PSVII-14 - Reduction in heart rate variability parameters in horses treated with a mixture of lavender and eucalyptus essential oil

Abstract: Routine medical examinations can produce stress which can negatively impact the health and well-being of horses. Heart rate variability (HRV) is a non-invasive and inexpensive method to measure the balance between sympathetic and parasympathetic nervous system activity, which can help identify stress in horses. This study examined the effect of a combination of lavender and eucalyptus essential oil on stress responses in horses undergoing a routine medical exam. After a five-minute stall rest (baseline reading) data was collected in three, five-minute intervals (walk to and enter stock, medical exam, and recovery in stall). This study utilized a switch-back design where each horse (n = 10) received both treatments on different dates. The treatment groups received lavender (20%) and eucalyptus essential oil (5%) dissolved in petroleum jelly and virgin sunflower oil applied to inner nostrils. The control treatment consisted of only petroleum jelly and virgin sunflower oil applied to inner nostrils. The root mean square of the successive differences of heartbeats (RMSSD) was significantly reduced (P < 0.05) when horses were treated with essential oils while walking to stocks (51.7±3.7), during the medical exam (50.5±4.9), and during the recovery period (64.1.9±5.7) compared to control treatment, to stocks (36.1±4.4), the medical exam (39.0.±4.5), and during the recovery period (49.7±5.5). The measured SD1 (Parasympathetic) was significantly higher (P < 0.008) at walk to stocks in horses treated with essential oils (37.2±1.9) compared to control treated (30.3±3.1). The measured SD2 (Sympathetic) was significantly lower (P < 0.008) at walk to stocks in horses treated with essential oils (62.8±1.9) compared to control treated (69.7±6.8). The ratio of SD1/SD2 was significantly lower (P < 0.008) at walk to stocks in horses treated with essential oils (1.7±0.17) compared to control treated (2.4±0.26). The High Frequency Percent (HF%) was also significantly greater (P < 0.04) at walk to stocks in horses treated with essential oils (39.6 ± 4.9) compared to control treated (26.0 ± 4.1). The Standard Deviation of RR Interval (SDNN) values were significantly increased (P < 0.03) in horses treated with essential oils during walking to stalks (50.8 ± 1.9), the medical exam (56.7 ± 5.0), and the recovery period (72.4 ± 12.9) compared to the control treatment, to stalks (44.5 ± 5.2), medical exam (44.0 ± 4.5), and during the recovery period (54.6 ± 6.2). The results of this study indicate that lavender and eucalyptus oil could be an effective means of reducing short-term stress in horses. The findings of this study can help develop more effective and humane management strategies for horses.