What South African horse owners need to know
If you’ve ever had a horse that was ‘just not right’ – a bit grumpy, slightly off their feed, not quite performing the way they should – there’s a very real chance gastric ulcers were part of the story. Equine Gastric Ulcer Syndrome, or EGUS, is one of the most prevalent conditions affecting domestic horses worldwide, and yet it remains widely misunderstood, underdiagnosed, and frequently mistreated. Here’s what the latest science tells us.
It’s common
Let’s start with a number that surprised us when doing our reading for the article. In Thoroughbred racehorses, the prevalence of squamous gastric ulcers starts at around 37% in untrained horses, and rises to between 80 and 100% within just two to three months of race training.
But, as we all know, ulcers aren’t just a racehorse problem. Sporthorses see rates of 17 to 58%, while pleasure horses aren’t far behind at 37 to 59%. Even endurance horses, whose management is often considered more natural, show a prevalence of 48% out of competition, rising to 66 to 93% during the competitive season, with elite horses most affected.
In short: if you own a horse in regular work, there is a real chance they have, or have had, gastric ulcers.
Two different diseases
This is where it gets important, and where a lot of confusion lies. EGUS is an umbrella term that actually covers two distinct conditions, and understanding the difference matters enormously for treatment.
Since the 1990s, the term Equine Gastric Ulcer Syndrome has been used to describe mucosal diseases of the equine stomach. More recently, specific nomenclature has been introduced to differentiate diseases affecting the squamous and glandular regions, as these vary widely in their nature and management.
Equine Squamous Gastric Disease (ESGD) affects the upper, non-glandular lining of the stomach – the pale, tissue-like region. This part of the stomach has no protective mucus lining, which makes it vulnerable to acid splash, particularly during exercise. Squamous ulcers are consistently associated with changes in appetite, slowed eating, and poor performance, with behavioural and attitude changes also occurring inconsistently.
Equine Glandular Gastric Disease (EGGD) affects the lower, glandular portion of the stomach – the pink region that normally produces both acid and the protective mucus that shields it. Glandular ulcers form slowly and reflect a failure of the mucus coat. Clinical signs are more variable and may or may not include changes in appetite or weight loss. The mechanism behind this mucus coat failure is not yet fully understood, but it is thought to involve physical, bacterial, and physiological factors.
Why does this distinction matter? Because the treatments are different, and confusing the two is one of the most common management mistakes made by well-meaning horse owners.
Recognising the signs
Horses with gastric ulcers may, but do not always, show clinical signs such as poor appetite, mild colic, discomfort during girthing, behavioural changes, and reduced performance.
The challenge is that these signs are non-specific. A horse that pins its ears when girthed could have ulcers, or back pain, a poorly fitting saddle, or a sore girth area. A horse that’s ‘a bit off’ could have ulcers, or be coming down with something else entirely. Clinical experience among practitioners shows many horses to be asymptomatic even in the face of severe gastric ulceration, and their symptoms are more readily overlooked.
This is why guesswork doesn’t really work here. Gastroscopy remains the only reliable method for the differential diagnosis of gastric ulceration in horses. A gastroscopy involves a long, flexible camera passed through the horse’s nostril and down into the stomach under standing sedation; it’s the only way to confirm ulcers, determine which type they are, and assess their severity.
What causes them?
The horse’s stomach is unusual in that it produces acid continuously, unlike humans, who produce acid mainly in response to food. Under natural circumstances, horses graze for up to 18 hours a day, which means there is almost always a steady stream of fibrous material buffering that acid. The problem begins when domestic management disrupts this natural pattern.
Key risk factors for squamous ulcers (ESGD) include:
- Forage deprivation, lack of access to water, high starch diets, pelleted feeds, straw feeding, intense exercise, changes in housing, transport, and lack of daily horse-to-horse contact.
- The commencement of training and resulting management changes, and diets high in concentrates and low in roughage, can result in the development of ulceration in as little as seven days.
For glandular ulcers (EGGD), the picture is more complex. Stress may play a role, with horses showing severe glandular ulcers being more stress-sensitive than controls. Research has also identified that individual trainers, metropolitan yard locations, lack of contact with other horses, solid partitions, and even playing talk radio can increase risk in racehorses. More recent research is also pointing toward the gut microbiome: horses with unclassified gastric disease have been shown to have lower gastric and faecal microbial diversity compared to healthy controls, opening up new avenues of investigation.
Treatment
One of the most important things about treating ulcers is that not all products are equal, and not all ulcers respond to the same treatment. The type of ulcer your horse has should dictate the treatment approach, and this is why a gastroscopy before treatment is so important.
Oral omeprazole – the gold standard for squamous ulcers
For squamous ulcers (ESGD), oral omeprazole remains the first-line treatment. The most reliable absorption occurs in horses that have been fasted and given the drug between 30 and 60 minutes before feeding, which is practically achievable for most owners by administering first thing in the morning. [Vet Times] Omeprazole is approved for a 28-day treatment course for ESGD; however, treatment of glandular gastric disease may require 45 to 60 days. [Merck Veterinary Manual]
A word of caution about generic and compounded oral products: Several studies have shown that the amount of active omeprazole in compounded products is lower than the label claims, and their ability to inhibit gastric acid production and resolve gastric ulcers has been variable [UC Davis School of Veterinary Medicine]. The apparent cost saving is often not a saving at all.
Injectable omeprazole, when oral isn’t working
Long-acting injectable omeprazole (administered intramuscularly, typically every five to seven days) is an increasingly used and well-supported alternative, particularly for horses that have failed to respond to oral treatment or where daily dosing compliance is difficult. 97% of horses treated with long-acting injectable omeprazole healed within 28 days, compared with 67% treated with oral omeprazole [PubMed Central] in one study. For glandular ulcers, injectable omeprazole was associated with healing rates of 80% versus 42% for oral omeprazole at four weeks. The key advantage is that it entirely bypasses the absorption variability that limits oral treatment in some horses.
The main practical consideration is injection site reactions. Across one study, 23% of injection sites reacted with oedema, heat, and pain, with reactions increasing with subsequent injections [EquiManagement]. These are generally self-limiting, but owners should monitor injection sites carefully and always have this treatment administered under veterinary supervision. In South Africa, this is a compounded product and must be sourced through a vet, not through informal channels.
Esomeprazole – an emerging alternative
Esomeprazole, the S-isomer of omeprazole and familiar to many as the human heartburn medication Nexium, is showing real promise as a second-line treatment. In a recent study, 85% of horses with squamous gastric disease treated with esomeprazole healed after 28 days, compared to 59% in the omeprazole group, with non-responders at just 5% versus 26% respectively [UK Vet Equine]. It is not yet licensed for equine use, but vets are increasingly considering it where omeprazole has failed.
Misoprostol – the preferred option for glandular ulcers
For glandular ulcers (EGGD) that are not responding adequately to omeprazole, misoprostol, a synthetic prostaglandin analogue, has become the preferred alternative. Research found that misoprostol-treated horses experienced superior healing over omeprazole/sucralfate-treated animals, with 72% versus 20% improvement in glandular lesions [The Horse]. It works by improving the stomach’s own protective mucus mechanisms rather than simply suppressing acid. An important safety note: misoprostol is not licensed for use in horses and has the potential to cause abortion in humans, so it must be handled with great caution; this is not a product to handle if you are pregnant or may be pregnant.
Sucralfate
Sucralfate is best understood as a combination partner, particularly in the treatment of glandular ulcers. It physically coats damaged mucosa, acting as a protective barrier while healing occurs. Combined omeprazole and sucralfate therapy for EGGD is superior to omeprazole alone [MDPI] though sucralfate used on its own does not resolve ulcers. If used alongside omeprazole, it should be given at least 30 minutes after the omeprazole dose.
A note on supplements and natural remedies
Many owners reach for supplements, and South African yards are no different, with aloe vera being particularly popular. The honest truth is that when formally tested, treatment with aloe vera was inferior to treatment with omeprazole [PubMed]. More broadly, aloe vera, corn oil, long-chain polyunsaturated fatty acids, pectin-lecithin complexes, and various herbal extracts have all been studied, with variable results [UK Vet Equine]. None has sufficient evidence to replace pharmaceutical treatment. Pectin-lecithin complexes show the most promise as a preventative adjunct, but if your horse has confirmed ulcers, supplements alone are not the answer.
For squamous ulcers (ESGD), the picture is relatively clear. Oral omeprazole remains the treatment of choice for the management of ESGD, but it is important to administer the drug to maximise efficacy. Specifically, the most reliable absorption appears to occur in horses that have been fasted and given the drug between 30 and 60 minutes prior to feeding, practically achievable for most owners by administering first thing in the morning.
Omeprazole is approved for a 28-day treatment course for ESGD; however, treatment of glandular gastric disease may require 45 to 60 days.
For glandular ulcers (EGGD), omeprazole alone is often insufficient. Multiple studies have shown that oral omeprazole is poorly effective for the treatment of EGGD and is not recommended as a sole therapy. Misoprostol, a prostaglandin analogue, has reasonably good efficacy for EGGD, and recent studies have shown it to be more effective than the combination of omeprazole and sucralfate.
Management: The real long-term solution
Treatment without management change is a recipe for recurrence. The evidence here is consistent and compelling.
Forage first. Dietary management should focus on maximising turnout or providing frequent access to forage. Concentrate feed should be minimised and split into multiple small meals.
Don’t exercise on an empty stomach. Horses should not be exercised on an empty stomach, as a fibre mat of food is important to buffer gastric pH and prevent acid splash injury. Feeding a small amount of hay or chaff 20-30 minutes before riding is a simple, effective step.
Turnout and social contact matter. Factors found to be protective against gastric disease include year-round open-front stabling, feeding hay through a hay net, keeping retired horses as companions, and using omeprazole during periods of stress.
Manage stress broadly. Competitions, travel, and changes in routine are all risk periods. A preventative dose of omeprazole is commercially available for use around transport or stressful events, and horses with a history of gastric ulceration may benefit from proactive treatment.
The bottom line
Gastric ulcers are not an inevitable cost of keeping horses in work; they are largely a consequence of management practices that conflict with the horse’s natural physiology. The good news is that with correct diagnosis, appropriate treatment, and thoughtful management changes, most ulcers heal within four weeks of treatment, and the prognosis for affected horses is generally good.
If you suspect your horse may have ulcers, resist the temptation to treat blindly. Speak to your vet about a gastroscopy; it’s the only way to know for certain what you’re dealing with, and to ensure the treatment you choose is actually the right one.
References
- Vokes J, Lovett A, Sykes B. Equine Gastric Ulcer Syndrome: An Update on Current Knowledge. Animals. 2023;13(7):1261. doi: 10.3390/ani13071261
- Sykes BW et al. European College of Equine Internal Medicine Consensus Statement — Equine Gastric Ulcer Syndrome in Adult Horses. Journal of Veterinary Internal Medicine. 2015;29(5):1288–1299. doi: 10.1111/jvim.13578
- Luthersson N et al. Risk Factors for Equine Gastric Ulcer Syndrome Incidence in Adult Icelandic Riding Horses. Animals. 2023;13(22):3512. doi: 10.3390/ani13223512
- Merck Veterinary Manual. Gastric Ulcers in Horses. Revised June 2022, Modified September 2024. merckvetmanual.com
- UC Davis Center for Equine Health. Equine Gastric Ulcer Syndrome. ceh.vetmed.ucdavis.edu