Pig Farrowing Nest-Building and Behavioral Needs

Nest-building is among the most strongly motivated behaviors in sows approaching farrowing, and its frustration in crated systems causes significant welfare harm that pen farrowing systems can address.

Key Facts

Wild sows spend 6 to 12 hours building elaborate nests from grass, leaves, and branches before farrowing
Nest building is driven by a hormonal surge in the 24 hours before birth and is extremely strongly motivated
Crated sows show frustrated nest-building behavior including rooting and pawing at the floor with no substrate available
Providing even small quantities of straw or other nesting material significantly reduces pre-farrowing distress
Pen farrowing systems that allow sow movement and provide substrate enable near-normal nest-building behavior
Studies show sows with nesting material have shorter labors and better piglet survival compared to crated controls
The EU requires that sows be given nesting material before farrowing but enforcement varies across member states

Welfare Considerations

The frustration of nest-building motivation in crated sows represents one of the most acute welfare harms in pig production. The hormonal drive to build a nest is overwhelming and the inability to complete the behavior creates intense, measurable distress in the hours before farrowing. Sows in crates show stereotypic pawing and rooting behavior that demonstrates the strength of the motivation. Providing straw or other substrate reduces this distress even in systems where the sow cannot build a full nest. Pen farrowing systems that allow free movement and substrate access restore near-normal behavior and reduce pre-farrowing cortisol. Consumer choice for pork from systems that provide nesting material and movement freedom drives producer adoption of more welfare-positive farrowing systems.

What You Can Do

Choose pork products certified under systems that require nesting material and farrowing movement freedom
Support legislation requiring provision of nesting material before farrowing in all pig production systems
Advocate for pen farrowing system adoption as an alternative to conventional crating
Donate to pig welfare research organizations developing commercially viable pen farrowing systems
Share information about sow nest-building needs to build consumer understanding of farrowing welfare