Understanding the Link Between Equine Gastric Ulcer Syndrome and Clinical Signs

This is the second article in our Snippets of Science series with Dr Sue Dyson, where we take a closer look at equine research and discover what the science really tells us.

In this article, Sue explores the complex relationship between Equine Gastric Ulcer Syndrome (EGUS) and the clinical signs owners commonly associate with it.

Why this research matters

Equine gastric ulcers are one of the most frequently discussed health issues in horses. Owners and riders often link ulcers to a range of performance and behaviour problems - from irritability and girthiness to weight loss and poor coat condition.

Are these signs really caused by ulcers? Or is something else going on?

A recent Dutch study set out to investigate exactly this and whether there’s a true, scientifically proven connection between owner-reported signs and the presence of gastric ulcers.

How the Research was Carried Out

Researchers examined 80 dressage horses competing nationally or internationally within the previous year. Each horse was referred for gastroscopy (a camera examination of the stomach) at the owner’s request.

Before the examination, owners completed a detailed questionnaire covering:

• Exercise routines and workload

• Feeding and management practices

• Medical history and any medications

• Observed clinical signs over the previous six months

The signs owners reported included:

• Weight loss or failure to gain weight despite appropriate diet and work

• Poor performance, such as lack of enthusiasm or exercise intolerance

• Behavioural changes, including irritability, stereotypes (crib biting, box walking), or antisocial behaviour

• Girth aversion – resistance when saddled or girthed

• Recurrent colic – more than one mild episode in two weeks

• Chronic diarrhoea – soft faeces or faecal staining on hind limbs

• Poor coat condition – dull or coarse coat without dietary changes

• Bruxism – grinding or clenching of teeth

What the gastroscopy revealed

Of the 80 horses examined:

• 55 horses (69%) had gastric ulcers

  • 38 had squamous lesions (including 21 with both squamous and glandular ulcers)

  • 17 had glandular lesions only

• 25 horses had no ulcers and served as the control group

The horses in this study were mainly Warmbloods, aged 4–18 years (median age 9), with a mix of geldings, mares, and stallions.

There were no significant differences between ulcer and control horses in:

• Age or sex

• Training status (61 were in regular work)

• Feeding practices

However, horses with ulcers were typically stabled for longer periods than controls.

What the data revealed

When researchers compared owner-reported signs with gastroscopy findings, none of the signs reliably predicted whether a horse had gastric ulcers.

In other words, a horse could show classic “ulcer symptoms” and have no ulcers at all, while others with confirmed ulcers showed no outward signs.

What happened after treatment

Horses diagnosed with ulcers were treated as follows:

• Squamous ulcers → Omeprazole (GastroGard®) at 4 mg/kg once daily for 3 weeks

• Glandular or combined ulcers → Omeprazole (4 mg/kg daily) plus sucralfate (12 mg/kg twice daily) for 4 weeks

Exercise regimes were maintained, and increased turnout was encouraged.

Only 19 horses underwent follow-up gastroscopy after treatment:

• 7 horses showed complete ulcer healing

• 12 horses still had ulcers despite treatment

Interestingly, the resolution of ulcers did not always match improvement in clinical signs:

• Of 11 horses whose girth aversion improved, 7 still had ulcers

• Of 6 horses whose performance improved, 4 still had ulcers

• Overall, the frequency of reported signs did not significantly change after treatment

What this means for horse owners

This study clearly shows that owner-reported clinical signs are not reliable indicators of whether a horse has gastric ulcers.

Even more importantly, ulcer healing doesn’t necessarily lead to improved behaviour or performance. This suggests that the true cause of the problem may lie elsewhere.

What might really be going on

Another recent publication [2] has highlighted that musculoskeletal pain, poor saddle fit, and oral lesions (often due to dental problems) can all cause discomfort and contribute to both ulcer development and behavioural issues.

In my own clinical experience, I’ve seen many horses treated with omeprazole for suspected ulcers, often multiple times - with no improvement. When these horses are fully investigated, we often find that pain or discomfort elsewhere in the body is the real problem.

Addressing these issues through proper diagnosis, treatment, and management - not only improves performance but can also lead to improvement or resolution of gastric ulcers.

The takeaway message

If your horse is performing below expectations, showing behavioural changes, or seems uncomfortable, don’t assume ulcers are the cause.

A full clinical work-up that includes a dental, saddle and lameness evaluation is essential to identify the true source of discomfort.

Treating ulcers without a proper diagnosis is often ineffective and expensive, and may delay finding and addressing the real issue.

Join us in 2026 for our transformative online course, “Movement and Behaviour" featuring the acclaimed Dr. Sue Dyson and her Ridden Horse Performance Checklist. This course is designed to empower you with the knowledge and skills needed to identify pain-related issues before they escalate.

References

1. Frippiat, T., Bonhomme, M., Dyson, S., Votion, D. (2025). Evaluation of owner-reported clinical signs and fecal occult blood tests as predictors of Equine Gastric Ulcer Syndrome in competition dressage horses. J. Vet. Int Med. 39(6), e70248. doi:10.1111/jvim.70248

2. Sykes, B., Lovett, A. (2025). Can all behavioral problems be blamed on equine gastric ulcer syndrome? Animals, 15, 306. doi:10.3390/ani15030306