Pig Farrowing Nest Building: Meeting Maternal Instinct at Parturition

Sows have a powerful drive to build nests before farrowing that conventional farrowing crates completely frustrate, causing measurable pre-farrowing stress.

Key Facts

Wild and feral sows spend several hours collecting plant material and building nests in the 24 hours before farrowing
The nest-building drive is hormonally primed and highly motivated, with sows working intensively at nesting even in barren environments
Sows in conventional farrowing crates perform vacuum nest-building behaviour, scratching at the floor repeatedly
Cortisol levels are higher in sows prevented from nest-building compared to those provided with nesting material
Straw provided before farrowing significantly reduces pre-farrowing stress and improves maternal behaviour after birth
Nesting material provision is required in some higher-welfare standards and has been shown to improve piglet welfare outcomes
Sows that complete nest building show calmer farrowing behaviour and better maternal responsiveness to piglets
The time spent in nesting behaviour would occupy the animal productively for hours that crates instead fill with frustrated vacuum behaviour

Welfare Considerations

Sow nest-building welfare is one of the clearest illustrations of how confinement systems frustrate fundamental biological drives at critical life moments. The nest-building drive in sows is hormonally triggered and highly motivated, preparing the animal physiologically and behaviourally for parturition. Preventing its expression does not reduce the drive but redirects it into vacuum behaviour that satisfies nothing. The welfare consequence is measurable pre-farrowing stress that may compromise maternal behaviour after birth. Providing nesting material addresses the welfare need directly and produces measurable improvements in both sow welfare during the pre-farrowing period and the quality of maternal care during and after farrowing. This is one area where welfare improvement has a demonstrable positive effect on the subsequent welfare of the piglets as well.

What You Can Do

Support campaigns for nesting material provision to be a mandatory requirement for all farrowing systems
Choose pork from welfare-certified producers who require nesting material before farrowing
Ask pork retailers and food companies about nesting material requirements in their farrowing welfare standards
Advocate for loose farrowing systems that allow sows to express full nest-building behaviour
Support research into farrowing system design that combines nesting opportunity with adequate piglet protection