Environmental nebulization of lavender essential oil (L. angustifolia): welfare assessment in growing pigs

Intensive farming conditions expose pigs to different type of physical and psychological stressors, such as limited possibility of expressing their natural behaviour and lack of stimuli, that determine a reduction in welfare and appearance of stress-related signs (tail biting, stereotypies, etc.). Lavender essential oil (Lavandula angustifolia; LaEO) is natural compound highly employed for medical and pharmaceutical purposes as it shows antibacterial and pesticide activity and, above all, for its carminative and sedative capabilities. Its positive effects, including relaxation and anxiety reduction, are reported in several species such as rat, horse, dog, human and pig [1-3]. Aim of the study was to analyse stress-related physiological and behavioural parameters in growing pigs exposed to environmental LaEO nebulization. The trial was performed in a porcine experimental facility. Ninety (n=90) crossbred barrows with undocked tails were allotted to three experimental groups, housed in different rooms. In the LaEO group room, a 1% solution of lavender essential oil was vaporized for 10min twice a day. Sham group (SHAM) was exposed to nebulization of the solution vehicle without LaEO, while Control (C) group did not receive any treatment. The trial lasted 63 days. Hair was shaved the day before the beginning of trial, and then sampled at the end to evaluate Cortisol (CORT) and Dehydroepiandrosterone (DHEA) by Radioimmunoassay. Individual behaviour, body weight and skin and tail lesions were recorded at three timepoints: beginning, middle and end of the trial. ANOVA and Chi-squared tests were used to analyse data. Hair CORT and DHEA did not show any statistically relevant differences, but CORT/DHEA ratio was lower in LaEO group (p=0.0212). No differences emerged between groups in growth parameters. Total number of body lesions was significantly reduced in LaEO group compared SHAM and CTR (p<0.0001) as well as the severity of tail lesions (p=0.0254). The overall level of activity was not different between C and LaEO. Although the positive effects of LaEO nebulisation were not strong enough to modify the overall behaviour and physiological balance, a decrease in animals’ aggressiveness and tail/skin damage was recorded overtime, also supported by the decrease in CORT/DHEA ratio. It can hypothesized that performing such trial in an experimental facility, rather than under farming conditions, may have impaired the results by not inducing high stress levels.