Permanently stabled horses are amonst those at risk of Equine Gastric Ulcer Syndrome
What is Equine Gastric Ulcer Syndrome?
Equine Gastric Ulcer Syndrome (EGUS) is the overall veterinary term used to describe erosive ulceration of the equine gastric mucosa (stomach lining), which is commonly known as “Gastric Ulcers”.
Equine Gastric Ulcer Syndrome actually encompasses two distinct disease conditions of the equine stomach; Equine Squamous Gastric Disease (affecting the squamous mucosa of the stomach) and Equine Glandular Gastric Disease (affecting the glandular mucosa of the stomach). The squamous mucosa and glandular mucosa of the equine stomach are two distinct anatomical regions with the cause of disease affecting each area being quite different.
For the ease of understanding, the rest of this article will discuss Equine Gastric Ulcer Syndrome in general terms.
What are the signs of Equine Gastric Ulcer Syndrome?
Clinical signs associated with Equine Gastric Ulcer Syndrome vary greatly along a broad spectrum in severity from mild subtle and often unrecognised signs through to overt and obvious signs.
- Inappetence, Poor body condition, Weight loss, “Picky-eater”
The degree of reduced appetite seen with EGUS varies greatly with subtle reductions often going unrecognised by owners. Occasionally reduction in appetite is interpreted by owners as a horse who is a “fussy eater”. Preference for one type of feed, such as hay or grass, over another type of feed such as grain or pellets is sometimes seen in horses with EGUS. Associated weight loss and loss of body condition can vary from subtle to overt obvious changes.
Poor coat condition
A loss of coat condition is a common but vague clinical sign reported to be seen with EGUS. Its true association with the presence of EGUS is difficult to evaluate with some studies showing a link between the two, whilst other studies have failed to identify a relationship between poor coat and the presence of EGUS.
- Behavioural Changes
Altered behaviour has long been perceived to be associated with EGUS. Nervousness, aggression, crib-biting and wind-sucking have all been reported to be associated with EGUS. Studies investigating EGUS are some-what conflicting in the exact relationship between behavioural change and EGUS. Despite this inconstancy, behavioural changes are not uncommon.
- Colic
A reasonable amount of evidence links the occurrence of colic and EGUS, particular low-grade recurrent colic seen after eating. Several studies have shown a reasonable proportion of horses presenting with colic signs to have EGUS, however it is not fully clear if this is a cause, or an effect of the primary colic.
- Poor Performance
Either as a primary cause of reduced performance via direct gastric pain, or through any of the aforementioned clinical signs, EGUS has been shown in several studies to result in reduced performance, particularly in thoroughbred racehorses. The concept of “poor performance” is extremely broad and all-encompassing with performance indicators varying greatly from stride length, speed and velocity to oxygen carrying capacity to complex concepts of inability to perform movements under saddle. Numerous contributing factors can result in poor performance with EGUS being only one of the possible causes.
How common is Equine Gastric Ulcer Syndrome?
The prevalence of Equine Gastric Ulcer Syndrome varies greatly amongst horses depending on a variety of different factors including breed, type and level of use along with several other risk factors. The highest prevalence of EGUS occurs in Thoroughbred racehorses with 37% of untrained horses being affected, increasing to 80-100% of Thoroughbred racehorses having EGUS whilst in race training. Standardbred racehorses are very similar with 44% of untrained horses having EGUS, increasing to 87% during training.
Studies into the prevalence of EGUS amongst show and sport horses have in general grouped all disciplines together, with a reported prevalence of 17-64%. Endurance horses show a prevalence of 48% increasing to 66-93% during competition time. Horses that compete infrequently, spending most of their time in their usual home environment, show an EGUS prevalence of 11%.
Pasture turnout has been shown to be protective against the development of EGUS
What are the risk factors for Equine Gastric Ulcer Syndrome?
Despite the high prevalence of Equine Gastric Ulcer Syndrome there have been few large scale epidemiological studies investigating all the potential factors affecting EGUS. However, there are several known risk factors for the development of EGUS.
- Level, intensity and duration of exercise and competition
It is well recognised that higher levels of competition in association with longer duration and greater intensity of exercise are associated with higher prevalence of EGUS. Travel associated with frequent competitions has been suspected to be a contributing factor for the development of EGUS in competition horses.
- Breed
Several studies have shown Thoroughbreds to have a higher predisposition for the development of EGUS than other breeds. The exact mechanism for this trend is not fully understood but is likely to be multi-factorial.
- Feeding / nutritional factors
Infrequent feeding, particularly infrequent feeding of concentrates without continued access to hay, has been shown to increase the risk of EGUS. The equine stomach is designed to receive a constant flow of feed material throughout the day as the horse grazes. Extended periods without food (such as between morning and night meals for a stabled horse) results in a reduction in gastric pH due to the continued production of gastric digestive acid, leading damage to the gastric mucosa. Pasture turnout has been shown to be protective against the development of EGUS, with free access to a continuous fibrous feed source such as hay also being shown to be protective. Diets containing large amounts of grain have been shown to increase the risk for EGUS. So too has intermittent access to water.
- Medication
Veterinary medications such as phenylbutazone (“bute”) and other non-steroidal anti-inflammatories have been shown to cause gastric ulceration by inadvertently inhibiting gastro-protective factors such as prostaglandin.
- Miscellaneous factors
Horses being trained in an urban area, a lack of direct contact with other horses and talk rather than music in a barn have all been shown by studies to increase risk of EGUS.
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How is Equine Gastric Ulcer Syndrome diagnosed?
Endoscopy of the stomach (gastroscopy) is currently the only technique to achieve a definitive diagnosis of Equine Gastric Ulcer Syndrome. The procedure is conducted standing in a sedated horse which has been fasted for 6-12hrs. A flexible endoscope of at least 3m in length is required so all parts of the stomach can be visualised. Not many ambulatory veterinarians are able to carry such a large endoscope along with all the associated equipment; as such most gastroscopies are performed within a clinic or hospital.
Due to the vague and often subtle non-specific signs associated with Equine Gastric Ulcer Syndrome, a diagnosis based on signs along is not recommended. However, many veterinarians will use the response to therapy after using an anti-ulcer medication as a way to retrospectively diagnose EGUS. The economics of a trial treatment compared to the expense of achieving a definitive diagnosis from a gastroscopy should always be considered when considering EGUS.
How is Equine Gastric Ulcer Syndrome treated?
Mild cases of Equine Gastric Ulcer Syndrome can be controlled simply with changes in management such as increased pasture access or ad-lib hay. Medical treatment of EGUS commonly involves the use of either Ranitidine or Omeprazole, both of which are oral veterinary medications. Ranitidine is an H2 blocker that stops acid production by certain cells within the lining of the stomach. Ranitidine is typically given 3 times per day. Omeprazole is a proton-pump inhibitor that also blocks the secretion of acid into the stomach. It’s is given once per day. Both medications are permitted to be used under all sport horse medication control regulations. For more information about the use of these medications you should contact your veterinarian.
Can Equine Gastric Ulcer Syndrome be prevented?
Yes, many management strategies can significantly reduce the likelihood for the development of Equine Gastric Ulcer Syndrome in your horse, but sometimes even the most well managed horse in the best kept barn can develop EGUS.
Below are several possible ways to help reduce some of the more common risk factors for EGUS;
- Divide your horses feed into smaller portions and feed more frequently throughout the day
- Allow all day access to grass if possible, otherwise free access to ad-lib hay
- Consider dividing large hay nets into small ones so they take longer to eat
- Try to reduce high carbohydrate diets
- Consider using ulcer medications as a preventative either on a continual basis, or during high risk periods such as during the competition season or prior to transport
What about Equine Gastric Ulcer Syndrome in the Event horse?
Despite no specific studies being performed into the prevalence of Equine Gastric Ulcer Syndrome in the event horse, extrapolations from other studies can be easily made. Studies looking at EGUS in general sport horse populations (including Eventers) showed a prevalence of 17-64%, with studies of Thoroughbred racehorses showing prevalence of 80-100%. The Event horse is likely to sit somewhere between these two groups of populations, especially considering that a reasonable proportion of event horses are either ex-thoroughbred racehorses or contain a certain degree of thoroughbred breeding. Due to the nature of the sport, the amount of training and specific management involved in producing an event horse ready for competition, a large number of risk factors for EGUS (if not all) are somewhat unavoidable. However, as mentioned above there are many ways in which EGUS can be managed and controlled.
With Equine Gastric Ulcer Syndrome is prevention better than cure?
In my opinion, yes, prevention is always better than cure. In both the low level and elite level competition horse alike, Equine Gastric Ulcer Syndrome can potentially play a significant role in the horses’ health and wellbeing, as well as its performance. It’s is challenging enough producing and training a competition sport horse, especially an Eventer, so if there are any ways to potentially prevent problems from occurring I don’t see any reason not to use them. Whether it is medical or management, or a combination or both, prevention of EGUS is far better than the cure.
As you can see, the signs of Equine Gastric Ulcer Syndrome can often be quite subtle, but many astute owners will easily notice these subtle changes. It is not un-common for a veterinarian to be asked to investigate a horse that the owner feels that the horse is “just not quite right”, especially performance sport horses. In the absence of anything else, EGUS is often the answer. The prevalence of EGUS in the event horse is quite high, often under-recognised and at times can be performance limiting. Hopefully this article has helped you understand Equine Gastric Ulcer Syndrome better, but if you have any further questions don’t hesitate to contact your veterinarian for more information about diagnosis and treatment.
Christopher Elliott BVSc (Hons) MRCVS has vetted at many of the major eventing competitions around the world; find out more about Christopher here or follow him on Twitter @REC_SportsMed
