Farmed Pig Nesting Behavior and Welfare

The nesting motivation of sows before farrowing is one of the strongest and most welfare-relevant behavioral drives in domestic pigs, yet it is routinely frustrated in conventional systems.

Key Facts

Wild boar sows spend 12-24 hours before farrowing constructing elaborate leaf and grass nests in secluded locations
Domestic sows retained this nesting motivation; it activates hormonally 24-48 hours before expected farrowing
Sows in farrowing crates deprived of nesting material perform stereotypic rooting — repeated futile contact with the floor and bars
Cortisol levels in crated sows deprived of nesting material are significantly elevated before farrowing compared to those with nesting substrate
Providing straw or other nesting material to sows in the 24 hours before farrowing reduces rooting stereotypies by over 80%
Sows given nesting material perform full nesting sequences — carrying material, pawing, and lying and rising repeatedly — that correlate with reduced pre-farrowing cortisol
Kit neonatal mortality is lower when sows have nesting material — nest construction creates a microclimate that reduces piglet chilling
EU Directive 2008/120/EC requires nesting material for sows before farrowing; implementation is variable across member states

Welfare Considerations

Sow nesting behavior is an intensely motivated pre-farrowing behavioral drive that, when frustrated, causes measurable physiological stress and prolonged stereotypic behavior. The drive activates hormonally — it is not a learned preference but a biological imperative — meaning that sows cannot simply adapt to its absence without cost. Providing nesting material in the 24-48 hours before farrowing costs little in practical terms and produces measurable welfare improvements: reduced cortisol, reduced stereotypic behavior, improved piglet microclimate, and behavioral expression of a strong drive. The regulatory requirement for nesting material exists in EU law; the implementation gap — where nesting material is technically present but inadequate for meaningful nesting behavior — represents a welfare deficit that outcome-based monitoring would reveal and enforcement would address.

What You Can Do

Support certification programs that verify adequate nesting material provision before farrowing, not merely its technical presence
Advocate for welfare auditing that uses behavioral indicators of nesting drive expression as an outcome measure
Choose pork from producers who document pre-farrowing welfare management including nesting material provision
Support research into the specific types and quantities of nesting material that best fulfill sow nesting motivation