Gastric Ulcers in Horses: Diet & Feeding Tips

Gastric Ulcers in Horses: Why Diet and Feeding Management Matter

Gastric ulcers are one of the most common — and most misunderstood — health problems in horses. Studies suggest that up to 90% of racehorses and 60% of performance horses have some degree of gastric ulceration. Even leisure horses and those living out at pasture are not immune.

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

Understanding the Horse's Stomach

To understand gastric ulcers, you first need to understand a little about how the equine stomach is designed.

The horse's stomach is relatively small for its body size — roughly the size of a rugby ball, holding around 8–15 litres. It's divided into two distinct regions:

The Squamous Region (Upper Portion)

This is the non-glandular lining at the top of the stomach. It has no protective mucus coating and is essentially defenceless against stomach acid. This is where the majority of gastric ulcers occur — a condition formally known as Equine Squamous Gastric Disease (ESGD).

The Glandular Region (Lower Portion)

This is the acid-producing part of the stomach. It has a thick mucus layer and bicarbonate secretion to protect itself from the acid it produces. Ulcers can still develop here — known as Equine Glandular Gastric Disease (EGGD) — but the causes and risk factors are somewhat different and less well understood.

Here's the critical point: horses produce stomach acid continuously, 24 hours a day, whether they are eating or not. This is because the horse evolved to be a trickle feeder, grazing for 16–18 hours a day. The constant flow of saliva produced during chewing — which contains bicarbonate, a natural acid buffer — was designed to neutralise this constant acid production.

When we change the horse's natural feeding pattern, we disrupt this finely tuned system.

How Diet and Feeding Cause Gastric Ulcers

Several dietary and management factors directly contribute to ulcer development:

Prolonged Periods Without Forage

This is the single biggest dietary risk factor. When a horse goes without food for extended periods — even as little as four to six hours — acid accumulates in the stomach with no saliva buffer to neutralise it. The acid splashes onto the unprotected squamous lining, causing irritation and eventually ulceration.

This commonly happens when:

• Horses are given two large meals a day with nothing in between
• Hay nets run out overnight
• Horses are stabled without ad-lib forage
• Horses are fasted before exercise, travel, or veterinary procedures

High-Starch, High-Grain Diets

Feeding large amounts of cereal-based concentrates (such as oats, barley, or high-starch mixes) increases the risk of ulcers in several ways:

• Rapid fermentation of starch in the stomach produces volatile fatty acids (VFAs), which damage the squamous lining, especially in an acidic environment.
• Large concentrate meals pass through the stomach quickly, leaving it empty sooner and allowing acid to build up.
• Less chewing time means less saliva production compared to fibre-based feeds.

Research has shown that horses fed diets containing more than 1g of starch per kg of bodyweight per meal are at significantly higher risk of gastric ulcers.

Insufficient Forage in the Overall Diet

Forage — hay, haylage, or pasture — forms a fibrous mat in the stomach that physically prevents acid from splashing onto the upper squamous region. When forage makes up too small a proportion of the diet, this protective mat is diminished.

As a general rule, forage should make up at least 1.5% of your horse's bodyweight per day in dry matter — and ideally more.

Type of Forage

Not all forage is equal when it comes to ulcer prevention. Alfalfa (lucerne) has been shown to have a particular buffering effect on stomach acid, likely due to its higher protein and calcium content. Including some alfalfa in the diet — as chaff or hay — can be a useful strategy for ulcer-prone horses.

Straw, on the other hand, while useful for extending eating time, has been associated with an increased risk of glandular ulcers (EGGD) when used as the sole or predominant forage source. It provides little buffering capacity and can irritate the stomach lining.

Water Availability

Dehydration and limited water access can also contribute to ulcer risk. Adequate water intake supports healthy mucus production in the glandular region and overall digestive function. Always ensure your horse has access to clean, fresh water.

Feeding Management Strategies to Prevent Gastric Ulcers

Now let's turn to practical strategies you can implement today.

1. Provide Ad-Lib or Frequent Forage Access

The most important change you can make is to ensure your horse is never left for long periods without something to chew. Aim for:

• Ad-lib hay or haylage whenever possible
• If you need to restrict intake (for overweight horses, for example), use small-holed hay nets, double-netting, or trickle feeders to slow consumption rather than limiting total access time
• Ensure forage is available overnight — this is when the longest fasting periods typically occur

2. Feed Forage Before Exercise

Exercise on an empty stomach is a significant ulcer risk. When the horse moves — especially at trot and canter — acid splashes up onto the unprotected squamous region. A handful of chaff or a small amount of hay 20–30 minutes before exercise helps create a fibrous buffer.

Alfalfa chaff is particularly useful here as a pre-exercise snack due to its buffering properties.

3. Reduce Starch Intake

Keep starch levels below 1g per kg of bodyweight per meal and below 2g per kg of bodyweight per day where possible. This means:

• Choosing fibre-based feeds over cereal-based mixes or sweetfeeds
• Replacing grain calories with oil (vegetable oil, linseed oil) or super fibres (beet pulp, soy hulls) for horses in hard work
• Splitting any concentrate feeds into three or more small meals per day rather than two large ones

If you're not sure how much starch your horse is currently consuming, analysing your horse's diet is a practical first step. A proper diet analysis will show you exactly where the starch is coming from and help you make targeted changes.

4. Include Alfalfa in the Diet

Adding alfalfa chaff or alfalfa hay can provide additional buffering against stomach acid. Even a double handful of alfalfa chaff before each ride or mixed into concentrate feeds can be beneficial. Research has demonstrated measurable reductions in ulcer severity when alfalfa is included in the diet.

5. Allow Pasture Turnout

Turnout on grass allows the horse to engage in its natural trickle-feeding behaviour. Horses at pasture have consistently lower ulcer prevalence than stabled horses. Even a few hours of daily turnout can make a meaningful difference.

6. Manage Meal Sizes and Frequency

If your horse needs hard feed:

• Feed little and often — three or four small meals rather than one or two large ones
• Never feed more than 0.5 kg of concentrates per 100 kg of bodyweight in a single meal
• Always feed forage before or alongside concentrates, never concentrates on an empty stomach

7. Minimise Stress

While not strictly a dietary factor, stress is closely linked to feeding management. Transport, competition, social isolation, and changes in routine all increase ulcer risk. During stressful periods, pay extra attention to forage availability and consider reducing concentrate feeds.

Recognising the Signs of Gastric Ulcers

Gastric ulcers can be subtle. Common signs include:

• Poor appetite or reluctance to finish hard feed
• Weight loss or difficulty maintaining condition
• Dull coat
• Mild, recurring colic — especially after feeding
• Behavioural changes — girthiness, grumpiness, reluctance to work
• Poor performance
• Loose droppings

If you suspect ulcers, the only definitive diagnosis is gastroscopy — a procedure where a vet passes a camera into the stomach. Don't rely on symptoms alone, as many conditions can mimic ulcer signs.

Can Diet Alone Treat Existing Ulcers?

It's important to be honest here: diet changes alone are unlikely to heal established ulcers, particularly moderate to severe ones. The gold-standard treatment for squamous ulcers is omeprazole, a proton pump inhibitor that reduces acid production and allows the stomach lining to heal.

However, dietary and management changes are essential alongside medical treatment. Without addressing the underlying feeding practices that caused the ulcers, they will almost certainly recur once medication is stopped. Studies have shown relapse rates as high as 80% when management isn't changed.

For mild squamous ulcers and for long-term prevention, dietary management is the single most important factor you can control.

A Quick-Reference Feeding Checklist for Ulcer Prevention

Final Thoughts

Gastric ulcers are a man-made problem in many ways. The modern management of horses — stabling, meal-feeding, high-grain diets, and intense exercise — goes against nearly everything the equine digestive system evolved to handle.

The encouraging reality is that simple, practical changes to how and what you feed can dramatically reduce your horse's ulcer risk. Focus on fibre first, keep the stomach buffered, reduce starch, and mimic natural feeding patterns as closely as your management setup allows.

Your horse's stomach will thank you for it.