This article reviews stomach ulcers in the horse, their diagnosis, and treatment options. Briefly, horses can get two different types of stomach ulcers which are defined by whether they occur in the top or bottom part of the stomach. Equine gastric ulcer syndrome (EGUS) is a general term describing equine stomach ulcer disease. The syndrome is still not fully understood and is an area of active research interest by equine scientists.
Anatomy
The stomach of the horse is small, holding only 8-12 L depending on the size of the horse. The inside of the stomach is covered by two different types of lining (mucosa). Approximately half of the stomach (the upper part) is covered by the same cells that line the oesophagus. These cells do not secrete any acid or mucus and are called squamous mucosa (Figure 1). The lower portion of the stomach contains cells that produce stomach acid and enzymes; this is called glandular mucosa (Figure 1) . To protect the stomach lining from this acid, the glandular mucosa is covered by a thick layer of mucus. There is no mucus layer over the squamous lining. The area where these two parts of the stomach meet is called the margo plicatus.
Clinical signs
It is impossible to tell from clinical signs alone if a horse has EGUS. Some horses make it very obvious that there is a problem; however, others can have terrible ulcers and show no clinical signs at all. Signs that have been documented in horses with EGUS are:
Change in eating habits
- Slower to eat meals
- Picky eating or leaving feed
- Pawing, ears back, grunting, leaving and coming back to the bowl during the meal
Change in behaviour
- Aggression
- Spooking
- Unsettled or on high alert
- Sensitivity to touch
- Reactive when being rugged / girthed / groomed
- Teeth grinding
Changes under saddle
- Being disunited in canter
- Kicking out or biting round to side with leg aids
- Not going forward
- Being spooky or irrational
- Poor / reduced performance
Changes in appearance
- Loss of top line
- Loss of condition or weight loss
- Dull coat
Changes to health
- Recurrent colic
- Loose droppings
Diagnosis
Even when it seems there is no doubt that a horse has gastric ulcers, gastroscopy (viewing the inside of the stomach with a camera) should always be performed. Although the signs listed above are highly suggestive of gastric ulcers, they are not diagnostic or exclusive to gastric ulcers. Not only is it expensive to “trial and treat” a horse which does not have ulcers, it is also not beneficial for the horse’s general health.
Additionally, different types of stomach ulcers can be present, which have separate treatments. We now understand that there are two types of ulcer disease seen in the equine stomach, and the causes, treatment and response to treatment of these differ. It is therefore essential that the horse is scoped to determine which type of ulcer disease (if any) the horse has.
Owners are often hesitant about having their horse gastroscoped, most commonly because the horse needs to be starved for 12-16 hours before the procedure to ensure that the stomach is empty of food so the stomach lining (and therefore any ulcers) can be seen. This is an understandable concern; however, horses usually deal with this period of fasting very well. Starving is usually performed overnight when the horse will naturally stop eating for 4-6 hours. The benefits of properly understanding the nature of the problem vastly outweigh any stress caused by a starvation period. The procedure itself is performed under light sedation and is tolerated extremely well.
Equine Squamous Gastric Disease (ESGD)
Squamous ulcers are the result of the squamous mucosa coming into contact with stomach acid. This part of the stomach (the upper region) is not designed to be in contact with acid, and as a result does not have a defence mechanism in place to protect against acid injury. Acid splashing up onto the squamous mucosa is more likely to happen when the horse moves faster than the walk and when the horse has an empty stomach. Squamous ulcers range from mild erosions to large bleeding craters and are graded 1-4 according to their severity (Figure 2).
Treatment
As ESGD is caused by acid splashing onto the squamous mucosa, ESGD is very effectively treated by switching off acid production. Read about the Equine Squamous Gastric Disease (ESGD) treatments here.
Management
Several risk factors have been recognised for the development of ESGD. These factors should be minimised in all horses but are particularly important to pay attention to for those horses with a previous history of ESGD. Without addressing these issues, ulcers are very likely to return.
- Acid splash: Feeding 2L of forage or chaff 30 minutes before exercise will help to soak up some stomach acid and also form a fibrous mat within the stomach on top of this fluid thereby limiting acid splashing.
- Time without forage: Time spent without access to forage increases the risk of squamous ulcers four-fold. Remember this includes time spent exercising/competing/travelling. Ensure constant access to forage where possible. For horses on restrictive diets forage can be soaked to reduce sugar content or even mixed with up to 25% straw which provides fibre but no nutritive value to the horse.
- High starch meals: Avoid using starch as an energy source. Where more energy is required, select a “high oil feed”; these should be around 10% oil. Feeds should not contain more than 20% non-structural carbohydrates (NSC). NSC is the sum of the sugar and the starch in a feed. Guidelines recommend less than 1g/kg bodyweight of starch per meal and less than 2g/kg bodyweight per day. For a 500kg horse this would equate to a maximum of 500g starch per meal, which would mean no more than 2.5kg of a 20% NSC hard feed twice daily. Ideally this quantity of feed should be split between more than two meals.
- Intense exercise: Moving at speeds faster than walk increases the risk of squamous ulcers. Explosive exercise, such as jumping or galloping, results in very high abdominal pressures. High abdominal pressure pushes the stomach contents towards the vulnerable squamous epithelium, causing acid splash injuries. Explosive exercise should be reduced where possible. When such activities need to be performed, make sure a fibrous meal is fed 30 minutes prior to exercise.
- Low dietary forage content: Forage (hay/ haylage or grass) should constitute a minimum of 75% of the diet. A horse of a healthy weight should be fed around 2% of its bodyweight a day in dry matter (the weight of feed once the water is removed) per day. For a 500kg horse this would be 10kg of feed (dry matter). In general terms, most hays and hard feeds are 85-90% dry matter. This would mean feeding a minimum 8.5kg of forage plus a maximum 2.8kg hard feed. Where possible, the amount of hay should be maximised, and the amount of hard feed should be minimised.
- Lack of pasture turnout: The exact role of pasture turnout in the management of EGUS is not clear. Increasing turnout is recommended, but there are certain caveats. Turnout should not cause the horse unnecessary stress (e.g. avoid solitary turnout if the horse does not like this). It is not uncommon for some performance horses to dislike field turnout; standing sulking by the gate is not of benefit to these horses. They would do better in their stable eating hay. Poor quality grazing can act in the same way as food deprivation. If there is not a lot of grass in the field and the horse enjoys turnout, ensure there is additional hay/haylage provided.
- Access to water: Restricted access to water while at pasture has been highlighted as a risk for ESGD and constant access to water should be always implemented. This is hard to do while travelling, which highlights again the increased risk transport poses. Some horses are particular about regional water differences and drink much less away from home. If this is the case, take water from home to competition.
Additionally, supplements may be useful in ongoing management of ulcer-prone horses. Current research suggests that providing an antioxidant to address oxidative stress within the stomach, buffers/antacids to reduce stomach acidity, and a mucus stimulant are all sensible ingredients for a gastric supplement to contain. Some horses may require a gastric supplement on a long-term basis, whereas others may only need additional support around stressful events, such as travel and competition. Certain supplements can also be used alongside medical treatment.
Equine Glandular Gastric Disease (EGGD)
Glandular ulcers are less straightforward than squamous ulcers. Research has shown that the lesions we have previously called glandular ulcers are often not true ‘ulcers’ but are regions of mucosal (stomach lining) inflammation. Therefore, these lesions should perhaps more accurately be referred to as regions of gastritis or inflammation. The exact cause of glandular disease is not yet fully understood. The glandular mucosa of the lower half of the stomach is designed to be in contact with acidic gastric fluid all the time and therefore, unlike ESGD, EGGD is not a simple case of acid injury. Where EGGD develops, it is thought that there is a breakdown in the normal mucosal acid defence mechanism. It is highly likely this breakdown is the result of multiple factors, instead of one single cause. Due to glandular ulcers being unlike squamous ulcers, they cannot be graded by the 1-4 system used for ESGD. Instead, lesions are simply described by appearance e.g. flat, raised, depressed, reddened, bleeding etc. (Figure 3).
EGGD can occur alone or with concurrent ESGD. Research has shown that horses with ESGD grade 2 or greater are 5 times more likely to have EGGD than horses without ESGD. Warmbloods appear to be more likely to suffer from EGGD than other breeds, suggesting a genetic component to their development. Exercising 5 or more days per week increases the risk of EGGD 10-fold and it has been proposed that exercise could be an example of physiological stress on the glandular mucosa. Increased number of caregivers (more than 3) has also been shown to significantly increase the risk of developing EGGD. Several studies have suggested that stress might play a role in the pathogenesis of EGGD.
Treatment
Despite EGGD not being directly caused by acid injury, acid suppression is still an important part of the treatment of glandular lesions as it is considered that the presence of acid will prevent glandular lesions from healing. Read about the Equine Glandular Gastric Disease (EGGD) treatments here.
Management
The previously mentioned risk factors should be minimised in horses with EGGD. Without addressing these issues, ulcers are very likely to return. Management factors to be optimised include:
- Pasture turnout: The exact role of pasture turnout in the management of EGGD is not clear. Increasing turnout is recommended, but there are certain caveats. Turnout should not cause the horse unnecessary stress (e.g. avoid solitary turnout if the horse does not like this). It is not uncommon for some performance horses to dislike field turnout; standing sulking by the gate is not of benefit to these horses. They would do better in their stable eating hay. Poor quality grazing can act in the same way as food deprivation. If there is not a lot of grass in the field and the horse enjoys turnout, ensure there is additional hay/haylage provided.
- Access to water: Constant access to water should be always implemented. This is hard to do while travelling, which highlights again the increased risk transport poses. Some horses are particular about regional water differences and drink much less away from home. If this is the case, take water from home to competition.
- Exercising more than 5 times per week: Although the intensity of exercise performed does not appear to be a risk factor for EGGD, the frequency of exercise is, which is thought to relate to a change in blood supply to the stomach while exercising. Horses with glandular disease should have a minimum of 2 days off work per week, ideally consecutive days.
- Experience: A young age seems to be an influential factor for the development of glandular ulcers. The likely reason being that older, more experienced horses do not find their job as stressful as younger horses who are less familiar with their role. An inexperienced horse cannot become experienced without work and competitions so design the training and competition routine considerately. Consider the risk that travel and intense exercise pose carefully (acid splash, time without forage and water, intense exercise, lack of rest days).
- Number of carers: Recommendations are to keep primary carers to a maximum of two people.
- Stress: It is difficult to quantify, and therefore measure, stress, as well as there being great individual variation in what is considered “stressful”. It is important to remember that different horses will find different things stressful, therefore advice on minimising stress must be based on the individual.
- Anti-inflammatories: When used at recommended doses, for short periods, non-steroidal anti-inflammatory drugs do not increase the risk of glandular ulcers. However, lesions can be seen when these drugs are used at excessively high doses, or for long periods of time. It is sensible to always discuss the use of anti-inflammatory medication with your vet, especially if your horse is at higher risk of developing ulcers.
Again, supplements may be useful in the ongoing management of ulcer-prone horses.
Looking for further information about Equine Gastric Ulcer Syndrome (EGUS), then check out all this further reading and information!
- ARTICLE – Gastric ulcer supplements for horses under the spotlight
Read this in-depth article assessing the Gastric Ulcer supplements on the market. Includes comparison tables and points to look out for. - ARTICLE – Equine Gastric Ulcer Syndrome (EGUS)
Another in-depth article about EGUS, written by Dr David Marlin - ARTICLE – Feed Materials In Focus
Is feeding corn oil good for treating or preventing Equine Gastric Ulcers? - WEBINAR – Equine Gastric Ulcer Syndrome – not all ulcers are the same! by Dr Kirstie Pickles
- ARTICLE – Why some horses need starch
- ARTICLE – Is your horse in pain?
- PODCAST – Moving your horse to a new home, by Dr David Marlin
