Pig Farrowing Nest Building: Meeting a Fundamental Behavioral Need

Nest building before farrowing is one of the strongest behavioral drives in sows, and its frustration in crated systems causes significant welfare harm.

Key Facts

Nest building behavior in sows begins 12-24 hours before farrowing and involves carrying, rooting, and arranging materials
The motivation to nest is so strong that sows deprived of materials show vacuum activities — rooting on concrete floors
Nest building reduces cortisol, improves piglet survival through better maternal behavior, and speeds farrowing
Farrowing crates prevent almost all nest building behavior by restricting movement
Providing straw, paper, or other materials in farrowing crates partially reduces frustration but cannot compensate fully
Free-farrowing systems with nesting material provided show improved sow welfare and equivalent or better piglet outcomes

Welfare Considerations

Nest building frustration is one of the most clearly documented welfare harms in commercial pig farming. The pre-farrowing period represents a peak in behavioral motivation, and the complete inability to perform nesting in farrowing crates causes measurable physiological stress. Vacuum nesting behaviors — rooting frantically on bare concrete — are direct indicators of this frustration. The welfare case for providing nest-building opportunities is unusually strong: the behavioral evidence, physiological data, and productive outcomes all point in the same direction. Legislative reform requiring nesting material access at farrowing is one of the most evidence-backed welfare improvements available in livestock agriculture.

What You Can Do

Choose pork products from farms providing nest-building materials and free-farrowing systems
Support organizations campaigning for minimum nest material requirements in farrowing legislation
Donate to research demonstrating the production viability of free-farrowing systems
Encourage supermarkets and food companies to require nesting material provision in welfare certification standards