The term equine gastric ulcer syndrome (EGUS) was first used in 1999 to describe gastric ulcers in the horse. Since then there has been much research looking at the prevalence, causes and treatment of equine gastric ulcers.

What is EGUS?

Equine gastric ulcer syndrome describes the ulceration of the horse’s stomach lining due to exposure to acid produced by the stomach.  Any horse can suffer from gastric ulcers, from racehorses to pleasure horses and ponies.

Anatomy of the equine stomach

The horse’s stomach has a unique anatomy. Thelower half of the stomach is lined by glandular mucosa. This is the area where acid is produced and because of this it has good protection from acid. The upper part of the stomach is lined by squamous mucosa. This is the same tissue that lines the oesophagus (food pipe) and it has poor protection from acid.

Anatomy of an equine stomach

Horses have evolved to be trickle feeders constantly consuming forage (grass or hay). This creates a layering effect within the stomach where the lower part is very liquid and acidic in the well protected glandular region. As you move up the stomach this becomes gradually more fibrous and less acidic, so that at the top of the stomach in the squamous region there is a dense fibrous mat which protects this area from the liquid acidic contents of the lower stomach. This means that there are actually two types of gastric ulcers. Squamous ulcers and glandular ulcers. These describe the region of the stomach that is affected and they are now considered to be two separate diseases.

How common is EGUS?

Gastric ulcers appear to be getting more common, however this is likely to be due to diagnostic techniques becoming more available and therefore more horses are being tested. There has been a lot of research into the prevalence of squamous gastric ulcers in horses which has shown that they are extremely common. Shockingly 80-100% of racehorses in training have ulcers. For sport and show horses this drops to 17-58% and 37-59% for pleasure horses. Glandular ulcer disease is less well understood, but recent research in the UK showed a prevalence of 54% of leisure horses and in 64% of sport horses.

What are the causes of EGUS?

Squamous ulcers are caused by a variety of management factors which all have the common trait that they increase the exposure of the squamous mucosa to acid. 
These management factors can be divided into 3 groups:

1. Diet

Cells in the horse’s stomach continually secrete acid. Horses are trickle feeders and this constant eating stimulates saliva to be produced which neutralizes the acid. With modern management, horses and ponies often have periods without food, but stomach acid is still produced and this excess acid may cause squamous ulcers. Feeding a diet rich in cereals also further increases stomach acidity and means that there will be less of a fibrous mat at the top of the stomach, giving the squamous area less protection.

2. Exercise

During exercise the stomach contracts and acid which is produced in the lower part of the stomach may be splashed up onto the squamous region if there is not a protective fibrous mat in place.

3. Stress

Stressors such as transportation, relocation, hospitalization, or a change in management can increase the acidity of the stomach increasing the risk of squamous ulcers. 
In contrast, the causes of glandular ulcers are poorly understood. The glandular region is designed to tolerate high levels of acid and glandular ulcers are thought to develop when there is a breakdown of these normal defence mechanisms that protect this region. We still do not understand what causes this breakdown, but in some horses it is thought that anti-inflammatory drugs or bacteria may play a role, but further research is required.

What are the signs of EGUS?

Unfortunately there are no characteristic clinical signs of gastric ulcers, as symptoms are very
variable and differ from horse to horse. They may include:

• Poor appetite
• Weight loss
• Poor coat condition
• Mild recurrent colic
• Changes in behaviour
• Poor performance

This means that it is not possible to diagnose gastric ulcers based on clinical signs.

How are gastric ulcers diagnosed?

Gastric ulcers are diagnosed by visual examination of the stomach using a specialised three metre long flexible camera called a gastroscope. Gastroscopy is a quick and simple procedure which is performed under sedation. The gastroscope is passed up the horse’s nose and down into the stomach. The vet can then view the horse’s stomach lining. To view the stomach it must be empty so horses must be starved and water withheld before gastroscopy. The vet will view both the squamous and glandular regions of the stomach and grade any ulcers that are seen.

Other diagnostic methods have been developed but unfortunately have very poor accuracy. One test looks for the presence of blood or albumin (a protein) in a sample of faeces, however recent research has shown that there is no association between their presence in droppings and the presence of gastric ulcers and so this test should not be used.

Treatment without first carrying out gastroscopy is not recommended. There are several reasons for this, firstly signs of gastric ulcers are highly variable and there is no one symptom or symptoms that are typical for gastric ulcers. Gastroscopy also means that the vet can determine whether squamous or glandular ulcers are present or both, as the type and duration of treatment will differ depending on the type of ulceration. Some horses will not show a response to treatment until the ulcers have healed completely, so it can be extremely difficult to gauge a response to tell if the treatment has worked if you are not using gastroscopy to diagnose and monitor the horse. Finally, treatment is costly and so it makes sense to treat the horse with the correct medication for the shortest duration possible to resolve the ulcers.


We know that gastric ulcers are caused by exposure to acid. This means that acid suppression therapy is the cornerstone of gastric ulcer treatment for both squamous and glandular ulcers, with the mantra being ‘no acid, no ulcer’. Unfortunately there is only one acid suppressing drug licensed for horses available in
the UK, which is highly effective but expensive. This is a prescription only medicine and so must be prescribed by your vet. The length of treatment will depend on the severity of ulcers present and their type. Glandular ulcers tend to take longer to heal and therefore need a longer duration of treatment. Currently there are no other treatment options that will suppress acid production sufficiently to allow healing. Some supplements have an antacid action however this is very short acting and is not enough to allow ulcer healing.


Happily gastric ulcers are preventable, with nutritional management being the optimal option.

Nutritional Management

Horses are trickle feeders and therefore should have continuous assess to forage (grass or hay). Follow these tips to help your horse stay ulcer free:
• Regular turnout at grass.
• Ad lib hay (or haylage) when stabled to promote a natural eating pattern. If this is not possible then feeding hay 4-6 times a day.
• Feeding hay or haylage in small-holed haynets so it lasts longer.
• Dividing hay up into 2 or 3 small-holed haynets and hanging these at different locations around the stable so that hay lasts longer and the horse has to move from one to the other for hay, providing more natural foraging type behaviour.
• Increasing the fibre content of hard feed meals and reducing the carbohydrate content will help to prevent ulcer formation. Alfalfa chaffs are ideal as they are high in calcium which is a natural buffer. Discuss the best strategy for your horse with your vet or a qualified equine nutritionist.
• Make sure your horse always has access to clean water, as restricted access to water has been shown to increase the risk of gastric ulcers. Do not withhold forage (hay, haylage or grass) before exercise, as if you do it increases the chances of splash ulcers in the squamous region.
• Feeding a small meal of fibre, such as half a scoop of alfalfa or chaff, half an hour before exercise will help stimulate saliva production to neutralise acid and provides a mat in the stomach to protect the squamous region.
• If you need to feed an electrolyte supplement and your horse has had gastric ulcers in the past or is at high risk of them the supplement can be safely fed when added to feed. For these horses it should not be given as a paste or in the water as this increases the risk of gastric ulcers.


• Supplements containing antacid-type ingredients may help to reduce signs and recurrence of ulcers, however these will not be sufficient to heal ulcers.
• The addition of corn oil to the diet (or its inclusion in a supplement) can help protect the glandular region of the stomach as it stimulates mucous production which acts as a protective barrier in the glandular region.
• There is research that found that supplements containing pectin-lecithin complexes may help prevent glandular ulcers.
• Research has shown that feeding the prebiotic fructo-oligosaccharide (FOS) made horses stomachs less acidic. So it is worth looking for FOS if you want to feed a supplement to support the stomach.
• There is also research that suggests that feeding the probiotic Saccharomyces cerevisiae may be beneficial to help prevent bacterial colonization of ulcers by harmful bacteria and help promote a stable environment within the stomach.

Prescription Treatment

• A low daily dose of the acid suppressing treatment will effectively prevent the recurrence of gastric ulcers and may be necessary for situations where nutritional management isn’t possible.

V.I.P.® Ulsa Shield

Unique nutritional blend supporting gastric health.
• Supports normal acid levels and soothes the stomach lining.
• Contains pre and probiotics to support a healthy gastric environment.
• Results visible from 5 Days.
• Ulsa Shield is an advanced, sugar free formula containing a unique blend of ingredients to maintain gastric health, soothe the stomach walls and support normal acid levels. Ulsa Shield is Vet Approved and is ideal to feed following veterinary treatment to help maintain a healthy gastric environment. Results visible from 5 days.
Benefits of Ulsa Shield:
• PROBIOTICS (Saccharomyces cerevisiae) - To support gastric health.
• PREBIOTICS - Diamond V, a unique prebiotic that has a positive effect on nutrient digestibility, FOS to support normal acid levels, plus MOS, Psyllium and Brewer’s Yeast.
• LIMESTONE FLOUR - To support normal acid levels.
• RICE BRAN OIL - To support gastric health in the glandular region of the stomach.
• ALFALFA MEAL - Naturally high in calcium to support normal acid levels.
• LINSEED MEAL - Rich in Omega-3 fatty acids.
• HERBAL EXTRACTS - Yucca, Fenugreek and Ginseng to support gastric health.
• VITAMINS & TRACE ELEMENTS - To support overall health, vitality and condition.
• SUGAR FREE - Highly palatable formula.
• The lifestyle of modern horses can predispose them to stress and poor gastric health. Ulsa Shield is the ideal gastric supplement which can be fed continually to achieve healthy performance in the stomach.