Bit & Bridle

Equine Gastric Ulcers

Other Names

  • Equine Gastric Ulcer Syndrome (EGUS)
  • Equine Squamous Gastric Disease (ESGD) — lesions in the squamous (upper) region
  • Equine Glandular Gastric Disease (EGGD) — lesions in the glandular (lower) region

What are Gastric Ulcers in Horses?

Gastric ulcers in horses are erosions or lesions of the stomach lining — the result of sustained acid damage to the mucosal surface. They are extraordinarily common: research suggests that between 60–90% of racehorses and 30–60% of pleasure horses have some degree of gastric ulceration at any given time, making EGUS one of the most prevalent health conditions in modern equine management.

The horse’s stomach is divided into two distinct regions, each susceptible to different types of ulceration:

  • Squamous (non-glandular) region: The upper portion, which is lined with relatively thin, unprotected tissue. It does not secrete mucus and has little defence against acid splashing up from below. ESGD is the most common form and is strongly associated with diet, exercise, and management.
  • Glandular region: The lower portion of the stomach, which is lined with mucus-secreting cells that provide significant natural protection. EGGD is less common and less well understood, but is increasingly recognised as a distinct entity from ESGD, with different causative factors and different responses to treatment.

What Causes Gastric Ulcers in Horses?

The horse evolved as a trickle-feeder — a continuous grazer designed to eat small amounts of fibrous forage throughout the day. The equine stomach produces acid continuously (unlike humans, who secrete acid primarily in response to food). In a grazing horse, the presence of fibrous feed and the resulting saliva buffer this constant acid production. Modern management often disrupts this natural balance.

Diet and Feeding Practices

  • Extended periods without feed: When the stomach is empty, acid splashes onto the unprotected squamous mucosa unchecked. Horses without access to forage for more than 4–6 hours are at significantly increased risk.
  • High-grain, low-forage diets: Concentrate feeds ferment rapidly, producing volatile fatty acids that damage the squamous lining at low pH. They also reduce the physical mass of fibre in the stomach that physically blocks acid from reaching the upper region during exercise.
  • Poor-quality or insufficient hay: Hay stimulates saliva production (roughly 10 times more than concentrates) which neutralises stomach acid. Horses on low-forage rations produce less buffering saliva.

Exercise

Strenuous exercise has been shown to cause acid to splash up against the squamous mucosa, particularly in horses with empty stomachs. The increased abdominal pressure during canter and gallop compresses the stomach. Racehorses, eventers, and other horses in high-intensity training are at particular risk of ESGD. Research has shown that gastroscopy immediately after exercise reveals significantly more acid in the squamous region than at rest.

Stress and Stabling

  • Stabling and confinement: Horses in stalls have less opportunity to graze continuously and often face psychological stress that increases cortisol levels, which in turn increases acid production.
  • Transport and competition: Travel, unfamiliar environments, and the stress of competition are all associated with increased risk of EGUS, particularly in competition horses that are regularly transported.
  • Social isolation: Horses are highly social animals; isolation from companions is a recognised stressor.

NSAIDs

Chronic administration of non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone (bute) and flunixin meglumine suppresses the production of prostaglandins that normally protect the stomach lining and maintain blood flow to the gastric mucosa. Long-term or high-dose NSAID use significantly increases the risk of both ESGD and EGGD.

Foals

Foals are particularly vulnerable, especially in the first months of life. Their gastric mucosa is immature, and stress associated with illness, weaning, transport, or separation from the dam can trigger severe ulceration. Foals with gastric ulcers may show signs of colic, interrupted nursing, tooth grinding (bruxism), and excessive salivation.

Signs and Symptoms

Gastric ulcers are notoriously difficult to diagnose from clinical signs alone, as signs are often vague, intermittent, and shared with many other conditions. Common presentations include:

  • Poor performance: Reluctance to work, resistance, loss of impulsion or enthusiasm — particularly when the horse is asked to flex or engage the hindquarters (abdominal pressure on the stomach)
  • Changes in temperament: Increased girthiness (reaction when girthing up), sensitivity along the flanks, irritability, or a general change in character
  • Weight loss and poor condition: Despite adequate feeding, horses with gastric ulcers may struggle to maintain condition. Dull coat is common.
  • Low-grade recurrent colic: Particularly mild, post-feeding colic or colic that resolves quickly but keeps recurring
  • Reduced appetite: Particularly around concentrate feeding or first thing in the morning when the stomach is empty and acid levels are highest
  • Yawning and stretching: Horses with gastric discomfort sometimes yawn or perform exaggerated stretching postures
  • Wood chewing or crib-biting: May develop or worsen in horses with ongoing gastric discomfort
  • Loose droppings: Can be associated with gastric ulcers, though this sign is non-specific

It is important to note that some horses with severe ulceration on gastroscopy show very few clinical signs, while others with mild ulceration appear very uncomfortable. Clinical signs alone cannot reliably predict the presence or severity of gastric ulcers.

Diagnosis

The definitive diagnosis of gastric ulcers requires gastroscopy — direct visual examination of the stomach using a long flexible endoscope. This is typically performed under standing sedation after a 12–18 hour fast (to empty the stomach). The procedure takes 10–15 minutes and allows the vet to directly visualise the squamous and glandular regions, assess lesion severity, and grade them using a standardised scoring system (Grade 0–4).

Diagnostic aids such as blood tests, urine sucrose permeability tests, and response to treatment have been studied but none are reliable enough to replace gastroscopy as the diagnostic standard.

Treatment

Omeprazole

Omeprazole is the primary and most effective treatment for gastric ulcers in horses. It is a proton pump inhibitor (PPI) that dramatically reduces gastric acid secretion, allowing the stomach lining to heal. Licensed equine omeprazole products (such as GastroGard or Ulcergard) are formulated specifically for horses — human formulations have different bioavailability and should only be used under veterinary guidance.

Standard treatment dosing is 4 mg/kg daily for 28 days, typically given in the morning before feeding. Repeat gastroscopy at the end of the treatment course is advisable to confirm healing — many horses show incomplete healing at 28 days and require extended treatment.

Sucralfate

Sucralfate forms a protective coating over ulcerated tissue and is often used as a complementary treatment, particularly for glandular ulcers (EGGD) which respond less well to omeprazole alone. It is most effective when given on an empty stomach and should be given separately from omeprazole to avoid interaction.

Misoprostol

A prostaglandin analogue, misoprostol is increasingly used for EGGD where omeprazole alone is insufficient. It helps restore mucosal blood flow and mucus secretion. It is an off-licence medication in horses and should only be used under veterinary direction.

Management Changes

Medication alone, without addressing management factors, leads to rapid relapse. Dietary and management changes are an essential component of both treatment and prevention:

  • Feed a small amount of hay (ideally 2–3 kg) before exercise to physically buffer the stomach
  • Ensure continuous access to forage — ad libitum hay or use of a slow feeder to extend eating time
  • Reduce or eliminate concentrate feeds where possible; increase fibre-based energy sources
  • Avoid prolonged fasting, particularly overnight
  • Reduce stress: maximise turnout, ensure social contact with other horses, minimise transport where possible
  • Review NSAID use and reduce dosage or frequency if clinically possible

Prevention

  • Forage-first: ensure horses have continuous or near-continuous access to forage throughout the day and night
  • Pre-exercise feeding: feed hay or chaff before exercise to buffer stomach acid
  • Reduce grain: minimise concentrate feeds and ensure energy requirements are met primarily through good-quality forage
  • Manage stress: maximise turnout, stable with a companion, minimise transport and isolation
  • Review NSAID protocols: use the lowest effective dose for the shortest necessary period; consider GI protective medication if long-term NSAIDs are required
  • Prophylactic omeprazole: for horses going through known high-risk periods (long-distance transport, change of yard, competition season), half-dose omeprazole can be used preventively under veterinary guidance
  • Consider regular gastroscopy: for horses in high-intensity training, a gastroscopy at the start and end of a competition season provides a useful health baseline

When to Call the Vet

You should discuss gastric ulcers with your vet if:

  • Your horse shows persistent, low-grade colic — particularly if post-feeding
  • A previously well-behaved horse develops increased girthiness or resistance to work
  • You notice unexplained weight loss, poor coat condition, or reduced appetite in a stabled horse
  • Your horse is on long-term NSAIDs and showing digestive disturbance
  • A young competition horse shows performance issues or changes in character

Frequently Asked Questions About Gastric Ulcers in Horses

How long does it take for gastric ulcers to heal?

With appropriate omeprazole treatment, most squamous (ESGD) ulcers show significant healing within 28 days. Glandular ulcers (EGGD) often take longer — 56 days or more — and may require additional medications. Without addressing the underlying management causes, ulcers frequently recur within weeks of stopping treatment. A repeat gastroscopy is strongly recommended to confirm healing before discontinuing medication.

Can gastric ulcers cause behavioural problems in horses?

Yes, absolutely. Gastric discomfort is a well-recognised cause of negative behavioural changes in horses, including increased girthiness, reluctance to go forward, bucking, rearing, and general irritability. These behaviours can easily be misinterpreted as training problems or bad temperament. If a horse develops a sudden or unexplained change in behaviour, gastric ulcers should be on the differential diagnosis list.

Can a horse have gastric ulcers if it lives out?

Yes, though the risk is generally lower for horses at pasture because continuous grazing closely mirrors the horse’s natural digestive rhythm. However, horses in hard work, horses that are frequently stabled during competition season, or horses given high-grain diets alongside turnout can still develop ulcers. Stress associated with competition, transport, and social factors also plays a role regardless of turnout time.

Are some horses more prone to gastric ulcers than others?

Performance horses — particularly racehorses, eventers, and showjumpers — have the highest prevalence, closely linked to diet, exercise intensity, and management. Horses in stressful environments (livery yards with frequent horse movements, competition yards) are also at higher risk. Foals, especially when ill or weaned, are particularly vulnerable. There may also be individual susceptibility differences between horses, though this is not yet well-characterised.