Prevalence of pharyngeal, laryngeal and tracheal disorders in thoroughbred racehorses, and effect on performance

Endoscopic examinations were performed on 1005 thoroughbred racehorses in South Africa a mean (sd) 24 (12.3) minutes after racing, to determine the prevalence of pharyngeal, laryngeal and tracheal disorders, and to determine the relationship of these disorders with performance (number of wins and placed finishes). Overall, there was a low prevalence of grade 2 and 3 laryngeal function (LF) (2.2 per cent), grade 4 LF (0.6 per cent), epiglottic entrapment (1.3 per cent), subepiglottic cyst (0.2 per cent) and epiglottic deformity (0.6 per cent), while a higher prevalence of grade 2 to 4 pharyngeal lymphoid hyperplasia (PLH) (63 per cent), laryngeal debris (43.5 per cent), tracheal debris (21.9 per cent), tracheal mucus (99.5 per cent) and tracheal cartilaginous nodules (TCNs) (6.8 per cent) was observed. Performance was not affected by the presence of epiglottic deformity, grade 2 and 3 LF, grade 4 LF, debris within the trachea or larynx, or epiglottic entrapment. Grade 3 PLH occurred in younger racehorses; performance was impaired in horses with grade 2 and 3 PLH. Furthermore, TCNs were more prevalent in male racehorses and were associated with better performance.