Equine Gastric Ulcer Syndrome (EGUS) in horses

Also known as ‘equine gastric ulcer syndrome’ or ‘EGUS’, gastric ulcers are a common problem for horses, with an estimated 1 in 3 equines affected by them. 

Sometimes, the symptoms of gastric ulcers are mistaken for behavioural issues or other health concerns – which can make EGUS challenging to spot in many horses.

In this article, we’re going to explore the causes, symptoms, and treatment options for gastric ulcers in horses, as well as discovering several ways you could prevent this condition…

• What are gastric ulcers in horses?
• Causes of gastric ulcers in horses.
• Symptoms of gastric ulcers in horses.
• Diagnosing gastric ulcers in horses.
• Treating gastric ulcers in horses.
• Preventing gastric ulcers in horses.

What are gastric ulcers in horses?

Gastric ulcers are lesions (wounds) within a horse’s stomach lining, due to damage caused by digestive acids, and can vary greatly in severity. 

Over time, horses evolved to trickle feed, meaning they eat small amounts throughout the day. For this reason, a horse’s stomach produces a steady flow of acid, even when they’re not eating. 

However, your horse’s stomach is small in comparison to their size, with the average horse’s stomach being roughly the size of a rugby ball! So, there’s an increased risk of digestive acids damaging a horse’s stomach lining when they’re exercised or fed in ways that don’t align with their natural grazing habits and behaviours.

Additionally, a horse’s stomach has an upper section and lower section. The upper section of a horse’s stomach doesn’t create digestive acid or mucus and is known as the ‘squamous mucosa’. This lack of protective mucus means the squamous mucosa is vulnerable to acid injury. Whereas the lower part of their stomach, the ‘glandular mucosa’, creates acid and enzymes to support digestion – along with a thick lining of mucus to protect their stomach wall. 

In line with these different parts of their stomach, there are two main types of gastric ulcers seen in horses:

• Squamous gastric ulcers – which occur in the upper part of the stomach. 
• Glandular gastric ulcers – that affect the lower two-thirds of the stomach.

Causes of gastric ulcers

Since a horse’s body is designed to graze for up to 18 hours a day, the forage they consume fills their stomach to manage levels of digestive acids naturally. As your horse chews, they also produce saliva that can help to decrease acidity. However, modern stable management practices and exercise routines can disrupt a horse’s natural digestive rhythm – resulting in a build-up of stomach acid. This extra acid can then splash around (especially during exercise) and damage the lining of a horse’s stomach, causing gastric ulcers to form.

It's thought that there’s a combination of risk factors that increase a horse’s chances of developing gastric ulcers, including:

• Not eating enough forage – horses are often expected to go without forage (hay, haylage, grass, etc.) for extended amounts of time, e.g. while they’re stabled overnight or being exercised.
• Stress – from travelling, intensive exercise routines (particularly fast work), limited opportunities to interact with other horses, lack of turnout, etc.
• Having a diet that’s high in concentrate feeds – which can cause a horse’s stomach to become more acidic, especially if they don’t have access to enough forage.
• Age – foals won’t have developed the protective layer in their stomachs yet, so those who experience stress (through illness or travelling, for example) could be at risk of gastric ulcers.
• Prolonged use of anti-inflammatory medication – the long-term use of some medications, like bute, is known to hinder the production of a protective layer of mucus in a horse’s stomach.

Equine squamous gastric disease (ESGD)

The primary cause of ESGD (occurring in the upper part of a horse’s stomach) is a low stomach pH (indicating acidity) because of an increased contact with acid. So, the risk factors linked specifically to ESGD tend to be feeding practices and stress levels.

Equine glandular gastric disease (EGGD)

While EGGD isn’t understood as well as ESGD, it’s believed the condition is primarily caused by the disruption of the protective lining of a horse’s stomach. For this reason, sensitivity to stress and exercising more than six times a week are considered risk factors for EGGD. 

Symptoms of gastric ulcers 

Unfortunately, not all horses will show symptoms of EGUS, or the signs can be so subtle that they’re mistaken for other conditions, which makes it difficult to detect. 

If your horse has gastric ulcers, they might develop the following symptoms:

• Signs of discomfort when doing up their girth, grooming, or rugging.
• Behavioural changes, e.g. bucking, rearing, crib biting, etc.
• Poor performance, e.g. struggling with ridden work, refusal to jump, etc.
• Loss of condition, e.g. dull coat, depressed demeanour, loss of topline, etc.
• Lack of appetite and/or weight loss.
• Mild or recurrent signs of colic.
• Chronic diarrhoea (particularly in foals). 

Please note: Many of these signs/symptoms may overlap with other conditions, like musculoskeletal pain or dental problems, so a full veterinary workup is recommended if any of these symptoms/signs persist.

Diagnosing gastric ulcers

To diagnose gastric ulcers, an equine vet would need to assess your horse’s symptoms alongside performing a gastroscopy. Your vet won’t be able to confirm whether your horse has gastric ulcers until they perform a gastroscopy, so it’s important to get this procedure done if you suspect EGUS.

A gastroscopy is a procedure that involves passing a long tube with a camera up through a horse’s nose and down their oesophagus (throat) into their stomach. This procedure is carried out while a horse is under sedation and allows the vet to find out whether there are any gastric ulcers present. 

For a clear view of the stomach lining, vets usually recommend that your horse isn’t fed for a set amount of time before the procedure, so their stomach is empty. 

If your horse is found to have gastric ulcers, a gastroscopy also helps your vet to determine the severity of those ulcers, so they can create a suitable treatment plan. 

Equine Gastric Ulcer Syndrome (EGUS) grading system

While there’s a grading system in place for ESGD (in the upper part of a horse’s stomach), the lesions of EGGD (lower part of the stomach) aren’t currently graded. Instead, the lesions of EGGD are described according to their location, distribution, and appearance. 

Here’s a basic guide to the grading system for horses with ESGD:

• Grade 0 – Stomach is normal, without reddening or lesions.
• Grade 1 – While the stomach lining is intact, there is some reddening.
• Grade 2 – Small lesions are present, could be single or multiple ulcers.
• Grade 3 – Large lesions are present, could be single or multiple ulcers.
• Grade 4 – Extensive lesions are present, with deep ulceration.

Please note: Since the above grading system is interpreted by equine vets according to their individual experience and training, there’s scope for inconsistency (i.e. two vets’ diagnoses may differ).

Treating gastric ulcers

The treatment of your horse’s gastric ulcers will depend on the type and severity of the lesions discovered during a gastroscopy. But some of the treatment options for gastric ulcers in horses can include:

• Reducing stress – by letting your horse enjoy more turnout in the company of other horses and providing hay while they’re travelling, for example.
• Adjusting their diet – to feed less concentrates and increase the amount of forage in your horse’s diet.
• Medication – like an equine-safe version of omeprazole, which acts as an acid inhibitor by slowing the production of stomach acid to allow ulcers to heal. For glandular ulcers, vets might also prescribe sucralfate or misoprostol, to act as a mucosal protectant.

Preventing gastric ulcers

Thankfully, there are ways to reduce the likelihood of your horse developing gastric ulcers, including:

• Ensuring your horse has 24/7 access to clean drinking water – to support a healthy digestive system.
• Making sure your horse has access to ad lib forage – where possible, provide plenty of hay or haylage while your horse is stabled. If they’re on a restricted diet, slow your horse’s eating speed by using 2-3 haynets (instead of one large haynet) or slow-feeder enrichment products (e.g. hay ball). By splitting their forage into multiple portions or using slow feeder products, you’re encouraging your horse to move around gently or mimic natural grazing behaviours.
• Adjusting your horse’s diet – upon veterinary advice, you could add a gut balancer to your horse’s food to support digestive health (especially during times of stress, e.g. travel).
• Allowing your horse to enjoy a more natural lifestyle – for example, increasing turnout time on good-quality pasture or feeding little and often.
• Feeding a small amount of hay or chaff 30 minutes before exercise – which could act as a ‘buffer’ in your horse’s stomach by preventing acid from splashing as they move.
• Monitoring your horse closely – in case they start to show any signs of gastric ulcers, like weight loss or aggression while you’re fastening their girth. 

Remember: Please contact an equine vet if you’re concerned your horse is at risk of or suffering from gastric ulcers.