Pen-rotation scheme for growing pigs : effects on pig aggression and social affiliation

Abstract: This master project aimed to assess if a pen-rotation scheme mitigated the effects of reuniting pigs after temporal separation. Six groups of crossbred (Yorkshire and Hampshire) growing pigs, (8 - 10 littermates per group) aged between 12 – 13 weeks, were video recorded separately in their original home pens for 2 h before a temporal separation to undergo the pen rotation scheme in pairs for 3 days. Each litter was video recorded once again after reuniting the paired littermates in their home pen. Behaviour was thus recorded before and after pigs were exposed to temporal separation, through a rotation scheme, based on an ethogram including aggression and social affiliation. Pig aggression was recorded in frequency of occurrence of the elements of aggressive behaviours over the 2 h period within the litter groups considering behaviours such as ear bites, head-anal-knocking, face bites, parallel push, head-to-head-knocking, head-to-side push, head-to-under push, head-to-shoulder push, levering, neck bites and shoulder bites. Social affiliation was also studied over the same period regarding behaviours such as anal-genital sniffing, nosing of other body parts, lying/resting in groups, back-scratching with snout, mounting and exploring in groups. This study found that pigs showed aggression and social affiliation before and after undergoing a pen-rotation scheme. Although some exceptions can be identified, there appears to be a resemblance between pig aggression and social affiliation before and after the temporal separation of littermates. A pen-rotation scheme may be applicable on pig farms to mitigate stress related to reuniting littermates after temporal separation, but this needs further testing with larger sample sizes, and with proper controls. If proven efficient, a pen-rotation scheme could be useful for scientific studies in need of splitting and later reuniting litters, as well as for commercial pig production when temporal splitting is needed.