Last updated: June 21, 2026
Any links on this page that lead to products on Amazon are affiliate links and I earn a commission if you make a purchase. Thanks in advance – I really appreciate it!
My two-year-old Thoroughbred refused breakfast one morning and stood at the back of his stall, ignoring feed he normally dove into. Within 72 hours, a gastroscopy confirmed what I suspected: gastric ulcers covering most of his stomach lining.
That is the problem with ulcers — they rarely look like ulcers. One horse gets dull and picky with grain. Another gets girthy under saddle. Another just loses form in training. By the time obvious symptoms appear, the stomach lining has usually been irritated for days or weeks. And in a barn where horses are worth real money and racing time is short, that lag costs you.
Horse ulcers — what you need to know:
- How common: More than 80% of Thoroughbreds in training develop gastric ulcers — it is as much a management disease as a medical one
- Key signs: Picky eating, girthiness at saddling, unexplained weight loss, performance decline, or recurring mild colic
- Only definitive diagnosis: Gastroscopy — treating based on symptoms alone misses ulcer type and location
- Gold standard treatment: Omeprazole (GastroGard) — the only FDA-approved equine ulcer medication; Most horses show improvement within 3–5 days, though some take longer depending on severity, ulcer type, and concurrent issues
- Treatment without management changes fails: Horses relapse if feeding and turnout habits do not change alongside medication
- Best prevention: Free-choice forage, smaller frequent meals, alfalfa before exercise, and less stall time
Experience & Veterinary Disclaimer: This guide reflects management practices used in our barn and aligns with current equine veterinary standards. I am not a licensed veterinarian — EGUS requires professional diagnosis and treatment. Always consult a licensed equine veterinarian before starting, stopping, or changing any treatment.
Table of Contents
What Are Horse Ulcers?
Equine gastric ulcer syndrome (EGUS) is what happens when painful sores form in a horse’s stomach lining. Horses produce stomach acid continuously — 24 hours a day, seven days a week, whether they are eating or not. In the wild, near-constant grazing kept the stomach buffered with forage and saliva. Modern barn life breaks that system. Twice-daily meals, stall confinement, and high-grain rations create long gaps where acid sits in an empty stomach with nothing to neutralize it, and the lining pays the price.
Understanding which type of ulcer you are dealing with matters because treatment protocols differ.
Squamous ulcers (Equine Squamous Gastric Disease) form in the upper stomach, where there is no protective mucus layer. Acid splashes up during exercise or accumulates during feeding gaps, and that unprotected tissue erodes. These are the most common type and usually respond well to omeprazole on a standard 28-day course.
Glandular ulcers (Equine Glandular Gastric Disease) develop in the lower stomach where acid is produced and the lining is normally protected by mucus. When that protection breaks down — through stress, NSAID use, or other factors — these deeper ulcers form. They affect roughly 25–65% of racehorses and are more stubborn than squamous ulcers. They often need a longer treatment course and may require medications beyond omeprazole alone.
Don’t overlook hindgut ulcers: Hindgut ulcers (Right Dorsal Colitis) occur further down the digestive tract and will not appear on a stomach scope. If gastroscopy comes back clean but symptoms persist, ask your vet about fecal occult blood tests or a response-to-fiber trial. Hindgut ulcers are often the hidden cause when standard gastric treatment does not resolve the problem.
Recognizing the Signs of Ulcers
Horses are masters at hiding pain. At the track, I have watched talented horses lose races because brewing ulcers made them unwilling to fully extend. The frustrating part is that symptom severity does not match ulcer severity — a horse with grade 3 ulcers might show almost nothing while a horse with grade 1 lesions acts miserable. You cannot read the stomach from the outside.
Warning signs — schedule a vet consult or scope if you see these:
- Picky eating: Leaving grain behind or eating hay eagerly but avoiding concentrates — the colt I mentioned at the top would dive into his tub, take a few bites, then walk away
- Girthiness: Pinning ears, biting, or attitude changes at saddling — 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. See girthiness causes and solutions
- Condition loss: Unexplained weight loss, loss of topline muscle, or a dull coat that won’t respond to adequate feed
- Performance decline: Reluctance to extend or collect, shorter stride, stiffness through the back, or slower works without a fitness explanation
- Recurring mild colic: Repeated low-grade episodes — especially after grain — are a red flag that belongs on a vet’s radar
- Foals show different signs: Colic shortly after nursing, teeth grinding, excessive drooling, diarrhea, lying on their backs, or a pot-bellied appearance — foal ulcers can progress quickly; call your vet immediately if you see these
| Symptom | How Common With Ulcers | Needs Vet Attention? |
|---|---|---|
| Picky eating or leaving grain | Very common — often the earliest sign | Yes, if persistent beyond 3–5 days |
| Girthiness at saddling | Common — frequently mistaken for back or saddle issues | Yes, especially if worsening |
| Recurring mild colic | Common — especially post-grain episodes | Yes — three or more episodes is a red flag |
| Condition or topline loss | Common — may appear gradually | Yes, if unexplained by feed changes |
| Performance decline | Common in performance horses | Yes, after ruling out lameness and back |
| Teeth grinding in foals | Serious early sign in foals | Immediately — foal ulcers progress fast |
Miles’s Take — What Symptom Patterns Actually Tell You: The most reliable early indicator in my barn is a horse that used to eat eagerly but now leaves part of his grain. Girthiness is the second most common pattern I see, and it almost always gets attributed to saddle fit or a sore back first. If your vet clears the back and the saddle fits correctly, scope the horse before you waste another month guessing.
This article is part of our racehorse stress hub. Ulcers are one of the most common stress-driven conditions in performance horses — if your horse is also showing stereotypies like cribbing or stall pacing, stress management belongs at the center of your plan.
What Causes Horse Ulcers?
In my experience it always comes down to several factors working together. Fix one and you help the horse; fix them all and you break the cycle. Here are the causes I see most often at the track.
Limited forage access is the single biggest contributor. When a horse goes hours without eating, acid builds up with nothing to buffer it — even four-hour gaps can do damage. Switching from twice-daily grain feeding to free-choice hay with slow-feed nets dropped our ulcer cases more than any other single change.
High-grain diets create problems in multiple ways. Grain triggers more acid production and generates far 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 — and performance horse diets almost always tip toward grain.
NSAID overuse — particularly Bute and 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 alongside. Prolonged NSAID use is also one of the primary causes of Right Dorsal Colitis — hindgut ulcers that will not show up on a gastroscope and are often missed when the stomach scope comes back clean.
Stress and transport physiology
Stress and exercise have been linked to reduced protective mucus and increased ulcer risk. Exercise also pushes acidic stomach contents up into the vulnerable upper region. Research confirms that even small routine changes can trigger ulcers within days in susceptible horses — something every trainer who has shipped a horse to a stakes race has probably learned the hard way.
Transport and competition are consistent triggers. Confinement, feed disruption, social upheaval, and unfamiliar environments combine to create conditions for rapid ulcer development. A horse that handles home training fine can be scoped clear on Monday and grade 2 by Friday after a hard ship.
How to Diagnose Horse Ulcers
Gastroscopy — scoping — is the only way to confirm an ulcer diagnosis, identify the type, and assign a grade. Your veterinarian passes a three-meter endoscope through the horse’s nostril and into the stomach to view the lining directly. The horse fasts 12–16 hours beforehand, water is pulled 2–4 hours before the exam, and mild sedation keeps the horse comfortable. The whole procedure takes 15–30 minutes.
Horse ulcer grading scale (0–4):
- Grade 0: Normal stomach lining — no lesions
- Grade 1: Mild irritation or reddening without distinct lesions
- Grade 2: Small, defined lesions — early ulceration
- Grade 3: Extensive lesions or deeper ulceration — significant mucosal damage
- Grade 4: Severe ulceration, often with bleeding or deep tissue involvement
Your vet uses this scale to confirm diagnosis and track healing on a follow-up scope after treatment. Grade determines protocol — a grade 2 squamous ulcer and a grade 3 glandular ulcer are not treated the same way.
If scoping is not immediately feasible, some veterinarians recommend an empirical treatment trial. If the horse improves meaningfully on omeprazole within 7–10 days, ulcers were likely involved. The limitation is that this approach cannot identify ulcer type or location — and that matters for how long you treat and whether additional medication is needed.
Miles’s Take — Why I Always Scope Before Treating: I have had horses present with every classic ulcer sign and scope clean, and I have had horses scope grade 3 while showing almost nothing. You cannot make confident management decisions from symptoms alone. The scope pays for itself in the clarity it gives you — you know what you are treating and can plan accordingly.
Horse Ulcer Treatment: What Actually Works
Gastric ulcers in horses are highly treatable. Many horses show meaningful improvement within 3–5 days of starting the right medication, though some take longer depending on severity and concurrent issues. In my barn, treatment always combines medication with management changes — because medication alone often leads to relapse once the course ends.
| Situation | Best Next Step |
|---|---|
| Mild or isolated symptoms | Vet consult and management review — check forage access, feeding schedule, and stress factors first |
| Recurring mild colic or picky eating | Schedule a gastroscope — empirical treatment is an option if scoping is not immediately feasible |
| Performance drop plus girthiness | Scoping strongly recommended — both signs together have high diagnostic value |
| Confirmed squamous ulcers | Omeprazole at full treatment dose for 28 days; recheck scope before stopping medication |
| Confirmed glandular ulcers | Longer course (60–90 days), and some cases extend beyond this range under veterinary guidance; may require additional medication — follow vet protocol closely |
| Symptoms don’t resolve after treatment | Consider hindgut ulcers, saddle fit, dental issues, or kissing spine — see “When Ulcers Are Not the Problem” below |
Omeprazole is the first-line treatment for equine gastric ulcers and the only FDA-approved medication for the condition. The prescription version is GastroGard. Veterinarians typically dose once daily based on weight — 28 days for squamous ulcers, longer for glandular. Give it on an empty stomach at least 30 minutes before feeding for best absorption. A small amount of molasses or applesauce after the paste helps picky horses accept it.
The biggest drawback is cost. A full 28-day GastroGard course runs $1,000–$1,500 for a full-size horse. Generic compounded omeprazole is significantly cheaper but is not FDA-approved and quality varies. If cost is a constraint, discuss compounded options with your vet — but confirm the pharmacy’s quality controls before committing.
GastroGard, UlcerGard, and generic omeprazole
UlcerGard uses the same active ingredient at a lower prevention dose and is available over the counter. I keep it on hand during racing season because the cost of a few syringes is far less than treating active ulcers or losing a horse’s training edge. For owners running horses through regular stress periods — shipping, shows, hard training blocks — preventive omeprazole is a practical and widely used tool.
Sucralfate coats ulcers and provides immediate mucosal relief while stimulating mucus production. It works well alongside omeprazole for severe ulcers, but requires dosing 2–4 times daily — which takes discipline in a busy barn.
Alfalfa hay is one of the most reliable and cost-effective management tools I use. Its high calcium content acts as a natural acid buffer, and research supports its role in both prevention and management. A flake of alfalfa 30 minutes before tacking up creates a forage mat that helps absorb acid splash during work. See our comparison of timothy, grass, and alfalfa hay if you are deciding what to feed.
Natural supplements like slippery elm or aloe vera are used by some horsemen as supportive additions. Evidence is limited compared to omeprazole-based treatment. In my experience they work best as a complement to a well-managed program, not as a standalone approach for moderate or severe ulcers.
The reason medication without management changes fails comes down to this: the drug treats the damage, but if you do not fix what caused the damage, the stomach goes right back into the same environment that produced the ulcers in the first place. Research consistently shows that horses redevelop ulcers within weeks of stopping medication when nothing else changes. Both levers — medication and management — have to move together.
Typical recovery timeline — what to expect after starting treatment:
- Days 1–5: Appetite usually improves as stomach acid decreases — though response varies by case
- Week 2: Attitude and performance typically improve; girthiness begins to resolve in many cases
- Week 4: Squamous ulcers are often substantially healed by ~28 days, though healing rates vary and should be confirmed with follow-up scoping
- Weeks 8–12: Glandular ulcers may require 60–90 days, though some cases extend beyond this range depending on severity and response to therapy
- After treatment: Management changes must stay in place or relapse is common within weeks
How to Prevent Horse Ulcers
Prevention is always cheaper than treatment — in money, in training time lost, and in the wear it puts on a horse. The changes below are what we run in our barn. After implementing them, our ulcer cases dropped significantly and relapses became the exception rather than the rule.
| Area | What We Do and Why |
|---|---|
| Forage access | Free-choice hay via slow-feed nets keeps the stomach from going empty. A horse produces acid around the clock — if they are not chewing, they are not buffering. |
| Exercise timing | Never work a horse on an empty stomach. Feed a small amount of alfalfa 30 minutes before tacking up. The forage mat reduces acid splash during exercise — this is one of the cheapest, most impactful habits you can build. |
| Grain strategy | Smaller, more frequent meals. Always feed hay before grain. Reduce starch and replace grain-based calories with beet pulp or oil where possible. More forage, less concentrate. |
| Turnout | Maximize pasture time. Grazing buffers the stomach continuously and social movement reduces cortisol — both protect the gut lining. |
| Routine | Keep daily schedules consistent. Small disruptions can trigger ulcers within days in susceptible horses. Predictability is not optional for horses prone to GI issues. |
| Preventive medication | UlcerGard during high-stress periods — racing season, hauling, shows. Discuss timing and dose with your vet. Prevention costs a fraction of what active ulcer treatment runs. |
Miles’s Take — The Change That Made the Biggest Difference: When I moved from twice-daily grain feeding to free-choice hay with slow-feed nets, the barn changed. Fewer ulcer cases. Faster healing when we did have them. Less relapse. Horses that had been tense and irritable in morning training became calmer and more willing. Free-choice forage is the foundation of everything else — without it, you are treating the same horses over and over.
When Ulcers Are Not the Problem
Not every girthy, picky-eating, or underperforming horse has ulcers. Several common conditions produce symptoms that overlap almost perfectly, and treating for ulcers when the real issue is something else wastes time, money, and horse. If a horse does not respond to ulcer treatment within 7–10 days, investigate these before assuming the treatment failed.
Conditions that mimic ulcer symptoms:
- Saddle fit issues — girthiness and back sensitivity are the most commonly misread ulcer symptoms; always eliminate saddle fit as a cause before scoping
- Kissing spine (dorsal spinous process impingement) — back pain, resistance under saddle, reluctance to collect; diagnose with X-rays
- Hindgut ulcers (Right Dorsal Colitis) — won’t appear on a gastroscope; suspect this if the scope is clean but symptoms persist
- Dental pain — quidding, weight loss, and food avoidance often attributed to ulcers; a float may resolve what a month of GastroGard won’t
- Subtle lameness or back soreness — a horse resisting work and looking sour does not always have GI involvement
- Ovarian issues in mares — behavioral changes tied to the estrous cycle are frequently mistaken for ulcer-related irritability
If your horse is losing weight alongside any of these behavioral signs, it broadens the differential — weight loss with no clear feed or dental explanation is always worth a full workup.
When to Call Your Vet Immediately
Most ulcer management is planned, not urgent. But certain signs mean same-day veterinary attention — because waiting turns a manageable problem into a serious one.
Call your vet today if you see any of these:
- Severe or escalating colic: Rolling, repeated pawing, or inability to settle within 20–30 minutes — see what to do when your horse colics
- Complete feed refusal: No interest in hay or grain for 12–24 hours
- Dehydration or systemic illness: Tacky gums, sunken eyes, marked lethargy, or reduced gut sounds
- Sudden dangerous behavior under saddle: Uncharacteristic bucking or rearing combined with other ulcer signs
- Blood in manure: Dark, tarry, or coffee-ground consistency stool
- Foals showing any ulcer-like signs: Teeth grinding, nursing-related colic, diarrhea, or poor weight gain — act immediately
These signs go beyond uncomplicated ulcers and may point to a complication or a different gastrointestinal condition that needs urgent diagnosis.
Can gastric ulcers go away on their own?
Small superficial ulcers may improve if a horse has continuous grass turnout and minimal stress, but performance-level ulcers rarely resolve without management changes and medication. Management-only approaches sometimes reduce symptoms while the ulcers themselves persist — scoping before and after treatment is the only way to confirm healing.
How long does it take for a horse to feel better after starting treatment?
Most horses show behavioral and appetite improvement within 3–5 days of starting omeprazole as stomach acid decreases. Complete 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 a follow-up scope confirms full healing.
Can horses continue training during ulcer treatment?
Yes. It is reasonable to reduce exercise intensity during the first week or two as the horse starts treatment, then return gradually to normal work as they improve. Many horses 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 backs what experienced horsemen have used for decades. Alfalfa’s 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 ulcer-prone horses.
Can horse ulcers heal without omeprazole?
Sometimes — mild ulcers may improve with significant management changes like continuous forage, reduced starch, and stress reduction. But moderate to severe ulcers typically need omeprazole or other veterinary medication to heal fully. Management changes reduce the conditions that cause ulcers; 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 around the clock, 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 where possible. More forage, less starch — that is the core of it.
What is the difference between GastroGard and UlcerGard?
Both contain omeprazole. GastroGard is prescription-strength, dosed for active ulcer treatment at 4mg/kg daily, typically for 28 days or longer. UlcerGard is the same product at a lower over-the-counter prevention dose (1mg/kg daily), used during high-stress periods like shipping, shows, or hard training blocks. 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 runs $300–600 depending on location. A 28-day GastroGard course costs $1,000–$1,500 for a full-size horse. Generic compounded omeprazole is significantly cheaper but is not FDA-approved. Glandular ulcers often require 60–90 days of treatment, sometimes with additional medications. UlcerGard for prevention runs roughly $35–50 per syringe. Prevention is far cheaper than treatment — that math gets clear fast once you have paid for a full course.
How do I know if my horse has ulcers without scoping?
You cannot definitively diagnose ulcers without a gastroscope — symptoms overlap with back pain, saddle fit problems, hindgut issues, and behavioral causes. However, if a horse shows multiple signs at once (picky eating, girthiness, condition loss, recurring mild colic) and other causes have been ruled out, many vets will recommend an empirical treatment trial. Meaningful improvement on omeprazole within 7–10 days is a strong indication ulcers were involved. A follow-up scope confirms healing.
Key Takeaways: Horse Ulcers
- Over 80% of Thoroughbreds in training develop ulcers — modern management causes it; better management prevents it
- Symptom severity does not match ulcer severity — scope to know what you are dealing with, not just how the horse looks
- Scope before you treat — ulcer type and location determine protocol; guessing leads to incomplete recovery and wasted money
- Omeprazole (GastroGard) is the only FDA-approved treatment — improvement usually within 3–5 days; healing takes 28–90 days depending on ulcer type
- Medication without management changes leads to relapse — free-choice forage, alfalfa before exercise, and turnout must run alongside treatment
- Alfalfa before work is cheap and effective — one flake 30 minutes before exercise buffers acid during the most vulnerable window
- UlcerGard during high-stress periods is standard prevention — shows, shipping, racing season; the cost is far less than treating active ulcers
- When something seems off and other causes are ruled out, scope the horse — ulcers hide behind girthiness, sour attitudes, and performance decline
Ulcers are manageable, but they don’t fix themselves. The horses that come back the strongest are the ones whose owners combined the right medication with honest management changes — more forage, less starch, more turnout. If something still seems off after treatment, don’t stop at gastric ulcers: scope for hindgut involvement, rule out saddle fit and dental pain, and look honestly at the stress picture. Most horses that get the complete program come back to work — and stay there.
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.
30 of their last 90 starts
Equibase Profile.
Connect with Miles: