How To Prevent Gastric Ulcers in Horses

By Dr Duncan Houston

A practical guide to lowering ulcer risk through forage, routine, stress control, exercise planning, and evidence based veterinary care.

Gastric ulcers in horses are common, frustrating, and often preventable. They are not just a “performance horse problem” and they are not always fixed by buying another tub of supplement.

The real issue is that many modern horse routines work against how the equine stomach is built. Horses are designed to eat frequently, produce stomach acid continuously, move regularly, and live with predictable social and environmental patterns. When we replace that with long fasting periods, high concentrate feeds, stall confinement, travel, intense training, and stress, ulcer risk rises.

The good news is that prevention does not need to be mysterious. It needs to be systematic.

Quick Answer

The best way to help prevent gastric ulcers in horses is to reduce long periods without forage, limit large grain meals, support turnout and social contact, manage travel and training stress, avoid unnecessary NSAID use, and use veterinary prescribed ulcer medication during high risk periods when appropriate. Horses produce stomach acid around the clock, and forage plus saliva help buffer that acid, which is why feeding pattern is one of the most important parts of prevention. (Horse Report)

Gastric ulcers should not be treated as one single condition. Equine gastric ulcer syndrome includes squamous and glandular disease, and these two forms can have different causes, risk factors, treatment responses, and prevention plans. (ScienceDirect)

What Are Gastric Ulcers in Horses?

Gastric ulcers are areas of damage, erosion, inflammation, or ulceration in the lining of the horse’s stomach. The broader term is equine gastric ulcer syndrome, often shortened to EGUS.

The important clinical point is that EGUS is not one simple disease. It is usually divided into:

1. Equine Squamous Gastric Disease, or ESGD

2. Equine Glandular Gastric Disease, or EGGD

The squamous region is the upper, less protected part of the stomach. It is vulnerable when acid contacts it, especially during fasting, exercise, or high acid exposure.

The glandular region is the lower acid producing part of the stomach. It has natural protective mechanisms, so glandular ulcers are more about failure of mucosal defence, inflammation, stress, pain, NSAID exposure, or other individual risk factors. UC Davis notes that identifying ulcer type matters because treatment differs by location. (Horse Report)

Why Prevention Matters So Much

Ulcers often come back if the original risk factors are not fixed.

This is one of the biggest owner frustrations. A horse improves on omeprazole, then relapses after treatment stops. That does not always mean the medication failed. It often means the horse returned to the same routine that helped create the ulcer risk in the first place.

In practice, medication may heal the ulcer, but management helps stop the ulcer coming back.

UC Davis states that prevention is essential because equine gastric ulcers often recur, and that without management changes, ulcers are likely to return. (Horse Report)

Are Horse Ulcers Really “Man Made”?

Partly, yes, but the truth is more nuanced.

It is too simplistic to say feral horses never get ulcers. Studies have found ulcers in feral horses, but domesticated horses, especially athletic horses, appear to have higher risk in many settings. The AAEP summary of a UK study reported that both squamous and glandular ulceration were more prevalent in domesticated horses than in the feral horses studied. (AAEP)

The better way to explain it is this: modern management can increase ulcer risk when it disrupts normal grazing, movement, social contact, and routine.

That matters because it gives owners something useful to act on.

Why Horses Are So Prone to Ulcers

Horses have relatively small stomachs and are built to graze for long periods. In natural grazing conditions, stomach acid is produced continuously and buffered by a steady flow of feed and saliva. When horses are fed only once or twice daily, the stomach may go through prolonged periods without feed to neutralise acid. (Horse Report)

This is why ulcer prevention starts with the feeding pattern, not the supplement shelf.

Risk increases when horses have:

1. Long gaps without hay, pasture, or forage

2. High starch or high concentrate meals

3. Large grain meals

4. Intense exercise

5. Frequent travel

6. Competition stress

7. Stall confinement

8. Social isolation

9. Many different handlers

10. Abrupt routine changes

11. Ongoing pain

12. Repeated NSAID use

13. Recent illness

14. Poor appetite

15. Previous ulcer history

MSD Veterinary Manual lists intense exercise, high concentrate diets, and food restriction as key risk factors for gastric ulcers in horses. (MSD Veterinary Manual)

How Common Are Gastric Ulcers in Horses?

Gastric ulcers are common, especially in horses in work. MSD Veterinary Manual reports that equine gastric ulcer syndrome is estimated in at least 90 percent of racehorses in active training and racing, while non racing performance horses vary from about 40 to 60 percent. (MSD Veterinary Manual)

That does not mean every girthy horse has ulcers. It also does not mean only racehorses get ulcers.

It means ulcers should be high on the list when a horse has compatible signs and risk factors.

Squamous Versus Glandular Ulcers: Why It Changes Prevention

This is where ulcer advice often becomes too basic.

Squamous ulcers

Squamous ulcers are usually linked to acid exposure. Long fasting periods, high starch feeding, and exercise related acid splash can all increase risk.

Prevention focuses heavily on:

1. More consistent forage access

2. Less fasting

3. Lower starch intake

4. Smaller concentrate meals

5. Feeding forage before exercise

6. Reducing intense work during high risk periods

Glandular ulcers

Glandular ulcers are more complicated. They are not simply “acid splash.” They are linked to failure of the stomach lining’s protective mechanisms.

Prevention may involve:

1. Reducing stress

2. Avoiding unnecessary NSAIDs

3. Managing pain elsewhere in the body

4. Improving turnout and social stability

5. Reducing excessive work intensity

6. Maintaining routine

7. Investigating horses that relapse quickly

The Veterinary Journal review explains that ESGD is caused by acid exposure, while EGGD is thought to occur when mucosal defence mechanisms are compromised. It also notes that EGGD can be less responsive to treatment than ESGD. (ScienceDirect)

Signs That Your Horse May Already Have Ulcers

Prevention matters, but owners also need to recognise when prevention may no longer be enough.

Possible signs include:

1. Picky eating

2. Walking away from feed

3. Reduced appetite

4. Weight loss

5. Poor coat condition

6. Girthiness

7. Flank sensitivity

8. Irritability

9. Behaviour changes under saddle

10. Poor performance

11. Reluctance to go forward

12. Mild recurrent colic

13. Teeth grinding, especially in foals

14. Dullness

15. Recurrence after previous ulcer treatment

The difficult part is that signs are not always reliable. UC Davis notes that some horses show mild signs and others may show no clinical signs at all. (Horse Report)

That is why diagnosis matters.

How Worried Should You Be?

Lower Risk

Your horse is eating well, maintaining weight, passing normal manure, performing normally, and has good turnout, forage access, and a stable routine.

This does not make ulcers impossible, but it lowers concern. Prevention is still worthwhile, especially before travel, competition, intense training, or major routine changes.

Moderate Risk

Your horse is girthy, picky with feed, slightly reactive, underperforming, losing condition slowly, or showing mild behaviour changes.

This is where you should review the full routine: forage access, grain, travel, stress, exercise, pain, NSAID use, and previous ulcer history.

High Risk

Your horse has recurrent mild colic, significant appetite change, weight loss, poor performance, marked girthiness, or signs returning after ulcer treatment.

This needs veterinary assessment. Guessing with supplements can waste time.

Critical Risk

Your horse has severe colic, repeated rolling, sweating, collapse, severe depression, fever, fast heart rate, or complete refusal to eat.

This is an emergency. Do not assume it is “just ulcers.”

When Is This an Emergency?

Gastric ulcers can cause discomfort, reduced appetite, and mild colic signs, but severe abdominal pain should never be dismissed as uncomplicated ulcers.

Call a vet urgently if your horse has:

1. Severe colic

2. Repeated rolling

3. Sweating with abdominal pain

4. Collapse or weakness

5. Fast heart rate

6. Pale, purple, dark red, or tacky gums

7. Complete refusal to eat

8. Persistent depression

9. Fever

10. No manure

11. Repeated colic episodes

12. Severe signs in a foal

MSD Veterinary Manual notes that clinical signs can be vague and nonspecific, and definitive diagnosis requires endoscopic examination. Severe colic needs veterinary assessment because other gastrointestinal problems may be present. (MSD Veterinary Manual)

The Best Prevention Strategy: Feed the Stomach Like a Horse’s Stomach

The horse stomach is not built for long empty periods.

The most important daily prevention steps are:

1. Provide frequent forage

2. Avoid long fasting periods

3. Use pasture turnout where safe and suitable

4. Use hay or hay nets when pasture is not available

5. Feed smaller, more frequent meals

6. Reduce large grain meals

7. Avoid sudden feed changes

8. Feed a small amount of forage before exercise

9. Make sure water intake is consistent

10. Monitor appetite daily

UC Davis notes that extended periods greater than 6 hours without forage are a risk factor for squamous gastric disease. (Horse Report)

In practice, I worry less about the horse eating hay “perfectly” and more about whether the stomach is being left empty for too long.

Reduce High Starch and Large Grain Meals

High grain diets can contribute to ulcer development. UC Davis notes that high grain diets produce volatile fatty acids that can contribute to ulcer formation. (Horse Report)

This does not mean every horse must be grain free. It means grain should be used thoughtfully.

A safer feeding approach often includes:

1. More forage as the foundation

2. Smaller concentrate meals

3. Lower starch options when appropriate

4. Gradual feed changes

5. Nutrition review for hard keepers

6. Avoiding large meals before stressful events

7. Feeding based on workload, not habit

The feed room is one of the most powerful ulcer prevention tools on the property.

Use Forage Before Exercise

Exercise can increase acid exposure to the squamous stomach. A small forage meal before work can help provide a fibre mat and stimulate saliva production.

This is especially useful for horses that are worked early, travel to competitions, or train intensely.

Practical approach:

1. Offer hay before exercise

2. Avoid working the horse on a completely empty stomach

3. Do not feed a large grain meal immediately before hard work

4. Consider alfalfa hay or chaff where appropriate for the individual horse

5. Keep the routine consistent

This is not about stuffing the horse before training. It is about avoiding an empty acidic stomach during work.

Minimise Stall Stress

Stall confinement is sometimes necessary, but it can increase ulcer risk when it reduces movement, social contact, forage access, and control over the horse’s environment.

If your horse must be stabled, improve the setup:

1. Provide consistent forage access

2. Allow visual contact with other horses where possible

3. Keep feeding times predictable

4. Use slow feeders if suitable

5. Maintain turnout when possible

6. Reduce unnecessary isolation

7. Keep bedding comfortable

8. Avoid constant disruption from changing handlers or routines

UC Davis lists transport and stall confinement as physical and environmental stressors that are additional ulcer risk factors. (Horse Report)

Manage Travel and Competition Like Ulcer Risk Events

Travel, shows, race meetings, sales preparation, clinics, and major competitions can all increase ulcer risk.

Before high risk periods:

1. Keep forage available during travel where safe

2. Avoid abrupt feed changes at events

3. Bring familiar hay if possible

4. Keep water access consistent

5. Allow recovery time after travel

6. Avoid sudden intense training increases

7. Monitor appetite closely for 48 to 72 hours after stress

8. Discuss preventive medication with your vet for high risk horses

UC Davis notes that UlcerGard can be used for ulcer prevention during travel and competitions, starting several days in advance and continuing for a few days afterward. Product availability and regulations vary by country, so this should be discussed with your veterinarian. (Horse Report)

Use NSAIDs Carefully

NSAIDs such as phenylbutazone and flunixin can be very useful medications, but they should not be treated casually.

Glandular ulcers and right dorsal colitis are both concerns when NSAIDs are used inappropriately, especially in horses that are dehydrated, off feed, systemically unwell, or receiving repeated courses.

Safer principles:

1. Use NSAIDs only as directed

2. Avoid combining NSAIDs unless specifically instructed

3. Be cautious in horses that are not eating

4. Be cautious in dehydrated horses

5. Recheck horses needing repeated pain relief

6. Ask your vet about monitoring if medication is ongoing

7. Do not mask repeated colic or pain with more medication

The real concern is not one appropriate dose in a well assessed horse. The concern is repeated pain relief without reassessing why the horse still needs it.

What Medications Actually Help Prevent Ulcers?

Omeprazole is the main evidence based medication used for equine gastric ulcers because it suppresses stomach acid production.

MSD Veterinary Manual states that omeprazole is approved by the US FDA for treatment and prevention of recurrence of equine gastric ulcer syndrome, with treatment typically given for 28 days, while glandular disease may require longer treatment and repeat gastroscopy to guide duration. (MSD Veterinary Manual)

Current product advice needs to be accurate because approvals change. In the United States, the FDA approved Gastrobim in 2026 as the first generic omeprazole oral paste for treatment of gastric ulcers and prevention of recurrence in horses and foals at least 4 weeks of age. The FDA states that it contains the same active ingredient as GastroGard and was determined to be bioequivalent. (U.S. Food and Drug Administration)

In Australia, veterinary only omeprazole products such as OMOGUARD are listed for treatment and prevention of gastric ulcers in horses and foals. Product names, availability, racing rules, and prescribing requirements vary by country. (Ceva Australia)

The practical message: use properly regulated veterinary products under veterinary guidance, not random ulcer pastes based on marketing claims.

What About Supplements?

Some supplements may support gut health, but they should not be treated as a replacement for diagnosis, management correction, or veterinary treatment when ulcers are suspected.

The problem is not that every supplement is useless. The problem is that many are marketed with confidence that exceeds the evidence.

Supplements may be reasonable as part of a wider plan when:

1. The horse is already being managed properly

2. A vet has assessed the likely risk

3. Diet and forage access have been corrected

4. There are no emergency signs

5. They are not delaying gastroscopy or treatment

Supplements are not a substitute for scoping a horse with recurrent colic, weight loss, appetite change, or significant performance decline.

How Are Gastric Ulcers Diagnosed?

Gastroscopy is the gold standard.

This involves passing an endoscope into the stomach so the veterinarian can directly see whether ulcers are present, where they are, how severe they are, and whether they involve the squamous region, glandular region, or both.

UC Davis states that gastroscopy is currently the only way to confirm the presence of ulcers and determine whether the horse has squamous ulcers, glandular ulcers, or both. (Horse Report)

This matters because a horse with glandular disease may need a different plan from a horse with straightforward squamous ulceration.

What Should You Do Next?

If you are trying to prevent ulcers, start with the routine.

Step 1: Audit forage access

Ask: does this horse go more than 4 to 6 hours without forage?

If yes, that is the first problem to fix.

Step 2: Audit concentrate feeding

Ask: is the horse receiving large grain or high starch meals?

If yes, review whether the same calories can be supplied with a safer feeding structure.

Step 3: Audit stress

Ask: is the horse stabled alone, travelling often, worked intensely, handled by many people, or going through major routine change?

If yes, ulcer prevention needs to include stress reduction.

Step 4: Audit pain and medication

Ask: is the horse receiving repeated NSAIDs, recovering from injury, or showing signs of pain elsewhere?

If yes, do not just treat the stomach. Treat the whole horse.

Step 5: Decide whether gastroscopy is needed

If signs are present, recurrent, or significant, gastroscopy is the cleanest way to stop guessing.

Common Mistakes Owners Make

Mistake 1: Trying supplements before fixing forage

If the horse is fasting for long periods, no supplement is going to make that a good ulcer prevention plan.

Mistake 2: Assuming girthiness always means ulcers

Girthiness can be ulcers, but it can also be saddle fit, back pain, learned behaviour, ovarian pain, muscle soreness, or general discomfort.

Mistake 3: Treating without diagnosis

Empirical treatment may be used in some cases, but repeated treatment without scoping can miss glandular disease or a completely different problem.

Mistake 4: Stopping after the ulcer heals

Healing is not the finish line. The long term goal is preventing relapse.

Mistake 5: Ignoring stress

Some owners focus only on feed. Stress, travel, social isolation, pain, and workload can be just as important.

Mistake 6: Using unregulated products as if they are equivalent

Compounded or unregulated products may not perform like licensed veterinary medications. UC Davis warns that compounded medications may not contain active ingredients at appropriate concentrations, which can delay healing. (Horse Report)

Myth vs Reality

Myth: Ulcers are only a racehorse problem

Reality: Racehorses are high risk, but ulcers can affect show horses, sport horses, pleasure horses, foals, and horses under stress.

Myth: A horse with ulcers always stops eating

Reality: Some horses keep eating. Others simply become picky, slower, duller, or less willing to work.

Myth: Supplements prevent ulcers on their own

Reality: Forage, routine, stress control, diagnosis, and proper medication matter more than marketing claims.

Myth: All ulcers are the same

Reality: Squamous and glandular ulcers are different and can need different treatment and prevention plans.

Myth: Once treated, ulcers are gone forever

Reality: Ulcers can recur if the original management risk remains.

Prevention Checklist

Use this as a practical routine review:

1. Does the horse have regular forage access?

2. Are there long gaps without hay or pasture?

3. Is the horse receiving large grain meals?

4. Has the diet changed suddenly?

5. Is the horse worked on an empty stomach?

6. Has training intensity increased quickly?

7. Is the horse travelling often?

8. Is the horse stabled alone?

9. Does the horse have visual or physical social contact?

10. Is the horse on repeated NSAIDs?

11. Has appetite changed?

12. Has performance changed?

13. Is there recurrent mild colic?

14. Has the horse relapsed after ulcer treatment before?

15. Has gastroscopy been discussed?

If several of these apply, the horse deserves a proper ulcer prevention plan rather than a hopeful supplement purchase.

FAQs

Can gastric ulcers in horses be prevented?

Yes, risk can often be reduced through better forage access, fewer long fasting periods, lower starch feeding, stress reduction, careful NSAID use, and veterinary directed medication during high risk periods. Prevention is not perfect, but management makes a major difference.

Should horses have hay all day to prevent ulcers?

Many horses benefit from regular or free choice forage access, depending on weight, metabolic status, dental health, and management needs. The goal is to avoid long empty stomach periods while still feeding safely for the individual horse.

Is omeprazole enough to prevent ulcers?

Omeprazole can be very useful, especially during treatment or high risk periods, but it should not replace management changes. If the horse returns to long fasting periods, high stress, intense work, and large grain meals, ulcers may recur.

What is the best test for gastric ulcers in horses?

Gastroscopy is the best test because it allows the vet to directly examine the stomach and identify whether ulcers are squamous, glandular, or both. This matters because treatment and prognosis can differ. (Horse Report)

Can stress alone cause ulcers in horses?

Stress can contribute to ulcer risk, especially when combined with fasting, high concentrate feeding, transport, stall confinement, intense training, pain, or illness. It is rarely just one factor.

Final Thoughts

The best ulcer prevention plan is not one product. It is a system.

Forage matters. Routine matters. Stress matters. Exercise timing matters. Pain control matters. Veterinary diagnosis matters. Medication matters when it is used properly and for the right horse.

The biggest mistake is thinking of gastric ulcers as something you fix only after they appear. In many horses, the better approach is to look at the daily routine and ask: is this stomach being protected, or is it being challenged every day?

If your horse is girthy, picky with feed, underperforming, losing weight, showing mild recurrent colic, or relapsing after treatment, do not keep guessing. Get the pattern assessed, consider gastroscopy, and build a prevention plan around how horses are actually designed to eat, move, and live.

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If you are unsure whether your horse’s routine, symptoms, or ulcer history needs veterinary attention, ASK A VET™ can help you organise the signs and decide what to discuss with your veterinarian next.