Thoroughbred yearlings sold at public auction here and abroad often are subject to endoscopic examination of their upper respiratory tracts. Veterinarians and potential buyers are looking for evidence of deformities that could affect the ability of that young horse to breathe normally when it reaches adulthood as a trained athlete. Since some people buy weanlings to resell as yearlings, months-old foals also are being "scoped." A research project by Geoffrey Lane, BVetMed, FRCVS, Senior Lecturer of Soft Tissue Surgery at the University of Bristol in England, recently found that foal endoscopy is, in fact, not useful in determining respiratory soundness when that animal is a yearling or adult. In another study, he found that some yearlings with an "imperfect" larynx have the ability to perform normally, if not exceptionally, as adults.

However, in a third research project, he followed yearlings which were returned to a panel of experts as not meeting conditions of sale. With that group, he found horses which were rejected by the panel usually did not perform well (if at all) as atheletic adults, and those passed by the panel usually were able to compete. Therefore, Lane concluded that such a panel is successful in safely identifying horses which will not perform well.

Lane conducted these studies at the Tattersalls Thoroughbred Sales in England and presented his results at the International Breeders' Meeting at San Siro Racecourse in Milan, Italy, in June.

The Studies

Lane studied three groups of horses for these projects. The first was a group of 187 foals examined with a video endoscope for upper airway abnormalities, then re-assessed a year later. A second group involved 2,676 yearlings endoscoped in an 11-year study. Finally, Lane studied yearlings which were referred to a "wind panel" at the Tattersalls sales facility after recurrent laryngeal neuropathy (RLN) was detected. RLN is very similar to laryngeal hemiplegia, or "roaring." Both involve paralysis affecting the larynx caused by damage to the nerves controlling the vocal folds. Lane defines them as hemiplegia meaning that one-half of the larynx is completely paralyzed, and RLN as any degree of paralysis. According to Lane, horses can have some degree of damage to the nerves and still have the larynx function "rather normally."

Palpation and endoscopy were used in the group of foals to look for congenital structural abnormalities and RLN. Lane estimated that only 0.5% of Thoroughbred foals are born with abnormalities such as cleft palate, cysts, and branchial arch defects, and there were none in the study group. Lane found inconsistencies in the results. Some of the foals which appeared normal seemed to have deteriorated over the year, whereas others which might have been turned away by a wind panel improved to normal within the year.

In the second study group of 2,676 yearlings, Lane tried to identify those with RLN which had little prospect of becoming successful athletes before entering training. In his studies, Lane graded the RLN in each horse on a scale of 1 to 5, with 5 being the most severe.

"I've have grave reservations of the value of some of (these yearling endoscopic results)," said Lane, who explained that a yearling given a poor outlook can turn out to run completely normally. "Conversely, horses could appear to be normal, and then later be re-evaluated as 'lemons.' Is it really a scientifically justifiable process?"

Almost 20% of the study horses fell into the Grade 3 group. In other research, 75% of Grade 3 horses have shown normal function in high-speed treadmill endoscopy in a university setting. Lane said this proved to be the case with the Grade 3 yearlings, because only a small number produced abnormal respiratory noises in training, and a number of them became Group 1 winners.

Lane says that no auction will ever be able to have the ability to recreate a situation to evaluate sale yearlings as athletes. "By (endoscopically) looking at anomalous movements at rest, an opinion is given. We're looking at the larynx during quiet breathing rather than looking at one during exercise."

In the final group, Lane followed horses which after the Tattersalls sale were returned to the wind panel for evaluation. Returnable conditions in the England and Ireland sales are limited to RLN--the horse must produce an inspiratory noise when actively exercised and must show endoscopic laryngeal disfunction. Of 9,524 horses which were sold at Tattersalls Newmarket Houghton and October sales between 1987-1995 (78% of which were examined by the purchasers' vet), only 149 were referred to panel assessment. Only 59 (0.65%) were found returnable to the vendor (which he says shows that the panel process serves as a deterrent against vendors who might knowingly sell a defective horse). Of those 59, only 2.2% had RLN of Grades 4 or 5. Also, no horse sustained an injury during panel testing, so the testing was deemed safe.

In athletic performance, horses which passed the panel raced just as well as the horses which were never put before the panel. But horses which were returned to their vendors were twice as likely to be unraced, had fewer starts, and were less likely to win or place (34% vs. 17% in a control group).

Lane notes that we're learning more and more about the dynamics of the respiratory tract in the horse, and his research will continue. He points out that most airway surgery is because of symptomatic causes and there needs a better, more scientifically based reason. He also wants to help practitioners and researchers in evaluation of the horses.

"We're trying to identify better ways (of testing horses) for those without treadmills, so that people within normal clinical practice can make a reliable and helpful diagnosis."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More