Equine Gastric Ulcer Syndrome – no acid no ulcer?
Written by Michael Hewetson BSc BVSc PhD DipECEIM CertEM (Int.med) FHEA using Exagus at the RVC
Equine gastric ulcer syndrome (EGUS) is a general term used to describe diseases that cause stomach ulcers in horses and is similar to the term peptic ulcer disease (PUD) in people. Unlike people, however, the horse is unique in that the stomach lining (mucosa) is divided into a squamous and a glandular portion; and it is important to realise that there are differences between these two regions. Therefore, when referring to EGUS, you will often hear your veterinarian using the terms Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD) in order to clearly distinguish which part of the stomach is affected.
EGUS is common and it is an important disease in the equine industry. Performance horses are particularly susceptible, with studies showing that between 47-100% of Thoroughbred racehorses; 33-93% of endurance horses and 58-64% of show and sport horses may have stomach ulcers. Unfortunately, non-performance horses are also susceptible to EGUS, and studies have shown that between 11% to 67% of sedentary horses and horses that partake in less strenuous activities (e.g. pony club activities) may have ulcers.
There does not appear to be a clear relationship between the presence of ESGD and EGGD, and the fact that both conditions may occur together in the same horse does not indicate that they are associated. In the case of ESGD, the cause of the ulcers is well understood, with a variety of managemental risk factors (e.g. increase in exercise intensity, increased starch intake and reduced pasture turnout) contributing to an increase in the exposure of the squamous mucosa to acid. The squamous mucosa is not normally exposed to acid. As such it is inherently susceptible to acid injury, and with prolonged acid exposure, ulcers may develop.
In contrast to ESGD, the cause of EGGD is poorly understood. The glandular mucosa is very different from the squamous mucosa in that it is exposed to a highly acidic environment under normal physiological conditions. As such, it is only when there is a breakdown of the normal defence mechanisms that protect the glandular mucosa from acidic gastric contents that EGGD occurs. While ulcers are most commonly seen with ESGD, horses with EGGD rarely present with ulcers. Rather, the lesions are more consistent with an inflammation of the stomach lining, and can vary widely in their appearance. A number of scientific studies have identified that stress, both psychological (e.g. multiple riders or caretakers; confinement; stress associated with transport and competition) and physiological (e.g. increases in the total amount and frequency of exercise without adequate rest periods) may increase the risk of EGGD in horses. This may be due to a variety of mechanisms including suppression of the immune system and a reduction in the mucus coating and blood supply to the glandular mucosa; all of which compromise the ability of the stomach lining to resist acid injury.
Symptoms that may indicate that your horse has EGUS include:
- Poor coat condition
- Bruxism (teeth grinding)
- Changes in temperament (including nervousness and aggression)
- Acute or recurrent colic
- Reduced appetite, altered eating patterns and unexplained weight loss
- Poor performance and changes in rideability (including reduced willingness to work and reluctance to go forward)
- Skin sensitivity (biting of the flanks or resentment of girthing, grooming, leg aids or rugging)
Gastroscopy is the only reliable method for the definitive diagnosis of EGUS. Your veterinarian will usually ask you to withhold food from your horse for 16 hours and water for 6 hours prior to the procedure. Following completion of fasting, your horse will be sedated and a 3-m equine video endoscope (camera) will be passed into the stomach via the nasal passages. This may require the use of a twitch in some cases. The stomach is then distended by air to enable your veterinarian to see the entire stomach. The procedure is painless and most horses appear to tolerate it well.
If your horse has stomach ulcers, your veterinarian will assess where they are and how severe they are by assigning a score that represents the appearance of the stomach lining at the time of gastroscopy.
Treatment of EGUS will vary depending upon the severity and the location of the ulcers. In most cases treatment consists of management and dietary modification in conjunction with the use of drugs that reduce the acidity of the stomach contents. Oral omeprazole is the drug of choice and is currently the only licenced product for horses.
Nutraceuticals may offer some protective effects in horses at risk of developing EGUS, and there is some evidence to suggest that Exagus may improve the rate of healing in horses with EGUS. This supplement contains alkaline buffers which help neutralise gastric acid. The product also contains sodium alginate which forms a gel on the surface of the gastric contents, thus acting in a very similar manner to the fibrous mat that normally protects the sensitive squamous epithelium from acid splash during exercise. In addition, amino acids like Threonine promote mucin synthesis, thereby improving the barrier function of the glandular epithelium and protecting it from acid injury.
Additional management and dietary adaptations which may help and can be implemented long term include:
- Increased turnout where possible
- Ad lib water
- Reduction/avoidance of any social stressors
- Provide regular rest days
- Feed a handful of chaff 20 minutes prior to exercise to reduce acid splash during exercise