Horse Ulcers: Signs, Causes, Treatment and Prevention

Last updated: January 29, 2026

By: Miles HenryFact Checked

Horse ulcers are the silent performance killer, and I learned that the hard way when my two-year-old Thoroughbred refused breakfast. That morning I found him standing at the back of his stall, completely ignoring his feed, I knew we had a problem. This colt had always been first to the feed tub, seeing him turn away from food sent me straight to my vet. Three days later, the gastroscope revealed exactly what I suspected: angry red ulcers covering his stomach lining.

After 30-plus years owning and racing horses at tracks like Fair Grounds and Delta Downs, I’ve learned that gastric ulcers are the “silent performance killer.” They don’t always look like a sick horse—sometimes they just look like a horse having an off day or acting “girthy.” Research shows that over 80% of Thoroughbreds in training develop gastric ulcers, especially during intense race conditioning.

In this guide, I share what I’ve learned from the barn floor about recognizing, treating, and preventing equine gastric ulcer syndrome. These insights come from decades managing performance horses and dealing with ulcers more times than I can count.

What Are Horse Ulcers? (Equine Gastric Ulcer Syndrome)

Equine gastric ulcer syndrome (EGUS) happens when painful sores form in a horse’s stomach. Horses don’t just make acid when they eat, they produce it constantly, up to 16 gallons a day. In the wild, that wasn’t an issue because they grazed nearly all day, and the constant forage plus saliva helped buffer the acid.

Modern barn life is a different story. Stall confinement, twice-daily meals, and high-grain feeds create long gaps where the stomach sits empty. Without forage to soak up the acid, it starts wearing away the stomach lining, and that’s how ulcers form.

It matters to know the type of ulcer because treatment differs. Squamous ulcers usually respond quickly to acid suppression, while glandular ulcers often require longer therapy and deeper management changes.

The Two Main Types

Squamous ulcers (Equine Squamous Gastric Disease) form in the upper stomach where there’s no protective mucus. This area is especially vulnerable when acid splashes up during exercise or builds up during long feeding gaps. These are the most common type and usually respond well to omeprazole.

Glandular ulcers (Equine Glandular Gastric Disease) develop in the lower stomach, where acid is produced and the lining is usually protected. These tend to be more stubborn and are often linked to stress, NSAID use, or a breakdown in the stomach’s defenses. They affect roughly 25–65% of racehorses and typically need longer treatment.

Important Note: Don’t forget hindgut ulcers (Right Dorsal Colitis). These occur further down and won’t show on stomach scopes. If gastroscopy is clear but symptoms persist, ask your vet about fecal occult blood tests or a response-to-fiber trial, because hindgut ulcers are often the hidden cause.

Recognizing the Signs of Ulcers: Is Your Horse Hurting?

Horses are masters at hiding pain. At the track, I’ve seen talented runners lose races simply because brewing ulcers made them hesitant to fully extend. Symptoms vary dramatically between horses—some show obvious discomfort while others suffer silently. After having hundreds of horses scoped, I’ve learned that the severity of symptoms doesn’t always match the severity of the ulcers.

Changes in eating behavior are often the first clue. Horses with ulcers rarely stop eating completely—instead, they pick at grain but leave some behind, especially sweet feeds. They might eat hay eagerly but avoid concentrates, or start meals normally and quit halfway through. That colt I mentioned would dive into his feed tub, take a few bites, then walk away—eating apparently caused him pain.

Attitude and behavior shifts include becoming “girthy” (pinning ears or nipping when you tighten the cinch), showing reluctance during grooming, resisting saddling, or refusing to move forward under saddle. I worked with a mare who’d always been sweet-tempered but started threatening to bite whenever I reached for the girth. Two weeks after starting ulcer treatment, her normal personality returned.

Physical condition changes signal problems: gradual weight loss despite adequate feed, loss of topline muscle, prominent ribs despite normal feeding, and a dull coat that won’t shine. When eating hurts, horses naturally eat less, and ulcers can affect nutrient absorption even when intake seems normal.

Performance decline without other obvious causes often points to ulcers in athletic horses. Watch for reluctance to extend or collect, shorter stride, stiffness through the back, resistance to lateral work, or slower times despite good fitness. It’s hard to perform your best when your stomach feels like it’s burning.

Recurring mild colic—looking at flanks repeatedly, pawing, lying down and getting up more than usual, or stretching as if to urinate—often stems from ulcers. These aren’t severe, rolling colics, but repeated mild discomfort. If you see three or more mild colic episodes over several months, ulcers are a common underlying cause. Learn more about colic signs here.

Foals show different symptoms: colic shortly after nursing, teeth grinding (bruxism), excessive drooling, diarrhea, lying on their backs (temporary relief), poor appetite, and a pot-bellied appearance. Foal ulcers can progress quickly—call your vet immediately if you see these signs.

What Causes Horse Ulcers? (Common Triggers & Risk Factors)

Understanding why horses develop ulcers is essential for prevention. In my experience, it usually comes down to a few main factors that often work together:

Limited forage access is the biggest contributor to horse ulcers. When a horse goes hours without eating, acid builds up with nothing to buffer it — even four-hour gaps can do damage. I learned this the hard way running horses on a twice-daily feeding schedule. After switching to free-choice hay or slow-feed nets, our ulcer cases dropped dramatically.

High-grain diets and dietary starch create problems in multiple ways. Grain triggers more acid production, and it produces less saliva than forage. The starch ferments in the stomach, creating volatile fatty acids that irritate the lining. Veterinary studies show horses on high-concentrate, low-forage rations have a significantly higher ulcer risk than those on forage-based diets.

Stress and high cortisol levels have been linked to reduced protective mucus and increased ulcer risk in horses. Exercise also causes acidic stomach contents to splash onto the vulnerable upper region. Transport, competition, routine changes, social isolation, weaning, and stall confinement all trigger stress responses that promote ulcer development. Research confirms even small routine changes can trigger ulcers within days in susceptible horses.

Medication overuse, especially NSAIDs like phenylbutazone (Bute) and flunixin meglumine (Banamine), can weaken the stomach’s protective mucus layer. When pain management requires NSAIDs, I work with my vet to use the lowest effective dose for the shortest time — and we often add gastric protectants during treatment.

Diagnosing → How to Diagnose Horse Ulcers

The gold standard for diagnosing equine ulcers is scoping, also called a gastroscopy. During the procedure, your veterinarian passes a three-meter endoscope through the horse’s nostril, down the esophagus, and into the stomach so they can see the lining directly. Your horse fasts 12–16 hours beforehand (no food), and water is usually removed 2–4 hours before to clear the stomach for a better view.

Under mild sedation, the whole exam takes about 15–30 minutes. Your vet will note the location, number, and severity of any lesions using a standardized 0–4 grading scale (0 = no ulcers, 4 = extensive deep ulcers). This gives you a baseline to track healing during treatment. The procedure typically costs $300–600, depending on whether it’s done on-farm or at a clinic. Most horses tolerate it very well—I’ve never had one have serious complications.

If scoping isn’t immediately feasible due to cost or availability, vets may recommend an empirical treatment trial—treating based on clinical signs and monitoring the response. If the horse improves on ulcer medication, it’s a strong indication ulcers were the issue.

Horse Ulcer Treatment: What Actually Works

Good news: gastric ulcers in horses are highly treatable. With the right medication and management changes, horses typically show improvement quickly and many achieve complete healing. In my barn, we use a combined approach that treats the ulcers and addresses the root causes.

Omeprazole: The Gold Standard

Omeprazole is the gold standard treatment for equine gastric ulcers, supported by clinical evidence demonstrating improved healing rates. It’s the only FDA-approved treatment for equine gastric ulcers, and the prescription version is called GastroGard. Most vets dose GastroGard once daily based on your horse’s weight (a 1,000-lb horse usually gets around 1,800 mg per day). Your vet will confirm the correct dose for your horse.

The biggest drawback is cost, a month of GastroGard treatment runs $1,000–$1,500 for a full-size horse. Generic compounded omeprazole is significantly cheaper, but it isn’t FDA-approved and quality can vary. I’ve used both with good results, preferring brand-name for severe cases.

Give omeprazole on an empty stomach for best absorption—I dose first thing in the morning at least 30 minutes before feeding. The paste formulation is easiest, and following it with a small amount of molasses or applesauce helps mask any aftertaste for picky horses.

UlcerGard (same active ingredient, lower dose) is available over-the-counter for prevention during stressful periods like showing, hauling, or intensive training.

Supportive Treatments

Sucralfate acts like a liquid bandage, coating ulcers and providing immediate relief while stimulating mucus production. It’s useful alongside omeprazole for severe ulcers, but it requires dosing 2–4 times daily, which can be hard to manage consistently.

Alfalfa hay is one of my secret weapons. Alfalfa’s high calcium content acts as a natural buffer, and the evidence supports its role in preventing gastric ulcers. I give my horses a flake of alfalfa 30 minutes before tacking up—it creates a protective forage mat that helps prevent acid splash during work.

Natural supplements like slippery elm and aloe vera can help soothe the stomach lining, but they aren’t substitutes for proven medication in severe cases. In my experience, they work best for prevention or mild flare-ups.

Management Changes: The Foundation That Makes Treatment Stick

Medication without management changes often leads to ulcer relapse once treatment stops. Veterinary research shows many horses redevelop ulcers within weeks if feeding and turnout habits stay the same. In my barn, prevention is 90% management, free-choice forage, stress reduction, and consistent routines.

Here’s the exact routine I use in my barn to prevent ulcers before they ever start:

Successful ulcer recovery depends on combining medication with management changes to prevent relapse.

How to Prevent Horse Ulcers: Proven Strategies

Preventing your horse from developing ulcers is always cheaper and more effective than treatment. Beyond the management practices in the table above, here are additional strategies that make a real difference:

Use preventive medication strategically for high-risk horses—those in intense training, traveling frequently, or with ulcer histories. UlcerGard during stressful periods can help reduce ulcer development in some horses. I use it during racing season because the cost is far less than lost training time or treating active ulcers. Always check with your veterinarian before starting preventive medication.

Minimize NSAID use when possible. When pain management is necessary, work with your vet to use the lowest effective dose for the shortest time, and consider adding gastric protectants during treatment.

Monitor for early warning signs and catch problems before they become severe. Stay vigilant for subtle changes in eating behavior, attitude, or performance. Quick intervention makes a massive difference in treatment success.

Common Questions About Horse Ulcers

Miles’ Daily Ulcer Prevention Protocol

• 01. Alfalfa Buffer: Feed 1-2 lbs of alfalfa 30 mins before exercise. The high calcium and protein act as a natural antacid against “acid splash” during work.
• 02. Continuous Forage: Use slow-feed nets to encourage near-constant chewing. Chewing is the only way a horse produces bicarbonate-rich saliva to buffer stomach acid.
• 03. Hydration & Salt: Monitor salt intake to support hydration and normal saliva production. Dehydrated horses produce less saliva, leaving the stomach lining vulnerable.
• 04. Low-Starch Priority: Replace grain-based calories with beet pulp or oil to reduce the risk of volatile fatty acid (VFA) buildup in the stomach.
• 05. Stress Management: Prioritize daily turnout and social interaction. High cortisol levels from confinement can directly inhibit the protective mucus lining of the stomach.

Final Thoughts on Horse Ulcers

After three decades managing horses, I’ve learned that you know your horse better than anyone. If they aren’t performing up to their potential or their personality has shifted, don’t just call them “moody.” Dig deeper. Catching ulcers early isn’t just about saving money on vet bills—it’s about ensuring your horse is comfortable enough to enjoy their job.

That first colt who refused breakfast years ago led me to completely rethink my feeding program. The mare who became girthy showed me how ulcers masquerade as behavior problems. Countless horses over the years have reinforced that prevention through proper management beats treatment every time.

Focus on maximizing forage access, minimizing stress, and staying alert to subtle changes in your horse’s behavior and appetite to prevent ulcers. These principles will keep your horse comfortable, healthy, and performing at their best.

Is your horse struggling with “girthiness,” weight loss, or performance issues? Drop a comment below—I’d love to hear your story and offer insights from the barn.

If you’re a visual learner, check out this video for an in-depth look at horse ulcers.

About the Author: Miles Henry (William Bradley) is a lifelong horseman and Louisiana-licensed racehorse owner (License #67012). He has spent decades hands-on with Thoroughbreds and Quarter Horses at tracks including Fair Grounds and Delta Downs, focusing on the intersection of traditional barn wisdom and modern equine science.