Factors that Cause Ulcers in Racehorses

Up to 86% of Australian Thoroughbred racehorses have been reported to have gastric ulcers. Many factors can contribute to ulcers, and researchers at Murdoch University set out to determine which ones were the most significant for this population.

Dr. Guy Lester, associate professor of large animal medicine at Murdoch University, presented the study results at the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla.

This extensive study evaluated 191 variables affecting 402 horses with 37 trainers in several locations across western Australia. Thirty-three percent of the horses were found to have moderate or severe gastric ulceration (defined as a score of 2-3 on an ulcer severity scale of 0-3). Here's what the researchers found:

Factors increasing ulcer risk:

• Cribbing/windsucking--this was the most significant risk factor at 7.6 times higher risk. Whether cribbing might be a cause or an effect of ulcers is unclear. Other stereotypic (continuous, repetitive, and serving no purpose) behaviors were also correlated with higher ulcer risk.

• Location of training--training in an urban environment conferred a greater risk of ulceration (3.9 times higher risk), but it was not retained in the final model. This indicated that it was factors common to this training environment rather than simply training in the city.

• Time in training--ulcer risk increased by a factor of 1.1 for every week in work, independent of the total time a horse spent on the property.

• Body condition maintenance--horses that had trouble maintaining weight were 3.4 times more likely to have ulcers. This factor was also correlated to weeks in work.

• Having a radio on in the barn--talk radio was correlated with a 3.6-fold increase in ulcer risk, while music radio increased risk 2.8-fold (this statistic brought chuckles from the audience). Lester noted that radio could be a surrogate factor for a more urban setting (known to increase ulcer risk), and that race radio with constant yelling of race status might, indeed, be more stressful to horses stalled nearby.
Factors decreasing ulcer risk:

• Training on the property where the horse was housed--3.3 times lower risk.

• Turnout with other horses--3.3 times lower risk.

Additional observations:                                                                                                                                     

• Ulcer prevalence varied widely by region, but management within those regions likely had more of an impact.

• Some trainers had no horses with ulcers, while others had ulcers in nearly every horse in the barn.

• Horses that were aggressive toward people seemed less likely to have ulcers. "Maybe they know how to manage their stress--they just let it fly," said Lester with a smile.

• Failing to race to expectation was highly significant, but was not used in the final model. "Trainers are quite perceptive in identifying clinically affected horses and not racing them," he noted.

• Diet did not have much of an impact, but feeding practices didn't vary much.

Gastric ulceration "is a multifactorial disease, and elimination of a single factor may fail to impact disease prevalence," Lester concluded. "Don't just go turn the radio off; it's more complex than that. Variations in the way individuals handle stress and ulceration make it tough to make consistent recommendations."

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