Can aggressive behaviour among piglets be stopped by a sound signal and reward treatment?

The aim of the study was to test whether aggressive actions among piglets could be redirected by an automatically generated sound signal followed by a sweet food reward. Per round, four litters of 25 days old suckling piglets (BHZP breed) were trained five times per day during eight days to expect a sweet food reward from a dog feeder after hearing a specific sound. In total 72 piglets in12 entire litters were trained in 3 rearing rounds. After the training period, the piglets were weaned and mixed in two pens, 12 piglets per pen. Immediately after mixing and 24 h later the animals were visually observed by two trained persons (one per pen) disguised behind a transparent blind for 3 h. They released the sound signal and feeder when aggressive behaviour started. Video records were taken by 2 cameras, in total 36 h of video (6h per pen, 3 rounds) for later analysis. During these 36 hours, 612 aggressive attacks were identified of which 55.3% could be redirected by the sound signal and reward treatment. The type of aggression and the moment in time during the aggressive action as well as the role of the piglet during a fight (initiator or receiver) influence significantly the effectiveness of the sound award system (P<0.001). Initiator piglets stopped aggressive action more often after feeder activation (Odds Ratio=0.75) than receivers (1.33). Attacks by jumping on the opponent could be easier redirected (0.55) than attacks with bites (0.61) and head trusts (0.67). Very few piglets responded to the sound signal (9.31) when the fight had already fully started. The chance to interrupt aggression by the sound signal and reward system decreased by 28% with every second passed from the start. The investigated sound reward system can reduce aggression in piglets when properly applied in time.