Equine Gastric Ulcer Syndrome explained

  • Our latest equine veterinary feature, written by Dr. Sarah Davidson, BVMS, MRCVS) of Sussex Equine Hospital at Ashington, explains equine gastric ulcer syndrome.

    Dr. Sarah Davidson, BVMS, MRCVS of Sussex Equine Hospital. Ashington.

    Equine Gastric Ulcer Syndrome (EGUS) can affect any horse or pony, even though we see it more frequently among high-performance horses.
    Some studies suggest prevalence of around 37 per cent of leisure horses, 60 per cent of performance horses and up to 90 per cent of racehorses. Foals are also particularly susceptible, with around 50 per cent of foals developing stomach ulcers, especially in times of stress.
    EGUS is one of the most commonly under-diagnosed condition in horses.
    So, what are gastric ulcers? To understand this, we first need to understand how the normal equine stomach functions.
    The horse’s stomach is divided into two regions, an upper ‘squamous’
    region and a lower ‘glandular’ region. The squamous region is covered by stratified squamous epithelium and lies on top of the glandular region, separated by a well-defined border called the margo plicatus.
    The glandular region is the region that contains and produces the stomach acid
    and digestive enzymes, this part of the stomach is protected by :
    a/bicarbonate protective layer; rapid cell turnover; prostaglandins; and intracellular tight junctions.  The upper squamous region does not have these protective adaptations and so is vulnerable to stomach acid.
    In a natural environment, the horse is designed and adapted to graze for 16-20 hours of the 24-hour day, what we call a ‘trickle feeder’. The horse’s acidic stomach contents are buffered (neutralised) by saliva produced from this regular and almost constant grazing. The horse constantly produces stomach acid (over a litre an hour) whether it is eating or not.
    It follows that domesticated horses that are stabled with restricted forage will be producing gastric acid and because they aren’t eating it won’t be being neutralised by the saliva, so the stomach pH will start to decrease. Horses are also naturally designed to move little and often only needing to move at high speed when evading predation.
    With this ‘normal’ gentle movement, the gastric acid is generally restricted to the lower glandular part of the stomach rather than the upper squamous region. Domesticated horses, however, spend less time eating (decreasing saliva production) and more time exercising (splashing the gastric contents on to the less protected squamous region).
    Gastric ulcers occur when the gastric acid and digestive enzymes overpower the protective factors in the stomach lining. There are two types of gastric ulcers:
    Squamous Ulceration: The dorsal (top) region ulcerates from
    extended exposure to acid secretions and a lack of protective mechanism. Glandular Ulceration:The ventral (bottom) region is covered in glandular epithelium and ulcers occur here when the protective mucus layer is compromised.
    Research has shown causes of EGUS include exercise training, high carbohydrate diets, stress and non-steroidal anti-inflammatory drugs such as Bute. There is also a mechanical mechanism: when galloping the pressure from the abdomen causes mthe stomach to contract, pushing acid from the glandular stomach up in to the more vulnerable upper squamous stomach region.
    The signs of EGUS are vague and variable and this contributes to the under diagnosis of the condition. Some signs that may be noted include:
    Reduced appetite or weight loss, poor performance, poor condition (including a dull coat)
    Behavioural changes or an altered temperament (bucking, rearing, refusing to jump, resenting the girth being done up)
    Mild or recurrent colic and or teeth grinding
    Diarrhoea and cribbing
    Foals may also show teeth grinding, excess salivation and excessive lying down, colicking,  infrequent nursing and diarrhoea
  • As you can see, these signs are vague and maybe confused with back pain, sacroiliac pain or bad behavior. Additionally, the severity of the clinical signs does not always correlate with the severity of ulcers.
    While we can be suspicious of EGUS, the only way to confirm, diagnose and monitor the condition is by having a gastroscope. This is relatively simple, painless procedure whereby your vet passes a three-meter-long video scope down into your horse’s stomach and visually assesses the oesophagus, stomach and proximal duodenum.
    Ulceration is graded on a scale of 1 to 4 with 1 being mild thickening and inflammation only, to 4 being deep widespread ulcers. Bleeding does not relate to the depth or the severity of the ulcers. Grades 2 or above are considered clinically significant.
    In the past, the only licensed drug was Gastrogard (omeprazole), a proton pump inhibitor given orally, which inhibits gastric acid secretion and is highly effective in healing gastric ulcers.
    However, there has now been an injectable form of omeprazole licensed which requires an injection intramuscularly weekly, for some horses and owners this is more convenient than administering an oral dose daily. Total healing time is usually between two and four weeks, although severe cases can take a little longer.
    A full course of treatment is usually prescribed for 28 days. The horse may need to be taken out of work during this period to minimise damage to the
    healing tissue, but it is not always necessary.
    You can help to reduce the potential for gastric ulcers developing in your horse by changing the management to resemble a more natural lifestyle:
    Increasing turnout and reducing concentrate feeds
    Allowing free-choice access to grass or hay in the stable
    Feeding more frequently to increase and prolong saliva production to help buffer the acid in their stomach
    Feeding a small amount of easily digestible feed before working to act as a sponge,  soaking up free gastric acid and reducing splashing onto the squamous part of the stomach
    Cutting down on the use of high carbohydrate diets
    Splitting the feeds into four feeds rather than two
    Using medication at times of greatest risk, like traveling or competition
    Where ever possible, reducing stress
    Additionally, there are feed supplements like activated charcoal and other veterinary preparations that may be of benefit. Unfortunately, if you don’t make the management changes, then it is likely EGUS will reoccur. If you have any concerns regarding your horse and EGUS then contact your vet for a consultation

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