Plasma cortisol concentration increases within 6 hours of stabling in RAO-affected horses.

The research examines the relationship between Cortisol, a hormone, and Recurrent Airway Obstruction (RAO) in horses. The findings reveal that Cortisol levels increase during acute exacerbations of RAO in horses, especially when exposed to a high dust environment.

Research Objectives and Method

• The study aimed to explore the hypothesis that plasma cortisol concentration (CORT) increases during acute exacerbations of Recurrent Airway Obstruction (RAO) in horses, a condition relatively comparable to asthma in humans.
• To investigate this, the researchers adopted a split-plot repeated measures design. This method involves measuring multiple variables over a series of moments in time, in this case, days and 3-hour intervals.
• The experiment involved eight horses, with four being susceptible to RAO (RAO-affected) and four serving as the control group.
• All horses were initially placed in a low dust environment (LDEnv) for two days and subsequently in a high dust environment (HDEnv) for another two days.
• The plasma samples from all horses were gathered every 6 hours to determine the levels of Cortisol.

Measures and Outcomes

• Some indicators of RAO exacerbation in horses are the increase in maximal change in pleural pressure (ΔPplmax) and decreases in breathing frequency variability (BFV).
• In the control group, both the ΔPplmax and BFV measures were unaffected by the HDEnv. However, in RAO-affected horses, the ΔPplmax significantly increased, and the BFV significantly decreased.
• A trace amount of circadian variation in Cortisol levels was observed in both control and RAO-affected horses while in the LDEnv.
• Upon introducing the horses to the HDEnv, Cortisol levels in the control group of horses were unaffected. Conversely, for RAO-affected horses, Cortisol levels significantly increased between 6 and 12 hours after their insertion into the HDEnv.

Conclusion

• The study concludes that elevated plasma cortisol concentration correlates with the developments of acute exacerbations of RAO among horses. Hence, the researchers’ original hypothesis is verified.