Gastric Ulcers in Performance Horses: Signs, Causes, and Treatment

By Dr Duncan Houston

Performance horses are at higher risk of gastric ulcers, but not every ulcer is the same, and not every sore, girthy, or poor-performing horse has ulcers.

Gastric ulcers are common in horses, especially horses in training, competition, travel, stall confinement, or stressful management routines. The tricky part is that the signs can be vague. A horse may not look “sick.” They may simply become picky with feed, resent girthing, lose condition, act irritable, or stop performing normally.

The key is understanding where the ulcer is, why it formed, and whether the horse has equine squamous gastric disease, equine glandular gastric disease, or another problem entirely.

Treating every horse with the same ulcer plan is where owners often lose time and money.

Quick Answer

Gastric ulcers in performance horses are common and usually fall under equine gastric ulcer syndrome, which includes squamous ulcers and glandular ulcers. Squamous ulcers are strongly linked with acid exposure, exercise, fasting, high concentrate diets, and reduced forage access, while glandular ulcers involve problems with the stomach’s protective lining and may respond differently to treatment. Gastroscopy is the only reliable way to confirm and assess gastric ulceration, and treatment usually involves veterinary-directed acid suppression, management changes, and sometimes mucosal protectants depending on the ulcer type. (MSD Veterinary Manual)

What Are Gastric Ulcers In Horses?

Gastric ulcers are erosions or open lesions in the lining of the stomach.

In horses, they are grouped under the term equine gastric ulcer syndrome, or EGUS. This is an umbrella term, not a single disease. EGUS includes ulcers affecting different parts of the stomach and sometimes the nearby oesophagus or proximal duodenum. (MSD Veterinary Manual)

The two main stomach regions owners need to understand are:

1. Squamous region
   This is the upper, non-glandular part of the stomach. It does not have the same acid protection as the lower stomach.

2. Glandular region
   This is the lower acid-producing part of the stomach. It has natural protective mechanisms, including mucus and bicarbonate protection.

Modern equine medicine separates gastric ulcer disease into two main categories:

Ulcer Type	Where It Occurs	Main Problem	Why It Matters
Equine squamous gastric disease	Upper squamous stomach	Acid exposure damages unprotected lining	Often linked with exercise, fasting, feeding patterns, and training
Equine glandular gastric disease	Lower glandular stomach, antrum, pylorus, proximal duodenum	Breakdown of mucosal defence and inflammation	Often needs a more targeted treatment plan and may be harder to heal

The distinction matters because squamous and glandular ulcers do not always have the same causes, treatment response, or prevention strategy. The 2023 review of current EGUS knowledge highlights that ESGD and EGGD are now treated as distinct disease entities because the regions differ in anatomy, pathophysiology, and management. (MDPI)

Why Are Performance Horses So Prone To Ulcers?

Performance horses are exposed to several ulcer risk factors at once.

These may include:

1. Intense exercise

2. Training on an empty stomach

3. Long periods without forage

4. High concentrate or high starch diets

5. Frequent travel

6. Competition stress

7. Stall confinement

8. Reduced turnout

9. Social isolation

10. Pain, lameness, or other illness

11. NSAID medication use

12. Changes in routine

AAEP notes that gastric ulcers affect up to 90 percent of racehorses and 60 percent of show horses, and that prevention and treatment focus on reducing predisposing factors and stomach acid production. (AAEP)

The mistake is thinking ulcers only happen to elite racehorses.

They can also occur in showjumpers, dressage horses, endurance horses, eventers, polo ponies, Standardbreds, Western performance horses, and even pleasure horses under moderate stress or inconsistent feeding routines.

How Exercise Causes Squamous Ulcers

Squamous ulcers are strongly linked with acid exposure.

During exercise, abdominal pressure increases and the stomach compresses. This can push acidic fluid upward into the squamous region, which is not designed to tolerate prolonged acid contact. MSD Veterinary Manual describes this “acid splash” effect, especially in unfed horses during exercise. (MSD Veterinary Manual)

This is why ulcers are so common in horses in active training.

The risk increases when a horse:

1. Exercises with an empty stomach

2. Goes long periods without hay or pasture

3. Eats large grain meals

4. Has limited turnout

5. Is trained intensely or frequently

6. Travels or competes often

The real concern is not one single hard workout. It is repeated acid exposure over time.

Squamous Ulcers Versus Glandular Ulcers

This is one of the most important parts of the article.

Many owners talk about “ulcers” as if they are all the same. They are not.

Squamous ulcers

Squamous ulcers are usually acid exposure problems.

They are more likely when:

1. The stomach is empty for long periods

2. Exercise pushes acid upward

3. Forage intake is limited

4. High starch meals increase acid and fermentation by-products

5. Training intensity is high

6. The horse is in active competition or racing

These ulcers often respond well to appropriate acid suppression and management changes.

Glandular ulcers

Glandular ulcers are more complex.

They involve the stomach region that produces acid but should also protect itself from acid. The problem is often not just acid exposure. It may involve reduced mucosal defence, inflammation, altered blood flow, stress physiology, medications, or local injury.

MSD notes that causes of glandular ulcers are less well defined, but proposed contributors include breakdown of mucosal defences, reduced blood flow, loss of mucus-bicarbonate protection, prostaglandin inhibition, environmental or psychological stress, and inflammation. (MSD Veterinary Manual)

The practical point:

If a horse does not respond to a standard ulcer plan, glandular disease, wrong diagnosis, poor formulation, inadequate duration, or another condition should be considered.

Are NSAID Ulcers Different?

NSAIDs such as phenylbutazone and flunixin can affect the gastrointestinal tract, but they should not be used as a simple explanation for every gastric ulcer.

NSAIDs can reduce protective prostaglandins and are associated with gastrointestinal ulceration and right dorsal colitis, especially with high doses, prolonged use, dehydration, illness, or individual sensitivity. MSD notes that NSAID injury can occur anywhere in the gastrointestinal tract, with the gastric mucosa and large colon, especially the right dorsal colon, being sensitive areas in horses. (MSD Veterinary Manual)

The important nuance is this:

Training-related squamous ulcers and NSAID-related gut injury are not the same problem.

A horse can have squamous ulcers from acid exposure during training. A horse can have glandular ulcers. A horse can have NSAID-associated gastric or colonic injury. A horse can also have more than one problem at the same time.

That is why guessing is risky.

Signs Of Gastric Ulcers In Performance Horses

Ulcer signs are often vague.

Possible signs include:

1. Reduced appetite

2. Picky eating

3. Leaving grain or concentrates behind

4. Weight loss

5. Poor body condition

6. Poor topline

7. Dull coat

8. Behaviour changes

9. Irritability

10. Girthiness

11. Sensitivity during grooming

12. Reluctance to go forward

13. Poor performance

14. Recurrent mild colic signs

15. Discomfort after feeding

16. Loose manure or manure changes

17. Increased anxiety during training or travel

MSD notes that adult horses with gastric ulcers often show nonspecific signs such as poor performance, abdominal discomfort, poor appetite, mild weight loss, poor body condition, and attitude changes. It also notes that the severity of clinical signs does not always match the severity of ulceration. (MSD Veterinary Manual)

That last point matters.

A horse with mild behaviour changes can have significant ulcers. A horse with dramatic behaviour may have ulcers, but could also have lameness, back pain, dental disease, poor saddle fit, hindgut disease, training pain, or another medical issue.

How Worried Should You Be?

Risk Level	What It Looks Like	What It May Mean	What To Do
Low risk	Horse is bright, eating, performing normally, but has upcoming travel, competition, or training stress	Increased ulcer risk without clear disease signs	Review feeding, forage access, and stress reduction
Moderate risk	Picky appetite, girthiness, mild weight loss, dull coat, attitude change, reduced performance	Gastric ulcers are possible, but other causes are also possible	Arrange a veterinary check and discuss gastroscopy
High risk	Recurrent mild colic, ongoing poor appetite, weight loss, poor performance, signs returning after treatment	Ulcers, failed treatment, wrong diagnosis, glandular disease, or another illness may be present	Veterinary reassessment is needed
Critical	Severe colic, collapse, black or bloody manure, severe weakness, fever, repeated reflux signs, foal with severe signs	This is not routine ulcer management	Emergency veterinary care immediately

The key decision point:

If your horse is losing weight, not eating properly, repeatedly colicky, or not improving on treatment, do not keep guessing. Get the diagnosis checked.

What Else Can Look Like Gastric Ulcers?

This is where owners often get caught.

Ulcers are common, but they are not the cause of every problem.

Important rule-outs include:

1. Lameness

2. Back pain

3. Poor saddle fit

4. Dental disease

5. Hindgut disease

6. Sand accumulation

7. Parasite-related disease

8. Liver disease

9. Kidney disease

10. Right dorsal colitis

11. Inflammatory bowel disease

12. Poor-quality feed

13. Training conflict or behavioural stress

14. Reproductive tract pain in mares

15. Chronic low-grade colic

16. Poor nutrition or inadequate calorie intake

17. Overtraining or inadequate recovery

The mistake I see most often is owners treating ulcers repeatedly because the horse is girthy or not performing.

Girthiness can be associated with gastric discomfort, but it is not specific. The 2023 EGUS review notes that behaviours attributed to ulcers, including girthiness and poor performance, are not specific for gastric disease and other gastrointestinal and musculoskeletal conditions should remain as differentials. (MDPI)

How Are Gastric Ulcers Diagnosed?

The gold standard is gastroscopy.

Gastroscopy allows the veterinarian to see the stomach lining directly, identify whether ulcers are present, determine location, assess severity, and decide whether the disease is squamous, glandular, or mixed.

The University of Melbourne veterinary prescribing guidelines state that gastroscopy with a 3 metre endoscope after fasting is the only reliable ante-mortem method of definitively diagnosing gastric ulceration. (Faculty of Science)

A treatment trial may be used when gastroscopy is not available, but it is less precise.

If the horse improves, ulcers may be involved, but that does not prove ulcers were the only problem. If the horse does not improve, ulcers may still be present, but the treatment may be incomplete, the product may be unsuitable, the ulcer type may be glandular, or another disease may be present.

How Are Gastric Ulcers Treated?

Treatment depends on ulcer type, severity, location, and the horse’s management.

Common treatment elements include:

1. Veterinary-directed omeprazole therapy

2. Management changes to reduce acid exposure

3. Improved forage access

4. Reduced fasting time

5. Lower starch feeding where appropriate

6. Review of training intensity

7. Reduced travel and stress where possible

8. Sucralfate in selected glandular cases

9. Repeat gastroscopy in non-responding or severe cases

10. Investigation of other pain or disease triggers

MSD lists omeprazole as the treatment of choice for equine gastric ulcers, with treatment objectives centred on suppressing gastric acidity, especially for squamous disease. It also notes that glandular disease may require longer treatment, and that repeat gastroscopy may guide treatment duration. (MSD Veterinary Manual)

The University of Melbourne guidelines state that proton pump inhibitors are the best acid suppressive therapy available, with stronger evidence for squamous disease and growing support for glandular disease when combined with mucosal protectants. They also recommend sucralfate in combination with omeprazole for glandular disease. (Faculty of Science)

Why Some Horses Do Not Improve

If a horse does not improve on ulcer treatment, do not automatically conclude that the horse is being difficult or that ulcers are impossible to treat.

Common reasons include:

1. The horse was never scoped

2. The ulcers are glandular and need a different approach

3. The treatment duration was too short

4. The product or formulation was unreliable

5. The dose was incorrect

6. The horse was still training hard with the same risk factors

7. The horse had long fasting periods during treatment

8. Pain from lameness or back disease was still present

9. There was hindgut disease or right dorsal colitis

10. The horse had another cause of poor performance

The most important clinical question is:

Are we treating the correct disease, in the correct stomach region, with the correct plan?

When Is This An Emergency?

Most gastric ulcer cases are not sudden emergencies, but some signs should not be treated casually.

Call a vet urgently if your horse has:

1. Severe colic

2. Repeated rolling or sweating

3. Persistent pain

4. Complete refusal to eat

5. Collapse or severe weakness

6. Fever

7. Black, tarry, or bloody manure

8. Severe diarrhoea

9. Signs of shock

10. Rapid weight loss

11. Marked depression

12. Foal with colic, teeth grinding, drooling, diarrhoea, weakness, or sudden deterioration

Foals require extra caution. MSD notes that foals with clinical signs of gastric ulcers often have severe disease and should be evaluated and treated immediately. (MSD Veterinary Manual)

For adult performance horses, the main emergency concern is that severe colic is unlikely to be caused by simple gastric ulcers alone. Severe abdominal pain needs a broader colic assessment.

What Should You Do If You Suspect Ulcers?

Step 1: Do not diagnose from behaviour alone

Girthiness, irritability, and poor performance are important signs, but they are not specific.

They should trigger assessment, not blind treatment forever.

Step 2: Speak to your vet about gastroscopy

If signs are persistent, recurrent, severe, or performance-limiting, gastroscopy gives the clearest answer.

It tells you whether ulcers are present and whether they are squamous, glandular, or both.

Step 3: Review feeding and fasting time

Long periods without forage increase risk.

Performance horses should not spend large parts of the day with an empty stomach if this can be avoided.

Step 4: Review exercise timing

Training on an empty stomach can increase squamous acid exposure.

For some horses, providing forage before exercise can help buffer stomach contents, but this should be tailored to the horse, workload, and veterinary advice.

Step 5: Review the full pain picture

If the horse is girthy, resistant under saddle, or not moving normally, look for lameness, back pain, saddle fit issues, dental disease, and hindgut disease as well.

Step 6: Treat based on ulcer type

Squamous disease and glandular disease may need different strategies.

A generic “ulcer treatment” plan is not always enough.

Common Mistakes Owners Make

1. Assuming all ulcers are the same

Squamous and glandular disease are different. Location matters.

2. Treating without changing management

Medication may heal ulcers, but the same feeding, fasting, training, and stress pattern can bring them back.

3. Blaming every behaviour problem on ulcers

Ulcers are common, but so are lameness, back pain, poor saddle fit, dental disease, and training stress.

4. Stopping treatment too early

Clinical improvement does not always mean ulcers are fully healed.

5. Ignoring glandular ulcers

Glandular disease may be harder to heal and may require a more targeted plan.

6. Using random supplements instead of diagnosis

Supplements may support management in some cases, but they should not replace proper diagnosis and veterinary treatment.

7. Forgetting about NSAID risk

NSAIDs can affect the stomach and colon. If a horse on NSAIDs develops poor appetite, soft manure, diarrhoea, colic signs, or dullness, call your vet.

Myth Versus Reality

Myth	Reality
“All performance horses with bad behaviour have ulcers.”	Ulcers are common, but behaviour signs are not specific. Pain, training, saddle fit, and other diseases must be considered.
“If the horse eats, they cannot have ulcers.”	Some ulcer horses still eat, especially forage, while becoming picky with grain or inconsistent with appetite.
“All ulcers need the same treatment.”	Squamous and glandular disease can require different management and treatment plans.
“Omeprazole fixes every ulcer case.”	Squamous disease often responds well, but glandular disease may need longer treatment or additional medications.
“Supplements can replace scoping.”	Gastroscopy is the reliable way to confirm ulcer location and severity.
“If signs improve, the ulcers are gone.”	Signs can improve before full healing, and recurrence is possible if risk factors remain.

How To Reduce Ulcer Risk In Performance Horses

Keep forage available

Horses are designed for frequent forage intake.

Long fasting periods increase acid exposure risk. Where possible, provide consistent access to hay or pasture.

Reduce high starch load

Large concentrate meals can increase gastric risk and alter fermentation patterns.

Consider smaller meals, lower starch options, and a forage-first feeding plan.

Avoid training on an empty stomach

For squamous ulcer risk, exercising with some forage in the stomach may help reduce acid splash.

This should be adjusted for the horse, discipline, and veterinary advice.

Increase turnout where possible

Turnout can reduce stress, increase movement, and support more natural feeding behaviour.

Build rest into the training program

The University of Melbourne guidelines note that exercise days may be associated with glandular disease and recommend rest days for horses with EGGD risk. (Faculty of Science)

Reduce travel stress

Travel, competition, isolation, and disrupted feeding routines can increase ulcer risk.

Plan forage, water, rest, and recovery around travel days.

Use NSAIDs carefully

NSAIDs are valuable medications, but they should be used under veterinary guidance, especially in horses with poor appetite, diarrhoea, colic signs, dehydration, or a history of gut disease.

Recheck recurring cases

If signs return after treatment, do not just repeat the same plan indefinitely.

Recheck the diagnosis, ulcer location, medication, management factors, and other possible pain sources.

Prevention Checklist

Risk Area	What To Review	Why It Matters
Forage access	Long gaps without hay or pasture	Empty stomach increases acid exposure
Exercise timing	Training with no forage onboard	Exercise can push acid onto squamous lining
Concentrates	Large grain or starch-heavy meals	Can contribute to gastric acidity and digestive stress
Turnout	Limited movement or isolation	Stress and confinement can increase risk
Travel	Long trips, disrupted feeding, competition routines	Travel commonly changes eating, hydration, and stress
Pain	Lameness, back pain, dental disease	Pain and stress can worsen behaviour and ulcer suspicion
NSAID use	Bute, flunixin, other anti-inflammatories	Can affect stomach, colon, kidneys, and overall gut health
Diagnosis	No gastroscopy or no recheck	Treatment is less targeted without knowing ulcer type

How Vets Think About Ulcers In Performance Horses

When I assess a performance horse with suspected ulcers, I am not just asking, “Does this horse have ulcers?”

I am asking:

1. Is this squamous disease, glandular disease, or both?

2. Is the horse being trained on an empty stomach?

3. How many hours per day is the horse without forage?

4. Is the horse travelling or competing frequently?

5. Is there lameness, back pain, or saddle fit pain?

6. Are signs related to feeding, exercise, girthing, or transport?

7. Has the horse been scoped?

8. Did the previous treatment actually heal the ulcers?

9. Are signs recurring because the cause was never changed?

10. Could this be hindgut disease, dental disease, or another cause of poor performance?

This is the difference between treating symptoms and solving the case.

Helpful Related Reading

This article fits naturally with:

1. Why some omeprazole products do not work for horse ulcers

2. NSAID side effects in horses

3. Right dorsal colitis from phenylbutazone use

4. What to do first if your horse has colic

5. Impaction colic in horses

6. Feeding performance horses safely

7. Poor performance in horses

8. Girthiness in horses

9. Stress and digestive health in horses

10. Post-travel appetite changes in horses

These articles belong together because gastric ulcers overlap with feeding, pain, training, travel, stress, medication safety, and colic signs.

FAQs

What are the first signs of gastric ulcers in horses?

Common signs include picky appetite, reduced grain intake, weight loss, poor performance, girthiness, behaviour changes, mild recurrent colic signs, dull coat, and attitude changes. These signs are not specific, so veterinary assessment is important.

Are squamous and glandular ulcers treated the same way?

Not always. Squamous ulcers are more directly linked with acid exposure and often respond well to acid suppression and management changes. Glandular ulcers can be more complex and may require longer treatment, sucralfate, or a different veterinary plan. (MSD Veterinary Manual)

Can a horse have ulcers without obvious signs?

Yes. Some horses show subtle signs or no obvious signs, while others show poor performance, appetite changes, or mild colic. The severity of signs does not always match the severity of ulceration. (MSD Veterinary Manual)

Is gastroscopy necessary?

Gastroscopy is the most reliable way to diagnose gastric ulcers and determine whether they are squamous, glandular, or both. A treatment trial may be used when scoping is not available, but it is less precise. (Faculty of Science)

Can ulcers come back after treatment?

Yes. Ulcers can recur if the original risk factors remain, such as long fasting periods, high training stress, frequent travel, high concentrate diets, limited turnout, or ongoing pain from another condition.

Final Thoughts

Gastric ulcers in performance horses are common, but they should not be treated like one simple diagnosis.

The stomach region matters. The risk factors matter. The horse’s management matters. And the signs need to be interpreted alongside pain, training, feeding, dental health, saddle fit, lameness, stress, and hindgut disease.

The horse that worries me is not only the one with obvious colic. It is the horse that slowly becomes picky, irritable, girthy, dull, underweight, or inconsistent in work while everyone assumes it is attitude.

Ulcers are treatable, but the best outcomes come from knowing what type of ulcer is present, treating it properly, and changing the conditions that allowed it to develop.

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If your horse has appetite changes, girthiness, weight loss, poor performance, recurrent mild colic signs, or has not improved after ulcer treatment, ASK A VET™ can help you understand what to monitor and when veterinary care is needed.