Stable microclimates and autonomic modulation in horses housed in different stable architectures during monsoon in a tropical environment.

Background: The impact of climate conditions and stable design on horses housed in individual stalls plays a significant role in their well-being, especially in tropical climates. Limited information exists regarding their conditions during the monsoon season.

Objective: This study focused on the stable microclimate and autonomic regulation of horses kept in different stable architectures during the monsoon in a tropical setting.

Methods: Twenty-two horses were assigned to one of three stable designs, each offering unique microclimates, including relative humidity, air temperature, and various levels of noxious gases. Autonomic modulation was assessed by observing multiple heart rate variability (HRV) metrics at one-hour intervals for 24 consecutive hours.

Results: The findings revealed significant variations in stable microclimates across the different designs, with notable differences between day and night. Horses housed in stables with solid external walls and a lower volume-to-horse ratio exhibited lower HRV (p < 0.05-0.0001), indicating more significant stress, compared to those in stables with solid walls and a higher volume-to-horse ratio or those without solid external walls. Furthermore, the study established a correlation between stable microclimates and HRV modulation based on stable design.

Conclusion: These results indicate that autonomic responses vary among horses in different stable designs, suggesting that stable architecture, microclimates, and the volume-to-horse ratio significantly influence horses' stress responses. Overall, these findings offer important insights for improving housing management to enhance the welfare of horses during the monsoon season in tropical environments.