Comparison of the adrenocortical response to both pharmacological and physiological stresses in sport horses.

The research investigates the impact of two types of stress, physiological and pharmacological, on the cortisol concentrations in the blood of sport horses. It concludes that a standardised pharmacological stress test may be used to predict the response to exercise-induced stress.

Objective and Methodology of the Study

• This study was done to compare the effects of physical (physiological) and drug-induced (pharmacological) stresses on plasma cortisol levels in sport horses. The physiological stress was generated by making the horses complete a cross-country course, while the pharmacological stress was induced by intravenous administration of ACTH.
• The researchers selected seven sport horses for this study. Blood samples were taken from these horses and analyzed for cortisol concentrations.
• The blood sample collection was done before and after subjecting the horses to each type of stress. The comparison of these cortisol levels would help in understanding the relative increase induced by exercise and ACTH administration.

Findings of the Study

• Both the exercise and ACTH injection resulted in a significant increase in cortisol levels in the horses. The cortisol increase was 79 +/- 0.10% due to exercise and 160 +/- 0.18% due to ACTH administration.
• The relative increases in cortisol levels due to exercise, and ACTH administration was also compared. The correlation was found to be 0.82, indicating a strong positive relationship between the cortisol response to exercise and ACTH administration.

Conclusion of the Study

• The researchers concluded that the cortisol response to a standardized pharmacological stress (ACTH administration) could be used as a predictor for the cortisol response to exercise-induced stress in horses.
• This means that the results for a pharmacological stress test could potentially provide a reliable way to predict how the horse will respond to the stress caused by a significant amount of exercise, such as completing a cross-country course. This conclusion could have important implications for the training and management of sport horses.