Equine Gastric Ulcer Syndrome (EGUS) is extremely common in horses, affecting up to 90% of racehorses, 60-70% of performance horses, and 50% or more of foals. EGUS encompasses two distinct conditions based on the affected region of the stomach: Equine Squamous Gastric Disease (ESGD), affecting the upper non-glandular portion, and Equine Glandular Gastric Disease (EGGD), affecting the lower glandular portion. Understanding the distinction is important because these two forms have different causes, risk factors, and treatment responses.

Overview

The equine stomach is divided into two regions by the margo plicatus (a distinct ridge). The upper squamous (non-glandular) region is lined with stratified squamous epithelium that lacks the protective mucus layer found in the lower glandular region. When acid splashes onto this unprotected area — particularly during exercise or periods of fasting — ulcers develop. The lower glandular region has its own protective mechanisms (mucus and bicarbonate secretion) but can develop ulcers when these defenses are compromised.

Horses produce gastric acid continuously (unlike humans, who produce acid primarily in response to food), making them uniquely susceptible to ulceration during periods when the stomach is empty.

Causes & Risk Factors

Squamous Ulcers (ESGD)

  • Intermittent feeding with prolonged fasting periods (the stomach is empty and acid contacts the squamous mucosa)
  • Intense exercise (increased intra-abdominal pressure splashes acid onto the upper stomach)
  • High-grain, low-forage diets (grain fermentation produces volatile fatty acids that damage squamous mucosa at low pH)
  • Stall confinement with limited turnout
  • Transport stress
  • NSAID use (contributes but is not the primary cause of squamous ulcers)

Glandular Ulcers (EGGD)

  • Mechanisms are less well understood than squamous ulcers
  • May involve impaired mucosal defense rather than excess acid exposure
  • Stress, NSAID use, and Helicobacter-like organisms have been implicated
  • Often does not respond as readily to acid suppression alone

Symptoms

Many horses with gastric ulcers show subtle or nonspecific signs, and some are asymptomatic. Common signs include:

  • Poor appetite or picky eating (especially reluctance to eat grain)
  • Weight loss or poor body condition despite adequate feeding
  • Dull coat
  • Mild recurrent colic, especially after eating
  • Behavioral changes (girthiness, resistance under saddle, reluctance to extend)
  • Poor performance or training regression
  • Bruxism (teeth grinding, more common in foals)
  • Excessive salivation
  • Loose stools or mild diarrhea

Gastric ulcers can cause subtle performance and behavioral changes that are easily attributed to other causes. If your horse is “not quite right,” gastric ulcers should be on the differential list.

Diagnosis

  • Gastroscopy — The gold standard for diagnosis. A 3-meter endoscope is passed through the nostril into the stomach, allowing direct visualization and grading of ulcers in both the squamous and glandular regions. Requires 12-16 hours of fasting and 4 hours of water withholding.
  • Ulcer grading — Squamous ulcers are graded 0-4 based on severity (0 = no lesions, 4 = extensive deep ulceration). Glandular lesions are graded by number, severity, and distribution.
  • Response to treatment trial — In some cases where gastroscopy is not available, a positive response to omeprazole treatment may support a presumptive diagnosis, though this approach cannot differentiate squamous from glandular disease.
  • Fecal occult blood testing — Not reliable for equine gastric ulcer diagnosis.

Treatment & Medications

Squamous Ulcers (ESGD)

  • Omeprazole (GastroGard) — The gold standard treatment. A proton pump inhibitor that suppresses gastric acid secretion. Treatment dose: 4 mg/kg orally once daily for 28 days. Must be given on an empty stomach (at least 1 hour before feeding) for optimal absorption. Generic formulations vary in bioavailability; GastroGard is the FDA-approved equine formulation with validated absorption.
  • Omeprazole (UlcerGard) — The same drug at a lower dose (1 mg/kg) used for prevention during high-risk periods (competition, travel).
  • Dietary management — Increased forage access (hay available continuously), reduced grain meals, and addition of alfalfa hay (which has a buffering effect due to its calcium and protein content).
  • Management changes — Increased turnout, reduced stall time, feeding hay before exercise, and frequent small meals.

Glandular Ulcers (EGGD)

  • Omeprazole — Used at the standard treatment dose, but glandular ulcers often require longer treatment courses (8-12 weeks) and may not respond to acid suppression alone.
  • Sucralfate — A mucosal protectant that binds to ulcerated tissue and forms a protective barrier. Often added to omeprazole for glandular disease. Typical dose: 12-20 mg/kg orally two to three times daily.
  • Misoprostol — A prostaglandin E1 analog that enhances mucosal defense in the glandular region. Used off-label for refractory glandular ulcers. Contraindicated in pregnant mares (can cause abortion).
  • Combination therapy — Omeprazole plus sucralfate is the most common approach for EGGD; duration is typically 8-12 weeks with gastroscopic reassessment.

Prevention

  • Provide continuous access to forage (free-choice hay)
  • Feed small, frequent meals rather than large grain meals
  • Include alfalfa hay as part of the diet
  • Feed hay or a small forage meal 30 minutes before exercise
  • Use UlcerGard (1 mg/kg omeprazole) during known high-risk periods
  • Minimize stall confinement and maximize turnout
  • Manage NSAID use carefully (lowest effective dose, shortest duration)

Prognosis

  • Squamous ulcers respond well to omeprazole, with healing rates of 70-80% after a standard 28-day course
  • Glandular ulcers are more challenging to treat and may require extended treatment and combination therapy
  • Recurrence is common (up to 80% within weeks) if management and dietary changes are not implemented alongside medical treatment
  • Long-term management focuses on dietary and environmental modification to reduce acid exposure and support mucosal health
  • Foal ulcers can be severe and may lead to perforation if untreated; prompt treatment carries a good prognosis

Frequently Asked Questions

Does my horse definitely have ulcers if they are girthy? Girthiness can be caused by gastric ulcers, but it can also result from musculoskeletal pain, poorly fitting tack, or learned behavior. Gastroscopy is the only way to definitively diagnose ulcers and assess their severity and location.

Can I use over-the-counter omeprazole instead of GastroGard? GastroGard is the only FDA-approved equine omeprazole formulation with validated bioavailability. Generic and compounded omeprazole products may have variable absorption and efficacy. Discuss options with your veterinarian.

How long after treatment can ulcers come back? Studies show that ulcers can recur within days to weeks of stopping omeprazole if the horse returns to the same management conditions. Ongoing dietary and management modifications are essential to prevent recurrence.

Should I scope my horse before treating for ulcers? Ideally, yes. Gastroscopy allows accurate diagnosis, differentiation between squamous and glandular disease (which require different treatment approaches), and provides a baseline for monitoring treatment response.

This information is for educational purposes only and does not replace professional veterinary advice. Consult your equine veterinarian for diagnosis and treatment of gastric ulcers in your horse.