Gastric ulcers are one of the most common and misunderstood conditions in horses. They affect pleasure horses, performance horses, school horses, broodmares, ponies, and even horses who never leave their paddock. Despite how widespread they are, many owners still believe ulcers only happen to thin, stressed, high-performance animals. In reality, the research tells a very different story.

Today, we’re going to explore the true risk factors for gastric ulcers – not the myths, not the internet chatter, but the clinically recognised contributors supported by evidence, physiology, and decades of veterinary experience. My goal is to give you clarity, confidence, and practical steps you can apply immediately to protect your horse’s stomach and overall welfare.

Understanding the Horse’s Stomach: The Foundation of the Problem

To understand ulcer risk, you must understand stomach structure and function. A horse’s stomach has two distinct regions:

1. The Squamous Region (upper half)

• No protection against stomach acid
• Easily irritated by acid splash
• Most ulcers occur here

2. The Glandular Region (lower half)

• Produces acid
• Has strong natural defences (mucus, bicarbonate)
  Ulcers here are often linked to stress or disrupted blood flow

The stomach continuously produces acid – even when the horse is not eating. This is where many risk factors begin.

The Real Risk Factors for Gastric Ulcers

Let’s explore the scientifically supported causes, one by one. You’ll notice many of these link directly to routine, environment, and feeding – not just stress or riding discipline.

1. Long Periods Without Forage

This is the single biggest risk factor for squamous ulcers. Horses are designed to consume fibre constantly. When they go more than 3-4 hours without forage:

• Stomach acid accumulates
• The stomach becomes more acidic
• Acid splashes into the unprotected squamous region
• The fibre “mat” that protects the stomach disappears
• The horse becomes uncomfortable, anxious, or reactive

Even two long fasting periods per day (such as overnight stabling) can be enough to cause ulcers in some horses.

Case example:
A pony that was scoped had moderate squamous ulceration despite being on “good feed.” The issue was that she ate her small hay ration in 45 minutes and then spent 10 hours with nothing. Once a slow-feeding system was introduced, her ulcers healed and her behaviour softened dramatically.

2. High-Starch or High-Sugar Diets

Concentrate feeds designed for performance horses are often high in:

• Corn
• Barley
• Oats
• Molasses
• Pelleted grain mixes

Large amounts of starch cause:

• Acid spikes
• Fermentation in the stomach
• Bacterial imbalance
• Increased gastrin production (stimulating more acid)
  Faster stomach emptying into an acidic environment

Horses fed large grain meals – especially on an empty stomach – are at much higher ulcer risk.

3. Intense or Frequent Exercise

Exercise increases acid splash and changes gut movement.

During work:

• The abdomen tightens
• The stomach compresses
• Acid splashes upward
• Blood flow shifts away from the stomach

Galloping, jumping, fast work, and collected schooling amplify this effect.

Even moderate-intensity work becomes risky when combined with:

• Riding before feeding forage
• Long periods without hay
• Travel stress
• Inconsistent routines

4. Stress: The Invisible Catalyst

Stress is a universal ulcer risk factor. And not just “emotional” stress — physiological stress.

Stress increases cortisol. Cortisol increases stomach acid. Stomach acid increases ulceration.

Common stressors include:

• Isolation from herd mates
• Moving paddocks or stalls
• New yard, new trainer, new rider
• Travel
• Competitions
• Weather changes
• Overwork
• Inconsistent routines
• Being the last horse left in the stable or paddock
• Social tension within the herd

Even the anticipation of stress can trigger changes in stomach physiology.

5. Travel and Transport

Transport is a major risk factor. Even short trips can cause measurable changes in stomach pH.

Transport creates:

• Dehydration
• Elevated cortisol
• Disrupted feeding patterns
• Limited access to forage
• Postural stress (balancing during movement)

Horses who travel regularly without structured management are significantly more ulcer-prone.

6. Stall Confinement and Limited Turnout

Stabling causes:

• Reduced movement
• Longer fasting periods
• Higher boredom and stress levels
• Limited social interaction
• Lower gut motility

Horses stabled for 12+ hours per day are significantly more likely to develop ulcers than horses on pasture.

7. Shortage of Water or Poor Hydration

Hydration supports:

• Gut motility
• Mucosal protection
• Buffering of acidity

Low water intake increases ulcer risk by:

• Thickening stomach fluid
• Reducing saliva production
• Increasing the concentration of acid
• Altering eating behaviour

Cold weather, travel, and dirty troughs all decrease water intake.

8. Medications Like Phenylbutazone (Bute)

Non-steroidal anti-inflammatory drugs (NSAIDs) can damage the stomach lining by:

• Reducing protective mucus
• Increasing stomach acid sensitivity
• Interrupting blood flow to glandular tissue

Short-term use is usually safe under veterinary guidance, but chronic NSAID use is a known ulcer risk.

9. High-Risk Breeds and Temperaments

Some horses are genetically or temperamentally higher risk:

• Thoroughbreds
• Warmbloods
• Arabs
• Performance ponies
• Naturally anxious horses
• “Sensitive” or “hot” types

Temperament affects stress response, and stress response affects ulcer vulnerability.

10. Previous History of Ulcers

Once a horse has had ulcers, their stomach becomes more sensitive long-term. Without consistent management, recurrence is common – even inevitable.

Prevention is essential for these horses.

Hidden Risk Factors Most Owners Miss

Beyond the well-known risk factors, there are subtle contributors many owners don’t recognise.

1. Inconsistent Feeding Routines

Variability increases cortisol and stomach acidity.

2. Undiagnosed Pain Elsewhere

Pain causes internal stress, which affects the stomach.

3. Over-rugging (heat stress)

Hot horses drink less and produce less saliva.

4. Under-rugging (cold stress)

Cold horses use more calories and become stressed.

5. Poor-quality hay

Dusty, stemmy hay increases ulcer risk by reducing chewing and saliva production.

6. Irregular handling or multiple trainers

Unpredictability is stressful.

7. Intense training for young horses

Young minds fatigue quickly, and fatigue increases stress.

8. Teeth problems

Poor chewing → poor saliva → poor buffering → higher ulcer risk.

9. Social isolation

Horses deprived of contact with others experience chronic low-level stress.

What Research Shows About Prevention

Thankfully, we know exactly how to reduce ulcer risk. Here are the most effective prevention methods, backed by research and clinical practice.

1. Provide Near-Constant Access to Forage

Aim for:

• 24/7 hay or pasture
• Slow feeders to extend hay supply
• No more than 3 hours without forage
• Grazing muzzles for overweight horses

Forage is the most powerful protective factor.

2. Feed Before Riding

A small amount of:

• Alfalfa
• Chaff
• Beet pulp

creates a protective fibre mat. This reduces acid splash dramatically.

3. Reduce Starch in the Diet

Choose:

• Low-NSC pellets
• Fibre-based feeds
• Alfalfa mixes
• Beet pulp
• High-quality hay

Avoid big grain meals or sugary feeds.

4. Maintain Predictable Routines

Feed at predictable times
Turnout at predictable times
Riding at predictable times

Routine stabilises cortisol.

5. Manage Stress Proactively

This includes:

• Companion animals
• Consistent handlers
• Calm environments
• Predictable routines
• Low-stress travel preparation
• Two rest days per week

Horses thrive on predictability.

6. Hydrate, Hydrate, Hydrate

Provide:

• Constant clean water
• Warm water in winter
• Extra buckets when travelling
• Electrolytes if sweating

Hydration protects the stomach.

7. Use Omeprazole Only When Needed

Omeprazole is powerful and effective when used correctly. However, it is not a long-term management tool by itself.

It must be paired with:

• Forage
• Routine
• Stress reduction
• Diet changes

8. Travel Wisely

Feed forage during transport
Stop frequently for water
Avoid fasting around travel
Give buffer feeds beforehand

Travel days count as work days – manage accordingly.

What NOT to Do

1. Don’t guess

You cannot diagnose ulcers based on behaviour alone.

2. Don’t medicate without a diagnosis

You risk masking symptoms of other medical issues.

3. Don’t rely on supplements alone

Supplements do not replace management.

4. Don’t restrict forage unless absolutely necessary

Forage restriction is one of the top ulcer triggers.

5. Don’t punish ulcer-related behaviour

It is pain, not disobedience.

When to Call Your Veterinarian

Contact your vet if your horse shows:

• Girthiness
• Behaviour changes
• Weight loss
• Colic signs
• Resistance under saddle
• Diarrhoea or loose manure
• Sensitivity around the flanks
• Dull coat
• Mood changes
• Reduced appetite

A gastroscopy remains the only way to diagnose ulcers accurately.

The Takeaway

Gastric ulcers are not just a training issue or a diet issue. They are a whole-horse, whole-management issue.

The biggest risk factors are:

• Long periods without forage
• High-starch diets
• Stress
• Travel
• Stabling
• Intense exercise
• Pain elsewhere in the body
• Inconsistent routines
• Poor hydration
• Prior ulcer history

The good news is that almost all of these risk factors are manageable.

With the right feeding strategies, predictable routines, stress reduction practices, and veterinary partnership, you can dramatically reduce ulcer risk and improve your horse’s comfort, behaviour, and long-term health.

A comfortable stomach creates a calmer, happier horse – and a stronger, safer partnership.

Disclaimer

This article provides general information only and does not replace veterinary advice for your individual horse. If you’re concerned, contact your veterinarian promptly.