Equine Gastric Ulcer Syndrome (EGUS)


The incidences and severity of cases of Equine Gastric Ulcer Syndrome (EGUS) are sadly, on the increase. Recent studies suggest that approximately 93% of thoroughbred, racehorses and endurance horses suffer from ulcers. We know that certain factors can contribute to all types of gastric ulcer formation, however, we also know that appropriate management, including diet can significantly reduce the prevalence of EGUS. In particular, reducing the total amount of starch fed each day, as well as the amount provided in each meal may significantly reduce EGUS prevalence. The Chestnut Horse Feeds range is focussed on high fibre, quality feeds and has multiple low starch options dependent on individual horses requirements.

Starting with the gastro-intestinal tract

In the natural environment horses spend 18 hours a day foraging, rarely fasting for more than 2–4 hours at a time. In response to these long periods chewing, saliva is generated which this helps to buffer the gastric acid that is secreted continuously into the stomach. These natural living conditions encourage the horse to move freely, which is also believed to assist with the normal movement of stomach contents through the gastrointestinal tract.

Modern management practices and intensive training programmes are believed to contribute to producing poorly buffered, acidic conditions in the stomach (Davidson and Harris, 2002, Andrews et al., 2006). This is thought to be associated with the high prevalence of gastrointestinal ulcers, particularly in more intensively managed horses.

Up until now, much of our diagnosis and traditional nutritional management of EGUS has concentrated on the upper, ‘squamous’ part of the horse’s stomach. Equines with ulcers present in this region are referred to as having, ‘Equine Squamous Gastric Disease’, ESGD; whilst equines with ulcers present in lower, ‘glandular’ section of the stomach constitute a distinct and different disease – ‘Equine Glandular Gastric Disease’, EGGD (Sykes et al., 2015a).

It’s important to draw a distinction between the two diseases as management of them differs. The nutritional strategies that we use for managing ESGD, such as ensuring ad-lib access to a high-fibre diet and reducing the amount of starch content levels in the ration, will not necessarily improve and reduce EGGD.

A number of contributory factors

Gastric ulcers occur when there is an imbalance between the factors that are protective to the gastric mucosa (such as mucus, bicarbonate, prostaglandins, mucosal blood flow and the epithelial restitution) and those that are ulcerogenic (including the presence of hydrochloric acid, volatile fatty acids (VFA), pepsin or bile acids) (Ethell et al., 2000; Lester, 2004). There are a number of factors that are thought to affect this balance.

1. Starch

The amount of starch fed per day, and per meal, in particular, is a very important factor.  There have been numerous studies showing the development of EGUS when equines are fed high starch content diets (Frank et al., 2006).

Diets that are high in starch tend to reflect a high cereal intake, which can also promote acid splashing (Argenzio, 1999, Lorenzo-Figueras and Merritt, 2002); in addition, cereals tend to be low in calcium and possibly, other buffering agents that might also be a factor of increased risk.

Reducing the amount of starch given each day as well as the amount provided in each meal, may reduce the likelihood of EGUS (Luthersson et al., 2009).

2. Feeding Straw as the only forage provided

Luthersson et al., 2009 also concluded that there was an increased likelihood of EGUS formation when straw was the only forage provided for horses.

Straw is low in protein and calcium and is thought not to provide buffering support. It can also be highly lignified and there is the potential therefore, that if not properly chewed, some irritation of the gastric mucosa could result from high levels of intake. It is also possible that the high lignin and silica nature of straw alters the fibrous mat in some way to increase the risk of the squamous epithelium being exposed to acidogenic factors (Luthersson et al., 2009).

3. Deprivation of food and water

Deprivation of food for repeated periods has been shown to cause gastric ulcers in the squamous non-glandular region (ESGD), but not the glandular region (Murray and Grady, 2002). Feed deprivation is associated with highly acidic conditions in the stomach. In addition, Luthersson et al., 2009 demonstrated that horses without access to water were more likely to have both EGUS and non-glandular ulcers (ESGD).

4. Transport

Transportation has been associated with an increased risk of EGUS (McClure et al., 2005) and may be associated with disturbances in feed as well as water intake.

5. Exercise

Several studies have demonstrated potential associations between EGUS and level of exercise (Murray et al., 1996, Orsini, 2000, Lester, 2004, Chameroy et al., 2006, Jonsson and Egenvall, 2006).

With squamous disease (ESGD), during a horse’s exercise, acid splashes up onto the squamous mucosa, so the longer spent exercising, the more damage that will be done. It is a cumulative effect, so that over a period of time, the amount of exercise done, at trot or above, will contribute to the risk of squamous disease.

For glandular disease (EGGD), although the risk factor is exercise, it’s the number of days spent exercising that matter.  In one study, show-jumping horses exercised six or seven times a week were found to be approximately three and a half times more likely to develop glandular disease than those exercising five days or less. Similar research focusing on racehorses who were exercised five days or more, versus those working four days or less, showed a ten-fold increase in the risk of glandular disease.  Rest days are therefore vitally important when managing EGGD.

6. Stress

Stress isn’t directly associated with squamous ulcers (ESGD), but it is with glandular (EGGD).  Indeed, we know that equines with glandular ulcers have a more pronounced response to stress testing, so effective management of the condition, involves giving them rest days as well as trying to reduce their daily stress levels.


It’s important to know which type of ulcers that your horse has, in order to manage the condition appropriately. Whilst squamous ulcers (ESGD), are undoubtedly, the most prevalent - the incidences of glandular ulcers (ESGD), are increasing. One recent report estimates that 30 – 50% of the domestic horse population are suffering with glandular ulcers, with environmentally stressed horses at high risk, even if they are in low-level work.

We know that certain factors can contribute to all gastric ulcer formation. In particular, reducing the total amount of starch fed each day, as well as the amount provided in each meal may significantly reduce EGUS prevalence. The Chestnut Horse Feeds range is focussed on high fibre, quality feeds and has multiple low starch options dependent on individual horses requirements.

Ensuring that water and food is available including an appropriate form of forage is important. Leaving horses without forage provision for more than 6 hours should be avoided (Luthersson et al., 2009); as well as a well-managed diet it is important to manage stressful situations and  exercise schedules ensuring appropriate levels of rest and recovery time.

If you would like more specific advice on the Chestnut Range for your horse or horses all you need to do is get in touch or complete our nutrition advice request form.