What is EGUS and how are ulcers treated in horses?

If you haven’t heard of EGUS before, it stands for Equine Gastric Ulcer Syndrome. This is what other horse owners refer to, when they say that their horse has ulcers. It can be pretty nasty and very uncomfortable for the horse. Depending on the horse or pony, it can cause changes in temperament, poor performance, reduced body condition or trouble maintaining weight, changes in eating habits, inappetence, and sometimes it may even cause colic. Alternatively, there are horses that don’t show any clinical signs at all. 

How well do you know the anatomy of the horse’s stomach? 

The stomach is probably not as big as you’d expect for such a large animal. It’s split into two parts by a ridge of tissue. First, there’s a squamous or non-glandular part (it’s more alkaline here, the pH is higher because there’s no stomach acid). Then, below the ridge, there’s the glandular part (where the pH is lower because of the acid produced).

The glandular part has defence mechanisms, such as the production of mucous and bicarbonate. This helps to protect the mucosa (the delicate inner lining surface) from the detrimental effects of stomach acid.

So, what exactly happens in EGUS?

When the non-glandular part is exposed to acid, it creates sores, erosions or even ulcers in the surface of this part of the stomach, because it’s not adapted for an acidic environment. That said, we also see horses who have ulceration of the glandular part of the stomach, this happens when the defence mechanisms fail to protect the underlying mucosa. In some horses the ulcer lesions are shallow or superficial, but, in others, they may well be very deep.

What are the risk factors for developing EGUS?

EGUS is more common in performance horses, especially racehorses, but there are many risk factors at play. The performance lifestyle often involves long periods of time stabled, so horses aren’t constantly grazing and producing saliva. When swallowed, saliva helps to protect the stomach, it contains bicarbonate which acts as a buffer against stomach acid. 

A lot of time stabled, travel and changes in environment all generate stress, which is associated with an increase in stomach acidity. High performance work can also cause splashing of the stomach acid from the glandular part onto the non-glandular part of the stomach, predisposing the horse to ulceration. However, EGUS is not just a disease of performance horses, there are many affected horses that are used just for pleasure riding. 

The additional risk factors for developing EGUS include:

A high concentrate ration in the dietNot enough roughage in the dietGoing long periods of time without eating, or starvation Not drinking enough water In foals, weaning can be a factor too.

How is EGUS diagnosed?

When we suspect a horse is being affected by EGUS or we want to rule it out, the test of choice is gastroscopy. This is where we use a camera to look down the oesophagus and into the stomach. It shows us what is happening to the stomach’s mucosa. Following gastroscopy, the vet will often give the ulcers a grade, and this is dependent on how severe the lesions are.