Susan Holmcombe, VMD, PhD, Dipl. ACVS, ACVECC, associate professor in the department of large animal clinical sciences at Michigan State University, told the group at the 50th annual American Association of Equine Practitioners (AAEP) Convention in Denver, Colo., Dec. 4-8, 2004, that mucus in the trachea of a racehorse can compromise his ability to perform. "The horse's ability to extract and use oxygen is vital to performance," she said, and added that mucus in the airways can prevent the horse from utilizing oxygen to the fullest.

Accumulation of airway mucus, she said, is common in young horses and often stems from inflammation. The number of racehorses affected approaches 33%.

However, she added that there were no definitive data on exactly what effect mucus had on racing performance, but there are indications that it might be associated with sub-par performance.

In an effort to find definitive answers, a study was conducted at Thistledown Racetrack in Warrensville, Ohio, during the race meet from April to December in 2002 and 2003. Each horse of the 527 horses in the study was checked via endoscopic examination of the nasopharynx, larynx, and trachea on a monthly basis