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EGUS – Equine Gastric Ulcer Syndrome – What is it?


Posted on 9 August 2023
by jess

EGUS – Ulcers

Does your horse have ulcers? Which type, and would you know?

By Kate Hore – NAF

What are ulcers?

Ulcers are lesions that occur on the inside of the stomach lining as a result of disruption of the normal mucosal layer. They can form quickly and leave the individual with varying degrees of discomfort, from mild to severe. The condition is often referred to as EGUS, or Equine Gastric Ulceration Syndrome. EGUS is further divided into two distinct conditions, dependent on where the ulcers occur, and these are known as ESGD, Equine Squamous Gastric Disease, or EGGD, Equine Glandular Gastric Disease.


The equine stomach is clearly divided into two areas. Gastric ulcers can occur in both the squamous region, the upper section which is not protected from acid, and therefore vulnerable to mucosal damage through acid splash (ESGD); and the lower glandular region, which benefits from a protective layer designed to defend against natural stomach acid (EGGD). EGGD is caused by breakdown of the protective layer, often associated with the use of high doses or prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs), such as phenlybutazone (Ahmadnejad et al 2022, Bishop et al 2021). ESGD, commonly known as ‘splash-ulcers’ are the much more common of the two, though both are considered a risk in all horses and ponies (Lo Feudo et 2021).

What conditions can lead to them?

Horses evolved as trickle feeders, designed to always have feed in the stomach. Therefore disruption of the dietary intake of fibre, which can occur during exercise, travel or in stabled horses once they have eaten all available roughage, is a risk factor for EGUS. When the horse is not grazing, production of saliva is reduced, lowering the buffering protection of saliva in the stomach. Constant forage can also provide a gastric mat, which sits on the acid in the stomach, protecting the more vulnerable squamous region. However, recent research shows that constant pasture access alone is not enough to protect from ulcers, and similar levels of both ESGD and EGGD can be found even in feral horses, when on pasture without supplementary feed or forage, compared to domesticated horses (Luthersson N et al 2022).

Exercise, particularly intense or constant exercise, is also seen as a risk factor. We all enjoy a couple of days off work a week, at the weekend, and the same can be said for our horses. Research in both racing Thoroughbreds and show jumpers finds that working more than four or five days a week is a risk factor, with research showing the risk of EGGD is over ten times higher when horses are exercised more than five times a week (Sykes et al 2018, Rendle et al 2018). Intensity of exercise is also important. The risk of ESGD increases with the intensity of work, so don’t forget to give your horse some easier, relaxed, sessions as part of their training regime (Hewetson & Tallon 2021).

How are they identified?

While only your veterinary surgeon can give you a positive diagnosis of EGUS, certain changes in a horse’s behaviour and condition can be highly suggestive of both ESGD and EGGD.

Unfortunately, many of these clinical signs are also seen in other conditions, and are not definitive for ulcers. It is important to keep an open mind when assessing changes, and consider all eventualities.

Body Condition Scoring (BCS) is a useful, non-invasive, way of assessing condition and fat reserves. Links between BCS and EGUS have been found in racehorses, and this could be due to a number of factors including poor appetite, reduced nutrient uptake and low grade recurrent colic. However, care should be taken, as it is likely this only applies to elite equine athletes. A recent trial of over 200 non-athlete horses found no correlation between BCS and EGUS, and so it cannot be relied on as a definitive sign (Busechian et al 2022).

Poor performance is recognised in horses with EGUS, and although a causal link is not easily established, it is one of the most common signs. Sykes et al (2018) found that horses racing below their expectation were significantly more likely to have EGGD, whilst Varley et al (2019) report that the majority of horses with EGUS will have at least two of the common signs, with the two most common combinations being a) Poor performance and girthing pain, and b) Poor performance and behaviour changes.

Therefore it is important to be aware of subtle signs, and if all you see is your horse ‘pulling his face’ while girthing up, don’t ignore it – they could be telling you something significant. In fact, it is worth considering gastric health in your horse, even if you see no signs at all. Research often finds that, particularly for the more common ESGD, there may be no signs seen at all, and where signs are seen they don’t necessarily relate to severity (Hewetson and Tallon 2021). Consequently it is important to be aware of the risk of EGUS, even when we’re not seeing clear signs in our horses and ponies, as Table 1 shows how common EGUS is in a range of horse populations. This result is from one review paper, whilst other papers report even higher prevalence in some trials.

Population Range of Prevalence No. of papers reviewed
Thoroughbred racehorses 52 – 93% 6
Standardbred racehorses 44 – 88% 6
Endurance horses* 48 – 93% 2
Performance horses (non-racing)* 17 – 58% 5
Non-Performance horses 11 – 66% 5
Broodmares 67 – 76% 1
Donkeys and wild equids 22 – 64% 31
Foals** 7 – 97% 3

* The lower prevalence was measured during non-competitive season
** High prevalence post-weaning.
Hewetson & Tallon, 2021

What do you do if you suspect your horse may have ulcers?

Ulcers are definitively diagnosed by a veterinary surgeon using a flexible camera called a gastroscope to look inside the stomach. However, scoping is not an ideal approach for all, as it can be considered both invasive and, potentially, expensive. Making management and dietary changes are a good start, and recent research has shown a reduction in ulcer score can be seen through diet and management alone (Luthersson et al 2022). However, do have a good discussion with your Vet, who may help to advise on different courses of treatment, and management options.

How can you prevent them occurring?

In addition to providing a fibre and forage based diet, the right supplementary nutrition can be key in management of EGUS. Look for key nutrients.

Contact us for further information on dietary support of horses prone to gastric ulcers.

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