Genetic differences in temperament determine whether lavender oil alleviates or exacerbates anxiety in sheep

Growing concerns about the risk of addiction to benzodiazepines have led to increasing interest in alternative therapies to treat anxiety and depression. Lavender oil (Lavendula augustifolia) is reportedly anxiolytic in a number of species but little is known about how it affects individuals that are more or less anxious when faced with a stressor. In this study, we used changes in locomotor activity and the plasma concentrations of cortisol to test whether lavender oil would reduce behavioral and endocrine correlates of anxiety in calm and nervous sheep exposed to an isolation stressor. During the non-breeding season, 'calm' or 'nervous' female sheep from the UWA temperament flock were exposed to a mask containing either 1 mL of 10% lavender oil (calm: n=8; nervous: n=8) or peanut oil (calm: n=8; nervous: n=8). After 30 min, each sheep was isolated for 5 min and then returned to the group. Blood was sampled prior to the mask, prior to isolation, 1 min and 30 min after isolation to profile changes in the plasma concentrations of cortisol. Agitation score, locomotor activity and vocalizations were recorded as correlates of anxiety associated with the isolation stressor. Irrespective of whether they were exposed to lavender oil, calm sheep had a lower agitation score (P<0.001), crossed the central lines of the isolation box less frequently (P<0.001), expressed fewer vocalizations (P<0.001) and had lower plasma concentrations of cortisol immediately after isolation (P<0.001) than nervous sheep. Exposure of calm sheep to lavender oil decreased the agitation score (P<0.001), frequency of vocalizations (P<0.05), decreased the number of crosses of the central lines of the isolation box (P<0.05), and the plasma concentrations of cortisol prior to isolation (P<0.05) (after mask application) compared to calm control sheep. Exposure of nervous sheep to lavender oil increased the frequency of vocalizations (P<0.05), the number of sheep attempting to escape (P<0.05) and the plasma concentrations of cortisol 30 min after isolation (P<0.05) compared to nervous control sheep. We conclude that genetic differences in temperament determine whether lavender oil alleviates or exacerbates the behavioral and/or endocrine correlates of anxiety in sheep.