Equine Gastric Ulcer Syndrome (EGUS) is a common and often frustrating condition that can affect horses of all types and disciplines. It does not always present in obvious ways. Some horses become irritable or underperform, while others show only very subtle changes. Without gastroscopic examination, or scoping, it can be difficult to confirm, meaning some horses may go undiagnosed for extended periods.

Awareness of EGUS has increased significantly in recent years, along with research into how feeding and management influence its development. As a result, horse owners now have a much clearer understanding of how to reduce risk and support horses that may be affected.

Understanding the horse’s digestive system

To understand EGUS, it helps to consider how the horse is naturally designed to eat. Horses are trickle feeders, evolved to graze for the majority of the day on fibrous forage. This near-constant intake supports a healthy digestive system and helps maintain balance within the stomach.

As horses chew forage, they produce large amounts of saliva. This saliva plays an important role in buffering the acid that is continuously produced in the stomach. Unlike humans, horses produce stomach acid all the time, not just when they eat. This means that long periods without forage can leave the stomach lining exposed and more vulnerable to irritation.

Modern management can interrupt this natural pattern. Stabling, limited turnout, feeding set meals and including higher levels of concentrate feeds can all reduce chewing time and increase the gap between forage intake. Over time, this can create conditions that increase the risk of ulcer development.

Types of EGUS

Although EGUS is often used as a general term, it actually refers to two distinct conditions, each affecting a different area of the stomach and with slightly different underlying causes.

Equine Squamous Gastric Disease (ESGD)

This form affects the upper part of the stomach, which has little natural protection against acid. ESGD is commonly linked to feeding and management practices, particularly periods without forage, high-starch diets and intensive exercise.

When a horse exercises on an empty stomach, acid can move upwards and come into contact with this sensitive area. Repeated exposure over time can lead to irritation and ulceration.

Equine Glandular Gastric Disease (EGGD)

EGGD affects the lower part of the stomach. This region is designed to cope with acid, but it relies on a strong protective lining. When this defence is weakened, ulcers can develop.

Stress is thought to play a significant role in EGGD, alongside factors such as illness, medication use and changes in routine. This type of ulcer can sometimes be more complex to manage and may require a combination of veterinary treatment and careful management changes.

Which horses are affected?

It is now clear that EGUS is not limited to racehorses. While it remains common in Thoroughbreds in training, studies have shown that many other horses are affected.

Performance horses such as eventers, dressage horses, endurance horses and show jumpers are frequently at risk due to the demands of training, travel and competition. However, leisure horses can also be affected, particularly if their routine includes restricted forage, limited turnout or inconsistent feeding patterns.

Horses and ponies of any breed, age or workload can develop EGUS, which is why it is important for all owners to be aware of the condition.

Risk factors associated with EGUS

EGUS rarely has a single cause. It is usually the result of several risk factors coming together over time.

Low forage intake is one of the most significant contributors. Feeding less than around 1.5 percent of bodyweight as forage, or leaving horses without forage for more than four to six hours, increases risk.

High-starch diets and large concentrate meals can also contribute, as they reduce chewing time and may increase stomach acidity. Exercising a horse on an empty stomach is another well-recognised risk, as it allows acid to move more freely within the stomach.

Additional factors include stress from travel, competition or changes in routine, restricted access to water, use of certain medications such as NSAIDs, and social or environmental pressures.

When horses eat forage, they produce far more saliva than when eating concentrate feeds. This saliva contains natural buffers that help neutralise stomach acid, which highlights just how important fibre is in the diet.

Clinical signs

The signs of EGUS can vary widely and are not always easy to recognise. Some horses show clear signs of discomfort, while others display more subtle changes in behaviour or performance.

Changes in eating habits are often one of the first indicators. A horse may become fussy with feed, eat more slowly or leave part of its ration. Weight loss or difficulty maintaining condition can also be seen.

Behavioural changes are common. Horses may become more irritable, less willing to work or sensitive when being groomed or girthed. In ridden horses, a drop in performance or reluctance to go forward is often reported.

Some horses may also experience recurrent, mild episodes of colic, particularly where no other cause can be identified.

Nutritional management to reduce risk

Forage provision

Providing adequate forage is one of the most effective ways to support gastric health. Ideally, horses should have access to forage at all times to mimic natural grazing behaviour.

If forage needs to be controlled, for example in good-doers, it is still important not to drop below around 1.5 percent of bodyweight. Using small-holed haynets, double netting or offering forage in several locations can help extend eating time and encourage more natural feeding patterns.

Spreading forage across the day and overnight also helps reduce long periods without food, which are a key risk factor for ulcer development.

Managing starch and concentrates

Keeping starch intake within recommended levels is important. Feeding smaller meals more frequently can help reduce the impact on the stomach and improve overall digestion.

Where possible, choosing fibre-based feeds instead of high-starch concentrates can support a healthier digestive environment. If additional energy is needed, adding oil to the diet can increase calorie intake without increasing starch levels.

Supporting gastric health

Simple feeding practices can make a noticeable difference. Offering a small amount of forage, such as chaff or alfalfa, before exercise can help reduce acid movement within the stomach.

Alfalfa is often included in diets for horses prone to ulcers because it is naturally higher in calcium, which may help buffer stomach acid. Oil can also be added to support energy requirements in a more digestive-friendly way.

Ensuring constant access to fresh, clean water is equally important, as hydration plays a key role in maintaining normal digestive function.

Reducing stress

Management and routine have a strong influence on gastric health. Horses benefit from consistency, so keeping feeding, turnout and exercise routines as regular as possible can help reduce stress.

Turnout and social interaction are also valuable, as they allow horses to express natural behaviours. For performance horses, balancing training with adequate rest is important. Managing travel carefully and avoiding long periods without forage when away from home can also help reduce risk.

Additional support

Some horses may require more than management changes alone, particularly in more severe cases. Veterinary advice should always be sought where EGUS is suspected, as diagnosis and treatment plans can vary depending on the type and severity.

There are also supplements available that are designed to support gastric health. These can be useful alongside good feeding and management, but they should not replace the basics of a fibre-rich diet and consistent routine.

Final thoughts

EGUS is a complex but increasingly well understood condition. By aligning feeding and management practices more closely with the horse’s natural behaviour, the risk can be significantly reduced.

A consistent routine, a fibre-focused diet and careful attention to stress all play an important role. With early recognition and thoughtful management, many horses can remain comfortable, healthy and able to perform to their full potential.