In equine practice, gastric disease is frequently blamed for behavior issues in horses, said Ben Sykes, BSc, BVMS, MS, MBA, Dipl. ACVIM, PhD, of BW Sykes Consultancy, in Coffs Harbour, Australia. While many clinical signs are attributed to equine gastric ulcer syndrome (EGUS), until recently we haven’t had much evidence for many of the signs ascribed to this disease.
“With an estimated 50-70% of the equine population having ulcers, can we confidently say they are all suffering?” Sykes asked during his presentation at the 2024 National Alliance of Equine Practitioners (NAEP) Saratoga Equine Practitioners Conference.
Signs commonly attributed to EGUS include weight loss, poor hair coat, poor performance, aversive ridden behaviors (especially for glandular disease), girthiness, spookiness, and more.
“Gastric disease gets blamed for everything, but correlation does not necessarily equal causation,” said Sykes.
What Can We Blame on Equine Gastric Disease?
Looking at squamous disease, Sykes said, “We know there is a strong association with appetite, especially in horses with high risk factors like racehorses or high-level sport horses. If a horse with high risk factors loses its appetite, squamous disease is likely present, and when we treat squamous disease their appetite improves.”
Veterinarians have also reported associations between squamous disease and poor hair coat and colic. Sykes believes there is an association—causation really—between glandular disease and warmbloods with recurrent colic.
Poor performance has also been linked to both squamous and glandular disease. Thoroughbred racehorses with glandular disease were almost four times more likely to be performing below expectation in one study. Show jumpers, warmbloods especially, competing at the international level, were surprisingly less likely to have glandular disease than national-level horses, which is the opposite of what we might think because they have a higher intensity of management.
“But perhaps what we see is a barrier in horses with glandular disease that stops them from moving up to the next level,” Sykes said.
Many other behavioral signs haven’t had much evidence to support an association between their presence and disease.
“Until recently,” said Sykes, “we clearly don’t have great data for when an owner brings a horse and says it is behaving poorly to link it to EGUS.”
Pineau et al. (2024) applied Dr. Sue Dyson’s Ridden Horse Pain Ethogram (HRpE) and found a strong association between EGUS, both squamous and glandular disease, and ethogram score.
“We see a lot of crossover between Dyson’s work relating the RHpE to musculoskeletal disease and Pineau’s work relating it to EGUS,” said Sykes, adding, “So, instead of saying the horse with aversive behavior has EGUS, we now say the horse has pain. Thinking like this encourages us to step back and think about aversive behavior as a pain-based behavior, especially in sport horses, and broadens the list of likely causes.”
Medically Evaluating a Horse With a Behavior Problem
“The first thing I do when an owner brings me a horse that has aversive behavior and wants gastroscopy is a basic lameness exam,” Sykes explained. “It might seem strange for an ‘Ulcer Guy’ to start with lameness, but many of my horses go home with a diagnosis of lameness that is considered, at least in part, contributory to the primary behavioral presentation.
“Others have EGUS,” he adds, “and some have both EGUS and lameness.”
Oral disease is also potentially important, so after gastroscopy, the next exam Sykes performs on a horse is an oral exam for dental pathology or oral ulcers.
“The lameness and oral exams together with gastroscopy allow me to determine if there is more than one potential explanation for the aversive behavior,” he said. “There isn’t always just one cause, and the summative effects of pain exceeding a ‘pain threshold’ can be important in some animals.”
Removing the source of pain, however, might not fix the behavioral issue because of some degree of learnt behavior, especially in cases of chronic pain.
Horses are intelligent animals and might form learnt associations between certain activities, such as tacking up and the anticipation of pain. “So, when we see the behavior persist beyond resolution of the identified sources of pain, we must consider what role learnt behavior plays and consider strategies to address this directly,” said Sykes.
In Summary
Identifying gastric ulcers doesn’t confirm them as the cause of a horse’s behavior problems.
“Where behavior abnormalities are present, we should consider if it is primarily pain-based behavior, not specifically EGUS. By taking a step back and looking for all causes of pain, we can improve the accuracy and speed with which a causative diagnosis is determined and, ultimately, well-being outcomes for the horse” concluded Sykes.
Related Reading
- Equine Gastric Ulcer Syndrome: Diet & Management Strategies
- Feeding Horses That Can’t or Won’t Eat
- Approach to Horses with Poor Performance
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