Equine gastric ulcer syndrome

Equine Gastric Ulcer Syndrome (EGUS) is an increasingly common problem in the Thoroughbred racehorse, causing a range of symptoms from depression to aggression, and often impacting negatively on performance.

Diagnosis is sometimes difficult, although there are methods by which they can be swiftly identified and treated. Equine gastric ulcers are graded on a scale of 0 to 4 where 4 is the most severe. A grade of 2 or more is clinically significant and usually warrants treatment. The primary objectives of treatment of equine gastric ulcers are to facilitate healing and relieve symptoms.

This can be accomplished by the use of antacids, histamine receptor antagonists or acid pump inhibitors. Ulcers are an issue - especially for racehorses- as they can be a source of chronic pain, leading to reduced appetite, loss of condition and sometimes colic. The clinical signs of the problem are often intermittent, and can vary tremendously depending on the horse and the types of discipline they compete in.

Two types of tissue line the equine stomach. The bottom of the stomach is lined with a pink glandular mucosa which constantly produces concentrated hydrochloric acid, whilst protecting itself with a sticky mucus and bicarbonate secretion.

At the top, the squamous (or non-glandular) mucosa is found – this tissue has no useful role in the stomach as it does not produce acid nor any protective mucus - squamous mucosa is therefore very susceptible to acid injury.Racehorses are more prone to ulcers in the squamous mucosa.
 


A pairing of equine vets that regularly diagnose and treat equine gastric ulcers are Rachael Conwell and Richard Hepburn, who are based in England. Hepburn estimates that 80% of ulceration is found in the top part of the stomach and Conwell's experience in practice also supports this. She explains: "With increasing intensity of exercise, it is thought that acid splashes up to cause ulcers in the squamous region.

This can vary from low grade to quite significant degrees of ulceration". "Quite often there can also be glandular ulcers at the exit from the stomach into the duodenum so it's important to look here," says Conwell.

Hepburn explains: "Horses may exhibit poor exercise tolerance, be reluctant to gallop and have slower race times. Post-race heart rates are higher when ulcers are present." Conwell adds: "A problem with ulcers is that they can manifest as low grade colic or failure to maintain bodyweight, particularly in racehorses." They may also have reduced exercise tolerance, refuse to gallop, and have poor jumping performance.

Poor coat hair can be another indicator. "Generally trainers are pretty good at spotting the signs. They may notice that feed doesn't get cleaned up in quite the usual hungry way. They also know their horse's character and so will notice small changes in attitude. The horse might become more grumpy, look miserable, resent being groomed or having their girth done up.

Perhaps they are just not the happy horse they used to be. It can be as subtle as that."  "In some situations there are no outward signs at all, only that the horse's performance is reduced." Says Conwell. 

According to Hepburn, the incidence of EGUS may be up to 100% in racehorses, with ulcers most severe in horses that are in full training or have just raced. 
Conwell and Hepburn regularly use gastroscopy as a method of ulcer detection. Gastroscopy is a visual examination technique through which a veterinarian will assess the stomach health of an animal using an endoscope, determining the presence and severity of ulcers and monitoring the success of prescribed treatment. Moreover it is a non-surgical and relatively simple procedure which takes less than fifteen minutes.

The same kit can also be used for airway examinations looking at the larynx, trachea and bronchi for respiratory problems, and inside the guttural pouch to check for infections such as strangles. This is useful as it means horses do not need to be sedated on more than one occasion to assess both airway and stomach health. 

Using gastroscopy to diagnose ulcers is a relatively simple procedure. The horse is starved for 8 hours but is allowed free access to water. It is then given a short acting sedative, and an endoscope is passed up the nose, down the esophagus and into the animal's stomach.

The stomach is inflated with air using a pump attached to the endoscope and any food is washed off with water- squirted through the endoscope. Once the end of the endoscope is in the stomach, it can be ‘driven' by the vet using hand-held controls to move it up or down, to the left or right. In this way the inside wall of the entire stomach can be examined.

A key difference between regular endoscopy and the specialist gastroscopy kits now available is that there is 3m of length to enable full examination of the entire stomach. Endoscope diameter is another difference, with 9 or 11mm being better tolerated by the horse for gastroscopy work than the standard size of 13mm.

Conwell has been using a 3m video-endoscope for two years now for diagnosing and treating racehorses. She says "I don't normally scope all horses in a training yard, only the ones where there is a suspicion that gastric ulcers could be affecting them. That said, it's rare that we don't find any ulcers in the racehorses we investigate." 

Other methods of detecting ulcers within the digestive system, anywhere from the stomach to the intestinal tract, are also proving effective. Kits which allow the handler to test for blood in the feces of the horse, an indicator of possible ulceration, are becoming more widely available, and may be a cheaper and less invasive method of diagnosing digestive health issues. 

In treating gastric ulcers, most vets will turn to a licensed acid suppressant product for equine use.

Treatment will vary in duration and intensity depending on the individual case, taking into account a number of factors including severity of ulceration and importantly, the horse's training regime, as there is some evidence that treatment effectiveness of some medications vary when the horse is still in full work. Antacids (which neutralize acids in the stomach), omeprazoles in paste and suspension (which suppress acid production) and histamine receptor antagonists are commonly used to reduce symptoms, heal lesions and reduce the likelihood of future problems.

Acid suppressants fed once a day are an effective remedy, believes Conwell, who adds: "Alternatively, histamine receptor antagonists, such as ranitidine, can be used. I normally re-scope horses about four weeks after treatment. If the problem has resolved then I recommend a quarter dose of an acid suppressant to prevent recurrence of ulcers during training." 

Trainers often notice a character change in their horses once treatment is started, according to Conwell.

Hepburn reports that some owners are ‘amazed' at the difference in horses given treatment for their ulcers: "Even though they may have been performing well before, resolving the problem makes their performance consistently good."

In addition to prescribing medication, ulcers can be reduced and in some cases, totally resolved by changing the feeding and/or stabling routine. High grain diets and a limited access to forage - which buffers stomach acid - are a factor in the prevalence of EGUS in racehorses. Ideally, horses should be given more access to a selection of forages, just as they would in the natural wild.

Conwell and Hepburn both recommend putting several haynets up, some with hay and others with haylage, to allow the horse to browse for forage. 
Hepburn says: "Turning horses out every day may help, although ulcers are just as common in NZ racehorses that are trained from pasture. Interestingly, some ongoing Danish work has shown that giving horses the choice of staying in or going out can reduce stress and associated gastric ulceration."

Various feed supplements are also available which help to maintain digestive health, both in horses which have received treatment for ulcers and are recovering, and in horses showing no symptoms of ulceration, in order to lessen the chance of digestive problems.

This is especially useful where it is not possible to radically change management practices, such as with horses stabled at the racetrack.
Hepburn concludes: "Some horses are more prone to ulcers than others – hence the need to assess each individual case. Also some ulcers heal more quickly depending on their location in the stomach."

Rachel Queenborough
 (10 July 2008 - Issue 9)