Gastric ulcers in horses have been a problem for trainers, owners, and managers for years now, and studies suggest a majority of racehorses and performance horses suffer from them. As a result, they've been a topic of much academic research in the past five years.
Dr. Ben Sykes, assistant professor of equine internal medicine at Massey University, sat down with the Grayson Jockey Club Research Foundation recently to give the public an idea of what we've learned in the past five years and what he and other researchers plan to focus on in the next five.
A complete replay of Sykes's seminar is below. A few key takeaways:
- First of all, the term most of us use to describe this issue in horses is a bit outdated. Equine Gastric Ulcer Syndrome (EGUS) is still the common terminology in lots of advertising and lay articles about the topic, but that's actually a holdover from before we knew that there were two distinct types of ulcer-like disorders that could be happening in a horse's stomach.
Technically, there are now two terms in use which are more specific: Equine Squamous Gastric Disease and Equine Glandular Gastric Disease. Squamous gastric disease refers to ulcers in the upper half of the stomach, characterized by ulcers easily viewed on gastroscope. Glandular Gastric Disease refers to lesions [which technically aren't ulcers, but look and behave similarly to true ulcers] in the lower half of the stomach, particularly around the part where the stomach empties into the gut.
- Until recently, gastroscopes were only long enough to reach the squamous part of the stomach, so we didn't really know if there could be problems lurking further along. The two terms really only came about in the last several years when the longer gastroscopes became common. Research we have on gastric ulcers in horses prior to 2015 is almost certainly referring to Equine Squamous Gastric Disease. Equine Glandular Gastric Disease is much less understood.
- Why does this matter? The two diseases exist independently of each other, with different possible causes and different treatments. For Sykes, squamous ulcers come about as a result of management decisions that increase damage of stomach acid to the top of the stomach. The ulcers are caused by two types of acid – hydrochloric acid, which is reduced by common treatments like omeprazole, and volatile fatty acids, which are not addressed by omeprazole and come about as a way to digest grain. Sykes said researchers think that this acid damage occurs during exercise.
Studies have shown that exercise drops stomach pH, increasing the acidity. This is primarily because the abdominal muscles at a trot or canter squeeze the stomach into an hourglass shape, pushing the acid that was at the bottom of the stomach, where it was being buffered by a lot of fibrous feed material, toward the top, which is more likely to be fairly empty or contain thinner, more watery material. It's quite easy for the acid to splash around at the top of the stomach and cause damage.
High carbohydrate diets can be a problem for horses with this disorder since they require more volatile fatty acids to break down the structure of the carbs. That doesn't mean you can't feed an ulcery horse grain, Sykes said – you just have to do it in moderation. A balanced commercially processed feed provides a lot of important nutrients to working horses. Low carb, high fat and high fiber diets are good choices for keeping a horse fed without increasing ulcer risk.
- Equine Glandular Gastric Disease on the other hand, occurs in the lower part of the stomach where the environment is commonly pretty acidic. Sykes said he thinks the disease occurs because the natural defense mechanisms of the stomach lining there have been compromised for some reason.
There's no evidence diet impacts Equine Glandular Gastric Disease, but workload might. Studies have shown that long stretches of work without days off make a horse more likely to exhibit signs of Equine Glandular Gastric Disease, and behavioral stress may be a factor as well. Horses with glandular ulcers have been shown to produce higher levels of cortisol in stressful situations than horses without glandular ulcers, though we don't know whether stress caused the ulcers or the ulcers worsened the horses' stress reaction.
- A few discoveries from recent data: Perhaps surprisingly, omeprazole, the go-to treatment for gastric ulcers, does its best work on a relatively empty stomach. One study compared the acidity of horse's stomachs when they were fed free choice hay round the clock versus the usual racehorse schedule of two big meals with some hay offered in between. Researchers found that the drug worked best when the horse had an empty stomach first thing in the morning.
- It seems misoprostal may be a better treatment for glandular ulcers than omeprazole, which works well on squamous ulcers. Both options improved horses' symptoms, but the misoprostal showed more healing of lesions on gastroscopy.
- A new form of omeprazole available via intramuscular injection may show promise for horses with both types of ulcers. The drug isn't accessible in most of the United States yet, but one peer-reviewed study showed 100% healing of squamous ulcers and 75% healing of glandular ulcers after two doses.
- For a long time, veterinarians have suspected a connection between prolonged use of non-steroidal anti-inflammatories like phenylbutazone and ulcers, so for a while they suggested giving omeprazole along with bute as a preventative. Sykes pointed to one peer-reviewed study from 2020 that showed that may not be a good idea. In the study, horses were examined after being given a course of drugs — either bute alone or bute given alongside omeprazole. The bute group did show signs of ulceration while the other group didn't, but there was a high rate of serious intestinal issues among the group receiving bute with omeprazole. In two cases, those intestinal problems proved fatal.
- One of the big questions Sykes hopes to answer in the coming years is the potential side effects of long-term omeprazole use in horses – particularly whether or not it increases fracture risk by changing calcium and magnesium absorption. Initially, long-term use of certain types of ulcer drugs in humans was thought to increase fracture risk only in geriatric patients but a recent study in pediatric patients showed that short term treatment of very young children resulted in a 13 percent increase of fracture by age 12 or 13.
We don't have any data to show whether or not the same thing occurs in horses, and part of the reason is that it's difficult to exclude other risk factors for a fracture. The human data does have Sykes worried – not only about the intersection of ulcer treatments and fatal fracture risk, but also about whether ulcer treatments could predispose a horse to bucked shins or other bone maladaptive disorders.
Sykes said thanks to Grayson Jockey Club Research Foundation, he and others are currently constructing studies to look at the impacts of common ulcer drugs on mineral absorption in horses. With any luck, we should know more about the issue in the coming years.
The post What We Know (And What We Don’t) About Equine Gastric Ulcers And The Impact Of Treatment On Bones appeared first on Horse Racing News | Paulick Report.
