Thoroughbred racehorses performing below expectations are 3.7 times more likely to have ulcers in the lower acid-producing part of their stomach, researchers have found.
The study team said their findings support the notion that equine glandular gastric disease (EGGD) should be considered as a distinct disease to equine squamous gastric disease (ESGD).
EGGD is ulceration that affects the lower half of the stomach, where hydrochloric acid and digestive enzymes are secreted to properly digest food.
ESGD involves ulceration of the upper non-glandular part of the stomach, called the squamous mucosa, where no acid is produced. It has limited defense mechanisms and is not normally exposed to a pH of less than 4, which makes it susceptible to damage from acid splashed from the lower part of the stomach.
Gastric disease is common in racing Thoroughbreds worldwide, affecting 80%‐100% when actively racing.
However, in ponies, there is low prevalence, with moderate prevalence seen in Warmblood athletes, and higher rates in Standardbreds and Thoroughbreds.
Researchers Benjamin Sykes, Mark Bowen, Jocelyn Habershon‐Butcher, Martin Green and Gayle Hallowell, writing in the Journal of Internal Veterinary Medicine, said while hydrochloric acid was the dominant factor, volatile fatty acids produced locally in the stomach associated with grain feeding were also considered important contributors to disease.
The development path of EGGD is not known, but it is believed to be caused by the failure of the normal gastric glandular mucosal defense mechanisms.
The researchers noted that the risk factors for EGGD had not been described in the Thoroughbred.
They set out to determine management factors associated with EGGD, identify clinical signs in affected horses, and compare these to ESGD.
The study involved 109 actively racing Thoroughbreds from eight training yards, three in Britain and five in Australia.
The horses underwent a gastroscopic examination, while caregivers were asked to fill out a questionnaire delving into management, feeding, exercise, and health.
The study team found that management factors and clinical signs were different for the two conditions.
Exercising five or more days a week was associated with a 10.4-fold increased risk of EGGD, although no effect from exercise intensity or duration was observed.
Horses racing below expectation were 3.7 times more likely to have this condition.
Individual trainers were also identified as a risk factor for the disease, a factor which, among others, pointed toward stress playing a role in development of EGGD.
Thoroughbreds in work for six weeks or fewer were less likely to have ESGD.
Those found to be aggressive to humans were less likely to have ESGD, while horses with stereotypies – unproductive repetitive behaviours – were more likely to have ESGD.
“The findings of our study further support the notion that EGGD should be considered as a distinct disease entity to ESGD,” the researchers wrote.
Exercising Thoroughbreds no more than four days a week could reduce the risk of EGGD, they concluded.
“Horses with EGGD are more likely to perform below expectation and, as such, EGGD might be performance-limiting in some affected individuals.”
Stress minimization could reduce the risk of this condition, they said.
The researchers, discussing their findings, said the prevalence of ESGD in their study was similar to previous reports, while the prevalence of EGGD was lower than previously described in Australian Thoroughbred racehorses.
“The prevalence of ESGD consistently increases as the intensity of management and exercise, and the feeding of high grain diets, increases; however, a similar effect is not consistently observed in EGGD.”
Horses with ESGD were more likely to have EGGD.
The authors said the potential association between stress and EGGD suggests that further studies evaluating the relationship of stress, stress responses, and EGGD in horses are warranted.
“Furthermore, studies investigating the potential for limiting the number of days of exercise as a preventative strategy in the management of EGGD appear warranted. Lastly, whether horses benefit from dedicated rest days, or complete rest, during the treatment of EGGD warrants investigation.”
Management factors and clinical implications of glandular and squamous gastric disease in horses
Benjamin W. Sykes, Mark Bowen, Jocelyn L. Habershon‐Butcher, Martin Green, Gayle D. Hallowell.
Journal of Veterinary Internal Medicine, https://doi.org/10.1111/jvim.15350