Bit & Bridle

Equine Gastric Ulcer Syndrome (EGUS)

Other Names

  • EGUS
  • Equine Squamous Gastric Disease (ESGD)
  • Equine Glandular Gastric Disease (EGGD)
  • Gastric ulcer syndrome in horses
  • Horse ulcers

What is Equine Gastric Ulcer Syndrome?

Equine Gastric Ulcer Syndrome (EGUS) is a collective term describing erosions, ulcerations, and lesions affecting the lining of the horse’s stomach. It is one of the most common conditions in domesticated horses, with prevalence estimated at 37–93% in sport horses and higher still in racehorses. Even leisure horses can be affected — studies suggest prevalence of up to 60% in horses in any form of regular work.

The horse’s stomach is divided into two distinct regions: the upper squamous (non-glandular) region, which lacks protective mucus secretion and is lined by squamous epithelium, and the lower glandular region, which is lined by glandular cells that secrete both acid and a protective mucus layer. EGUS now encompasses two distinct syndromes:

  • Equine Squamous Gastric Disease (ESGD): Ulceration of the squamous region, primarily caused by exposure to gastric acid splashing up from below. This is the more common form and is most frequently associated with management, feeding, and exercise factors.
  • Equine Glandular Gastric Disease (EGGD): Lesions in the glandular region, which is naturally protected by mucus. EGGD has a different aetiology and is less well understood — psychological stress and Helicobacter-like organisms have been implicated.

Understanding which region is affected matters because treatment protocols differ. Related gastrointestinal conditions include equine ulcerative colitis.

Causes

The horse evolved as a trickle feeder, grazing for 16–18 hours per day. The stomach continuously secretes acid regardless of whether food is present. In the wild, constant roughage intake buffers this acid and stimulates saliva production (which also neutralises acid). Modern management practices that deviate from this pattern significantly increase ulceration risk:

  • Stabling and restricted forage access: Horses without continuous access to hay or grazing have unprotected squamous mucosa exposed to pooled acid for prolonged periods
  • Intermittent feeding: Large concentrate meals with long gaps between them (the typical twice-daily feeding regime) dramatically raises acid exposure time in the squamous stomach
  • Exercise: Cantering and galloping cause the stomach to compress and bounce, splashing acid onto the unprotected squamous region. Horses working on an empty stomach are at particular risk.
  • High-starch diets: Grain and concentrates ferment to produce volatile fatty acids, which exacerbate squamous mucosal damage
  • NSAIDs: Phenylbutazone and other NSAIDs reduce prostaglandin synthesis, compromising the protective mucus layer and increasing acid damage — particularly in the glandular region
  • Stress: Transport, competition, training changes, social disruption, and stabling all increase cortisol levels, which impairs mucosal protection, particularly in EGGD

Symptoms and Signs

Clinical signs can be subtle and non-specific, which is why EGUS is frequently missed:

  • Poor body condition despite adequate nutrition: Weight loss or difficulty maintaining condition
  • Reduced appetite or fussy feeding — often selective refusal of concentrates
  • Recurrent mild colic: Particularly after feeding, exercise, or during periods of restricted forage
  • Behavioural changes: Increased irritability, reluctance to be girthed or tacked up, resistance under saddle, or changes in temperament
  • Reduced performance: Loss of impulsion, reluctance to work forward, or generalised loss of willingness
  • Teeth grinding (bruxism)
  • Excessive salivation
  • A dull, rough coat

Foals may show more obvious signs including intermittent nursing, colic, diarrhoea, teeth grinding, and lying on their backs (a posture thought to relieve gastric discomfort). Severe ulceration in foals can be life-threatening.

Diagnosis

Definitive diagnosis requires gastroscopy — endoscopic examination of the stomach:

  • Gastroscopy: A 3-metre flexible endoscope passed via the nostril into the stomach allows direct visualisation of both squamous and glandular regions. The horse is fasted for 12–18 hours beforehand to ensure an empty stomach. Lesions are graded on a standardised scoring system (grade 0–4 for ESGD) based on severity and extent of mucosal damage.
  • Response to treatment: Some practitioners initiate empirical omeprazole treatment and use a positive clinical response as indirect diagnostic evidence. However, this does not provide definitive diagnosis and may miss concurrent disease — gastroscopy before and after treatment is the recommended standard.
  • Blood tests and faecal testing: Non-specific but may support the diagnosis by ruling out other causes of weight loss and poor condition

Treatment

  • Omeprazole (GastroGard/UlcerGard): The gold standard medical treatment. A proton pump inhibitor that dramatically reduces gastric acid secretion. The treatment dose (4 mg/kg daily for 28 days) heals squamous ulcers effectively. Prevention dose (1 mg/kg daily) reduces recurrence. Omeprazole is less reliably effective for EGGD — higher doses or combination therapy may be needed.
  • Sucralfate: A mucosal protectant that binds to ulcer surfaces and promotes healing. Particularly useful as an adjunct for glandular disease.
  • Misoprostol: A prostaglandin analogue that increases mucosal protection. Used in EGGD cases, often in combination with omeprazole.
  • Management changes: These are as important as medication for long-term control. Key changes include:
    • Ad libitum forage — continuous access to hay or haylage at all times
    • Feeding hay before exercise to buffer the stomach
    • Reducing or eliminating high-starch concentrates
    • Feeding small, frequent meals if concentrates are required
    • Minimising stress — reduce unnecessary stabling, maintain social interaction, provide turnout where possible

Treatment response should be confirmed by repeat gastroscopy at the end of the treatment course.

Prevention

  • Maximise forage intake and minimise time spent with an empty stomach
  • Never exercise a horse on a completely empty stomach — provide forage at least 30 minutes before work
  • Reduce high-starch concentrate feeding where possible
  • Minimise unnecessary stabling and isolation
  • Use NSAIDs at the lowest effective dose for the shortest necessary duration
  • Consider prophylactic omeprazole during periods of high stress (transport, competition, hospitalisation)

Prognosis

For horses with ESGD, the prognosis for healing and return to full work is excellent with appropriate medical treatment and management changes. The challenge is preventing recurrence — ulcers frequently return if management is not permanently improved. EGGD carries a more variable prognosis and may require longer treatment periods and ongoing maintenance therapy.

When to Call the Vet

  • Any horse with recurrent colic, particularly around feeding or exercise time
  • Unexplained weight loss or difficulty maintaining condition
  • Behavioural changes — particularly reluctance to be girthed, resistance under saddle, or changes in temperament
  • Reduced performance with no orthopaedic explanation
  • Foals showing colic, teeth grinding, or lying in unusual positions

Frequently Asked Questions

How common are gastric ulcers in horses?

Extremely common. Prevalence in racehorses is reported at up to 90%. In performance horses across disciplines, figures of 50–80% are routinely reported. Even leisure horses in moderate work have prevalence rates of 40–60% in some studies. It is fair to say that any horse in work is at meaningful risk.

Can gastric ulcers be managed without medication?

Management changes alone — particularly improving forage access and reducing dietary starch — can improve mild gastric ulceration, but established ulcers (grade 2 and above on the ESGD scale) require omeprazole treatment for reliable healing. Management changes are essential to prevent recurrence once treatment has finished.

Are all omeprazole products equally effective?

Not necessarily. The bioavailability of omeprazole varies between formulations. Licensed veterinary products (GastroGard, UlcerGard) are formulated with an enteric coating to protect omeprazole from gastric acid and allow absorption in the small intestine. Some unlicensed or compounded products may have inferior bioavailability and should be used with caution. See BEVA guidance on EGUS for licensed treatment recommendations.

Do horses on pasture get gastric ulcers?

Pasture-kept horses that graze freely have significantly lower ulcer rates than stabled horses. The continuous intake of grass and the associated saliva production provide natural acid buffering. However, horses at grass that also undergo significant training, competition, or restricted grazing periods are not immune. Management during competition and transport periods remains important even for horses primarily kept at grass.