Gastric ulcers are one of the most common health issues affecting our horses and ponies today. They can develop in horses of any age, breed or discipline, from happy hackers and family ponies through to elite competition horses. Left unmanaged, they can have a significant impact on comfort, behaviour, performance and overall wellbeing.
The encouraging news is that, with the right feeding and management, we can often reduce the risk of ulcers developing and help keep our horses feeling comfortable and well.
Understanding Stomach Acid
Stomach acid is often misunderstood, but it plays a vital role in our horses’ digestive systems. Unlike us, where acid production is mainly triggered by eating and chewing, horses produce stomach acid continuously, 24 hours a day, whether they are eating or not. This is because the equine digestive system has evolved for near constant grazing, with a steady intake of forage helping to maintain balance within the stomach.
In humans, even chewing alone can stimulate the release of stomach acid. This is why chewing gum on an empty stomach can sometimes lead to a rumbling or uncomfortable feeling, as the digestive system begins preparing for food that never arrives. Our horses, however, do not have this on off system. Their stomachs are always producing acid because, in a natural environment, they would rarely go for long periods without forage.
When everything is functioning as intended, stomach acid is highly beneficial. It helps break down feed so nutrients can be digested and absorbed efficiently, and it also acts as an important defence mechanism by helping to control harmful bacteria and pathogens that may be consumed with feed or water.
The issue is not the presence of acid itself, but the loss of balance. When long periods without forage, restricted turnout, travel, stress or intensive exercise reduce the buffering effect of saliva and fibre, acid is no longer being neutralised effectively. This allows it to come into contact with the more sensitive areas of the stomach lining, increasing the risk of irritation and, over time, ulcer development.
The goal is not to reduce acid production, but to support the horse’s natural digestive process by ensuring a steady supply of fibre, regular forage intake and appropriate nutritional support to help maintain stomach protection.
Understanding Risk in All Horses
Research into Equine Gastric Ulcer Syndrome (EGUS) has shown that ulcers are not limited to performance horses or those under obvious stress. They have been identified in foals, leisure horses and ponies, as well as in populations experiencing relatively low levels of training and travel-related pressure. This demonstrates that ulcer development is not solely linked to workload or competition environments.
While prevalence is generally higher in horses under more intensive management, evidence across different groups suggests that all horses and ponies carry some level of susceptibility. As a result, supporting the digestive system through consistent feeding and management is increasingly viewed as part of everyday care, rather than something only considered when clinical signs appear.
Prevalence of EGUS in our horses and ponies:
TB's in training: 80-100%
Performance horses: 50-90%
Foals: 25-50%
Non domesticated: 0-30%
Why Do Our Horses Develop Gastric Ulcers?
Our horses’ digestive systems are designed for almost continuous grazing. Every time they chew forage, they produce saliva, which helps naturally buffer stomach acid. At the same time, the stomach is producing acid around the clock, regardless of whether they are eating.
In a natural environment, this balance is maintained by long periods of grazing, often up to 16 hours a day, ensuring a steady flow of fibre and saliva to help protect the stomach lining.
Modern management can interrupt this natural pattern. Periods without forage, restricted turnout, stabling, travelling, competition environments, high-starch diets and general stress can all reduce the buffering effect within the stomach. This disruption allows acid to interact more directly with sensitive areas of the stomach lining, increasing the likelihood of irritation and ulcer formation.
The Two Types of Gastric Ulcers
Equine Gastric Ulcer Syndrome (EGUS) is generally divided into two main types.
Squamous ulcers (ESGD) occur in the upper part of the stomach. This area has very limited natural protection against acid, making it particularly vulnerable when acid splashes upwards during exercise or when the stomach is empty.
Glandular ulcers (EGGD) occur in the lower part of the stomach. This region normally produces protective mucus, but when this defence system is compromised through stress or other factors, the stomach lining becomes more susceptible to damage.
Signs Our Horses Could Have Gastric Ulcers
Signs can vary between individuals and are not always obvious. Common indicators include:
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Becoming fussy with feed or showing reduced appetite
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Difficulty maintaining weight or condition
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Changes in behaviour such as irritability, girthiness or reluctance to work
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Reduced performance or lack of enthusiasm
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Mild or recurring colic-type symptoms
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Dull coat or general lack of bloom
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Crib-biting or wind-sucking behaviours
Because these signs can overlap with other conditions, veterinary investigation is always important. Gastroscopy remains the most reliable way to confirm the presence of gastric ulcers and guide appropriate treatment.
Feeding for Better Gastric Health
Good feeding management is one of the most effective ways we can support our horses’ stomach health.
Make Forage the Foundation
Forage should always form the basis of the diet. Continuous or near-continuous access to grass, hay or haylage encourages chewing and saliva production, which helps naturally buffer stomach acid.
For stabled horses, providing forage little and often or using slow feeders helps reduce long gaps without fibre intake.
Keep Starch Levels Low
High-starch cereal feeds can increase acid production and may contribute to gastric irritation. Fibre-based feeds are generally more supportive of a healthy digestive environment.
Feed Before Exercise
A small fibre feed before exercise can help form a protective layer within the stomach and encourage saliva production, helping reduce acid splash during work.
Avoid Empty Stomachs
Because horses produce stomach acid continuously, long periods without forage allow acid to come into direct contact with the stomach lining. Maintaining regular fibre intake helps preserve the stomach’s natural protection.
Fresh Water Matters
Access to clean, fresh water is essential, particularly during travel, competition or warm weather, as dehydration can place additional strain on the digestive system.
Supporting Gastric Health with the Right Nutrition
Alongside good management, a well formulated supplement can provide valuable support for horses in work, those that travel frequently, or individuals that are more sensitive to digestive stress.
A quality product should support the whole digestive system, while also helping to maintain a healthy and resilient stomach environment.
Live yeast and prebiotic fibres such as Fructo-oligosaccharides (FOS) help maintain a stable hindgut environment by supporting beneficial bacteria and encouraging efficient fibre digestion. A healthy hindgut plays a key role in overall digestive stability and nutrient utilisation.
Pectin rich fibres help form a natural, gel like protective layer within the stomach environment. This viscous structure is thought to support the stomach lining by creating a more protective interface against gastric acid.
Phospholipids such as lecithin support the integrity of the gastric mucosal barrier and may assist in maintaining a healthy protective lining within the stomach. When combined with pectin, they are often used to support a more resilient gastric environment.
Soothing plant based ingredients such as marshmallow provide naturally occurring mucilage, helping to form a gentle, protective coating over the stomach lining and supporting overall gastric comfort.
L-glutamine plays an important role in gut health as a primary fuel source for enterocytes, the cells that line the digestive tract. It supports the natural maintenance and repair of the gastric lining, particularly in horses exposed to training, travel or dietary change.
MOS-based ingredients support gut immune function and microbial balance, helping to promote a more resilient digestive environment from within.
Magnesium glycinate contributes to neuromuscular relaxation and may help support horses prone to stress-related digestive tension, which is often a contributing factor in gastric sensitivity.
Together, these ingredients provide a multi-layered approach to digestive support, working across the stomach and hindgut to help maintain a healthy, resilient and comfortable digestive system.
Everyday Management Matters
Small, consistent changes can make a significant difference:
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Maximise turnout where possible
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Prioritise forage intake
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Feed fibre before exercise
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Avoid long gaps without food
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Keep routines consistent to reduce stress
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Choose fibre based, low starch feeds
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Support with a well formulated supplement
Murray, M.J., Schusser, G.F., Pipers, F.S. & Gross, S.J. (1996) Factors associated with gastric lesions in Thoroughbred racehorses. Equine Veterinary Journal, 28(5), pp.368–374.
Sykes, B.W., Hewetson, M., Hepburn, R.J., Luthersson, N. & Tamzali, Y. (2015) European College of Equine Internal Medicine consensus statement—Equine gastric ulcer syndrome in adult horses. Journal of Veterinary Internal Medicine, 29(5), pp.1288–1299.
Andrews, F.M. & Nadeau, J.A. (1999) Clinical syndromes of gastric ulceration in foals and mature horses. Equine Veterinary Journal, 31(S2), pp.30–33.
Vatistas, N.J., Snyder, J.R., Carlson, G., Johnson, B., Arthur, R.M. & Thurmond, M. et al. (1999) Cross-sectional study of gastric ulcers of the squamous mucosa in Thoroughbred racehorses. Equine Veterinary Journal, 31(1), pp.34–39.