Evaluation of upper respiratory tract function during strenuous exercise in racehorses.

The study examines the cause of poor racing performance in horses, through an assessment of upper respiratory tract functions under strenuous exercise. The exercise was performed on a high-speed treadmill and certain dysfunctions and abnormalities were found.

Method of Investigation

• The researchers carried out an endoscopic evaluation of the laryngeal and pharyngeal functions in 46 racehorses which were known for poor performance.
• These horses were made to exercise on a high-speed treadmill as part of the evaluation.
• This method of investigation allowed the researchers to decisively identify if an intermittent or continuous upper respiratory tract obstruction was contributing to the observed poor performance and document the dynamic functional anatomy of the obstruction.

Findings of The Study

• Out of the 46 horses, functional abnormalities of the upper respiratory tract were identified in 10 horses (representing 22% of the study group).
• These functional abnormalities included epiglottic entrapment (in one horse), persistent dorsal displacement of the soft palate during exercise (in four horses), and left laryngeal hemiplegia (in five horses).
• Additionally, signs of left laryngeal hemiparesis—which encompasses asynchronous arytenoid movement—were noted in 32 horses while at rest. However, this condition did not hamper full laryngeal abduction during heavy exercise.

Conclusion

• From this study, it is evident that upper respiratory tract problems can contribute significantly to the poor performance of racehorses.
• The findings indicate that conditions such as epiglottic entrapment, persistent dorsal displacement of the soft palate, and left laryngeal hemiplegia are not uncommon among racehorses.
• While left laryngeal hemiparesis was noted among the majority of the horses, it did not appear to affect their performance during strenuous exercise.