Reasons for performing study: Little information is available regarding the prevalence of abnormalities of the upper airway and their association with performance in the general population of Thoroughbred racehorses.
Objectives: To describe the prevalence of selected abnormalities of the upper airway and their association with performance in Thoroughbred racehorses in Australia.
Hypothesis: That abnormalities of the upper airway of Thoroughbred racehorses are associated with poor race performance.
Methods: Rhinolaryngoscopy was performed after racing and presence and characteristics of abnormalities of the larynx and pharynx were recorded in a prospective cross-sectional study of Thoroughbred horses racing in Victoria, Australia.
Results: Rhinolaryngoscopy was performed once on each of 744 horses over 3.5 months. Fifty abnormalities of the upper airway were detected in 47 horses (6.3%, 95% confidence interval [CI] 4.7–8.3%). Epiglottic entrapment was detected in 7 horses (0.9%, 95% CI 0.4–1.9%) and was significantly (P = 0.015) associated with superior performance. Grade 2 asymmetry (4 grade scale) of the left arytenoid cartilage was detected in 9 horses (1.2%, 95% CI 0.5–2.4%) and was also associated with superior performance (P<0.001). Ulceration or erosion of the mucosa of the axial surface of one or both arytenoids was detected in 18 horses (2.4%, 95% CI 1.3–3.8%) and was not associated with alterations in exercise performance (P = 0.31).
Conclusions: Epiglottic entrapment, Grade 2 laryngeal asymmetry and mucosal erosions detected in Thoroughbred racehorses were not associated with impaired performance; therefore, surgical correction and concern over laryngeal function in horses with Grade 2 asymmetry may not be necessary in individuals performing to expectation.