Gastric ulcers in Horses

Ulcers of the stomach, or rather, gastric ulceration, is perhaps one of the most common disorders affecting the gastrointestinal system of the horse. Whilst racehorses are reported to have the highest prevalence (up to 93%) of gastric ulcers, very few horses are immune to the potential for developing this problem. So, let’s take a little bit more of an in-depth look at ulcers, and why they pose such a problem.

Why do Gastric ulcers in horses occur?

As we touched on in the previous article, horses have evolved over time as “trickle feeders”. Their stomachs are small which means they have a need to graze constantly and can do so for up to 17 hours a day. Because of this, the horses’ stomach is constantly producing acid throughout the day and night. An adult horse can produce approximately 16 gallons of acidic fluid in a 24-hour period.

What is a gastric ulcer and where do they occur?

Put simply, a gastric ulcer is an injury to the lining of the stomach, referred to as the mucosa. Gastric Ulcers can present themselves in all areas of the stomach but it is more common to find them in the non-glandular region. Ulceration of the non-glandular area occurs as a result of digestive acids coming into contact with the upper part of the stomach lining, which has less of a protective layer than the lower part of the stomach. Ulceration of the glandular area is thought to be much less common. The lower part of the stomach has evolved to be exposed to highly acidic contents and as such has developed a protective mucus layer. Damage to this protective layer exposes the mucosal lining, thereby facilitating the formation of ulcers.

Causes and Contributing Factors of Gastric Ulcer in Horses

Anything that interrupts grazing time for a period of time can have the potential to increase the risk of ulcers in horses. However, many other factors have also been thought to cause a potential increased risk, including:

• Strenuous exercise, particularly when performed on an empty stomach increases the risk of acidic contents splashing around and damaging the non-glandular area.
• Irregular feeding times and restriction in feed intake, especially roughage.
• Volatile fatty acid productions as a result of fermentation of carbohydrates.
• Prolonged treatment with non-steroidal anti-inflammatory drugs (NSAIDs). This is thought to precipitate ulcer development in the lower, glandular part of the stomach.
• Increased levels of stress.

Foals begin to secrete gastric acid from as early as 2 days of age. Infrequent nursing and prolonged time between feeding play a key role in the incidence of gastric ulcers in foals. Other bowel diseases, such as diarrhoea, can also play an important role.

What are the clinical signs associated with gastric ulcers?

There are no specific clinical signs directly associated with gastric ulcers in horses and many have no symptoms at all.  However, there are a number of signs that may increase the presumption of occurrence, including:

• Reduced or lack of appetite
• A decrease in performance ability
• Poor body condition which may be seen as a difficulty in maintaining weight or weight loss
• Low-grade colic
• Changes in behaviour or attitude; i.e. a reluctance to work

Unfortunately, there is only one definitive means of diagnosing gastric ulcers. This can only be achieved by video-endoscopy. It is common practice to fast a horse (for approximately 12 hours) prior to this procedure to enable a thorough examination and assessment of all parts of the stomach wall. Diagnosis also includes grading the level of ulceration presented on a set scale from 0 to 4. Using a grading system allows for a follow-up examination to appropriately assess for signs of recovery and improvement. With appropriate management and treatment, low-grade ulcers typically heal quite quickly (within 2-3 weeks) whereas those higher-grade ulcers will take a much longer period of time.

How can we reduce the incidence of gastric ulcers?

Good management and digestive support are of the utmost importance when trying to prevent ulcers in horses and also as an aid to recovery when they’ve already occurred. The simplest approach in trying to reduce the incidence of ulcers is to increase the amount of time they spend out in the paddock or at pasture. This is not always possible, or even practical in some instances so a compromise in this respect would be to try and feed multiple small meals throughout the day. A good quality hay or haylage should be offered and the use of a hay net (or slow feeder) may offer a benefit to increase chewing and slow down intake. Breaking up concentrate feeding into 3 meals rather than 2 also offers a great benefit to the stabled horse. And of course, we need to ensure that there is access to clean, fresh water throughout the day. In addition, digestive supplements can play a crucial role in the health of the horses’ gut.

The importance of management cannot be overstated when it comes to this condition. Anything we can do to reduce the incidence and severity of gastric ulcers will benefit our equine friends and thereby result in a happy and healthy animal; and hopefully a better performer.

Written by Dr Ian Rountree MVB