We’re heading into the season that every equestrian dreads – winter. It’s not just the cold, dark nights that cause us concern, but also the knock-on effects on our horses, many of whom will have less time outside than they do during the rest of the year. One of the most common concerns we hear when horses spend more time stabled is ulcers – so, how can we help to reduce the risk and support their digestive health?
What are ulcers?
Equine gastric ulcer syndrome (EGUS) is characterised by ulceration in the foregut organs, namely the oesophagus, proximal (squamous) stomach, distular (glandular) stomach, or duodenum. Studies have shown that up to 90% of horses will be affected by ulcers in their lifetime!
The most common cases tend to be squamous and glandular, which are diagnosed via a gastroscopy. Generally, squamous ulcers are associated with acid exposure, whilst glandular are thought to occur when defence mechanisms in the glandular region of the stomach are compromised.
What causes ulcers?
There are several risk factors that have been identified with regards to EGUS, and it is important to understand the contributing factors in order to help reduce the risk. Diet plays an important role in both types of ulcer, with a high-starch, low-fibre diet being a significant risk factor. Feeding more than 2kg of starch per kg bodyweight per day has been associated with increased risk of EGUS, because the volatile fatty acids produced by fermentable carbohydrates can have a negative effect on gastric mucosa – the protective layer of the stomach. Increased periods of fasting because of a lack of foraging opportunity can also increase the risk of glandular ulcers.
Stable confinement has been cited as a significant risk factor in several studies, even when ad lib forage has been provided. One study found that 55% of dietary-induced squamous ulcers healed when horses were turned out to pasture, but, this is not to say that turnout will always remedy the issue.
Other risk factors include travelling and stress, which tend to go hand-in-hand with one another. Stressors such as temporary relocation, change of owner or caretaker, and higher levels of oxidative stress have all been associated with increased risk of EGUS.
Interestingly, most studies have failed to determine a link between stereotypical behaviours such as cribbing with the prevalence of EGUS, despite the anecdotal evidence associated with this.
Reducing the risk
There are several management practises that we can utilise to help reduce the risk of EGUS, particularly as we battle with the demands of winter.
1) Prioritise access to forage
Intermittent feeding means that there are prolonged periods when the stomach is empty between meals. Horses are natural grazers, spending up to 18 hours per day doing so. The continuous supply of forage means that the stomach can maintain gastric acid levels in the glandular region, and provide the squamous region with saliva to buffer the acidic pH.
For horses on restricted diets, or prone to metabolic conditions, slow feeders such as hay nets, hay balls, or similar, can help to prolong feeding time without oversupplying calories.
2) Provide constant access to water
Hydration is incredibly important for overall health, and research has shown that horses with limited access to water have a 2.5 times higher chance of developing EGUS compared to those with constant access.
Water consumption helps to reduce stomach acidity, and support gut motility, enabling food to pass through the gastrointestinal tract.
3) Avoid diets that are high in starch
Starch is a carbohydrate that produces volatile fatty acids (VFAs) when fermented. These VFAs can reduce the pH in the stomach and increase acidity, which in turn can increase the prevalence of EGUS. Try to ensure that the diet remains less than 20% starch for all horses, not just those who are prone to ulcers.
4) Choose high-quality forage
Ensuring constant access to high-quality forage is important for all aspects of your horse’s health and wellbeing. Providing adequate fibre keeps the gut working correctly and efficiently, and promotes microbial fermentation. It also means that horses are chewing properly, producing saliva and helping to control the acidic pH of the stomach.
5) Keep stress to a minimum
As mentioned previously, stress is a major risk factor for ulcer development. Try to reduce your horse’s stress levels by making management and dietary changes slowly. If you know your horse well, then you likely already know what their stressors are, so try to keep these to a minimum where possible.
6) Assess your exercise regime
Did you know that one study found that horses who are exercised 5 times a week or more had a 10.4 times higher likelihood of developing ulcers? Exercise causes changes in gastric motility and increases the hydrochloric acid content of the stomach. This means that when exercising, the stomach is more readily exposed to acids and more likely to experience irritation.
Be mindful of how often you’re exercising your horse, and try to ensure that they are not exercising on an empty stomach to ensure that it has as much protection as possible.
7) Increase turnout where possible
The more time horses are outside with free access to pasture, the better for their digestive systems. Even when forage is provided ad lib, stabled horses consume less than those out on pasture.
Generally, being turned out also helps to reduce stress and improve hydration levels, two other considerable risk factors for EGUS.
8) Consider targeted nutritional support
A suitable digestive supplement may help support the stomach’s natural protective mechanisms as part of a balanced diet and appropriate management routine. Supplements should complement, rather than replace, good feeding and management practices.
Take Away
EGUS is a prevalent and potentially serious condition, making prevention and early intervention important aspects of equine management. While no single approach can eliminate the risk, understanding the contributing factors and making appropriate changes to feeding, exercise and daily routine can help support digestive health. Alongside good management practices, targeted nutritional support may offer an additional layer of support. If you suspect your horse may be suffering from gastric ulcers, always seek veterinary advice to ensure they receive appropriate diagnosis and treatment.
References
Lensing, R., & Barton, A. K. (2025). Update on diagnosis, nonpharmacological treatment and prevention of Equine Gastric Ulcer Syndrome (EGUS). Equine Veterinary Education, 38(4), 206–219. https://doi.org/10.1111/eve.70037
M, A. F., R, B. B., B, E. S., A, C. N., & H, E. L. (2005). Gastric ulcers in horses 1. Journal of Animal Science, 83(suppl_13), E18–E21. https://doi.org/10.2527/2005.8313_supplE18x
van den Boom, R. (2022). Equine gastric ulcer syndrome in adult horses. The Veterinary Journal, 283–284(1), 105830. https://doi.org/10.1016/j.tvjl.2022.105830
Videla, R., & Andrews, F. M. (2009). New perspectives in equine gastric ulcer syndrome. Veterinary Clinics of North America: Equine Practice, 25(2), 283–301. https://doi.org/10.1016/j.cveq.2009.04.013
Witherow, B. (2023). Nutritional management of equine gastric ulcers. UK-Vet Equine, 7(5), 164–172. https://doi.org/10.12968/ukve.2023.7.5.164
Written by Anna Jones BSc (Hons) Equine Science - Customer Care & Marketing Associate