Effect of Aromatherapy on Equine Heart Rate Variability

This study investigated the effect of aromatherapy on heart rate variability (HRV) in horses.
Focused on two essential oils: lavender (Lavandula angustifolia) and chamomile (Matricaria recutita).
Conducted on eight dressage horses using a crossover design with control and experimental treatments.

Heart Rate Variability (HRV): A measure of the autonomic nervous system's regulation of heart function, particularly the parasympathetic component (RMSSD).
Parasympathetic Component: Increased RMSSD indicates enhanced relaxation and calmness.
Aromatherapy: Use of essential oils to promote relaxation, historically used for over 6,000 years.

Horses are sensitive and easily stressed animals with a strong sense of smell, potentially benefiting from aromatherapy.
Previous studies have shown that lavender can produce a relaxing effect on the autonomic nervous system in various subjects.

Participants: 9 riding horses from a private boarding facility.
Design: Crossover design where each horse underwent both lavender and chamomile treatments, each separated by 1 week.
HRV Measurement: Recorded for 7 minutes before, during, immediately after, and 30 minutes after the treatment using Polar Equine RS800CX monitors.
Aromatherapy Application: Six drops of each essential oil were vaporized and presented to the horses in a familiar environment.

Lavender significantly increased RMSSD from 86.5 ms to 104.3 ms (p = 0.020).
Reduced percentage of very-low-frequency (VLF) HRV oscillations from 81.2% to 72.1% immediately after treatment (p = 0.039).
The heart rate (HR) did not significantly change, indicating that lavender did not induce a physiological stress response, but rather promoted and sustained parasympathetic activity temporarily.
Notably, one horse (Pluto) showed a decrease in RMSSD, possibly due to age-related factors.

Chamomile demonstrated variable effects, with only two out of eight horses showing increased RMSSD.
The remaining six horses had decreased RMSSD during chamomile treatment, suggesting a lack of consistent relaxation response.
No significant changes in HR or SDNN were observed during or after the treatment.

Results indicated that lavender is effective in increasing parasympathetic activity in horses, while chamomile did not yield consistent or statistically significant results.
Lavender's potential calming effect might be linked to its ability to interact with serotonin receptors.
Chamomile's mechanisms remain less understood, highlighting the need for further research on its effects.

Only a limited number of horses participated in both treatment sessions.
Effects evaluated were based on a single dosage of each essential oil.
Future studies should include a broader range of doses and stress-testing scenarios.

Lavender significantly increased the parasympathetic component of HRV (RMSSD) in horses not subjected to external stressors, affirming its potential for calming effects.
Chamomile did not demonstrate a consistent relaxation effect and requires further exploration for its potential uses in equine aromatherapy.

The study acknowledges contributions from the University of Arizona Honors College and student researchers who assisted with data collection and analysis.