Comparison of tracheal aspirates before and after high-speed treadmill exercise in racehorses.

This was a study to examine the changes in neutrophil percentages in the tracheal aspirate samples of racehorses before and after high-speed treadmill exercise. The study found that exercise significantly increased the neutrophil percentages in the samples, suggesting that the timing of sample collection can influence the diagnostic results.

Research Methods

The researchers followed a case series methodology, selecting a sample of 40 young Thoroughbred and Standardbred racehorses which had presented for evaluation due to poor performance. Tracheal aspirate (TA) samples were collected from these horses endoscopically before and after high-speed treadmill exercise. Specifically, the samples were taken 24 hours prior to exercise and 1 to 2 hours after the exercise.

In order to analyze the samples:

• TAs were cytocentrifuged and the resultant fluid was treated with a Diff-Quik stain.
• Mean neutrophil counts were calculated and expressed as percentages of the total inflammatory cells.
• The neutrophil percentages were then classified as either above or below a set 20% cut-off.

Study Findings

This study revealed:

• An increase of neutrophil percentages in TA samples from racehorses after undergoing high-speed treadmill exercise.
• For horses having 20% or less neutrophils in their TA before exercise, their post-exercise TA showed raised neutrophil percentages that were above the 20% cut-off.

Conclusion and Recommendations

Based on their findings, the researchers concluded that intense exercise can alter the ratio of neutrophils in the lower airways of racehorses. This fact has implication for vets who need to consider the influence of exercise when interpreting TA results.

The study suggested that to achieve the most diagnostically valid results, TA samples should ideally be collected after a “washout” period of 1 to 2 hours following intense exercise. This is to allow for any temporary fluctuations due to the exercise to subside, providing a more accurate reflection of the horse’s normal inflammatory cell profile.