Group Housing for Pigs: Welfare Science & Practice

Group Housing and Pig Welfare

Pigs are highly social animals that benefit from group housing when managed appropriately. EU and UK law requires that breeding sows and gilts must be housed in groups for most of their pregnancy. Understanding the welfare science of group housing is essential for implementing it effectively.

Why Group Housing Matters

• Pigs are highly social; isolation causes stress, stereotypic behaviour, and impaired welfare
• Group housing allows expression of natural social behaviours — rooting, play, and exploration together
• EU Directive 2008/120 and UK equivalent require group housing for pregnant sows from 4 weeks after mating until 1 week before expected farrowing
• Individual stall housing for pregnant sows is illegal in the UK and EU — welfare evidence supports this ban

Challenges in Group Sow Housing

• Aggression and bullying: Dominance hierarchies in mixed groups cause welfare harm for subordinate sows; mixing unfamiliar sows causes intense fighting
• Resource competition: Inadequate feeder space or restricted feeding systems create competition, particularly around feeding time
• Body condition variation: Individual nutritional needs differ; group feeding systems must accommodate this
• Lameness: Sow lameness is exacerbated by hard, slippery floors in group housing

System Options

• Electronic sow feeders (ESF): Individual computer-controlled feeding based on ear tag identification; minimises competition at feeding; requires adequate training of sows
• Trickle feeding: Ad libitum low-density diet reduces aggression around feeding; requires careful nutritional management
• Straw-based systems: Deep straw yards provide enrichment, rooting opportunity, and thermal comfort — high welfare systems
• Concrete slatted systems: More economical but poorer welfare than straw yards; flooring quality critical

Welfare Best Practice

• Maintain stable groups — minimise mixing after initial group formation
• Adequate floor space (minimum 2.25m² per sow; more for larger breeds)
• Sufficient feeder and drinker provision to reduce competition
• Enrichment provision (rooting material, objects) to redirect investigative behaviour
• Regular monitoring for aggression injuries, lameness, and body condition
• Appropriate flooring with rubber mats or straw to reduce leg injuries

Key Takeaways

Group housing for pigs is both a legal requirement and a welfare improvement over individual confinement when managed effectively. Minimising mixing, ensuring adequate resources, providing enrichment, and maintaining appropriate flooring conditions are the welfare foundations of effective group sow housing.