Porcine ear necrosis (PEN) is a worldwide health issue and its aetiology is still unclear. The aim of this study was to describe the prevalence and the severity of PEN in a commercial farm, associated with behavioural changes and health biomarkers measures. On two consecutive batches, PEN prevalence was determined at the pen level. PEN scores, blood haptoglobin concentration and oxidative status biomarkers were measured on two pigs per pen (n=48 pens), 9, 30 and 50 days (D) after arrival to the post-weaning unit. For two to three other pigs per pen, social nosing, oral manipulation, aggression of pen mates and exploration of enrichments were observed twice a week from D9 to D50. At the pen level, the higher the time spent nosing pen mates, the lower the proportion of pigs affected by PEN during both the D9-D30 and the D31-D50 periods (P<0.002). On the opposite, the higher the time spent manipulating orally pen mates during the D31-D50 period, the higher the percentage of affected pigs within a pen (P=0.03). Mean PEN scores on D50 were higher in pens in which focal piglets spent more time nosing pen mates during the D31-D50 period (P=0.02), and to a lesser extent, during the D9-D30 period (P=0.08). At the pig level, the higher the increases in hydroperoxides and haptoglobin during the D9-D30 period, the higher the PEN scores on D30 (P<0.001). Our study evidenced that an increase in inflammatory and oxidative stress biomarkers might be associated with PEN severity. In addition, this study is the first to suggest that social nosing and oral manipulations have opposite associations with PEN syndrome.