A note on the effect of handling quality prior to mixing on behaviour at mixing in pigs

Previous research has raised the possibility that levels of aggression between pigs may be influenced by their state of arousal and excitement at the time of mixing. This may, in turn, be affected by factors such as the way in which pigs are handled prior to mixing. We attempted the first systematic test of this idea. Sixty four growing pigs were housed in groups of four for 4 weeks to allow them to become familiar with their group mates. Each pig was then tested in a 10min encounter with another pig in an unfamiliar test pen. Pigs were either handled gently (G) or firmly (F) on their way to the encounter. In addition, pigs either met a familiar (F) or an unfamiliar (U) pig in the test pen. Thus, there were four types of encounter (FF, FG, UF, UG) with N=8 tests of each. Two-way analysis of variance showed no effects of handling quality and no interactions between handling quality and familiarity on behaviour during encounters. Unfamiliar pigs showed higher levels of aggressive behaviour. Any fights were stopped immediately. On a second test day, pigs were handled as previously, but all now encountered a familiar individual. Again, there were no effects of handling quality or interactions between handling quality and familiarity. The results, thus, failed to support the idea that the quality of handling prior to mixing influences the levels of aggression subsequently observed.