Gastric Ulcers by Dr Nerida Richards

This article is from the January 2019 Horse Deals magazine.

Equine gastric ulcer syndrome (EGUS) is a major equine health problem worldwide. Multiple studies have reported an incidence of ulcers in performance horses in excess of 90% of horses training.

Ulcers negatively and sometimes severely affect a horse’s ability to perform. They cause pain and discomfort. They may reduce a horse’s appetite which in turn limits its capacity to maintain bodyweight and they possibly lead to the development of vices including windsucking and crib biting.

While gastric ulcers have long been recognised as a major health concern there is an evident lack of understanding in the horse owning community about what causes them and how they can be prevented.

What are gastric ulcers?

Gastric ulcers are lesions that are found in the stomach of horses. The horse’s stomach is made up of two major regions, the upper ‘squamous’ area and the lower ‘glandular’ area. The majority of ulcers in adult performance horses occur either in the squamous area or at the junction of the squamous and glandular regions.

Why do gastric ulcers occur in the upper section of the stomach?

The horse evolved as a grazing animal and when left to their own devices will eat for 17 hours or more per day. This means they are constantly chewing and salivating and their stomach is always full. Because of this pattern of eating, their stomach never developed an on-off-switch for gastric acid production. So their stomach secretes gastric acid 24- hours a day, regardless of whether they are actually eating or not.

When you think about this from the perspective of our modern day horses it is not an ideal situation. Many horses are now stabled with limited access to free choice forage. Or they work, compete and travel, leaving them in situations where they go for extended periods of time without feed.

When a horse eats it produces saliva, and one of saliva’s roles is to buffer the gastric acid in the stomach. So when they aren’t eating, they aren’t salivating. BUT they are still secreting gastric acid. This results in a pool of unbuffered (and therefore very acidic) gastric fluid accumulating in the lower section of the horse’s now empty stomach.

The lower part of the horse’s stomach was smart enough to protect itself from gastric acids, and, provided it is well nourished, is able to produce enough sticky mucus to protect itself from its own acid secretions. BUT, the upper part of the stomach doesn’t have this same protection. In a grazing horse the stomach is always full, so the top of the stomach was never exposed to gastric acid simply because the forage a horse ate stopped the acid from ever splashing up there. In modern day, meal fed horses however, the stomach is often empty and the upper section of the stomach is left totally exposed to the highly acidic fluids that are allowed to accumulate in empty stomachs.

When a horse with an empty stomach trots, canters, gallops or even simply tenses up its abdominal muscles the gastric fluids are splashed or squeezed up onto the unprotected upper section of the stomach. The acid simply starts to burn holes in the stomach wall lining. If you allow this to occur repeatedly the horse will eventually develop ulcers. This can happen in just a matter of days.

What factors influence the risk of ulcers?

Gastric ulcers are a ‘mulit-factorial’ disease, meaning they are caused by many things. The following situations have been identified as factors that can influence the risk of gastric ulcers:
1. Exercise on an empty stomach – as a horse exercises th other horses are even less likely to develop ulcers than horses turned out alone.
2. Training – horses in training are known to have a higher incidence and also more severe gastric ulceration than horses not in work. It has been reported that the risk of developing moderate to severe gastric ulceration increased 1.7 times for every week that a horse was in training.
3. Training location – in Thoroughbreds, horses that were exercised on a track on the property where they lived had 3.3 times less chance of having gastric ulcers.
4. Turnout/paddock time – horses that were given access to some turnout time were less likely to develop ulcers.
5. Turnout time with paddock mates – horses turned out with other horses are even less likely to develop ulcers than horses turned out alone.
6. Stress/nervousness – talkback radio playing in stables was found to increase the likelihood of Thoroughbred horses developing ulcers, suggesting stress is a risk factor for ulcers.
7. Forage type – lucerne hay appears to have a protective effect on the equine stomach and appears to reduce the incidence of gastric ulcers in horses.
8. Feeding Frequency – feed deprivation such as might occur during transport and long periods between meals lowers the pH in the equine stomach and allows the stomach to empty, both of which will increase the risk of gastric ulceration.
9. Non-Steroidal Anti-inflammatory Drugs (NSAID) – drugs like phenylbutazone (bute) have been shown to increase the risk of ulcers, particularly in the glandular (lower) region of the stomach.

How can feeding management reduce the risk?

To reduce the risk of gastric ulcers you need to assess your horse management systems and make changes wherever your horses are exposed to one of the above risk factors. Some feeding management practices that may help reduce the incidence and severity of gastric ulcers are:

• Don’t exercise horses on an empty stomach – providing a small meal of lucerne hay prior to exercise will:
1. Help to stop the acidic contents from the lower region of the stomach from splashing up onto the upper region where it can cause ulcers;
2. Provide a buffering effect by causing the horse to produce saliva while it is chewing the hay and through the buffering effect of lucerne hay itself. If you don’t have lucerne hay then your horse’s regular hay will also work well.

• Provide a small meal of lucerne hay immediately following exercise – the Western Australian study which found horses trained off site had a higher incidence of gastric ulcers suggests that the time taken to return home following training and thus time between the completion of training and breakfast and perhaps the stress associated with travelling is increasing the incidence of ulcers. Providing a small meal of lucerne following training will again help buffer the horse’s stomach and protect it from gastric ulceration. Again if you don’t have lucerne hay your horse’s regular hay will help.

• Provide turnout time (with paddock mates where possible) as often as possible – paddock turnout will help to reduce a horse’s stress level and if pasture is available will provide the horse with an opportunity to graze, and thus continuously produce saliva to help buffer the stomach and to keep their stomach full.

• Provide regular small meals and constant access to hay – allowing the horse to feed continuously during the day and night will help to reduce the likelihood of gastric ulcers developing. Divide the horse’s daily concentrate ration into as many meals as you can to be fed during the day and evening and provide hay at all times (preferably not all as lucerne hay, some grass hay will provide variety in the diet and keep the horse’s protein intake in check).

• If you are travelling long distances with your horse take regular breaks to provide small meals during the trip. Providing hay in a hay net will also provide the horse with an opportunity to continue eating during transport. Just beware of dusty hay increasing the risk of travel-sickness and of course the risk of entanglement in the net. If you are traveling with your horse over long distances on a regular basis, consider using a gastric ulcer medication (omeprazole or ranitidine) just prior to and during travel to cut the acid production and reduce the risk of ulcers. Speak with your veterinarian about this.

If you are concerned, with feeding a lot of hay, about your horse’s gut fill leading into a competition, you can reduce the amount of hay you are feeding for 2 days leading up to an event. However be careful not to reduce total forage intake to less than 1.5% bodyweight per day.
Using these feeding management strategies in combination with strategies to reduce stress will help to reduce a horse’s risk of developing gastric ulcers.

If your horse already has ulcers you must treat them

While one study has shown that feeding lucerne hay has been shown to reduce the severity of ulcers already present in horses and long periods of pasture turnout will sometimes allow a horse to resolve gastric ulcer issues, if your horse already has ulcers you must treat them with a registered ulcer treatment (omeprazole or ranitidine). Talk to your vet about the best treatment regime for your horse.

Finally...

Gastric ulcers are a serious and common health problem in horses that will affect their overall wellbeing and performance. While we still don’t have a full understanding of how and why they occur with such a high incidence, using the feeding and management strategies outlined above will help to reduce your horse’s risk of developing gastric ulceration. If you remember nothing else, just remember this… never work your horse on an empty stomach!

Source: FeedXL.com
References: Lester GD, Robertson I, Sercombe C. Risk factor for gastric ulceration in thoroughbred racehorses.
Rural Industries and Development Corporation, 2008 Australian Government publication 08/061.

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