Maintaining stable pig social groups reduces aggression and improves welfare, with regrouping being one of the most significant welfare stressors in pig systems.
Regrouping is so stressful that it has been described as one of the most significant acute welfare events in commercial pig production. The injuries and stress from hierarchy re-establishment cause measurable suffering. Systems designed to minimise regrouping by keeping litter-mates or stable groups together throughout production represent a significant welfare improvement.