Mixing unfamiliar pigs triggers intense aggression causing injury and welfare harm, with evidence-based management strategies significantly reducing conflict at these critical transition points.
Pig mixing aggression is a predictable and partially preventable welfare harm at farm management transition points. The combination of stable group management — minimising how often groups are reconfigured — with evidence-based mixing interventions provides the most effective welfare protection. Farms that keep pigs in stable groups from weaning to slaughter dramatically reduce total aggression exposure compared to systems with frequent regrouping. When mixing is unavoidable, providing enrichment, deep bedding and access to multiple retreat spaces at transition reduces the welfare impact.