Association of tracheal mucus or blood and airway neutrophilia with racing performance in Thoroughbred horses in an Australian racing yard.

This research looked into the correlation between tracheal mucus, tracheal blood and transendoscopic tracheal wash cytology with the racing performance of Thoroughbred racehorses. The study concluded that visible tracheal blood post heavy exercise was a risk factor for poor racing performance, however, the presence of airway neutrophilia was not. The research also found no association between tracheal mucus score or cytology and racing performance.

Research Methodologies

• The study was conducted on a population of 155 Thoroughbred (TB) racehorses, with a total of 220 endoscopic examinations performed and transendoscopic tracheal wash (TW) samples obtained.
• These samples were collected 60-120 minutes after the horses had done gallop work, i.e., a type of strenuous exercise.
• 3 key factors were analyzed: tracheal mucus score, tracheal blood score, and TW cytology and their association with racing performance.
• Out of the samples and examinations conducted, 194 from 135 horses met the inclusion criteria for the study.

Results & Findings

• The overall prevalence of visible tracheal mucus was found to be 2.5% (5 out of 194) and of increased tracheal mucus was 0%.
• Visible tracheal blood had a prevalence of 8.8% (17 out of 194), with increased tracheal blood at 4.6% (9 out of 194).
• A total of 36% (70 out of 194) of TW samples showed elevated levels of neutrophils, of which 96% (67 out of 70) had no visible tracheal mucus.
• There was a significant correlation found between increased tracheal blood scores and poor racing performance, which had a p-value of 0.004, clearly indicating statistical significance.
• Contrarily, there was no significant correlation found between tracheal mucus scores or TW cytology and racing performance.

Conclusion

• The study concluded that visible tracheal blood seen after strenuous exercise in clinically normal TB racehorses was a risk factor for poor racing performance.
• However, the presence of airway neutrophilia, which is an increase in the number of a type of white blood cell, was not a risk factor.
• The study did not find any horses with increased tracheal mucus, hence, the association of increased tracheal mucus with racing performance could not be assessed.