Gastric ulcers in horses

We find them across all riding disciplines and in all types of horse keeping. Those bad-tempered, barely or exaggeratedly eager to please, nervous and often tense horse personalities that display strange behaviour such as being girthy and teeth grinding. The cause is often thought to be the horse's character ("s/he's always been like that") But what happens if all of this is a sign of stomach “pain"? Studies of different breeds, types of husbandry, feeding and workloads show a staggeringly high number of over 70% of proven gastric inflammations of varying degrees in horses of different breeds and areas of use. A very painful condition that can affect any horse.

How do I identify stomach problems in my horse? 

The clinical symptoms also manifest in different intensities in different horses. It is not possible to infer the severity of the stomach ailment directly from the strength of the symptoms. Some horses show severe signs of stomach problems and a gastroscopy would reveal only very slight inflammatory processes. Other animals, in turn, display barely noticeable differences in behaviour and / or appearance, but are already suffering from a very bad case of gastric ulcers. Thus, in the absence of a diagnostic imaging method one should not attach too much importance to the signs with regard to the severity of the disease.

Possible clinical symptoms:

• Decreased appetite or incessant eating
• Frequent bouts of colic, especially during or after feed intake
• Emaciation (rather rare)
• Lack of motivation, sluggishness
• Burping and a sour smell from the mouth
• Dull coat
• Bloated belly
• Chewing without food in the mouth, licking disease
• Grinding teeth, cribbing, frequent yawning
• Saddle shyness
• Watery stool/diarrhoea over longer periods of time
• Significant behavioural changes such as aggressiveness, nervousness, self-injury

Not all these symptoms should immediately or exclusively be attributed to ulcers! A veterinarian will obtain an overall picture and make a diagnosis.

How does the horse stomach work? 

The horse's stomach is relatively small in relation to body size, with an average volume of 15 litres in a large horse. It is designed to almost continuously absorb and utilise small quantities of nutrient-poor roughage / steppe grass. Therefore, gastric juice containing hydrochloric acid is constantly produced in the stomach, even if the horse is not eating. The stomach basically consists of two parts that are not rigidly separated (margo plicatus).

In the upper area, at the end of the oesophagus, there is a spongy section that is pink when healthy. It doesn't contain any glands and has a mucous membrane that does not have its own protective layer against stomach acid. That is why more saliva is produced by long chewing of rough fibres. The saliva contains bicarbonate (basic), which is important as a buffer against stomach acid. Generally, the pH in the upper part of the stomach is between 5-7. In the lower part, however, the pH is between 2-4 (very corrosive).

The lower sector permanently produces the necessary stomach acid, with which the already pre-digested feed is processed into pulp. At the end of the stomach, the pre-digested feed goes through the pylorus (stomach exit) into the duodenum. The process between being transport through the oesophagus to entering the duodenum is very rapid compared to other mammals. All other digestive processes and utilisation of nutrients take place mainly in the intestinal tract.

What must I know about non-infectious gastric ulcers?

Gastric ulcers are one of the most common disorders of the horse's stomach, together with not necessarily associated gastritis. According to Gerber and Straub, ulcers are the sequelae of an imbalance between aggressive, mucosa-damaging factors (such as gastric acid, pepsin, bile acid and volatile fatty acids) and factors that protect the mucosa (such as mucus production, bicarbonate in saliva, local circulation and high rate of cell division). An elevated cortisol level triggered by stress prevents good gastric mucosal perfusion and thus plays a major role in the development of gastric ulcers.

After lengthy research and several studies on gastric diseases in horses, it has been found that it is mainly the transitional part between cutaneous mucosa (pars non glandularis) to the glandular mucosa (pars glandularis) that is affected by stomach ulcers. This transition is called margo plicatus. Here, for example when training on an empty stomach, the stomach acid sloshes around in the section that has no natural protection against it and causes skin lesions there that can eventually turn into ulcers. However, inflammatory processes may also be found at the pylorus, caused by the reflux of pre-digested food from the duodenum (intestinal reflux caused, for example, by a mechanical disruption of the intestinal passage).

What can cause gastric ulcers?

Despite numerous studies, it is not possible to identify the full range of causes. It appears to be a combination of genetic and environmental factors. In his report, Sykes et al. mentions a higher probability of stomach disease in Thoroughbreds than in cold-bloods and an increased risk in stallions and mares compared to geldings. However, environmental factors such as feeding, living conditions and stress, and thus the general mental state, are decisive. 

The horse's stomach produces gastric acid all the time. If the intervals between feeds are too long, or food intake and the chewing and saliva processes are severely shortened, it leads to an imbalance in the stomach. The unprotected mucous membrane is attacked, resulting in lesions and even bleeding and ulcers. High concentrate intake, including quickly digested starches and carbohydrates as contained in typical horse feed mixtures, leads to the gastric acid not getting enough saliva and thus not enough basic buffer to increase the pH level. 

How can gastric ulcers be detected?

Inflammatory processes in the stomach can only be definitely identified by viewing them directly. A so-called gastroscopy through the nose allows the veterinarian to take a close look at the condition of the oesophagus, the stomach entrance, the gastric mucosa and the pylorus. Since horses have to fast for 24 hours before a gastroscopy, the question arises whether this does not lead to additional stress, especially in animals with gastric ulcers. Therefore, studies have indicated that suspected ulcers are often treated with acid blockers and/or proton pump inhibitors over a short period of time. If there is clear improvement in the symptoms and the general condition of the affected horse, the suspicion is thus "confirmed", and the classic therapy continues. Only a veterinarian can decide on this course of action.

How are diagnosed gastric ulcers treated?

Depending on the severity and occurrence of inflammation, bleeding or ulcers, the classical therapy is by means of a proton pump inhibitor such as omeprazole and often in combination with an H₂ receptor blocker such as cimetidine / ranitidine and / or a mucosal protection such as sucralfate. Average treatment lasts between 21 and 28 days. Experience from reports on the Internet and in forums shows that the susceptibility to gastric ulcers increases, even after successful treatment. According to studies, this is probably because the underlying causes have not been eliminated.

How can I support my horse's stomach?

• Feed high-quality hay (ideally first cut)
• Straw can be fed as a low-calorie filler, but not as a complete feed
• Avoid products and feeds that contain sugar and starch
• Avoid concentrates if possible, otherwise feed in small quantities throughout the day, and never on an empty stomach
• High-quality vegetable oils such as linseed oil, hemp oil or black cumin oil are recommended as energy sources instead of concentrates
• Feed sufficient hay before riding and no concentrates!
• Reduce or avoid stress in all areas of the horse's life (adapt the keeping conditions, calm herd, measured training, competitions only if the horse is resilient)
• Treat your horse with serenity - the calmness will transfer to the animal and its stomach!

Compiled by: Bianca Becker-Slovacek on 28/11/2018

Bibliography and further reading

• Bass, L., Swain, E., Santos, H., Hess, T., & Black, J. (16.. Februar 2018). Effects of Feeding Frequency Using a Commercial Automated Feeding Device on Gastric Ulceration in Exercised Quarter Horses. Journal of Equine Veterinary Science(64), S. 96-100.
• Gerber, V., Venner, M., & Straub, R. (2016). Pferdekrankheiten: Innere Medizin (2. Auflage Ausg.). (V. Gerber, & R. Straub, Hrsg.) Bern: utb.
• Sykes, B., Hewetson, M., Hepburn, R., Luthersson, N., & Tamzali, Y. (2015). European College of Equine Internal Medicine Consensus Statement - Equine Gastric Ulcer Syndrome in Adult Horses. Journal of Veterinary Internal Medizin, S. 1288-1299.