Equine Gastric Ulcer Syndrome (EGUS)


The preferred term currently is Equine Gastric Ulcer Syndrome (a syndrome is a group of symptoms which consistently occur together or a condition characterised by a set of associated symptoms as distinct from a disease which is characterised by specific symptoms). EGUS comprises two diseases – Equine Glandular Gastric Disease (EGGD) and Equine Squamous Gastric Disease (ESGD). These refer to the regions where the ulcers occur. EGGD refers to ulcers in the glandular, acid-secreting lower part of the stomach, whilst ESGD refers to ulcers in the upper (non-acid secreting) part of the stomach (covered by a type of tissue referred to as squamous epithelium).

ESGD is believed to occur primarily due to management associated with stabling, training, travelling and competing (as opposed to horses kept in low stress extensive management). ESGD in exercising horses has been suggested to be due to acid splashing up from the lower part of the stomach (hence the recommendation to feed forage prior to exercise to reduce the splashing). EGGD appears to primarily occur due to delayed gastric emptying caused by other disease processes. Thus, ESGD and EGGD can often occur together but may have different underlying causes.

How common is EGUS?
EGUS has generally been found to be lowest in pleasure horses and highest in Thoroughbred and Standardbred racehorses in training. However, occurrences of over 60% have been found in some studies of showing horses, endurance horses and eventers.

What factors appear to increase the risk of horses having EGUS?
Most studies have not found any clear association of risk of EGUS with age or sex. It may be that certain breeds, such as Thoroughbreds, are more predisposed to EGUS.

Factors that appear to significantly increase the risk (risk factors) of horses developing EGUS include:
* High-stress environments
* Living in an urban area
* Lack of direct contact with other horses
* Lack or minimal pasture turnout
* Forage restriction
* Straw feeding
* Low fibre intake
* Feeding sharp forage e.g. chaff that has been chopped to leave sharp ends
* Large meal size
* High starch content
* Long intervals between meals
* Few meals (e.g. two per day)
* Intermittent access to water
* Hard or prolonged exercise

What are the signs suggested to be linked to the gastric ulcers?
Signs that have been suggested as likely to indicate gastric ulcers (a combination of signs suggested from controlled studies, clinical experience and popular culture):
* Change in appetite
* Being fussy about new foods
* Change in behaviour
* Change in behaviour at feeding time
* Weight loss
* Poor coat condition
* Loss of performance
* Colic
* Signs of abdominal discomfort
* Crib-biting
* Rearing
* Bucking
* Back pain
* Diarrhoea/loose droppings
* Grinding teeth
* Resenting saddle
* Resenting girthing
* Not going forward

Of these, the more reliable signs that point to EGUS include:
Colic – Some studies indicate an increased risk of colic in horses with gastric ulcers. In one study over 80% of horses with repeated episodes of colic had gastric ulcers.
Poor appetite and loss of condition – At least three studies have suggested poor appetite or being a ‘fussy feeder’ is associated with an increased likelihood of gastric ulcers. In racehorses, poor body condition appears to indicate a high chance of gastric ulcers being present.

Behaviour – Horses showing stereotypical behaviour such as box-walking, wind-sucking and crib-biting, or a change in behaviour, were found to be more likely to have ulcers in two separate studies. Anxious horses in one study were more likely to have ulcers.

Loose droppings – Very loose droppings (diarrhoea) was reported to be associated with an increased risk of gastric ulcers in one study. However, this has not been supported by other studies. Stress can lead to loose droppings and gastric ulcers, but it appears at this time that loose droppings and gastric ulcers are not directly connected.

Loss of performance – Whilst believed to be an important effect of gastric ulcers amongst horse owners and racehorse trainers, only a few studies have examined this aspect. The best evidence for a negative effect of gastric ulcers on performance comes from a study where horses were treated for gastric ulcers.

The use of clinical signs to diagnose gastric ulcers is best summed up by this consensus statement of the European College of Equine Internal Medicine (ECEIM):

“Although a wide variety of clinical signs might be present in individual cases of EGUS, they are nonspecific and are poorly associated with the presence of EGUS. The committee, therefore, does not support the practice of diagnosing EGUS based on ‘characteristic’ clinical signs and recommends that EGUS be confirmed by performing gastroscopy…”

[European College of Equine Internal Medicine Consensus Statement—Equine Gastric Ulcer Syndrome in Adult Horses. B.W. Sykes, M. Hewetson, R.J. Hepburn, N. Luthersson, and Y. Tamzali (2015)]

However, that said, the more risk factors your horse has from the list above and the more clinical signs – especially colic, reduced appetite and or loss of condition and altered behaviour (especially around feeding) – then it would be reasonable to consider that gastric ulcers may be present.

Diagnosis of EGUS
A definite diagnosis of EGUS can only be made by gastroscopy: passing an endoscope – a tube with a camera on the end up the nostril and down the oesophagus into the stomach. However, due to cost or other reasons, it has not been uncommon for horses suspected of having gastric ulcers to be treated with medications or gastric ulcer supplements. In these cases, a significant improvement following treatment would suggest that ulcers had been or are present.

Treatment of EGUS
So, let’s assume your vet has visited your horse, undertaken a gastroscopy and there are gastric ulcers present. What next? Firstly, when reading this article please bear in mind that this is general information that may not apply to every case. Your vet will have assessed your horse and may take into account other factors in prescribing treatment that may appear different to general advice given in this article.

The type of treatment and management your vet will recommend will likely depend on:
* The type of ulcers
* The severity of the ulcers
* The suspected cause of the ulcers e.g. stress, low forage, high starch diet, etc
* Any other health issues your horse has e.g. colic
It is likely that your vet will recommend treatment if ulcers are present, particularly as only around 5% of squamous ulcers will heal spontaneously (Zavoshti and Andrews, 2017).

Important: Please do remember that if you are competing in any affiliated competitions or racing, let your vet know – because certain medications are restricted for competition.

Drugs that suppress acid-secretion
The most commonly used type of drug for ulcers in either the squamous (upper) region (ESGD) or glandular (lower) region of the stomach (EGGD) are drugs that decrease secretion of acid into the stomach and raise the pH of the stomach contents. The best known of these is the proton pump inhibitor (PPI) omeprazole (known by trade names such as GastroGard, Peptizole and UlcerGard). Another drug which may be prescribed for your horse’s ulcers is ranitidine (known by the trade name Zantac). Ranitidine also makes the stomach less acid but by a different mechanism and is known as an H2-receptor antagonist. Omeprazole is generally considered more effective than ranitidine.

For squamous ulcers, omeprazole at 4mg/kg (2g in a 500kg horse) once a day for 28 days has been shown to result in healing of 70-77%. For glandular ulcers, whilst older studies and one recent study showed healing rates of 70-80% within 28 days of treatment, more recent studies have suggested the healing rate with omeprazole at 4mg/kg once a day may be as low as 25%.

Omeprazole alone or without management changes may not be effective for all horses, as 50% of horses with squamous ulcers were the same or worse after 90 days of treatment with the standard dose of omeprazole (4mg/kg/day).

Long-term use of drugs that reduce acidity in the stomach may also be undesirable for other reasons. The stomach is acidic for two main reasons. Firstly, to kill potentially harmful micro-organisms such as bacteria, moulds and yeasts ingested with feed. Secondly, the acidity in the stomach is the first stage in protein digestion. In addition, whilst not demonstrated in horses, long-term use of PPIs in people can lead to bone loss and an increased risk of gastrointestinal infections.

Drugs that coat the stomach
The most commonly used coating agent is a drug called Hexadeca-μ-hydroxytetracosahydroxy[μ8-[1,3,4,6-tetra-O-sulfo-β-Dfructofuranosyl-α-D-glucopyranoside tetrakis(hydrogen sulfato)8-)]]hexadecaaluminum – or Sucralfate for short! Sucralfate binds to stomach ulcers and aids healing. Sucralfate is not usually considered effective in treating squamous ulcers and is usually given with acid-suppressors such as omeprazole for treating glandular ulcers.

In people, stomach ulcers are often associated with infection by Helicobacter pylori and treatment with appropriate antibiotics is often highly effective. Helicobacter pylori does not seem to be a cause of gastric ulcers in horses and the current advice is “the use of antibiotics should be limited to treatment of chronic non-healing ulcers”.

Antacids such as aluminium hydroxide or magnesium hydroxide are not controlled drugs but may be prescribed in combination with other medications, particularly for squamous ulcers. They may offer short term pain relief but are not considered to be effective treatments on their own.

New medications
A number of new medications are being investigated for treatment of EGUS but these are not commonly in use. These include drugs that increase the rate of emptying of the stomach (e.g. Bethanechol), somatostatin analogues (Octreotide) and synthetic prostaglandins (e.g. Misoprostol).

Management and nutrition
* Unrestricted access to good quality pasture or forage (hay or haylage).
* If your horse needs a hard feed, this should be split into four or five smaller meals throughout the day. High starch feeds should be avoided if possible.
* Feed forage before a hard feed.
* For horses that need energy, oil is a safer source of energy than starch. The Pure Feed range is ideal for horses with or tendency towards EGUS high in fibre, low in starch and uses oil as the main energy source*.
* Avoid feeding sharp chaffs as these can cause or worsen ulcers.
* If your horse is in work, consider feeding fat-coated electrolytes as ordinary electrolytes can cause or worsen gastric ulcers – think of rubbing salt in an open wound (for more information about our Pure+ Electrolytes, click here).
* Increase turnout time.
* Ensure water available at all times.
* Minimise stress.
* Feed a small meal of non-sharp chaff 30 minutes before exercise.
* As hindgut discomfort may lead to stress and altered eating behaviour, if your horse suffers from signs of hindgut dysfunction (e.g. mild colic, loose droppings), consider a high dose protected live yeast pre and probiotic.

Oil as a treatment or preventative for gastric ulcers
There appears to be a lot of advice on various forums about feeding corn oil to treat or prevent gastric ulcers in horses. Much of this has supposedly been on the advice of vets!

The idea of feeding corn oil to horses with gastric ulcers goes back to a paper published in 2004 by Cargile et al. However, these authors likely got the idea from a 1987 study which showed that feeding oil to rats prevented experimentally induced peptic ulcers (Jayaraj et al, 1987).

One poorly designed study reported that feeding 45ml of corn to four ponies slightly decreased gastric acid secretion, BUT they did not scope the stomachs.

In a larger and properly designed study, feeding 240ml per day of refined rice bran oil or crude rice bran oil or corn oil for five weeks had no effect on gastric ulcer formation. Conclusion? Oil will not treat or prevent ulcers. Replacing starch energy in the diet with oil as an energy source may help in the management of gastric ulcers.

Nutritional supplements for treating or managing gastric ulcers
Important: Please do remember that if you are competing in any affiliated competitions or racing, use supplements from companies that are part of the BETA NOPS scheme. This will significantly reduce the risk of testing positive for prohibited substances.

There has been a significant amount of research into herbs, nutraceuticals, trace minerals, vitamins and plant extracts for the management of EGUS. Zavoshti and Andrews (2017) suggest the following reasons for this:
* The high expense of pharmacologic agents.
* Daily handling and oral administration of paste or tablet formulations.
* Pharmaceutical agents require a prescription.
* Gastric ulcer recurrence is common once treatment is discontinued.
* Long-term treatment with omeprazole results in high gastric juice pH and might negatively affect digestion in the stomach or small intestine.
* Use of medications in performance and show horses is now forbidden or under tight control.
* Cost of gastroscopy and cost of medication.
For these reasons, many owners may choose to try feeding a supplement. A variety of evidence supports the use of ingredients such as vitamin E, lecithin, pectin, sea buckthorn, ficus glomerata extract and thioredoxin (from crushed yeast) for gastric ulceration. In contrast, corn oil and aloe vera have not been shown to be effective.

If a horse has signs suggestive of EGUS, then feeding a supplement should produce a rapid improvement in behaviour, especially around feeding, temperament and, over a longer period, improvement in condition. If you try a supplement, then it would be advisable to try one that has undergone some clinical trials.

Whichever approach you try, if your horse’s condition does not improve or worsens, then you should consult your vet as soon as possible.

Diagnostic accuracy of blood sucrose as a screening test for equine gastric ulcer syndrome (EGUS) in adult horses. Hewetson M, Sykes BW, Hallowell GD, Tulamo RM. Acta Vet Scand. 2017 Mar 11;59(1):15.
Therapeutics for Equine Gastric Ulcer Syndrome. Zavoshti FR and Andrews FM. Vet Clin North Am Equine Pract. 2017 Apr;33(1):141-162.
European College of Equine Internal Medicine Consensus Statement—Equine Gastric Ulcer Syndrome in Adult Horses. J Vet Intern Med. 2015 Sep-Oct;29(5):1288-99. Sykes BW, Hewetson M, Hepburn RJ, Luthersson N, Tamzali Y.


About Author

Dr David Marlin is a physiologist and biochemist who has worked in academia, research and professional sport. He has worked in the equestrian and veterinary world and in human sport, healthcare, medicine and exercise science. In 1989 David obtained his PhD from the UK’s leading sports university, Loughborough University following a four-year study on the responses of Thoroughbred racehorses to exercise and training, undertaken at the renowned Animal Health Trust in Newmarket. You can read David's full biography in the Our Website section.