Gastric Ulcers in Racehorses: Why Almost Every Horse in Training Has Them

If you keep a horse in hard training, the odds are not in your favour. Studies of Thoroughbreds in active training and racing put the prevalence of equine squamous gastric disease at 80 to 100 per cent, and Standardbreds are not far behind, with up to 87 per cent of horses in training affected. Gastric ulceration is not an unlucky complication of race training. It is close to the default state.

That figure surprises owners, because an ulcerated horse often looks normal. It eats, it works, it does not colic. What it does instead is subtle: it loses a little condition, it gets picky about grain, its coat dulls, it becomes resistant under saddle or slower off the gate. Horses racing below expectation have been found to be 3.7 times more likely to have glandular gastric disease.

Two different diseases in one stomach

The term “equine gastric ulcer syndrome” covers two conditions that happen in the same organ but behave differently, and treating them as one thing is the most common mistake in the field.

Equine squamous gastric disease (ESGD) affects the upper portion of the stomach. This part of the lining has no mucus layer and no bicarbonate defence — it is essentially unprotected tissue that evolution did not expect to meet acid. Under normal grazing it never does, because a raft of fibre and a steady flow of saliva keep acid in the lower stomach. Under race conditions everything changes: intense exercise raises abdominal pressure and pushes acidic contents upward against that unprotected wall, and the horse works on an empty or near-empty stomach.

Equine glandular gastric disease (EGGD) affects the lower, glandular portion — the part that produces acid and is built to withstand it. Here ulceration is less about acid exposure and more about a failure of the mucosal defences themselves. That is why EGGD responds less predictably to acid suppression alone and why it is more closely tied to stress, workload and management.

What actually causes it

The documented risk factors are remarkably consistent across studies:

• Exercise frequency. In Thoroughbred racehorses, working five or more days per week was associated with a 10.4-fold increase in the risk of glandular disease.
• High-concentrate diets. Grain ferments to volatile fatty acids and produces less saliva per kilo chewed than forage does.
• Intermittent feeding. A horse fed two or three bolus meals a day spends long stretches with an empty stomach and nothing to buffer acid. A grazing horse chews almost continuously.
• Stall confinement compared with pasture turnout.
• Transport, competition and social stress — including changes of neighbours in the barn.
• Concurrent illness, and treatment with non-steroidal anti-inflammatory drugs.

Read that list again and notice something: almost every item describes the normal life of a racing horse or camel. This is a management-created disease.

Guessing is not diagnosis

There is no blood test for gastric ulceration, no reliable field sign, and no way to grade severity from behaviour. Gastroscopy is the only reliable method of diagnosis. The procedure is quick, performed under light sedation, and needs the horse fasted for 8 to 12 hours beforehand so the stomach can actually be seen.

What gastroscopy gives you that guesswork cannot: whether the problem is squamous or glandular, where the lesions sit, how severe they are, and — on a repeat scope — whether the treatment worked. Given that squamous and glandular disease respond differently, that distinction changes the plan rather than merely confirming it.

It also protects you from the opposite error. Not every poor performer has ulcers, and a horse treated blindly for a month with an acid suppressant while the real problem is a sore hock has lost a month.

How acid suppression works

The treatment of choice for squamous disease is a proton pump inhibitor, most commonly omeprazole, which is approved for use in horses.

The mechanism matters for understanding why it works better than older approaches. Parietal cells in the stomach lining secrete hydrochloric acid through a hydrogen-potassium ATPase enzyme system — the proton pump. An antacid neutralises acid that has already been produced, and its effect lasts as long as the antacid does, which is not long. A proton pump inhibitor shuts down production at source. The stomach spends the day at a pH the mucosa can heal at, rather than dipping back into acid between doses.

Two points that owners routinely get wrong:

Treatment is measured in weeks, not days. Omeprazole treatment for equine gastric ulcer syndrome is based on oral administration for at least 28 days. Stopping when the horse starts eating better is stopping in the middle.

Glandular disease often needs more. Because EGGD is a defence failure rather than a pure acid problem, acid suppression alone frequently fails, and treatment typically combines it with agents that support the mucosal barrier, alongside genuine management change.

Recurrence is the real problem

Here is the part that gets skipped. A horse that heals on a 28-day course and then goes straight back to five-day weeks, grain meals and box rest will ulcerate again. Studies of recurrence in Thoroughbred racehorses after the withholding period are not encouraging on this point.

Treatment buys you a healed stomach. Only management keeps it healed:

• Forage before work. A small feed of hay or chaff before exercise puts a physical raft over the acid. It is free and it is one of the better-supported interventions there is.
• Shorten the empty stretches. More frequent, smaller feeds, or ad-lib forage, beat two large meals.
• Reduce concentrate where the work allows it, and replace calories with oil or fibre-based feeds where possible.
• Turnout. Time at pasture consistently comes out protective in the risk-factor studies.
• Rest days. The 10.4-fold risk figure attached to working five or more days a week is not a rounding error.
• Be deliberate about NSAIDs. They have a real place, but they are on the risk list; use them on veterinary direction rather than as routine cover.

Before a competition

Acid-suppressing medicines are regulated substances under most racing and competition rules, and withholding periods apply. Those periods differ between jurisdictions and between products, and getting them wrong costs a placing or worse. Check the rules that govern your specific competition, and plan the treatment course backwards from the race date with your veterinarian rather than forwards from today.

The short version

Gastric ulceration in performance horses is common enough to be assumed rather than suspected. It is invisible in the ways owners usually look for disease, and visible only in performance. It cannot be diagnosed without a scope, and it cannot be held at bay without changing how the animal is fed and worked. Medication heals the stomach; management is what keeps it healed.

This article is general information about a condition, not veterinary advice, a diagnosis or a treatment plan. Gastric ulceration should be confirmed by a veterinarian, and any medication, its dose and the length of the course must be determined by the veterinarian attending the individual animal.