Dorsal displacement of the soft palate in 92 horses during high-speed treadmill examination (1993-1998)

Abstract

Objective: To evaluate the occurrence of dorsal displacement of the soft palate (DDSP) during high-speed treadmill (HSTM) exercise in racehorses, and determine treatment efficacy relative to the endoscopic findings observed during resting and HSTM endoscopic examination.

Study design: Retrospective study. Animals-Ninety-two racehorses (74 Thoroughbreds, 18 Standardbreds).

Methods: The signalment, history (clinical and race), treatments, and video recordings made during resting and HSTM endoscopy were reviewed in 92 racehorses that developed DDSP during HSTM exercise. Only horses that completed 3 starts before and after HSTM examination were included in performance-outcome analysis. Statistical associations were made between the independent variables (the historical findings and the resting and HSTM endoscopic findings) and performance outcome.

Results: Forty-five horses (49%) displaced their palate in an uncomplicated manner, whereas the other horses either had another upper-respiratory abnormality in association with DDSP (35) or displaced after swallowing (12). Although respiratory noise was not recorded during HSTM exercise, only 57 horses (62%) that developed DDSP during HSTM examination had a history of abnormal upper-respiratory noise. For the 45 horses that met the criteria for performance outcome analysis, there were no independent variables recorded during resting or HSTM endoscopy that had a significant association with performance outcome. Treatment for DDSP varied by clinician. Overall, 29 horses (64%) had improved average earnings per start after diagnosis and treatment.

Conclusions: Thirty-five horses (38%) that had DDSP during HSTM endoscopy had no previous history of abnormal upper-respiratory noise, and 74 (80%) had no structural abnormalities noted on resting endoscopic examination.

Clinical relevance: HSTM examination is an excellent tool for diagnosis of DDSP and the manner in which it occurs. DDSP did not occur similarly in all horses, and was often associated with another upper-respiratory abnormality. Thus, it is unlikely that a single treatment can be applied effectively for all horses that experience DDSP. Both surgical and medical treatments can be beneficial in improving a horse's performance after a diagnosis of DDSP is made. Neither resting nor HSTM endoscopic findings were clearly prognostic.