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Symptoms of Gastric Ulcers in Horses

20th April 2017

Gastric ulcers appear to be becoming increasingly common with reports of up to 92% of racehorses, up to 75% of eventing and dressage horses, and even up to 40% of horses used for general riding being affected by gastric ulcers.

What are Gastric Ulcers?

Gastric ulcers are erosions in the stomach lining caused by over exposure to the acid produced by the stomach.


Clinical signs are not always easy to spot because they can be vague and non specific and also vary greatly from horse to horse.  Signs that we see commonly include:

  • A change in temperament -normally well behaved and placid horses can become bad tempered even biting and kicking out in severe cases
  • Poor performance - this can range from simply not wanting to go forwards and reduced performance all the way to severe bucking and bolting behaviour when ridden
  • Recurrent colic episodes - often seen after eating food. Multiple occurrences may be seen over weeks to a couple of months
  • A dull coat
  • Pain when the girth is tightened - often seen as the horse turning and nipping or just putting its ears back as the girth is done up
  • Loss of or reduced appetite - owners may see the horse refusing its normal feed or becoming fussy over forage offered
  • Weight loss

It is important to remember that a horse may only show one of these symptoms and not all of them.

It is still possible for a horse that is eating well and hasn’t lost weight to have gastric ulceration.

Risk factors for the formation of gastric ulcers include high concentrate feeds, prolonged periods without feeding, lack of access to grass and an increase in competition work including increased training regimes and transport.

They may also be seen more commonly in highly strung horses.


There is only one way to diagnose gastric ulcers and this is with Gastroscopy.

Gastroscopy is performed under sedation. A flexible endoscope is passed up the horse’s nostril and into the throat where it is swallowed and passed down the oesophagus and into the stomach to allow direct visualisation of the ulcers.

To enable the entire stomach to be viewed the horse needs to be starved overnight beforehand.

Horses tend to tolerate this well and are usually back in their stables and eating again once the sedation has worn off which is usually within around 45 minutes.

When looking with the gastroscope into the horse’s stomach we can see that the stomach is split into two distinct areas.

The top section is pale pink and the lining of the stomach is a single layer which has no protection from the stomach acid.

Ulcers occur in this region when excess acid splashes up onto the unprotected stomach lining.

The lower section (the glandular region) is a deeper pink because this area has a natural mucus coating to protect it from the acid.

Ulcers occur in this region when the protective coating is lost and the stomach acid contacts the unprotected lining underneath.

The two areas are separated by a distinct line called the margo plicatus.

The severity of ulceration in both these areas can vary from just mild inflammation of the stomach lining to severe deep erosions.

During gastroscopy the entire stomach is visualised and any ulcers are graded from 0 (no ulceration) to 4 (large areas of deep bleeding ulceration).

This may sound like a design flaw to have a big part of the stomach unprotected from acid but horses have evolved this way.

This is because horses are designed to be grazing constantly which means there is fibre in the stomach soaking up the acid and also a constant stream of saliva that neutralises the acid in the stomach.

These mechanisms prevent the top half of the stomach being contacted.

However, with modern management and high concentrate feeds, excess acid can quickly build up leading to problems with gastric ulceration.

The good news is that the majority of cases of gastric ulceration can be treated and once resolved a dramatic change in the horse’s clinical signs can often be seen.

It is important to remember, however, that both medical treatment and management changes need to be used in combination to allow the ulcers to heal.

A medicine called Omeprazole is used to treat ulcers.  This works by reducing the amount of acid released into the stomach allowing the ulcers time to heal.

It is important that the medication is given in the form of a paste specifically designed for horses. This ensures the medicine is not broken down in the stomach before it can have its effect.

There is no proven link between bacteria and gastric ulcers in horses but ulcers can become infected and so antibiotics are required in some cases.

A supplement containing pectin-lecithin also helps to reform the mucus barrier.

In addition to this, changes to diet and management are key.  It may not be possible for horses to have constant access to grass but as much turn out as possible is beneficial.

It is also important to make sure that hay or haylage is constantly available within the stable.

At least three small feeds should be given during the day and these should include mostly chaff, such as alfalfa, and little or no concentrate.

Chaffs in the diet help to encourage the horse to chew and produce saliva which is a natural acid buffer.

They also help to form a fibre matt within the stomach that stops the acid from splashing around.


Gastric ulcers do take time to heal.

With squamous ulceration healing tends to be quicker and we often see a good improvement if not complete resolution when gastroscopy is repeated after 28 days.

Glandular ulceration can be more complicated.  The reason for the loss of the protective layer is not always known and it is not possible to completely prevent acid exposure.

We therefore find that these ulcers can take longer to heal and can require more medication.

It is for this reason that we always recommend repeating gastroscopy after 28 days to check progress.

If you are concerned that your horse may be suffering from gastric ulcers then contact your veterinary surgeon to discuss it with them.

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