continuous supply of acidproduced in the stomach. By cutting down the high percentage of concentratesand replacing this with good quality hay, alfalfa or grass will achieve this result4.Ensure at all times the horse has access to clean fresh water, as this is a simple stepto reduce the risk of stomach ulcers.For horses in training, altering the diet to provide enough nutrients to performand prevent stomach ulcers can be done by consulting a nutritionist to design aprogramme to suit the horse’s needs and maximise potential.

Rule 3:  Avoid physiological stress

Stress can be induced by shock, respiratory disease, injury and changes in management or routine such as travelling, moving fields or a change in field companions and this can subsequently result in the development EGUS. In the event of such occurrence consult your vet so that preventative measures can be put into place.


  1. Andrews. F., Bernard. W., Byars. D., et al Recommendations for the diagnosis and treatment of equine

gastric ulcer syndrome (EGUS). The Equine Gastric Ulcer Council. Equine Vet ED 1999:11: 252-272.

  1. Andrews, F.M., Buchanan, B.R., Elliot, S.B., Clariday, N.A., and Edwards, L.H. 2005. Gastric ulcers in horses.

Journal of animal science. 83 (E.Suppl.) E18-E21.

  1. Murray, M.J., Grodinsky, C., Anderson. C.W., Radue. P.E., et al Gastric ulcers in horses; a comparision of

endoscope findings in horses with and without clinical signs. Equine Vet Journal. 1989:7 (suppl):68-72.

  1. Buchanan, B.R., and Andrews, F.M., 2003. Treatment and prevention of equine gastric ulcer syndrome.

Vet Clinic Equine. 19, 575-597.

  1. Shin, J. M and Sachs, G., 2008. Pharmacology of Proton Pump Inhibitors. Curr Gastroenterol Rep. 2008 Dec; 10(6): 528–534.

Kindly produced by Norbrook® manufactures of Peptizole®




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