## 4 Discussion
The improper handling practices may have caused the higher number of total animal events at T2 noticed with the regression tree analysis for severe middle lesions. Total animal events are indeed the total number of events, such as pigs falling, slipping, being reluctant to move, turning back, jumping, huddling, and pushing other animals. Those events are behaviors expressed in particular when pigs are experiencing fear and distress [59; 60]. Events such as slipping and falling are associated with wounds and lesions on the pigs' bodies, which finally result in damaged carcasses. A consistent body of literature outlines the association existing between animal handling, stressed animals, and low-quality meat and carcasses. [PERSON] et al. observed a positive correlation between handling (with pigs slipping and falling) in the race towards the stunning area and the plasma concentration of glucose and lactate in blood gathered at exsanguination [61]. Similar results have also been found by other authors [29; 62; 63], suggesting that those events, coupled with the fasting period applied before slaughter, can cause stress and wounds on pigs' bodies, ultimately resulting in lower pork quality and damaged carcasses. Handling practices are of primary importance in reducing stress in animals transported to the abattoir, and despite the negative welfare and meat quality implications of improper handling practices (such as the use of electric goods and sticks or tubes), operators often continue using those tools to manage movements of pigs at loading, unloading and in the race toward the stunning area. [PERSON] et al. [64] tested the effect of different handling devices, comparing the effects on meat quality and animal welfare of the use of an electric good or board and paddles for moving the pigs at the abattoir. The authors clearly found the use of electric goods had a detrimental effect on pork quality and carcass damage [64]. Our results thus confirm those reported in the literature, and strongly emphasize the need to apply more careful handling practices at unloading and in the abattoir in order to protect both the welfare of the animals and the quality of the carcass. A higher prevalence of severe lesions in the shoulder of heavy pig carcasses was noticed for the batches transported in the trailer, subjected to a longer waiting time before unloading and liarage in wider pens. The effects of waiting time before loading and pen space allowance on carcass lesions have already been discussed. This association seems to confirm the hypothesis that longer waiting and wider liarage pens may have caused more fights among the pigs within each batch, as lesions on the neck and head are typically caused by fights and aggressions between pigs [55]. Concerning the effect of the trailer identified in the present study, several authors have already investigated the effects of vehicle design on pig welfare and carcass lesions [1; 27; 38; 65]. Our results are in agreement with evidence reported in previous studies, highlighting that pigs transported in the rear region of the vehicle are more likely to lose balance, fall, or get trampled, resulting in a higher prevalence of lesioned carcasses [66; 67]. Furthermore, higher stress levels were observed in pigs transported in a twin-axle trailer when compared with pigs transported in a fixed body truck [68]. The association we found between trailer transport and shoulder severe lesions may thus be the effect of the lesions and physical stress caused by the necessity of the animals to keep the standing position and balance while coping with the vibrations and movements of the trailer. Compared to the lorry, which is directly bound with the driver's cabin, the trailer may have increased the animals' instability, resulting in more falls and an increased likelihood of injury in the front region of the animals' bodies.