REASONS FOR PERFORMING STUDY : Exercise-induced pulmonary haemorrhage (EIPH) occurs commonly in Thoroughbred racehorses worldwide. While EIPH
is believed to be an important cause of impaired performance in these horses, there is limited evidence from sufficiently powered studies to evaluate this
OBJECTIVES : To evaluate whether EIPH is associated with finishing position, distance finished behind race winners and differences in race earning among
Thoroughbred horses racing in South Africa.
STUDY DESIGN : Prospective cross-sectional study.
METHODS : One thousand Thoroughbred horses racing in South Africa were enrolled prior to a single race and underwent tracheobronchoscopic
examination within 2 h of racing. Three observers, blinded to the horses’ identity and race performance, independently evaluated EIPH occurrence and
severity using video recordings of the examination. Data were analysed using multivariable logistic and linear regression while controlling for important
horse and race factors as potential confounding variables.
RESULTS : Overall, 68% of horses had evidence of EIPH (grade ≥1). Horses without evidence of EIPH (severity grade 0), when compared with horses with any
evidence of EIPH (grade ≥1), were >2 times more likely to win races (odds ratio = 2.3; 95% confidence interval 1.4–3.7; P = 0.001), finished an average of one
length ahead of horses with EIPH (P = 0.03), and were 2.5 times more likely to be in the highest decile in race earnings (odds ratio = 2.5, 95% CI 1.5–4.1,
P<0.001). However, no association was identified regarding finishing in the top 3 positions or earning money when analysed as a continuous variable or
analysed as any winnings vs. none.
CONCLUSIONS : Exercise-induced pulmonary haemorrhage was associated with impaired performance in Thoroughbred racehorses not medicated with
furosemide and not using nasal dilator strips. These findings provide strong corroboration of previous research indicating that the occurrence of EIPH has a
major impact on the ability of Thoroughbred racehorses to compete successfully as elite athletes.