Pig Group Housing Aggression Management

Mixing unfamiliar pigs in group housing systems causes aggression and injury that evidence-based management strategies can minimize.

Key Facts

Social mixing of unfamiliar pigs triggers aggression establishing dominance hierarchy over 24-72 hours
Injury rates at mixing peak in the first 48 hours with skin lesions, ear damage, and occasional fractures
Gilts mixed before first farrowing show lower aggression than those mixed after
Strategic use of barriers, hiding spaces, and extra space during initial mixing reduces injury rates
Electronic sow feeders eliminate feeding aggression by feeding individuals in sequence
Stable social groups not remixed once established have dramatically lower aggression rates

Welfare Considerations

The transition to group housing for sows brings welfare benefits from freedom of movement but welfare risks from social mixing aggression. The aggression at mixing is predictable and manageable rather than inevitable and uncontrollable. Management strategies that reduce the welfare cost include pre-mixing familiarization, providing adequate space and retreats during hierarchy establishment, timing mixing strategically, and maintaining stable groups. The welfare outcome of group housing depends on whether the management investment in transition protocols is made.

What You Can Do

Support pig welfare certification schemes that include aggression management protocols
Engage with pig producers about evidence-based mixing management to reduce aggression
Advocate for training requirements in stockperson education covering pig social behavior
Choose pork from operations with certified group housing systems verified through welfare auditing