Sow Housing Welfare Science 2025

Overview: Sow (female pig) housing represents one of the most scientifically examined and contested areas in farm animal welfare. The transition from gestation stalls to group housing systems has been driven by decades of behavioral research showing that pigs have complex social and movement needs fundamentally incompatible with stall confinement.

Gestation Stall Welfare Evidence

Individual gestation stalls (also called sow stalls) confine pregnant sows in spaces approximately 2.0m x 0.6m — insufficient for the animal to turn around. Scientific evidence consistently documents welfare deficits in stall-housed sows including:

Scientific Consensus: The European Food Safety Authority (EFSA) concluded in multiple opinions that gestation stalls severely compromise sow welfare. The EU banned stall use beyond 4 weeks post-service (2013). Several US states have enacted phase-out requirements.

Group Housing Systems

Group housing allows sows to move, socialize, and express behavioral repertoires. However, welfare outcomes depend critically on system design. Key system types include:

Electronic Sow Feeding (ESF) Systems

Individual computerized feeders within group pens allow precise nutrition management while permitting social housing. Sows learn to use feeding stations and can be managed individually. ESF systems represent the gold standard for combining group welfare with production management. Initial capital costs are higher than stall systems.

Free Access Stalls

Sows can voluntarily enter and exit stalls, providing refuge from aggression while maintaining group access. This system reduces injury from social competition while allowing natural behaviors between feeding periods.

Floor Feeding in Group Pens

Simpler and less expensive, but creates competition and aggression if space allowances and management are inadequate. Welfare outcomes are more variable and depend heavily on stocking density and producer skill.

Group Housing Welfare Factors: Space allowance (EU minimum: 2.25m²/sow); enrichment provision; stable social groups; management of aggression during mixing; nutrition management

Farrowing Crate Science

Farrowing crates — used at birth and for 3-5 weeks post-partum — restrict sows' movement to prevent piglet crushing. Welfare science identifies:

Alternative farrowing systems (loose housing with welfare features) can achieve acceptable piglet mortality rates with adequate management. Several European countries (Norway, Sweden) allow only loose farrowing. Research continues on optimizing farrowing pen design to balance sow and piglet welfare simultaneously.

2025 Reform Progress

Global progress on gestation stall phase-out has accelerated through a combination of legislation and corporate commitments. As of 2025, the EU, UK, and several other jurisdictions have legally banned or restricted gestation stalls. Major food companies including McDonald's, Burger King, Walmart, and Nestlé have made group housing commitments affecting global supply chains.

Farrowing crate reform has proceeded more slowly due to concerns about piglet mortality. Research into alternative farrowing systems continues, with promising results from enriched loose-farrowing designs that meet both sow welfare needs and acceptable production outcomes.