Pig Nesting Behaviour: A Fundamental Need Before Farrowing

Pre-farrowing nesting is one of the strongest behavioural drives in sows. Preventing it causes measurable distress and is a key welfare indicator in farrowing systems.

Key Facts

Wild sows travel up to several kilometres to find ideal nesting sites before farrowing.
Nesting behaviour is driven by hormonal changes in the 24 hours before birth and is highly time-sensitive.
Sows in farrowing crates perform vacuum nesting — the complete motor sequence with no substrate — for hours.
Providing straw or other substrate allows nesting expression and significantly reduces pre-farrowing stress.
Sows that cannot nest show elevated cortisol and are more likely to exhibit aggression post-farrowing.
Loose farrowing systems with straw provision allow nesting and improve both sow and piglet welfare.

Welfare Considerations

Nesting behaviour in sows represents one of the most clearly documented examples of behavioural need frustration in farm animals. The drive to nest before farrowing is so strong that sows will perform the complete motor sequence even in bare concrete farrowing crates — an unambiguous indicator of frustrated motivation causing psychological distress. Providing even minimal substrate allows partial expression of nesting behaviour and measurably reduces stress indicators. Full nesting expression in loose systems with deep straw satisfies the drive completely. The welfare case against farrowing crates is strengthened by the visibility of this frustrated nesting behaviour and the ease with which it can be prevented.

What You Can Do

Choose pork products from systems that provide substrate for nesting before farrowing.
Support campaigns for mandatory straw provision and loose farrowing systems in pig welfare legislation.
Learn about sow nesting behaviour as a clear example of how farm systems frustrate animal needs.
Advocate for retailers to commit to sourcing pork from loose farrowing systems.
Donate to farm animal welfare organisations campaigning for farrowing crate bans.