Last updated: April 27, 2026
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My two-year-old Thoroughbred refused breakfast one morning — standing at the back of his stall, ignoring feed he normally dove into. At first it looked like a bad day, but within 72 hours a gastroscope confirmed what I suspected: gastric ulcers covering the stomach lining.
That’s the problem with ulcers — they rarely look like ulcers. One horse gets dull and picky with grain, another gets girthy or sour under saddle, and another just loses form in training. By the time obvious symptoms appear, the stomach lining has usually been irritated for days or weeks.
Horse ulcers — what you need to know:
- How common: Some studies report more than 80% of Thoroughbreds in training develop gastric ulcers — it’s a management disease as much as a medical one
- Key signs: Picky eating, girthiness at saddling, unexplained weight loss, performance decline, or recurring mild colic episodes
- Only definitive diagnosis: Gastroscopy (scope) — treating based on symptoms alone often misses the ulcer type and location
- Gold standard treatment: Omeprazole (GastroGard) — the only FDA-approved equine ulcer treatment; most horses show improvement within 3–5 days
- Treatment without management changes fails: Horses frequently relapse if feeding and turnout habits don’t change alongside medication
- Best prevention: Free-choice forage, smaller frequent meals, alfalfa before exercise, and minimizing stall time
- High suspicion — act now: Two or more signs together — especially picky eating, girthiness, or performance drop — OR any signs following a stressful event (travel, training change, stall rest). Schedule a gastroscope or vet consult.
- Moderate suspicion — monitor closely: One persistent behavioral or appetite change lasting more than 7–10 days with no clear saddle, dental, or lameness explanation. Discuss empirical treatment vs. scoping with your vet.
- Low suspicion — rule out other causes first: Isolated mild sign with no recent stressors. Check saddle fit, teeth, and workload before assuming ulcers.
Bottom line: Ulcers are only confirmed by gastroscopy — this guide is about deciding when that step is justified.
This guide is based on 30 years of owning and racing Thoroughbreds at Fair Grounds, Delta Downs, and Evangeline Downs in Louisiana, where gastric ulcers are a constant management challenge in performance horses. Management strategies here reflect practices used in our barn and align with current equine veterinary standards.
I am not a licensed veterinarian. Equine Gastric Ulcer Syndrome (EGUS) is a medical condition requiring professional diagnosis and treatment. Because definitive diagnosis requires gastroscopy and treatment protocols vary by horse and ulcer type, always consult a licensed equine veterinarian before starting, stopping, or changing any treatment. Miles Henry, Louisiana Owner License #67012.
Table of Contents
What Are Horse Ulcers?
Equine gastric ulcer syndrome (EGUS) occurs when painful sores form in a horse’s stomach lining. Horses produce stomach acid continuously — up to 16 gallons a day — because in the wild they grazed nearly around the clock, and constant forage plus saliva helped buffer that acid. Modern barn life breaks that system. 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 begins wearing away the stomach lining.
The Two Types of Gastric Ulcers
Squamous ulcers (Equine Squamous Gastric Disease) form in the upper stomach where there is 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 treatment.
Glandular ulcers (Equine Glandular Gastric Disease) develop in the lower stomach where acid is produced and the lining is usually protected by mucus. These tend to be more stubborn, are often linked to stress or NSAID use, and affect roughly 25–65% of racehorses. They typically require longer treatment than squamous ulcers and may need additional medication beyond omeprazole alone.
Recognizing the Signs of Ulcers
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, others suffer silently. After having hundreds of horses scoped over the years, I’ve learned that the severity of symptoms doesn’t always match the severity of the ulcers. A horse with grade 4 ulcers may appear slightly off while a horse with grade 2 ulcers seems miserable.
- Picky eating: Leaving grain behind or eating hay eagerly but avoiding concentrates — the colt I mentioned would dive into his feed tub, take a few bites, then walk away
- Girthiness: Pinning ears, biting, or attitude changes while saddling — learn more about girthiness causes and solutions. A mare I worked with threatened to bite every time I reached for the girth; she was back to normal within two weeks of treatment
- Condition loss: Unexplained weight loss, loss of topline muscle, or a dull coat that won’t shine despite adequate feed
- Performance decline: Reluctance to extend or collect, shorter stride, stiffness through the back, or slower times despite good fitness
- Recurring mild colic: Repeated low-grade episodes — looking at flanks, pawing, stretching — especially after grain; three or more mild episodes over several months is a red flag
- Foals show different signs: Colic shortly after nursing, teeth grinding, excessive drooling, diarrhea, lying on their backs, or pot-bellied appearance — foal ulcers can progress quickly, call your vet immediately
If symptoms last more than a few days or your horse has recurring mild colic, don’t guess — call your veterinarian. A gastroscopy is the only way to know for certain, and early detection means quicker relief and less downtime.
What Causes Horse Ulcers?
Understanding why horses develop ulcers is essential for prevention. In my experience it usually comes down to several factors working together — fix one and help the horse; fix them all and prevent recurrence.
- Limited forage access is the biggest single contributor. When a horse goes hours without eating, acid builds up with nothing to buffer it — even four-hour gaps can do damage. After switching from twice-daily feeding to free-choice hay and slow-feed nets, our ulcer cases dropped dramatically.
- High-grain diets create problems in multiple ways. Grain triggers more acid production and generates less saliva than forage. The starch ferments in the stomach, producing volatile fatty acids that irritate the lining. Horses on high-concentrate, low-forage rations have significantly higher ulcer risk.
- Stress and exercise have been linked to reduced protective mucus and increased ulcer risk. Exercise also causes acidic stomach contents to splash onto the vulnerable upper region. Research confirms that even small routine changes can trigger ulcers within days in susceptible horses.
- Transport and competition are consistent triggers. The combination of confinement, feed disruption, social stress, and unfamiliar environments creates the conditions for rapid ulcer development — often within 24–48 hours of a stressful event.
- NSAID overuse — especially phenylbutazone (Bute) and flunixin meglumine (Banamine) — weakens the stomach’s protective mucus layer. When pain management requires NSAIDs, use the lowest effective dose for the shortest time and consider adding gastric protectants during treatment.
How to Diagnose Horse Ulcers
The gold standard for diagnosis is gastroscopy — a scope. During the procedure, your veterinarian passes a three-meter endoscope through the horse’s nostril, down the esophagus, and into the stomach to view 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. Under mild sedation the exam takes about 15–30 minutes. Your vet notes the location, number, and severity of any lesions using a standardized 0–4 grading scale, which 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.
If scoping isn’t immediately feasible, veterinarians 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. The limitation is that this approach doesn’t identify ulcer type or location, which matters for treatment duration and protocol.
Horse Ulcer Treatment: What Actually Works
Gastric ulcers in horses are highly treatable. With the right medication and management changes, horses typically show improvement within days and many achieve complete healing. In my barn, the approach combines medication with addressing root causes — medication alone reliably leads to relapse once treatment stops.
Omeprazole: The Only FDA-Approved Treatment
Omeprazole is the gold standard treatment for equine gastric ulcers and the only FDA-approved medication for the condition. The prescription version is GastroGard. Veterinarians typically dose it once daily based on the horse’s weight — your vet will confirm the correct amount. Treatment courses typically run 28 days for squamous ulcers and 60–90 days for glandular ulcers based on veterinary protocol; your vet will confirm the correct duration after scoping.
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 to administer, and following it with a small amount of molasses or applesauce helps for picky horses. The biggest drawback is cost — a month of GastroGard runs $1,000–$1,500 for a full-size horse. Generic compounded omeprazole is significantly cheaper but isn’t FDA-approved and quality varies.
UlcerGard (same active ingredient, lower dose) is available over-the-counter for prevention during stressful periods — shows, hauling, or intensive training. I use it during racing season because the cost is far less than treating active ulcers or losing training time. For owners managing horses through regular competition or transport schedules, keeping a few syringes on hand is standard practice in our barn.
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Supportive Treatments
Sucralfate coats ulcers and provides immediate relief while stimulating mucus production. It’s useful alongside omeprazole for severe ulcers but requires dosing 2–4 times daily, which can be hard to manage consistently in a busy barn.
Alfalfa hay is one of my most reliable management tools. Alfalfa’s high calcium content acts as a natural buffer and the research supports its role in both preventing and managing gastric ulcers. I give horses a flake of alfalfa 30 minutes before tacking up — it creates a protective forage mat that helps prevent acid splash during work. See our guide on the difference between timothy, grass, and alfalfa hay for a full comparison.
Natural supplements like slippery elm and aloe vera can help soothe the stomach lining but aren’t substitutes for proven medication in moderate to severe cases. In my experience, they work best for prevention or mild flare-ups in horses already well-managed.
Why Management Changes Must Come With Treatment
Veterinary research shows many horses redevelop ulcers within weeks of stopping medication if feeding and turnout habits remain the same. Successful recovery depends on combining medication with management changes that remove the conditions that caused the ulcers in the first place. Medication treats the symptom; management prevents the cause from reasserting itself.
How to Prevent Horse Ulcers
Prevention is always cheaper and more effective than treatment. The management changes below are what we use in our barn — after implementing them, our ulcer cases dropped significantly and relapses following treatment became rare.
| Area | What We Do and Why |
|---|---|
| Forage Access | Free-choice hay via slow-feed nets to prevent the stomach from going empty. A horse’s stomach produces acid 24/7 — if they aren’t chewing, they aren’t buffering. This single change dropped our ulcer cases dramatically. |
| Exercise Timing | Never work a horse on an empty stomach. Feed a small amount — ideally alfalfa — 30 minutes before tacking up. This creates a protective forage mat that reduces acid splash during exercise. Slow-feed nets make this easy overnight. |
| Grain Strategy | Smaller, more frequent meals. Always feed hay before grain. Use low-starch concentrates and replace grain-based calories with beet pulp or oil when possible. Hay chewing is a horse’s natural saliva-based antacid — more forage, less starch. |
| Turnout | Maximize pasture time. Social interaction and grazing reduce cortisol and keep the stomach buffered continuously. Movement is as good for gut health as it is for mental wellbeing. |
| Stress Management | Maintain consistent daily routines. Make all management changes gradually. Small routine disruptions can trigger ulcers within days in susceptible horses — predictability is foundational. |
| Preventive Medication | UlcerGard during high-stress periods — racing season, hauling, shows, or major routine changes. Always discuss with your vet first. The cost of prevention is far less than treating active ulcers and lost training time. |
- Alfalfa buffer: 1–2 lbs of alfalfa 30 minutes before exercise. The calcium and protein act as a natural antacid against acid splash during work.
- Continuous forage: Slow-feed nets for near-constant chewing. Chewing is the only way a horse produces bicarbonate-rich saliva to buffer stomach acid.
- Low-starch priority: Replace grain-based calories with beet pulp or oil to reduce volatile fatty acid buildup in the stomach.
- Hydration and salt: Monitor salt intake to support hydration and normal saliva production. Dehydrated horses produce less saliva, leaving the stomach lining vulnerable.
- Turnout and routine: Daily turnout and predictable schedules. High cortisol from confinement directly inhibits the stomach’s protective mucus lining.
When to Call Your Vet Immediately
Most ulcer management is a scheduled, non-emergency process. But certain signs indicate a horse needs same-day veterinary attention. Delaying in these situations can allow a manageable condition to escalate rapidly.
- Severe or escalating colic: Rolling, repeated pawing, or inability to settle within 20–30 minutes
- Complete feed refusal: No interest in hay or grain for 12–24 hours
- Signs of dehydration or systemic illness: Tacky gums, sunken eyes, marked lethargy, or reduced gut sounds
- Sudden dangerous behavior under saddle: Uncharacteristic bucking, rearing, or refusal combined with other ulcer signs
- Blood in manure: Dark, tarry, or coffee-ground consistency stool
- Foals with any ulcer-like signs: Teeth grinding, nursing-related colic, diarrhea, or poor weight gain
Why this matters: These signs go beyond uncomplicated ulcers and may indicate complications or a different gastrointestinal condition that needs urgent diagnosis.
FAQs About Horse Ulcers
Can gastric ulcers go away on their own?
Small superficial ulcers may improve if the horse is turned out on continuous grass with minimal stress, but performance-level ulcers rarely resolve without management changes and medication. Management-only approaches sometimes improve symptoms while the ulcers themselves persist — scoping before and after is the only way to know for certain whether healing has occurred.
How long does it take for a horse to feel better after starting treatment?
Horses typically show behavioral and appetite improvement within 3–5 days of starting omeprazole as stomach acid decreases. Complete ulcer healing takes longer — roughly 28 days for squamous ulcers and 60–90 days for glandular ulcers depending on severity. Many horses show significant performance improvement before full healing is confirmed by a follow-up scope.
Can horses continue training during ulcer treatment?
Yes. Reducing exercise intensity during the first week or two is reasonable as the horse starts treatment, then gradually return to normal work levels as they improve. Many horses actually perform better once treatment begins because they are no longer working through constant gastric discomfort. Always feed a small amount of hay or alfalfa before exercise during treatment to buffer the stomach during work.
Is alfalfa really effective for horse ulcers?
Yes — research supports what experienced horsemen have used for decades. Alfalfa’s high calcium and protein content acts as a natural acid buffer, and studies show horses fed alfalfa have lower ulcer rates than those on grass hay alone. Feeding 1–2 lbs of alfalfa 30 minutes before exercise is one of the most practical and cost-effective management tools for horses prone to gastric ulcers.
Can horse ulcers heal without omeprazole?
Sometimes — mild ulcers may improve with significant management changes like continuous forage access, reduced starch, and stress reduction. But moderate to severe ulcers typically need omeprazole or other veterinary medication to heal fully. Management changes alone reduce the conditions that cause ulcers, but they do not suppress the acid production that prevents existing ulcers from healing. Both together produce the best outcomes.
What is the best diet to prevent horse ulcers?
A forage-first feeding plan is the most effective dietary prevention. Keep hay available 24/7, feed smaller and more frequent meals, use alfalfa as a buffer before exercise, and reduce high-starch concentrates. Replace grain-based calories with fat sources like oil or beet pulp when needed. Penn State Extension’s research on using nutrition to prevent stomach ulcers in horses confirms these principles.
What is the difference between GastroGard and UlcerGard?
Both contain omeprazole as the active ingredient. GastroGard is prescription-strength (2.28g omeprazole per syringe) dosed for treatment of active ulcers, typically at 4mg/kg daily for 28 days or longer. UlcerGard is an over-the-counter prevention dose (same product, lower dose — 1mg/kg daily) used during high-stress periods like shows, travel, or intensive training. If your horse has confirmed active ulcers, your vet will prescribe GastroGard at the full treatment dose.
How much does it cost to treat horse ulcers?
Gastroscopy for diagnosis runs $300–600 depending on location and whether it’s done on-farm or at a clinic. A full 28-day treatment course of GastroGard costs $1,000–$1,500 for a full-size horse. Generic compounded omeprazole is significantly cheaper but isn’t FDA-approved. Glandular ulcers often require 60–90 days of treatment, sometimes with additional medications, which increases total cost. UlcerGard for prevention during high-risk periods costs roughly $35–50 per syringe. Prevention is far cheaper than treatment.
How do I know if my horse has ulcers without scoping?
You cannot definitively diagnose ulcers without a gastroscope — symptoms overlap with other conditions including back pain, saddle fit issues, hindgut problems, and behavioral issues. However, if your horse shows multiple ulcer signs simultaneously (picky eating, girthiness, condition loss, recurring mild colic), and other causes have been ruled out, many vets will recommend an empirical treatment trial. If the horse improves significantly on omeprazole within 7–10 days, that is a strong indication ulcers were present. A follow-up scope confirms healing.
- Over 80% of Thoroughbreds in training develop ulcers. It’s a management disease — the conditions of modern barn life cause it, and management changes prevent it.
- Symptom severity doesn’t match ulcer severity. A horse with grade 4 ulcers may show subtle signs while a horse with grade 2 appears miserable. Scope to know.
- Scope before you treat. Ulcer type and location determine treatment protocol. Treating without knowing what you’re treating leads to incomplete recovery.
- Omeprazole (GastroGard) is the only FDA-approved treatment. Most horses show behavioral improvement within 3–5 days; complete healing takes 28–90 days depending on ulcer type.
- Medication without management changes leads to relapse. Free-choice forage, smaller frequent meals, alfalfa before exercise, and maximizing turnout must accompany treatment.
- Alfalfa before exercise is one of the simplest and most effective tools. A flake 30 minutes before work creates a forage mat that buffers acid splash during exercise.
- UlcerGard during high-stress periods prevents new ulcers. Shows, hauling, racing season — preventive medication costs far less than treating active ulcers and recovering lost condition.
- If something seems off, investigate. Ulcers mask as behavior problems, back pain, girthiness, and performance decline. When symptoms don’t resolve and other causes are ruled out, scope the horse.
Research and Clinical References
- Thoroughbred ulcer prevalence in training — New Zealand Veterinary Journal
- Equine Gastric Ulcer Syndrome overview — PubMed Central
- Omeprazole efficacy for equine gastric ulcers — PMC
- Stress and cortisol effects on equine gastric mucosa — PubMed
- Routine changes triggering ulcers in susceptible horses — PubMed
- Starch fermentation and volatile fatty acid irritation — ScienceDirect
- Alfalfa as acid buffer — Utah State University Extension
- Treatment overview — Texas A&M Veterinary Medicine
- Nutrition for ulcer prevention — Penn State Extension
About Miles Henry
Racehorse Owner & Author | 30+ Years in Thoroughbred Racing
Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
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