Endoscopic evaluation of arytenoid function and epiglottic structure in Thoroughbred yearlings and association with racing performance at two to four years of age: 2,954 cases (1998-2001).

The study investigates the potential correlation between the results from endoscopic evaluations of arytenoid function and epiglottic structure in young racehorses and their subsequent performance at the age of two to four years. The results show a significant association between certain grades of arytenoid function and epiglottic structure and a decrease in racing performance and earnings.

Methodology

• The researchers conducted a retrospective case series involving 2,954 Thoroughbred yearling horses. The subjects’ medical records were examined, specifically looking at endoscopic evaluations of their larynx between 1998 and 2001.
• The horses’ arytenoid function (AF) and epiglottic structure (ES) were assessed using standardized scales. For AF, a modified Havemeyer scale was used with grades ranging from I to IV. For ES, the grading was from 0 to IV.
• Additional observations were made if the epiglottis appeared short or narrow. Performance data for the horses’ racing careers were obtained from an online database and analyzed in relation to the endoscopic results.

Results

• Horses with grade II.2 AF were found to have significantly lower earnings at 4 years of age compared to horses with an AF grade of less than II.2.
• Grade III AF was associated with fewer racing starts and lower earnings at 3 and 4 years old. None of the horses involved in the study met the criteria for grade IV AF.
• Horses with an ES grade above II had lower earnings at 2 and 4 years old in comparison to those with an ES grade below II.
• Also, a short epiglottis was associated with lower earnings at 2 and 3 years old.

Conclusions and Clinical Relevance

• The analysis revealed that horses with grade III AF are likely to have reduced athletic capacity. Yearlings with grade II.2 AF, ES grade above II, or a short epiglottis were found to generally have decreased racing performance.
• The researchers recommend that these factors should be carefully evaluated when deciding whether to purchase a racehorse, as they could impact athletic performance and potential earnings seriously.