Gastric Ulcers in Horses: The Role of Diet and Feeding Management

Gastric ulcers are one of the most common — and most underdiagnosed — health problems in the modern horse. Studies suggest that up to 90% of racehorses and 60% of sport and leisure horses have some degree of gastric ulceration. Those numbers are startling, and they tell us something important: the way we keep and feed horses often works against their digestive design.

The good news? Diet and feeding management are among the most powerful tools you have for both preventing and managing equine gastric ulcers. In this article, we'll break down exactly how the horse's stomach works, why ulcers develop, and what you can do with everyday feeding decisions to protect your horse's gut health.

Understanding the Horse's Stomach

Before we talk about ulcers, it helps to understand a few basics about equine stomach anatomy.

The horse's stomach is relatively small — only about 8 to 15 litres in capacity. It was designed for a trickle-feeding lifestyle, where the horse grazes for 16 to 18 hours a day on fibrous forage. The stomach is divided into two distinct regions:

The Squamous Region (Upper Portion)

The upper third of the stomach is lined with squamous epithelium — a thin, non-glandular lining with very little natural protection against acid. Think of it like the lining of your mouth. It's not designed to sit in an acid bath.

The Glandular Region (Lower Portion)

The lower two-thirds is lined with glandular mucosa, which secretes hydrochloric acid, mucus, and bicarbonate. This region has built-in defences against its own acid production — but even these defences can be overwhelmed.

Here's the critical point: horses produce stomach acid continuously, 24 hours a day, regardless of whether they're eating or not. In a natural grazing scenario, the constant flow of saliva (which contains bicarbonate) and the presence of food in the stomach help buffer that acid. Remove the food, and the acid has nothing to work on except the stomach lining.

What Are Equine Gastric Ulcers?

Equine Gastric Ulcer Syndrome (EGUS) is the umbrella term for ulceration affecting the horse's stomach. It's now divided into two conditions:

• Equine Squamous Gastric Disease (ESGD) — ulcers in the upper, non-glandular region. These are strongly linked to diet and management.
• Equine Glandular Gastric Disease (EGGD) — ulcers in the lower, glandular region. These are more complex and may involve stress, exercise, and immune factors.

Both types can exist simultaneously, and both benefit from good feeding management — though ESGD is the form most directly influenced by what and how you feed.

Why Diet Is Central to Gastric Ulcers

The link between diet and gastric ulcers is well established. Here are the key dietary factors:

Prolonged Fasting

This is the single biggest dietary risk factor. When a horse goes without forage for more than four to five hours, the stomach empties, and hydrochloric acid begins to erode the unprotected squamous lining. Overnight fasting, small hay nets that run out too quickly, and restricted turnout all contribute.

High-Starch, Low-Fibre Diets

Diets heavy in cereal grains (oats, barley, processed feeds) produce volatile fatty acids (VFAs) during fermentation in the stomach. These VFAs, combined with a low stomach pH, can damage the squamous mucosa. At the same time, low-fibre diets reduce chewing time and therefore reduce the flow of acid-buffering saliva.

Insufficient Forage

Forage does two important things: it stimulates saliva production, and it forms a fibrous mat in the stomach that helps prevent acid from splashing up onto the squamous lining. Without adequate forage, both of these protective mechanisms are compromised.

Meal Feeding Patterns

Feeding two large concentrate meals a day — as is common in many yards — creates spikes in acid production and periods of an empty stomach between meals. This pattern is the opposite of what the horse's stomach was designed for.

Signs Your Horse May Have Gastric Ulcers

Gastric ulcers don't always produce dramatic symptoms. Many horses show subtle signs that are easily attributed to behaviour or temperament. Watch for:

• Poor appetite or fussiness at feed time
• Weight loss or difficulty maintaining condition
• Dull coat
• Mild, recurring colic — especially after eating
• Girthiness or sensitivity around the belly
• Changes in behaviour — grumpiness, reluctance to work, or anxiety
• Poor performance
• Teeth grinding (bruxism)
• Loose droppings without obvious cause

If you suspect ulcers, the only definitive diagnosis is gastroscopy — a scope examination of the stomach performed by your vet. Don't rely on symptom checklists alone.

Feeding Management Strategies to Prevent and Manage Ulcers

Whether your horse has been diagnosed with gastric ulcers or you want to reduce the risk, these feeding management principles form the foundation of gut health.

1. Maximise Forage Intake

Forage should be the cornerstone of every horse's diet. Aim for a minimum of 1.5% of body weight per day in forage dry matter — that's around 7.5 kg of dry hay for a 500 kg horse. For horses prone to ulcers, offering more is even better.

• Use ad-lib forage wherever possible
• If you need to restrict intake (for overweight horses, for example), use small-holed hay nets or trickle feeders to slow consumption — but never allow the horse to go without forage for extended periods
• Provide hay or haylage before turnout, before exercise, and last thing at night

2. Reduce Starch and Sugar in the Diet

Keep total starch intake below 1 g per kg of body weight per meal, and ideally below 2 g per kg of body weight per day. For a 500 kg horse, that means no more than 500 g of starch per meal.

In practical terms:

• Choose fibre-based feeds (such as unmolassed sugar beet, chaff, and high-fibre cubes or mashes) over cereal-based mixes
• If your horse needs extra energy, consider oil (vegetable oil, linseed oil) as a calorie source rather than starch
• Read feed labels carefully — many commercial feeds marketed as "conditioning" or "performance" feeds contain surprisingly high levels of cereals and starch

3. Feed Little and Often

If you must feed concentrates, split them into three or more small meals rather than two large ones. This reduces the acid spike after feeding and keeps something in the stomach more consistently.

Better yet, consider replacing bucket feeds with forage-based alternatives wherever your horse's workload allows.

4. Never Let the Stomach Stay Empty

This is worth repeating: avoid prolonged periods without forage. The most critical window is overnight, when many horses run out of hay by midnight and then stand with an empty stomach until morning.

Strategies include:

• Double-netting hay (one small-holed net inside another) to slow intake
• Providing a late-night hay top-up
• Offering straw as a low-calorie fibre source alongside hay (avoid straw as the sole forage — it has poor nutritional value and can cause impaction in large quantities)

5. Feed Forage Before Exercise

During exercise — especially trotting, cantering, and jumping — the stomach contracts and acid splashes upward onto the squamous lining. Feeding a small amount of forage (about 0.5 to 1 kg of hay or a double handful of chaff) 20 to 30 minutes before exercise helps create a fibrous buffer that reduces acid splash.

This is one of the simplest and most effective ulcer-prevention strategies, yet it's often overlooked.

6. Consider Alfalfa

Alfalfa (lucerne) has been shown in research to have a beneficial buffering effect on stomach acid, likely due to its high calcium and protein content. Including some alfalfa chaff or hay in the diet — particularly before exercise or as part of a concentrate meal — may help protect the stomach lining.

A small bucket of alfalfa chaff before riding is an easy addition to any routine.

7. Ensure Adequate Water Access

Dehydration reduces saliva production and gut motility. Always provide clean, fresh water — in the stable, in the field, and at competitions. In cold weather, horses often drink less, so monitor intake carefully.

The Role of Supplements

You'll find a wide range of gastric supplements on the market, from pectin-lecithin complexes to antacid pastes and herbal blends. While some may offer supportive benefits, it's important to be realistic:

• No supplement replaces good feeding management. Fix the diet first.
• For diagnosed ulcers, your vet will likely prescribe omeprazole (for squamous ulcers) or sucralfate (for glandular ulcers). These are the evidence-based treatments.
• Supplements may play a role in ongoing management after treatment, but always discuss options with your vet.

Stress, Lifestyle, and the Bigger Picture

Diet isn't the only factor. Stress — whether from transport, competition, social isolation, stabling, or changes in routine — contributes to ulcer risk. NSAIDs (such as phenylbutazone) can damage the glandular lining. Intensive training increases acid splash.

A truly ulcer-preventive management plan addresses the whole lifestyle: maximum turnout, social contact, consistent routines, and appropriate workload alongside optimal nutrition.

Analysing Your Horse's Diet: A Practical First Step

One of the most effective things you can do is take a close, honest look at what your horse is actually eating each day. Many owners are surprised to find that starch levels are higher than they thought, forage intake is lower than ideal, or the overall diet is unbalanced in ways that contribute to gut problems.

Analysing your horse's diet can help you identify these gaps and make targeted changes. Even small adjustments — like switching to a lower-starch feed, adding alfalfa chaff before exercise, or ensuring forage lasts through the night — can make a meaningful difference to your horse's gastric health.

Key Takeaways

• Gastric ulcers are extremely common in horses and strongly linked to how we feed and manage them
• The horse's stomach produces acid 24/7 — forage is nature's buffer
• Prolonged fasting is the number one dietary risk factor
• High-starch, low-fibre diets increase ulcer risk significantly
• Feed forage first, feed forage often, and feed forage before exercise
• Alfalfa has beneficial acid-buffering properties
• Supplements don't replace good management — but veterinary treatment does work for diagnosed ulcers
• A balanced, forage-first diet is your best long-term defence against gastric ulcers

Gastric ulcers are a modern management problem — and the solution starts in the feed room. By aligning your horse's diet and routine with their natural digestive design, you can dramatically reduce ulcer risk and support lasting gut health.