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Equine Gastric Ulcer Syndrome: One of the most under-recognised equine conditions

Louise Radford BVetMed Cert.VR MRCVS of Merial Animal Health - 26/05/2013

Equine Gastric Ulcer Syndrome: One of the most under-recognised equine conditions


Since the first Gastric Ulcer Awareness Month in 2007, it has been well documented that prevalence of gastric ulcers in racehorses in training is approximately 93%¹, 60%²,³ in performance horses and 40%⁴ of leisure horses. And yet despite this, it is believed that gastric ulceration is still one of the most under-recognised problems in the equine field.

The main reason for this lack of diagnosis is likely to be the vague and non-specific nature of the clinical signs, which are often put down to back pain or behavioural issues.


Horses are fairly unique in that they secrete stomach acid continuously. Short periods of feed deprivation will increase acidity from pH 3.1 to pH 1.55, making them susceptible to gastric ulceration. A pH gradient (gastric stratification) exists within the stomach with the squamous fundus typically being in the region of pH 5.5, margo plicatus pH 4.1 and the pyloric mucosa pH 2.7.

Squamous lesions have a high incidence in comparison to glandular lesions but there is no association between the presence of squamous vs. glandular lesions. It is easy to underestimate glandular lesions particularly in the antrum or fundus. There is no consistently reliable diagnostic test for equine gastric ulcer syndrome (EGUS) other than gastroscopy using a 3m video endoscope. 

There are three main types of ulceration: Primary squamous ulceration; primary glandular ulceration; and secondary squamous ulceration.

Primary squamous ulceration disease occurs due to increased acid exposure. Contributing factors are feeding practices, exercise and stressors including transport. Gastric ulcers can form even after food deprivation for fairly short periods e.g. 24-48 hours.

Exercise (faster than walk) disrupts gastric stratification. Abdominal pressure results in increased mucosal acid exposure and squamous ulcers can form within 5-7 days of a simulated training regime commencing. Diets high in cereals can also disrupt gastric stratification if roughage levels are reduced.

Primary glandular ulceration occurs as a result of failed mucosal defences. The two main factors thought to be most commonly associated are stress and bacteria.

On-going research has found that horses may have Helicobacter spp. but it is not known how pathogenic they are. Increased numbers of bacteria have been demonstrated in ulcer beds in comparison to normal mucosa. Clinically, in persistent cases of glandular ulceration, antibiotics have been shown to bring a successful resolution.

Finally, secondary squamous ulceration usually occurs as a result of increased acid exposure due to impaired gastric emptying.

Presenting Signs

These vary from one horse to another, and do not always correlate with  the severity of the ulcers, and some horses appear to be more ‘stoic’ than others. Symptoms can include some or all of the following; reluctance to work or jump; dull ‘starey’ coat; poor or picky appetite; weight loss; mild or recurrent colic; discomfort on girth tightening and salivation, and teeth grinding and diarrhoea in foals.


Diagnosis requires a 3m video endoscope. The procedure needs the animal to have been starved for long enough for the stomach to have emptied of food – usually around 16 to 18 hours, with 4 hours without water. It is almost impossible to navigate and visualise the equine stomach if the starvation procedure has not been followed. Both the greater and lesser curvature must be visualised as well as the pylorus.

Ulcers are graded according to severity. 0 = a healthy stomach and 4 = severe ulceration. The location is also noted.


Treatment centres on suppressing the acid, promoting healing and improving feeding and management practices. GastroGardTM  (omeprazole) is a proton pump inhibitor, and the only licensed (POM-V) treatment for gastric ulcers in the UK. If glandular ulceration is persistent then a course of an appropriate antibiotic may be prescribed in conjunction with acid suppression.

For the prevention of gastric ulcers roughage is important. Multiple forage sources are advisable as it encourages natural foraging. Pasture turnout helps but ulcers can still occur, or persist if untreated. Reducing carbohydrates will also help prevent recurrence.

Case Study


A 12 year old gelding, Irish Sport Horse showjumper. Purchased by current owner in June 2011.

Presenting signs

A poor eater, he easily loses bodyweight and ‘energy’. He never eats up. Always worse when travels away for training or competition. Also losing jumping performance. Mostly stabled as difficult to handle when out in hand and can bolt. Can appear unwell or ‘out of sorts’ every few months when stressed or has an increased workload.

Diet: Barley rings, topline, redigrass and additional vegetable oil with ad-lib haylage.



Blood tests and orthopaedic investigation unremarkable.

Gastroscopy in March 2012 found mild squamous ulcers on the lesser curvature (graded (2/4). A solitary large swollen ulcerated lesion was present with associated linear ulceration along the mucosal folds within the gastric antrum.


Initial 7 day trial course of omeprazole (GastroGardTM) at 4mg/kg, followed by 21 days to complete the treatment. Prince showed a marked improvement in appetite and demeanour after 48 hours. Once a clinical response to treatment had been determined, a 14 day course of trimethoprim-potentiated sulphonamides (TMPS) was introduced.

Owner advised to feed multiple small meals of his current diet plus ad-lib access to hay and as much pasture turnout as possible.

9th May 2012, still doing well with significant improvement in bodyweight, performance and appetite, and he is reported to be more relaxed. Repeat gastroscopy showed all squamous ulcers had healed, and whist the glandular area had improved some lesions in the antrum / pylorus persist.

On-going treatment: A half dose of 2 mg/Kg GastroGardTM for a further 4 weeks and a further 14 days of TMPS, along with 14 days of sucralfate. Advise to re-scope in July 2012.

*This case study was kindly provided by Dr Tim Brazil BVSc PhD Cert EM (Internal Medicine) DECEIM MRCVS, European Specialist in Equine Internal Medicine, Equine Medicine on the Move Ltd.

This article was kindly provided by Merial, makers of GastroGardTM:


1. Murray MJ et al. Factors associated with gastric lesions in thoroughbred racehorses. Equine Vet J 1996; 25 (5): 368-374

2. McClure SR, Glickman LT, Glickman NW. Prevalence of gastric ulcers in show horses. J Am Vet Med Assoc. 1999; 215: 8 1130-1133.

3. Mitchell RD. Prevalence of gastric ulcers in hunter/jumper and dressage horses evaluated for poor performance. Proceedings of the Association of Equine Sports Medicine Annual Meeting 2001.

4. Murray MJ, Grodinsky C, Anderson CW, Radue PF, et al. Gastric ulcers in horses:A comparison of endoscopic findings in horses with and without clinical signs.Equine Vet J. 1989; Suppl 7: 68-72.

About Merial

Merial is a world-leading, innovation-driven animal health company, providing a comprehensive range of products to enhance the health, well-being and performance of a wide range of animals. Merial employs approximately 5,600 people and operates in more than 150 countries worldwide. Its 2011 sales were more than €2 billion ($2.8 billion).

Merial is a Sanofi company. For more information, please see

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