Lanark Branch: 01555 660000

Lanark branch: 01555 660000

Ulcers in horses: Treatment, cause and symptoms of equine ulcers

It’s been well documented that gastric ulceration is a condition known to affect many racehorses. However, it’s perhaps less well known that around 60% of performance horses and approximately 40% of leisure riding horses are also affected by this underrated condition.

Developments in diagnosis

The non-specific nature of the symptoms of equine gastric ulcer syndrome (EGUS) means that it is possibly very much an under-recognised problem. However, progress in the development of diagnostic equipment has helped veterinary surgeons identify and confirm the presence of ulcers in horses. A long endoscope (gastroscope), two to three metre long passed down into the horse’s stomach, is the only definitive test to verify the presence of gastric ulcers.


One of the challenges of this condition is the variability and vagueness of the symptoms, which can include some or all of the following; reduced appetite, slow eating, poor physical condition, dullness, changes in attitude such as sourness or irritability, colic, poor performance and reluctance to work. However, at times it is difficult to attribute these signs specifically to gastric ulceration. To add to the complication, the correlation between clinical signs and the severity of ulceration is not always consistent. On examination, some horses that have shown relatively few clinical signs are found to have severe ulceration, whereas others have been found to be the reverse.

How And Why are Ulcers thought to form

Horses were designed as ‘trickle feeders’ with free access to light grazing. In contrast, depending on the level of work and yard regime, our modern horse in training is usually stabled, often with restricted access to food. An important feature of equine gastric ulcers is that horses secrete gastric acid continuously, whether or not they are eating.   An adult horse will produce approximately 1.5 litres of gastric acid per hour, and with restricted access to food, continued secretion means the pH level can rapidly become very acidic, and ulcers can begin to develop. In contrast, horses constantly eating hay or grass have a higher average stomach pH providing a much healthier environment. 
The horse’s stomach is effectively divided in to two portions, the lower and upper regions. The lower part of the stomach has gastric pits containing the glands that secrete hydrochloric acid. Its lining is less susceptible to acid attack than the upper part, which is lined with squamous mucosa which has no secretory or absorptive function and is therefore vulnerable to acid attack. Gastric ulcers usually form when the lining of the upper part of the stomach is exposed to acid for extended periods of time.

Exercise And Travel

Research has also shown that training has an effect on stomach acid levels. Horses fed the same diet prior to and during training had higher acid levels during the training period. More recent studies have also discovered what is known as the ‘mechanical’ effect. During galloping, pressure from the abdomen causes the stomach to contract, pushing acid from the lower stomach up in to the more vulnerable upper stomach, thus further increasing acid exposure in these animals.
In addition to the feeding regime and exercise, other factors that can influence the formation of ulcers are transportation, frequent competitions and unfamiliar surroundings. The use of non-steroidal anti-inflammatory drugs, such as ‘bute’, has also been shown to contribute to equine ulcers.

Diagnosis And Treatment

If a horse is suspected of having gastric ulcers, gastroscopy will confirm the presence, severity and location of the ulceration. Although the most common location for ulcers is the upper region of the stomach, ulcers have been known to develop in other areas, including the lower portion and the duodenum.  Ulcers are graded from 0 to 4 reflecting the severity of ulceration, with grade 0 being a normal healthy stomach, and grade 4 demonstrating extensive lesions with areas of apparent deep ulceration.  Clyde Vet Group Equine Hospital as of 15/08/07 have a 3 metre video gastroscope to examine the horses stomach.

Studies have shown the most effective treatment is the acid inhibitor, omeprazole.  This is sold under the name GastroGard®, this is the only licensed treatment for equine ulcers in the UK. An oral paste, it is a potent inhibitor of gastric acid secretion and is highly effective in healing gastric ulcers. It takes three to five days for a steady state of acid suppression to be reached and total healing time is usually between two to four weeks, although severe cases can take a little longer. 
 A full course of treatment is usually prescribed for 28 days, with one treatment per day. The horse can be taken out of work during this period, but it is not always necessary, and really depends on the individual circumstances and preference of the owner/rider. 
If you have a horse or horses you suspect may have gastric ulcers, we recommend that you consult your veterinary surgeon.

Re-occurrence And Prevention 
Many owners and riders note a significant improvement in their horse, sometimes within days of commencement of treatment.  However, once the ulcers have healed, unless changes are made to the horse’s management, training and/or environment, it’s highly likely that they will re-occur. For a horse in hard work, ulcers can start to reappear as quickly as three to four days after the end of treatment, however even subtle changes to their daily regime can make a difference.

Because horses are trickle feeders, we try to emulate the horses’ natural environment as closely as is possible. Free access to hay, daily turnout – even for short periods – can help significantly. Access to grazing plays a significant role in the prevention of ulcers in horses. We know that where horses have been turned out for rest for a few weeks, the incidence of ulcers in these animals will be minimal. However once brought back into work, and particularly if stabled full time, a significant proportion will develop ulcers within three to four weeks of stabling and exercise. 
Administration of hard feed in smaller quantities more frequently i.e. the same total amount given in four instead of two feeds a day can also help.

In addition to management modifications, or where the regime already emulated a more natural environment, horses at high risk of recurrence may also require an ongoing preventive dose of GastroGard to keep them clear of ulceration. 

If you have a horse that you suspect may have ulcers please phone the Hospital, 01555660000


(GastroGard® is a registered trademark of the AstraZeneca Group of Companies.  Legal Category POM-V.  GastroGard® contains Omeprazole.)



The material contained in this website is presented for information purposes only . The material is in no way intended to replace professional veterinary care or attention from a professional veterinary surgeon. 

The advice given in any of our web pages cannot be used as the basis for a diagnosis or choice of treatment.

Clyde Vet Group advises that you should always consult a veterinary surgeon about any queries with animals under your care.