Can Donkeys Get Stomach Ulcers?

By Dr Duncan Houston

Stomach ulcers are usually talked about as a performance-horse problem. Racehorses, sport horses, travel stress, hard work, high-grain diets, limited turnout. That is the classic picture.

But donkeys can get gastric ulcers too, and the worrying part is that they may show very little on the outside.

A donkey with ulcers may not look dramatic. They may not roll, sweat, paw, or behave like a colicky horse. They may simply seem dull, eat less, lose condition, stand apart from the group, or look “not quite right.” With donkeys, that quiet change matters.

Quick Answer

Yes, donkeys can get stomach ulcers. In one gastroscopy study of 39 live donkeys with no obvious signs of gastric ulcer disease, 51.3% had gastric lesions, and 95% of affected donkeys had lesions in the non-glandular squamous region of the stomach. (pubblicazioni.unicam.it)

This means ulcers should not be ruled out just because a donkey is not athletic, not stabled, or not showing dramatic signs. If a donkey is dull, off feed, losing weight, showing mild colic signs, or repeatedly “not right,” a vet check is sensible, and urgent care is needed if appetite drops significantly.

What Are Stomach Ulcers in Donkeys?

Gastric ulcers are sores or erosions in the lining of the stomach. In equids, the stomach has two main regions that matter clinically:

In horses, modern terminology separates gastric disease into equine squamous gastric disease and equine glandular gastric disease because these two regions behave differently. Their causes, treatment response, and prevention are not identical. (researchportal.scu.edu.au)

Donkeys are not just “small horses with better ears.” Their behaviour, metabolism, feeding needs, and disease presentation can differ. That is exactly why gastric ulcers in donkeys deserve their own attention.

What Did the Donkey Ulcer Study Find?

The key study looked at 39 live adult donkeys using gastroscopy. These were not racehorses. They were not performance animals. They were not showing obvious signs of equine gastric ulcer syndrome.

The findings were still striking:

The study also found Gasterophilus intestinalis larvae in all animals, but that does not prove the larvae caused the ulcers. The important clinical message is simpler: donkeys can have gastric ulcers without obvious outward signs. (pubblicazioni.unicam.it)

That changes how we should think about a donkey that is dull, losing weight, eating poorly, or having recurring mild colic signs.

Are Donkey Ulcers Rare?

No. They appear to be more common than many owners expect.

A separate necropsy survey from The Donkey Sanctuary found gastric ulceration in 41% of donkeys studied over a two-year period. The donkeys were not working, had a sedentary lifestyle, and had access to forage, so they were not the classic high-risk performance-horse group. (Semantic Scholar)

That same study found cereal-based concentrate diets, hyperlipaemia, and kidney disease were associated with higher ulcer risk. Donkeys fed cereal-based diets had a higher prevalence of gastric ulceration than those fed fibre-based concentrates or forage-only diets. (Semantic Scholar)

So, no, ulcers in donkeys are not just a theoretical problem. They are real, and they are often easy to miss.

Why Can a Calm Donkey Have Ulcers?

This is the important part. The horse explanation does not fully fit.

In performance horses, squamous ulcers are often linked to acid exposure, exercise, feeding gaps, stress, and management. UC Davis explains that horses produce stomach acid continuously, and that long periods without feed can leave acid unbuffered. During exercise, acidic stomach contents can splash onto the vulnerable upper stomach. (ceh.vetmed.ucdavis.edu)

But many donkeys with ulcers are not exercising intensely. That suggests other factors may be involved.

Possible contributors include:

• High-cereal or high-starch feeding

• Periods of reduced appetite

• Underlying illness

• Dental disease limiting forage intake

• Hyperlipaemia or metabolic stress

• Kidney disease

• Parasites or bot larvae

• Pain elsewhere in the body

• Social or environmental stress

• Long gaps without appropriate fibre intake

• Donkey-specific physiology that is not yet fully understood

The honest answer is that donkey gastric ulcers are likely multifactorial. In practice, the mistake is assuming a quiet, non-working donkey is automatically low risk.

What Signs Should Owners Watch For?

Donkeys are very good at under-reporting illness. Unfortunately, they are not being stoic for our convenience. They are often genuinely unwell before we realise how serious things are.

Possible signs of gastric ulcers in donkeys include:

One equine veterinary source notes that donkeys with colic may show less dramatic signs than horses, and that owners may simply report a donkey as “dull” or “off-feed.” It also describes sham eating, where an inappetent donkey appears to chew or swallow but is not actually taking in enough food. (avonridgeequine.com.au)

That is why appetite changes in donkeys deserve more respect than they sometimes get.

How Worried Should You Be?

Not every ulcer sign is an emergency, but donkeys can deteriorate quickly if they stop eating. The concern is not only the ulcer itself. The concern is also dehydration, colic, hyperlipaemia, and the underlying disease that may be driving the problem.

A dull donkey should not be brushed off. Buckingham Equine Vets notes that dullness and depression may be the only signs of serious disease in donkeys, including life-threatening conditions, and that any dull donkey should be promptly examined by a vet to help prevent hyperlipaemia. (Buckingham Equine Vets)

When Is This an Emergency?

Call a vet urgently if your donkey:

• Stops eating or eats much less than normal

• Appears dull, depressed, weak, or isolated

• Shows colic signs, even mild ones

• Lies down more than usual

• Rolls, paws, sweats, or breathes quickly

• Has reduced or absent manure output

• Has pale, brick-red, purple, or muddy gums

• Has a swollen or painful abdomen

• Loses weight rapidly

• Seems dehydrated

• Is pregnant, lactating, obese, elderly, or already unwell

Donkeys are particularly vulnerable to hyperlipaemia, a serious metabolic condition linked to reduced intake and negative energy balance. A 2024 review describes hyperlipaemia as one of the most common metabolic diseases in donkeys, with non-specific signs such as dullness, inappetence, and behavioural change. (MDPI)

That means “off feed” in a donkey is not a casual wait-and-see situation. It can become serious quickly.

How Are Stomach Ulcers Diagnosed in Donkeys?

The best way to diagnose gastric ulcers is gastroscopy. This means passing a long endoscope into the stomach so the vet can directly examine the stomach lining.

Clinical signs can raise suspicion, but they cannot confirm ulcers. UC Davis states that gastric ulcers can only be definitively diagnosed by gastroscopy, which allows the vet to see the stomach surface directly. (ceh.vetmed.ucdavis.edu)

In donkeys, the vet may also want to check for other problems at the same time, especially because signs are often vague.

Useful investigations may include:

• Full physical exam

• Dental exam

• Body condition assessment

• Manure and parasite evaluation

• Blood triglycerides to assess hyperlipaemia risk

• Kidney and liver blood markers

• Inflammatory markers

• Ultrasound if colic or other abdominal disease is suspected

• Gastroscopy where appropriate and safe

Gastroscopy usually requires fasting, but fasting a donkey must be planned carefully. Sick, obese, pregnant, lactating, or inappetent donkeys are at higher risk of metabolic complications, so this is not something to improvise at home.

What Else Can Look Like Ulcers?

This is where veterinary reasoning matters. A donkey that is dull, eating poorly, or losing weight may have ulcers, but ulcers are not the only possibility.

Important rule-outs include:

• Dental disease

• Colic

• Impaction

• Parasite burden

• Liver disease

• Kidney disease

• Hyperlipaemia

• Laminitis pain

• Pituitary pars intermedia dysfunction, also called PPID

• Insulin dysregulation or donkey metabolic syndrome

• Poor-quality forage

• Social stress or bullying

• Chronic pain

• Respiratory disease

• Infection

• Pregnancy or lactation-related metabolic strain

This is why the goal is not simply to “try ulcer treatment.” The goal is to work out why the donkey is unwell.

Can Donkeys Be Treated With Omeprazole?

Omeprazole is commonly used to reduce stomach acid in equids, but donkey treatment should be vet-directed.

In the United States, GastroGard® is labelled for horses and foals 4 weeks of age and older, and the labelled horse treatment dose is once daily for 4 weeks at 4 mg/kg. (DailyMed)

There is also a current product update: the FDA approved Gastrobim as the first generic omeprazole oral paste for treatment and prevention of gastric ulcer recurrence in horses and foals 4 weeks of age and older on April 6, 2026. (U.S. Food and Drug Administration)

The key wording is horses and foals. These products are not simply “donkey-labelled” just because donkeys are equids. Donkey dosing, treatment length, monitoring, and safety decisions should be made by a veterinarian.

This matters because a 2024 review notes that while many equine treatment protocols are applied to donkeys, donkey-specific pharmacological information is limited for many drugs. (MDPI)

In plain English: do not dose a donkey as though it is just a smaller horse.

What Should You Do Next?

1. Take appetite changes seriously

If your donkey is eating less, do not wait days to see what happens. Check whether they are truly eating or only mouthing food.

Watch hay piles, droppings, chewing behaviour, and whether the donkey is actually swallowing normal amounts.

2. Call your vet if signs persist or worsen

A donkey that is dull, losing weight, mildly colicky, or repeatedly off feed needs a veterinary assessment. If the donkey stops eating, becomes very dull, or shows colic signs, treat it as urgent.

3. Do not give NSAIDs casually

Do not give phenylbutazone, flunixin, or other anti-inflammatory drugs without veterinary advice. Pain relief may be needed, but the vet needs to consider hydration, kidney function, gut disease, ulcer risk, and the donkey’s overall condition.

4. Ask whether ulcers belong on the problem list

If your donkey has vague recurrent signs, ask your vet whether gastric ulcers are worth investigating. This is especially important if other tests are unrewarding, signs recur, or the donkey has risk factors such as illness, weight loss, metabolic disease, high-cereal feeding, or reduced intake.

5. Consider gastroscopy where appropriate

Gastroscopy is the clearest way to know whether ulcers are present and where they are. It can prevent weeks of guessing.

6. Review the whole management picture

Treatment is only one part of the plan. Diet, forage access, dental health, parasites, water, stress, pain, and metabolic disease all matter.

Common Mistakes Owners Make

Assuming donkeys do not get ulcers

They do. The studies are clear enough that ulcers should be considered in dull, off-feed, colicky, or poor-doing donkeys.

Waiting because the signs are subtle

Subtle does not mean safe. In donkeys, subtle may be the only warning you get.

Mistaking sham eating for real eating

A donkey may look as though it is nibbling, chewing, or participating at feed time while actually taking in very little.

Treating the donkey like a small horse

This is a classic trap. Donkeys have different nutritional needs, metabolic risks, and sometimes different drug considerations.

Using high-cereal feeds to “build condition”

Cereal-based diets were associated with increased ulcer risk in the Donkey Sanctuary necropsy survey. If a donkey needs extra calories, fibre-based options are usually a safer starting point than grain-heavy feeds. (Semantic Scholar)

Trying supplements before diagnosis

Supplements may support gut health in some cases, but they should not replace a vet exam, dental check, blood work, or gastroscopy when a donkey is unwell.

How To Reduce Ulcer Risk in Donkeys

You cannot prevent every ulcer, but you can reduce the risk.

Feed like a donkey, not like a sport horse

Most donkeys do best on a high-fibre, low-energy, low-sugar diet. Suitable straw, moderate-quality hay, controlled grazing, and appropriate fibre-based feeds are usually safer than rich pasture or cereal-heavy concentrates.

Avon Ridge Equine Veterinary Services notes that donkeys should be fed a diet high in fibre and low in energy and sugar, supported by an environment that allows browsing, movement, and normal behaviours. (avonridgeequine.com.au)

Avoid long gaps without suitable fibre

Donkeys are trickle feeders. Their stomachs and behaviour suit frequent small amounts of fibrous feed, not long empty periods followed by rich meals.

Keep dental care up to date

Dental disease can reduce forage intake, cause weight loss, and contribute to poor condition. Older donkeys are especially vulnerable.

Monitor weight carefully

Obesity is common in donkeys and increases risk for metabolic disease. Sudden or severe feed restriction can also be dangerous because of hyperlipaemia risk. Weight loss plans should be gradual and vet-guided.

Use fibre-based calories when extra feed is needed

If a thin or older donkey needs support, ask your vet or nutritionist about fibre-based options rather than cereal-based feeds.

Control parasites thoughtfully

Parasite management should be based on veterinary advice, fecal testing, local risk, and appropriate treatment. The live-donkey gastroscopy study found Gasterophilus larvae in all animals, but the exact role of parasites in ulcer development remains uncertain. (pubblicazioni.unicam.it)

Reduce stress and social disruption

Donkeys are highly bonded animals. Separation, loss of a companion, transport, yard changes, bullying, pain, and illness can all affect appetite and health.

Check appetite every day

For donkeys, daily appetite monitoring is not just routine care. It is early warning medicine.

Will a Donkey With Ulcers Be Okay?

Many donkeys can do well if ulcers are identified early, treated properly, and the underlying triggers are addressed.

The outlook becomes more guarded when the donkey is not eating, has hyperlipaemia, has kidney or liver disease, has severe colic signs, is elderly and frail, or has ongoing disease that has not been diagnosed.

The practical takeaway is this: do not wait for dramatic signs. With donkeys, the quiet ones can be the sick ones.

FAQs About Stomach Ulcers in Donkeys

Can donkeys have stomach ulcers with no symptoms?

Yes. In the live-donkey gastroscopy study, none of the donkeys showed clinical signs of gastric ulcer syndrome, yet 51.3% had gastric lesions. (pubblicazioni.unicam.it)

Are donkey ulcers caused by exercise like in racehorses?

Not always. Exercise and acid splash are important in performance horses, but ulcers have been found in non-working donkeys too. In donkeys, diet, illness, reduced appetite, metabolic stress, parasites, and other factors may all play a role.

How do I know if my donkey has ulcers?

You cannot confirm ulcers by behaviour alone. Dullness, reduced appetite, weight loss, mild colic, and poor condition can raise suspicion, but gastroscopy is the definitive test.

Can I give GastroGard® to my donkey?

Only under veterinary direction. GastroGard® is labelled for horses and foals, and donkeys should not be dosed casually as small horses. Your vet needs to calculate the dose and decide whether omeprazole is appropriate.

Is a dull donkey an emergency?

It can be. Dullness may be the only sign of serious illness in donkeys, and reduced appetite can lead to hyperlipaemia. A dull or off-feed donkey should be assessed promptly, especially if signs are new, worsening, or accompanied by colic signs.

Final Thoughts

Stomach ulcers in donkeys are easy to underestimate because donkeys rarely make a fuss. That is exactly why owners and vets need to pay attention.

A calm donkey can still have ulcers. A grazing donkey can still have ulcers. A non-working donkey can still have ulcers. The research shows that gastric lesions are not limited to high-performance horses.

The safest mindset is simple: when a donkey is dull, eating less, losing weight, or showing recurrent mild colic signs, ulcers should be on the list, but not the only thing on the list. A good plan looks at the whole donkey: stomach, teeth, diet, parasites, pain, kidneys, liver, metabolism, stress, and environment.

Donkeys are hardy, but they are not invincible. They are just quieter about being unwell.

If you are unsure whether your donkey’s signs could be ulcers, colic, hyperlipaemia, or something else, ASK A VET™ can help you work through the safest next step.