Gastroscopy and gastric ulcers

Stomach ulcers in horses are a frequent cause for concern in horse owners, and because they can have multiple and varied clinical signs they can be a source of confusion. There are also a multitude of products on the market which claim to help with ulcers – so it can be hard to know what to do. 

How do you know your horse has ulcers?

  1. Physical signs: Some horses with ulcers have a poor coat, and struggle to gain weight despite adequate feeding. Ulcers have also been implicated as a cause of recurrent episodes of colic. Horses (particularly foals) with severe ulcers sometimes grind their teeth. 
  2. Behavioural signs: Ulcers have been associated with changes in temperament, picky eating behavior or periods of going off feed. Some studies have shown an association with ulcers, reduced time to fatigue, reduced stride length and poor performance. Horses may also show sensitivity on their abdomen, particularly around the girth area and may resent being brushed. There may also be a link between ulcers and crib biting. 
  3. Some practitioners use the presence of reactive acupuncture points to diagnose ulcers. While this can raise suspicions of their presence, it is quite nonspecific and has not been confirmed as an accurate or valid diagnostic test for ulcers.
  4. Gastroscopy. To date, direct visualization of the ulcers in the stomach using a 3m endoscope remains the only reliable method to diagnose presence or severity of ulcers. The procedure will be discussed further along in this article. 
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Tolerance and outward signs of ulcers will vary considerably between horses. Some horses show signs with only mild ulcers and with others, they are more stoic and the only sign may be picky eating or poor performance.

How common are ulcers?

Prevalence of ulcers varies with breed, and the type of exercise the horse does. In thoroughbred racehorses, rates of 37% of spelling horses and 80-100% of horses in training have been reported. Rates of 54% in pleasure horses and 64% of sport horses have also been found in some surveys. The lowest prevalence was 11% in horses being ridden at home and not competing.  Ponies who are on feed restriction for weight loss are at a high risk if they are not able to chew continuously. 

What causes ulcers?

The horse’s stomach is divided into two main areas, each with a different lining (mucosa). The top part, called the squamous or non-glandular portion, has a mucosa similar to skin, and although it has a thin surfactant layer, it doesn’t have a protective mucous coating and it has a poor blood supply so its healing capacity can be variable. The bottom two thirds is the glandular area, which is responsible for acid secretion. It also secretes a thick layer of mucous as well as bicarbonate to buffer acid. The blood supply to this area is better, and is one of the main protective mechanisms. 

This gastroscopy image clearly shows the demarcation between the paler pink squamous mucosa of the nonglandular portion and the darker pink glandular mucosa. This line is called the Margo Plicatus. The black tube you can see is the scope entering the stomach at the oesophagus 

Figure 1 Norm stom-707-602-670

Gastric ulceration in horses can be divided into two kinds, squamous ulceration (ESGD) and ulceration of the glandular region (EGGD). ESGD is the more common condition. EGGD can be more difficult to treat and its causes are less well understood. Medications that decrease gastric blood supply and some of the hormonal protective mechanisms of this area, such as phenylbutazone (bute) can potentially contribute. However, it takes a prolonged course of high doses to have a clinically significant effect. 

The photo on the left shoes a normal pyloris, the lower valve of the stomach before it empties into the intestine, showing healthy pink lining. The photo on the right shows ulceration of this area.

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Horses, unlike humans, secrete gastric acid continuously. When horses have continuous access to feed, particularly roughage, the presence of feed buffers the acid, protecting the vulnerable squamous portion. Eating also causes saliva to be produced, and this is high in bicarbonate which also helps to neutralise acid. When the stomach is full, the pH at the squamous part, is much less acidic than lower down. Exposure to acid is thought to be the cause of ulcers in the squamous part of the stomach. Certain feeds can also be broken down into acidic by-products. High starch feeds create more acidic conditions than roughage or fat. 

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 This image shows severe ulceration just above the margo plicatus.

When horses exercise, the pressure in the stomach increases, and causes acid to splash onto the squamous mucosa, causing damage. The more strenuous the exercise, the more pronounced this effect is. Added to this is the fact that many horses are held off feed before exercise, so there is more acid, and less feed and saliva to neutralize it. Even when horses aren’t exercising, periods of feed restriction put them at a higher risk of ulcers. This can even happen at pasture if grass is short and insufficient hay is to allow continuous supply is fed.

The type of diet also contributes to ulcer risk. High starch, grain diets increase acid production and can directly injure cells in the squamous part of the stomach. Higher fibre feeds are eaten more slowly, and also form a ‘mat’ that sits on the acid to reduce splashing. Lucerne is a particularly good feed because the high calcium content assists in buffering the acid, and it also has a low sugar and starch content. 

Stall confinement and stress can also increase the likelihood of ulcers developing. 

Nonsteroidal anti-inflammatories (NSAIDs)  such as phenylbutazone (bute), can contribute to ulcers, because they can reduce benefical prostaglandins which make up part of the defence mechanism of the gut. However, in most cases it takes a prolonged period of quite high doses to have a measurable effect. One study found no increase in ulceration after 10 days treatment at 2g (10ml/2 sachets) twice daily.  Newer, selective NSAIDs such as meloxicam have less detrimental effect (among other advantages), but this feature must be balanced in individual cases by its higher cost and reduced efficacy for significant orthopaedic pain, especially for laminitis. 


Gastroscopy for ulcer diagnosis

Gastroscopy is the only way to conclusively diagnose ulcers, and to tell how severe they are. This helps you to get a more complete picture more quickly, and guides the treatment course. It also allows for the diagnosis of pyloric ulceration which requires an additional drug to treat it, and a longer course of acid suppression. It is also a good way to be sure that ulcers have healed after treatment, as stopping medication too early can lead to recurrence of the ulcers. In rare cases, other problems such as tumours of the stomach and heavy infestations of bots can be seen.

Your horse will need to have an overnight fast of at least 12 hours, and then water needs to be withheld for 4 hours prior to the procedure. We prefer horses to come in the night before so that we can carefully control access to feed and water and so the horse is more settled for the scope. Once the horse is sedated, a large stomach tube is passed, and a 3 metre long fibreoptic endoscope is passed inside the tube, down the oesophagus into the stomach. The procedure can take 30-40 minutes, as the residual feed needs to be washed from the lining and reaching the pyloric area can take some time.  As soon as the horses have recovered from sedation, they are given a feed. 


Treatment recommendations are based on the severity of the ulcers. You will also receive a written report with pictures of the ulcers. The photo below shows severe ulceration.

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Treatment of ulcers.

Prevention is much easier than treatment. It has been shown that turnout alone is poor at resolving gastric ulcers. In fact, some of the horses studied developed new ulcers. There are a huge number of products and supplements available that claim to heal or prevent stomach ulcers. Currently, the only treatment with widespread scientific validation is suppression of acid. For significant ulcers, suppression of acid levels seems to be crucial. There are two main drugs which block acid secretion, ranitidine (zantac is a common trade name) and omeprazole (losec for humans). In horses only omeprazole is registered for horses. Omeprazole also has the advantage of once daily dosing, compared to 8 hourly for ranitidine, and is the more effective of the two. 

Omeprazole products

Somewhat confusingly, there are three different omeprazole formulations available and it can be tough to know which is best. The first main distinction is between the gastric coated drug and the buffered formulation. The coated formulation (products include gastrozol made by virbac, gastropell daily and gastropell forte, made by Randlab) was thought to be superior because of higher absorption due to the protective coating. Subsequently it has been found that it is only slightly more absorbable than the buffered formulation, which survives the stomach because it buffers the acid. The buffered formulation (the original product is called Gastroguard) uses a higher dose of active drug and was the drug that all of the initial ulcer healing research was done with, so it is known to be very effective. The buffered product commonly available here is called Ulcershield (also made by Randlab). Another factor with the coated product, is that if the horse chews any of the paste, the coating is removed and it is rendered less effective. This means when you dose it, you need to be very careful to avoid the teeth, easier said than done. 

Duration of treatment varies depending on the gastroscopy findings, but at least 30 days at the full dose of omeprazole is recommended at this time. 

Other products

Unfortunately, despite many products claiming to promote stomach health and prevent ulcers or help them heal, there is a deficiency of controlled studies published to support the effectiveness of most of these. There is some evidence that products containing seabuckthorn help, but for severe cases it cannot be recommended in isolation. It may be that there are other products available that do assist in ulcer healing or prevention, but until there is published data confirming this, it is difficult to recommend these above acid suppression. 

Depending on the horse’s workload, once healing of the ulcers is complete it is better to stop acid suppressive therapy to allow the horse’s stomach to function as nature intended. This is when one of the supplementary products may be very worthwhile.  However, if the horse is in strenuous work, or there are periods where the horse goes without feed or is under stress, preventative treatment is warranted. Racing horses, especially picky eaters are probably better to remain on a 3ml dose of ulcershield throughout strenuous training. 

The most important factor in preventing gastric ulcers is to make sure the horse has a constant supply of roughage to eat. This buffers the acid and also stimulates saliva production, which is rich in bicarbonate. Before strenuous exercise, giving a handful or two of lucerne will help, because the fibre forms a mat that decreases the splashing of acid. Lucerne is superior because of the high calcium content, which also helps buffer the acid. When the horse goes out to compete it is important to allow access to hay straight after competition as well. Racehorses should be given hay between racing and transport back to the stable. 

In summary, gastric ulcers are common in horses performing at high levels, but can also occur in any horse. The clinical signs shown, if any, vary depending on the horse. If the horse is showing clinical signs suggestive of ulcers, gastroscopy is a good way to tell if there are ulcers present and how severe. Properly treating ulcers can be expensive, and gastroscopy costs roughly the same as a week of ulcer treatment, and less than four days of training fees for a racehorse. Considering that ulcers can reduce feed efficiency and contribute to poor performance, properly diagnosing gastric ulcers is good horse management and can improve results. It is also the only way to tell for sure whether the treatment given has been effective.  If the ulcers have been successfully treated and the horse has not improved, seeking another source of discomfort is the next step. 


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Cambridge Equine Hospital is the largest equine practice in the country, with fifteen veterinarians solely dedicated to equine work. Situated in Cambridge, we have been providing top quality equine veterinary services to clients in the Waikato area for over 30 years. We cater for all types of horses, from ponies through to elite performance and breeding horses.



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