## 1 Introduction
Overall, as shown by the reviewed studies, lavender administration in relation to a stressful event (during or immediately after transportation) did not show consistent effects on animal welfare. In particular, unexpected results were found in some cases, with lavender administration (either as straw or as extract) increasing animals' overall activity level during transport [7; 9] and even aggression levels immediately after transportation [8]. Under these circumstances, LEO was nonetheless suggested as a means to promote animal adaptation to the new environment (either by reducing motion sickness or by settling hierarchy earlier) rather than as a method to promote calmness. The present study tested the hypothesis that the inhalation administration of LEO to pigs for an extended period of time (i.e., during the entire finishing period) and when animals are not subjected to acute stressors may have beneficial effects on animal welfare by increasing calmness level and reducing aggressive behaviors. Long-term positive effects on animal welfare and adaptability could reflect also on growth parameters and on meat and carcass quality, a particularly important aspect when animals are raised underspecific production rules [10] and their meat and carcass must comply with strict quality requirements in order to be suitable for the dry curing process. With respect to the effects of LEO on meat quality, to the best of our knowledge, no studies are available on pigs. Studies on broilers demonstrated a positive impact on growth parameters of lavender powder in feed (400 ppm), suggesting its use as an alternative to antibiotic growth promoters. In this species, LEO did not affect carcass traits but improved meat quality (lower cooking loss and lipid peroxidation) [11]. Similar effects, together with a reduction in pathogens and an increase in probiotic bacteria in the gut microflora, were observed after LEO administration to broilers in drinking water (0.4 mL/L) [12]. So far, no studies investigated the possible presence of LEO residuals in the meat of treated animals. This assessment is particularly important within certified food schemes, since residuals may determine an odor/taste which could potentially affect the quality of the final product. In the present study, the HS-SPME (headspace solid-phase microextraction) technique coupled with gas chromatography analysis was chosen in order to verify the absence of any residues of LEO in the animals' tissues [13; 14] after inhalation administration and the preserved suitability of the raw thighs for the dry-curing process. In recent years, the most frequently used analytical techniques for the extraction and concentration of volatile compounds are those based on headspace (HS) analysis. This represents a reliable tool for the analysis of volatile organic compounds and eliminates most drawbacks to extracting organics, including high cost and excessive preparation time. In particular, SPME is a simple and fast modern tool used to characterize the volatile fraction of medicinal plants and foods. In biological materials, SPME has been successfully applied to the characterization and analysis of the volatile compounds from plasma and biological fluids. In this study, the HS-SPME technique combined with gas chromatography coupled with a flame ionization detector (GC-FID) was applied to study the volatile compounds in animal tissues after the administration of LEO [15]. The overall aim of the present study was therefore to assess, under common farming conditions for Italian heavy pigs intended for the production of Parma ham, the effects of the environmental diffusion (either once or twice a day) of LEO. The variables measured included welfare and health indicators (growth traits, skin and tail lesions, blood indicators), as well as carcass, meat and fat quality in order both to monitor potential welfare effects and to exclude alterations in meat quality traits.