Gastric ulcers affect up to 90% of performance horses and many leisure horses as well. Yet most owners miss the subtle signs until the condition becomes severe. Understanding gastric ulcers in horses can help you catch problems early, get proper treatment, and prevent recurrence. In this guide, we’ll cover the behavioral and physical signs that often go unnoticed, what causes ulcers to develop, and exactly how to respond when you suspect your horse is affected.
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What Are Gastric Ulcers in Horses?
Gastric ulcers are lesions or erosions that form in the lining of a horse’s stomach. The medical term is Equine Gastric Ulcer Syndrome (EGUS), and it affects the stomach lining when protective mechanisms fail against gastric acid. Horses produce stomach acid continuously—up to 16 gallons per day—but they evolved to graze almost constantly, which buffers that acid with saliva and food.
When horses go without food for even a few hours, acid builds up and begins eroding the stomach lining. The stomach has two distinct regions: the squamous region (upper, non-glandular) and the glandular region (lower, where acid is produced). Ulcers can form in either area, but they behave differently and may require different treatment approaches.
Squamous ulcers occur when acid splashes onto the upper stomach region, which lacks natural protection. This area is not designed to handle acid exposure. Glandular ulcers develop in the lower stomach where the mucosa should protect itself, but factors like reduced blood flow, stress, and certain medications can compromise this defense. Both types cause significant pain and can seriously impact your horse’s well-being and performance.
Gastric Ulcers in Horses: Signs You’re Missing
Recognizing gastric ulcers early requires paying attention to subtle changes that many owners dismiss as “just behavioral issues.” The signs of gastric ulcers in horses fall into three main categories: behavioral changes, physical symptoms, and performance issues under saddle. Here’s what to watch for.
Behavioral Signs: The Subtle Ones Owners Often Miss
Behavioral changes are often the first sign that something is wrong, yet they’re easy to dismiss or misattribute. A horse with gastric ulcers may become grumpy during grooming, pinning ears or wringing the tail when touched around the girth area. This girthiness is one of the most commonly overlooked indicators.
Some horses develop resistance to being tacked up, expressing discomfort before work even begins. You might notice your horse shifting away from the saddle, flinching, or showing a dull, depressed demeanor in the stall. Teeth grinding, especially during or after eating, signals discomfort that warrants investigation.
Changes in social behavior also matter. A normally social horse might isolate itself from herd mates, stand with its head in the corner, or show reduced interest in its surroundings. These subtle shifts often develop gradually, making them easy to rationalize as “just how he is lately.”
Physical Signs to Monitor
Physical symptoms tend to be more obvious but may not appear until ulcers have progressed. Poor appetite ranks among the most common signs—horses with ulcers often eat slowly, leave grain behind, or show more interest in hay than concentrates. Weight loss and a dull, rough coat can develop over time as the horse struggles to maintain condition.
Recurrent mild colic episodes are a red flag. Some horses experience repeated low-grade colic that resolves with minimal intervention, only to return days or weeks later. Diarrhea or changes in manure consistency may also accompany gastric ulcer syndrome.
Teeth grinding, excessive salivation, and lip curling (the Flehmen response) can occur during eating when acid causes discomfort. Some horses stretch out as if to urinate frequently, attempting to relieve abdominal pressure. These physical signs warrant veterinary evaluation when they persist or recur.
Performance Issues Under Saddle
Gastric ulcers frequently manifest as performance problems that trainers and riders struggle to explain. A horse that previously worked willingly may suddenly become resistant, refusing to move forward, spooking unexpectedly, or freezing during work. These behaviors stem from genuine discomfort, not attitude.
Under saddle, horses with ulcers might rush through transitions, hollow the back, or resist bending. They may become increasingly reactive to leg pressure or show reluctance to engage the hindquarters. Some horses develop a habit of stopping suddenly during work, appearing to “shut down” mid-ride.
Decreased stamina and a general lack of enthusiasm for work commonly accompany gastric ulcer syndrome. A horse that once loved its job might seem lackluster or even resentful of being ridden. These changes often progress gradually, leading some riders to assume the horse is simply “sour” rather than considering an underlying medical issue.
Quick Reference: Signs Checklist
Use this checklist to track potential ulcer signs in your horse:
Girthiness or sensitivity during tacking
Poor appetite or slow eating
Weight loss or poor body condition
Dull, rough coat
Teeth grinding during or after meals
Behavioral changes: grumpiness, depression, isolation
Recurrent mild colic
Performance decline: resistance, spooking, freezing
Reluctance to train or decreased enthusiasm
Excessive lying down or stretching out
Multiple signs present together strongly suggest gastric ulcer syndrome and justify veterinary investigation.
What Causes Gastric Ulcers in Horses?
Understanding why ulcers develop helps you prevent them from occurring or returning after treatment. Several factors contribute, often working together in performance horses.
Intermittent feeding is the primary culprit. Horses evolved to graze 16-18 hours daily, producing saliva that buffers stomach acid. When meals are spaced hours apart, acid accumulates in an empty stomach with nothing to neutralize it. Even overnight fasting significantly increases ulcer risk.
High-grain, low-forage diets contribute by reducing chewing time and saliva production. Grain moves through the stomach quickly, leaving it empty and vulnerable. Additionally, high-starch feeds can increase volatile fatty acids that may damage the stomach lining.
Stress and travel trigger cortisol release, which reduces blood flow to the stomach lining and impairs its protective mechanisms. Horses in training, those traveling frequently to shows, or horses in new environments face elevated ulcer risk. The stress of shipping alone can cause ulcers to develop within days.
Intense exercise increases abdominal pressure and causes the acidic contents of the lower stomach to splash onto the vulnerable squamous region. This mechanical effect explains why racehorses and upper-level performance horses have such high ulcer rates—studies show up to 90% are affected.
Certain medications, particularly non-steroidal anti-inflammatory drugs (NSAIDs) like phenylbutazone (Bute), can compromise the stomach’s protective mucosal barrier. Prolonged use increases ulcer risk, especially in the glandular region.
How Are Gastric Ulcers Diagnosed?
Gastroscopy remains the gold standard for diagnosing gastric ulcers. This procedure involves passing an endoscope through the nose and down the esophagus into the stomach, allowing the veterinarian to directly visualize the stomach lining. The horse must be fasted for 12-16 hours beforehand to ensure the stomach is empty enough for proper viewing.
During gastroscopy, the veterinarian evaluates both the squamous and glandular regions, grading ulcer severity on a scale of 0-4. Grade 0 means no lesions, while grade 4 indicates extensive, deep ulceration. This grading guides treatment decisions and helps predict recovery time.
The procedure typically takes 20-30 minutes and is performed under light sedation. Most horses tolerate it well, and complications are rare. While gastroscopy requires investment, it provides definitive diagnosis and ensures you treat the right condition rather than guessing based on symptoms alone.
Cost varies widely depending on location and veterinary practice, but typically ranges from $200-500 for the procedure itself. Some practices offer mobile gastroscopy services at farms, while others require hauling to a clinic. The investment pays off by confirming the diagnosis and guiding appropriate treatment.
Some owners attempt empirical treatment without diagnosis, but this approach has limitations. Not all horses with ulcer symptoms actually have ulcers, and treatment for squamous ulcers differs from treatment for glandular ulcers. Misdiagnosis delays proper care and wastes money on unnecessary medication.
How to Respond: Treatment Options for Gastric Ulcers
Once diagnosed, treatment depends on ulcer type, severity, and your horse’s circumstances. Here’s how to respond effectively.
Omeprazole: The First-Line Treatment
Omeprazole is the primary medication for treating squamous gastric ulcers. It works by suppressing acid production, allowing the stomach lining to heal. GastroGard is the FDA-approved formulation specifically designed for horses, delivering consistent medication levels in a palatable paste.
Treatment typically lasts 28 days, with once-daily administration. Many horses show clinical improvement within the first week, though completing the full course is essential for proper healing. Ulcers often recur if treatment stops too early.
Sucralfate for Glandular Ulcers
Glandular ulcers often require a different approach. Sucralfate acts as a protective coating, binding to ulcerated tissue and forming a barrier against acid. It’s commonly prescribed alongside omeprazole for horses with glandular ulcer disease.
Because glandular ulcers are harder to treat than squamous ulcers, management changes become even more critical. Dietary adjustments, stress reduction, and continuous forage access support healing and prevent recurrence.
Why Ulcers Keep Coming Back
Ulcer recurrence frustrates many owners. The most common reason is incomplete management change after treatment. If the underlying causes—intermittent feeding, high-grain diet, stress—remain unchanged, ulcers return once medication stops.
Some horses benefit from ongoing preventive doses of omeprazole, particularly those in demanding training programs. However, medication alone cannot replace proper feeding management and stress reduction. Addressing root causes is essential for long-term success.
Dietary and Management Support
Treatment works best when combined with dietary changes. Provide continuous access to forage—grass, hay, or soaked hay products—to keep the stomach buffered. Slow-feeder nets or multiple small hay meals reduce gaps when pasture isn’t available.
Reduce grain concentrates where possible, substituting high-fiber feeds that promote chewing and saliva production. Adding alfalfa to the diet can help, as alfalfa’s calcium and protein content buffers acid effectively. Fresh water must always be available, as dehydration concentrates stomach acid.
Some owners explore natural support options. Aloe vera juice may soothe the digestive tract, though scientific evidence in horses remains limited. Always consult your veterinarian before adding supplements, especially during active medical treatment.
Recovery Timeline: What to Expect After Treatment
Recovery depends on ulcer type and severity. Squamous ulcers typically heal within 2-4 weeks of proper treatment, with most horses showing clinical improvement within the first week. Gastroscopy at 14-28 days confirms healing progress.
Glandular ulcers often take longer—sometimes 6-8 weeks or more—and may be more resistant to treatment. These ulcers require persistent management changes alongside medication. Some horses need multiple treatment courses.
Behavioral improvements often precede complete ulcer healing. You may notice your horse eating more enthusiastically, showing brighter demeanor, and working more willingly before gastroscopy confirms full resolution. This doesn’t mean treatment can stop early, but it provides encouraging feedback.
Performance horses returning to work should reintroduce exercise gradually. Jumping straight back into intense training risks recurrence. Allow time for the stomach lining to fully heal and make management adjustments permanent.
Warning Signs That Require Immediate Veterinary Attention
While most gastric ulcers cause chronic, low-grade discomfort, some situations demand urgent care. Contact your veterinarian immediately if your horse shows any of these signs.
Severe colic that doesn’t resolve within 30 minutes or causes violent pain behaviors may indicate a perforated ulcer. This is a life-threatening emergency requiring immediate intervention.
Refusal to eat entirely for more than 12 hours signals significant pain or complications. Horses cannot tolerate prolonged fasting without serious health consequences.
Blood in manure or digested blood appearance (dark, tarry stool) suggests gastrointestinal bleeding. While not always from gastric ulcers, it warrants prompt investigation.
Sudden, dramatic behavior changes—extreme lethargy, unresponsiveness, or inability to rise—indicate serious illness. These signs extend beyond typical ulcer symptoms and require urgent assessment.
When in doubt, call your veterinarian. Delayed treatment for serious complications can be fatal.
How to Prevent Gastric Ulcers in Horses?
Prevention focuses on supporting the stomach’s natural defenses and minimizing acid exposure. Here’s how to reduce your horse’s ulcer risk.
Maximize forage access. Horses should never go more than 4-6 hours without something to eat. Use slow-feeder nets, hay balls, or frequent small hay meals to extend chewing time. If your horse finishes hay quickly, consider adding a second feeding or using slower-consuming hay types.
Feed before work. Providing a small amount of hay or chaff before riding buffers stomach acid during exercise. Even a handful of soaked alfalfa pellets gives the stomach something to work with, reducing acid splashing onto the squamous region.
Reduce grain, increase fiber. High-starch concentrates contribute to acid production and reduce chewing time. Where possible, substitute high-fiber feeds like beet pulp, soaked hay pellets, or chopped forage products. Multiple small meals are better than two large grain feedings.
Minimize stress. Consistent routines, familiar handlers, and gradual introduction to new environments help reduce cortisol spikes. For horses that must travel, maintain their feeding schedule as closely as possible and provide hay during transport.
Regular dental care ensures your horse can chew effectively, producing adequate saliva to buffer acid. Dental problems reduce chewing efficiency and increase ulcer risk indirectly.
Consider preventive medication for high-risk horses. Performance horses in intense training may benefit from a preventive omeprazole protocol during competition seasons. Discuss this option with your veterinarian.
Monitor continuously. Watch for early signs of ulcer development, especially during periods of stress, increased training, or management changes. Early intervention prevents severe disease and shortens recovery time.
Frequently Asked Questions About Gastric Ulcers in Horses
How long does it take for gastric ulcers to heal in horses?
Squamous gastric ulcers typically heal within 2-4 weeks of proper omeprazole treatment. Glandular ulcers often take longer—6-8 weeks or more—and may require additional medications like sucralfate alongside management changes. Completing the full treatment course is essential for lasting healing.
What are the red flags of gastric ulcers?
Red flags include poor appetite, weight loss, recurrent mild colic, girthiness during tacking, teeth grinding, and performance decline under saddle. Behavioral changes like depression, irritability, and reluctance to work often appear before physical signs. Multiple symptoms together warrant veterinary investigation.
What helps with gastric ulcers in horses?
Omeprazole (GastroGard) is the primary treatment for squamous ulcers, suppressing acid production so the stomach lining can heal. Dietary management with continuous forage access, reduced grain, and slow feeding supports recovery. Glandular ulcers may also require sucralfate as a protective coating agent.
What is the behavior of a horse with gastric ulcers?
Horses with gastric ulcers often become grumpy, depressed, or isolated. They may pin ears during grooming, resist tacking, grind teeth while eating, and show reduced enthusiasm for work. Under saddle, they might resist moving forward, spook unexpectedly, freeze during rides, or hollow their backs. These behaviors stem from genuine discomfort, not attitude problems.
Can gastric ulcers in horses heal on their own?
Mild ulcers might improve with management changes alone, but most require medical treatment for proper healing. Untreated ulcers tend to worsen over time and can lead to complications. Veterinary diagnosis and appropriate medication provide the best outcome and prevent unnecessary suffering.
Taking Action on Gastric Ulcers
Gastric ulcers in horses are common but treatable when recognized early. The signs you’re missing—subtle behavioral shifts, girthiness, performance changes—often appear before obvious physical symptoms. Understanding what causes ulcers helps you prevent them, and knowing how to respond with proper veterinary care and management changes sets your horse up for lasting recovery.
If you suspect your horse has ulcers, contact your veterinarian for gastroscopy and appropriate treatment. Combine medication with continuous forage access, stress reduction, and dietary adjustments. Watch for warning signs that require urgent care, and implement preventive strategies to keep your horse comfortable and performing at its best. Your horse’s well-being depends on your ability to recognize the signs and act decisively.