The welfare of breeding sows in commercial pig production has been the subject of intense scientific scrutiny and public concern. Understanding the evidence base for sow welfare informs management decisions and policy development across this economically important sector.
The farrowing crate—a metal frame that confines the sow but allows piglets access to suck—has been the standard farrowing system for decades. It reduces piglet mortality from crushing (sow overlying) but severely restricts sow movement and natural behaviour. Sows in farrowing crates cannot turn around, perform nest-building behaviour fully, or respond naturally to piglet distress. The welfare cost to sows is significant. Alternative systems (free farrowing pens, temporary confinement systems) aim to balance sow welfare with piglet survival.
Nest building is a highly motivated behaviour in sows, occurring in the 24 hours before farrowing. Research demonstrates that sows deprived of nest-building materials show higher stress hormone levels and more restless behaviour before farrowing than those provided with straw. The frustration of nesting motivation in confined systems is a significant welfare cost. Providing even limited nesting material (straw, paper) in farrowing systems improves sow welfare indicators.
Lameness is the primary reason for culling sows (along with reproductive failure) and a major welfare concern. Contributing factors include: concrete flooring causing foot pad lesions and joint problems, inadequate floor grip causing slipping injuries, nutritional deficiencies affecting bone and joint health, and rapid growth selection creating musculoskeletal stress. Regular locomotion scoring, foot care, appropriate nutrition, and floor surface management are essential welfare interventions.
The transition from individual to group housing following the EU stall ban has created new welfare challenges around aggression management. Mixing unfamiliar sows causes acute aggression, injuring lower-ranking individuals. Chronic social stress in poorly designed group systems (inadequate space, insufficient feed access, poor group composition) causes sustained welfare compromise. Evidence-based group management protocols can substantially reduce aggression-related welfare problems.
Average sow longevity in commercial systems is low—many sows are culled after 2-3 parities, often due to reproductive failure or lameness. Short productive lives mean sows do not benefit from improved welfare in later life and may experience rapid health deterioration. Genetic selection for robustness and longevity, alongside management improvements, can improve average lifetime welfare outcomes. Stockperson training in recognising lameness and disease early improves intervention timing and welfare outcomes.
Validated welfare assessment tools for sows include: body condition scoring (BCS 1-5 scale), locomotion scoring, skin lesion scoring, vulval scoring (indicating fighting), reproductive performance metrics, and behavioural observation. Integrating these indicators into a farm welfare assessment protocol enables objective monitoring of sow welfare status and identification of areas for improvement.