Researchers have been telling us that we sometimes create health problems, such as gastric ulcers, in horses because we don’t manage them as nature intended—eating small quantities of grass almost continuously throughout the day. But are wild and feral horses really ulcer-free? And how do those rates compare to domestic horses?

At the 2015 American College of Veterinary Internal Medicine Forum, held June 4-6 in Indianapolis, Indiana, Ben Sykes, BSc, BVMS, MS, Dipl. ACVIM, ECEIM, MBA, of BW Sykes Consultancy in Upper Orara, New South Wales, Australia, presented those study results in a poster presentation.

A horse’s stomach consists of two sections: the acid-producing glandular region (the bottom half) and the smooth squamous region that has a lining similar to the esophagus (the top half). While traditionally ulcers were thought to occur most commonly in the squamous region, it is becoming increasingly apparent that ulcers can affect the glandular region, as well.

“Equine squamous gastric disease (ESGD) has been reported in 50% to 100% of performance horses in various studies, while the prevalence of equine glandular gastric disease (EGGD) has been reported as being between 30% to 65% in a number of different horse types,” Sykes explained. “But, to date, littler information has been published on the prevalence of either in feral horses.”

So Sykes and colleagues from Oxford Brookes University, in Oxfordshire, and Abingdon and Whitney College, in Abingdon, in the United Kingdom, conducted a study in which they evaluated the prevalence of ESGD and EGGD in feral and domestic horses presented to an abattoir (slaughterhouse) in the U.K.

The team classified horses as feral (all of which originated from the Dartmoor and Exmoor regions in this study) if they were free-ranging with little to no human contact and domestic if they’d been under human care with a designated purpose. Sykes said the team did not have any history on the study horses, such as their ages, sexes, breeds, or what disciplines they were used for.

Following processing, Sykes graded the lesions present in all horses’ stomachs on a scale of 0 to 4 (with 4 being most severe) via photographs; he was blinded to whether the horses were feral or domestic. He classified horses as being ESGD or EGGD positive (scoring 2 or higher for each region) or negative (scoring 1 or less).

The team evaluated data on 51 domestic horses and 27 feral horses and determined that:

  • 22.2% of feral horses and 60.8% of domestic horses had ESGD; and
  • 29.6% of feral horses and 70.6% of domestic horses had EGGD.

“The results of this study suggest that the prevalence of both ESGD and EGGD are higher in domestic horses than in feral horses,” Sykes said.

Interestingly, he added, while researchers have long known that the risk of ESGD rises with increasing human intervention in their care, “this report is, to the authors’ knowledge, the first documenting that a similar effect may be present for EGGD.

“The … prevalence of ESGD in the feral horses was surprising,” Sykes told The Horse. “However, it has been previously shown that ESGD may develop rapidly with fasting and transport, both of which the feral horses were exposed to.”

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Similarly, he said, the finding of an EGGD prevalence of 29.6% in the feral horse population was also surprising.

“Factors such as fasting and transport are known to be associated with the development of ESGD, but, to date, have not been demonstrated to cause EGGD,” he said. “A further understanding of the factors that cause EGGD is needed before this finding can be explained.

“The findings of this study support the idea that factors imposed through domestication and intensive management increase the risk of both ESGD and EGGD,” he relayed. “Risk factors for ESGD are well-described, and simple management changes such as permitting free-choice access to good-quality roughage (forage), increasing pasture turnout, and reducing grain intake are likely to reduce the likelihood of disease.”

In contrast, he said, despite several research groups’ ongoing efforts, we still don’t understand the risk factors for EGGD.

“The findings of this study suggest that intensive management may play an overall role in increasing the risk of disease, but the individual risk factors are not known,” Sykes said. “As such, it is not possible at this point in time to make specific recommendations to reduce the risk of EGGD. It is logical to follow the dietary and lifestyle changes advocated for the prevention of ESGD, but their efficacy in reducing the risk of EGGD is questionable.”