Equine Gastric Ulcer Syndrome James Wallace BVMS GP CertEP CertEM (Int Med) MRCVS CertEP RCVS Advanced Practitioner Internal Medicine Equine Veterinary Surgeon
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hysiotherapists are often the first point of contact for a client concerned with poor ridden behaviour and performance. It is often necessary to rule out nonorthopaedic problems before embarking on treatment. Equine gastric ulcer syndrome (EGUS), is one such common cause of poor performance, bad ridden behaviour, weight loss, and colic (Sykes & Jokisalo, 2014). As with all poor performance issues, teamwork, and liaison between different professions (physiotherapists, nutritionists, farriers, and veterinarians) is essential for a successful outcome. EGUS is a broad group of inter-related conditions, which have different causal factors and management regimes. In this article we will summarise what EGUS is, and how you can identify it.
Figure 1: Evolution of the horse Horses have evolved over the last 50 million years from a mainly herbivorous omnivore, with a similar diet to modern pigs, to the modern horse on a forage based diet. The digestive system of the modern horse is configured to digest poor quality grass based diets, which are low in soluble carbohydrates (starch and fructan), and high in structural carbohydrate (cellulose and hemi-cellulose). Horses are well adapted to living in an arid climate with sparse grassland with high mineral contents such as the steppes middle Asia and themid-west of the USA; in conditions which would not allow other herbivores such as cattle and sheep to thrive (Mihlbachler et al., 2011).
Figure 2: Diagram of equine gastric anatomy The stomach is highly acidic (pH<1.4), and is split into 3 main portions (Sykes et al., 2015). The squamous portion (1) is an extension of the oesophageal lining and is a food storage vat. It has poor defence against acid exposure but has high stretch ability. If exposed to acid and bile from the gastric juices, it will oxidise and form squamous ulcers or EGSD (Figure 3). In a wild horse this is unlikely because the stomach would likely be full of fibre, which naturally floats on the gastric juice pool, and slowly makes its way down into the pylorus and further on into the digestive system. The glandular portion (2) is an acid secreting mucous membrane. This has good defences against acid, assuming there is no disruption to normal blood flow and hormone balances.Equine gastric glandular disease (EGGD) is not well understood, but can be erosions, ulcers, or thickened and inflamed membrane (Figure 4). The pylorus (3) has the same coating as the glandular portion, but is the barrier between the stomach and the small intestine. In addition, it acts as a pump and the trigger for normal intestinal propulsion of the food,measuring its sugar, fibre, and protein content; adjusting the digestive cycle using hormones and changes in the intestinal smooth muscle contraction. A more serious condition, delayed gastric emptying/gastric dilation can also be linked to ulceration, and is a cause of severe poor ridden behaviour (Bezdekova et al., 2020). There is no current link between the organism which can cause ulceration in humans (H. pylori) and horses.
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Figure 3: Squamous ulceration
Figure 4: Glandular and pyloric disease Initially, gastric ulcers were thought to predominately occur in highly stressed horses, or those under metabolic stress such as race horses and intensively stabled event horses. Recent work suggests the incidence in the general equine population of 45% increasing markedly with excessive exercise, cereal based diets, and stabling. In unpublished work by the author and other internists, there is a tentative link between obese horses with equine metabolic syndrome and EGGD. There is also emerging evidence of refractory EGGD and dietary allergens detected by serum IgE well testing (Wallace, 2021). Horses with EGUS can show a wide variety of signs from weight loss, soft stools, teeth grinding, not finishing feed, colic, difficulty girthing, and poor ridden behaviour (Sykes & Jokisalo, 2014). Often they are uncomfortable on deep palpation of the left epigastric area, or application
