Gastric ulcers in horses: the important facts every owner needs to know

  • A white check mark
    This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.
  • Gastric ulcers in horses (also known as equine gastric ulcer syndrome or EGUS) are a common problem, particular among racehorses and elite competition horses, although horses of all ages and types can have them, particularly if they have limited access to forage. Foals are also susceptible, not least because they have relatively thin gastric mucosa.

    Squamous gastric ulcers occur when the digestive stomach acids come in to contact with the upper part of the stomach lining, which does not have the same protective layer as the lower part of the stomach. Glandular ulcers affect the bottom two-thirds of the stomach, which is submerged below the acidic gastric juices.

    It can be hard to interpret the significance of gastric ulcers in the horse, as some positive cases will have no definitive clinical signs and it is important to review the whole horse health picture and not just the ulcers themselves.

    Equine gastric ulcers [1,106 words]: Causes | Diagnosis | Treatment | Prevention

    Causes of gastric ulcers in horses

    In a natural environment the horse will graze for up to 16hr a day, so the acidity is reduced by the forage filling the stomach almost constantly, as well as by bicarbonate in the saliva that is produced as the horse chews.

    If stabled horses have access to ad-lib hay, haylage or grass, this natural preventative process continues. But if they are fed high-concentrate diets with only limited access to forage, the acidity in the stomach increases.

    Any prolonged period without forage intake, whether due to management practices or illness, leads to increased gastric acidity and a risk of ulcers.

    Training which includes fast work, especially on an empty stomach, increases the risk of the acid splashing around, resulting in damage the upper part of the stomach.

    Stress can also be a factor.

    Research undertaken in the UK1 on the stomachs of slaughtered horses showed that even feral ponies living on the moors can develop gastric ulcers, although it was unclear whether they were living with them all the time or had developed them during the brief period between round-up and slaughter. The samples were all taken from animals slaughtered in mid-summer, when grazing was at its best and the predicted environmental stress at its lowest.

    Diagnosing gastric ulcers in horses

    There are no definitive external signs that a horse is suffering from gastric ulcers, but clues suggesting a performance horse may be suffering include:

    • decreased performance
    • attitude change (reluctance to work/not wanting to be tacked up)
    • poor body condition
    • reduced appetite
    • low-grade colic

    Studies show that stride length in racehorses with ulcers decreases significantly. Equally in sports horses, the discomfort associated with stomach ulcers can cause a reluctance to engage abdominal muscles to extend, collect or jump.

    To confirm that ulcers are present and what grade they are, a vet will use a 3metre long videoendoscope to view the stomach lining of the horses (gastric endoscopy).

    Treatment options

    Gastric ulcers have been most commonly treated with an equine-specific form of omeprazole, given at a dose based on bodyweight. Other medications are now being used in some cases, so consult your vet for the most up-to-date advice. How long the horse requires this will depend on how bad the ulcers are and the management of that horse and its diet.

    Squamous lesions that are widespread and shallow typically heal faster (within 14-21 days) than more focal, deep lesions, which can take up to a month or even longer.

    After this period gastric endoscopy can be repeated to check how the healing is progressing. If all is well treatment can move on to the maintenance stage to avoid the ulcers from reoccurring. If all treatment is stopped at this point there is a high risk that the ulcers may reform (approximately 80% within six weeks).

    For maintenance owners can continue using equine-specific omeprazole, but reduce the amount to a quarter dose. This is relatively effective in most cases and also user-friendly as it is a once-a-day treatment.

    The alternative is to use an acid-neutralising feed supplement (containing aluminium hydroxide, magnesium hydroxide and calcium carbonate — think “Rennie” for your horse). This approach is less consistent and the supplement must be given three to four times daily, as its effect is short-lived.

    There are a variety of other supplements containing different fibrous material or proteins, seaweed, plant or mineral extracts; however, none of them have been proven to be clinically effective in either the treatment or prevention of squamous ulceration.

    A horse that has ulcers in the glandular area of the stomach, known as Equine Glandular Gastric Disease (EGGD), which is a different type of condition, will require different treatment.

    These glandular ulcers will often need additional treatment with the mucosal protectant sucralfate as well as omeprazole. Another option is a coating agent supplement containing pectin and lecithin, given up to twice daily, which is often started at diagnosis and then continued for at least three months.

    Also, a specific prostaglandin analogue is being used as an increasingly popular treatment. This has multiple mechanisms of action that may be of benefit, including suppressing acid production and helping healing, which is particularly beneficial for the glandular form of ulceration.

    Different treatment options should be discussed with your vet, depending on the precise type of ulceration affecting your horse.

    Preventing gastric ulcers in horses

    Any horse that has been diagnosed as having gastric ulcers, alongside horses that are high-risk of developing them, need their management reviewed in order to reduce the likelihood of the ulcers taking hold.

    The following steps are recommended2:

    • Allow access to high-quality forage, predominantly during the day (7am to 11pm), at a minimum daily rate of 1.5kg/100kg body weight (BWT). This should ideally be given continuously or at no more than 6hr intervals
    • Create multiple forage sources in the stable to improve eating consistency and allow foraging activity
    • Either hay (dry, soaked or steamed) or haylage can be used as the main forage source — there’s no difference between them in relation to ulceration
    • Feed no more than 0.25kg/100kgBWT of straw. This should not be the only forage source
    • Provide continuous access to fresh, clean water 24hrs a day
    • Split the concentrate ration into three rather than two meals per day
    • Opt for grains such as barley and oats instead of sweet feeds
    • Add chaff to all meals
    • Completely pelleted diets generate more stomach acid than the same diet formulated as a coarse mix
    • Buy high-quality feed, but bear in mind that there is no scientific evidence to support the use of specific “gastric healthy” commercial diets, nor of one manufacturer’s feed being better than another’s
    • Add a little corn oil or rapeseed oil (50-100ml per day) to help reduce the amount of stomach acid produced
    • Consider using fermented probiotics and the yeast Saccharomyces cervasii, which may increase the digestibility of the horse’s diet, so improving large intestinal function
    • Feed chaff before exercise — 2 litres chaff given within 30mins of exercise may trap acid and limit ulceration, and improve gastric blood supply. Use a 2-litre plastic drink bottle with the top cut off as a measure
    • Remember turn out at grass is beneficial for the majority of horses.

    Research by feed manufacturer Dengie published in October 20183 found while knowledge of EGUS management techniques was good among the owners that took part in its online survey, many were not implementing all the advice.

    Specifically, while 67% of respondents who believed their horses had EGUS had increased access to hay or fibre, only 55% were feeding chaff before work, while only 38% had cut cereals and starch out of their horse’s diets.


    1: https://onlinelibrary.wiley.com/doi/full/10.1111/eve.12491A comparison of the prevalence of gastric ulceration in feral and domesticated horses in the UK – October 2015

    2: https://www.horseandhound.co.uk/exclusive/heal-gastric-ulcers-horses-522173How to keep gastric ulcers at bay: simple 12-step plan – January 2016

    3: https://www.horseandhound.co.uk/news/owners-failing-act-help-horses-ulcers-667289Owners failing to act to help horses with ulcers – October 2018