[ACTH stimulation test for the determination of salivary cortisol and of cortisol responses as markers of the training status/fitness of warm-blooded sports horses].

The research attempts to validate the use of saliva cortisol measurement as a reliable indication of a horse’s training status and fitness. However, the study concludes that the correlation between saliva cortisol levels and blood cortisol levels is unreliable.

Measurement methodology

• This study aimed to assess the reliability of using saliva cortisol concentration as an indicator of horses’ training status.
• Traditionally, plasma cortisol responses to treadmill exercise or an injection of adrenocorticotropic hormone (ACTH) are considered reliable markers for determining warm-blooded sports horses‘ performance and training status.
• The research attempted to use salivary cortisol measurements rather than plasma cortisol measurements so as to provide an easier, less invasive, and less time-consuming means of determining a horse’s fitness and training status.
• The study also investigated the repeatability of the cortisol response to a single ACTH injection (of either 50 micrograms or 250 micrograms).

Training regimen

• Horses were subjected to an 8-week training schedule, with three training sessions per week, covering distances that progressively increased from 3.5 km in the first week to 8 km in the last week.
• The horses were trained either by trotting (approximately 240 m/min) or by cantering (375 m/min).
• The initial sample used for this study consisted of ten four-year-old Hannovarian geldings, all reared in the same state stud.

Results and conclusion

• The correlation between salivary cortisol and plasma cortisol concentrations overall was found to be 0.64, based on measurements at various points of time.
• However, correlations at distinct points in time in different tests were insufficiently reliable (with a coefficient of 0.85, p < 0.02 only observed in one test).
• Thus, the study concluded that salivary cortisol measurements are not reliable or useful for diagnostic purposes.
• The repeatability of plasma cortisol responses to ACTH was found to be similar in both untrained and trained horses.
• The fitness indicators were unaffected by the type of training (either trotting or cantering) the horses went through.
• The final conclusion of the study is that saliva cortisol measurement is not a sufficiently reliable means of assessing a horse’s fitness or training status. Plasma cortisol measurements remain the standard.