Pig Farrowing Nest Building Motivation

Sows have a strong instinctive motivation to build nests before giving birth - a behavioral need that farrowing crates deny entirely. Understanding this motivation is central to farrowing system welfare debates.

Key Facts

Wild and outdoor sows travel up to 6km in the 12-24 hours before farrowing to find an appropriate nest site
Nest building begins 12-24 hours before birth, with sows collecting and arranging vegetation into a nest structure
Sows confined in farrowing crates show vacuum nest-building behavior - rooting and pawing at bare floors
Frustration from inability to nest build causes elevated cortisol, increased aggression, and abnormal behavior
Providing nest material to crated sows reduces some distress but cannot fully substitute for actual nest building
Nest building is not merely comfort behavior - it serves thermoregulation and predator concealment functions
Free-farrowing sows given adequate space and material construct structured nests indicating strong behavioral drive
Nest quality correlates with colostrum production and piglet survival in some studies

Welfare Considerations

The nest-building motivation in sows before farrowing represents one of the clearest examples of a behavioral need being systematically denied by conventional farming systems. A sow in a farrowing crate experiencing the peak of nest-building motivation but unable to perform the behavior is in a state of acute behavioral frustration that is measurable through elevated stress hormones and visible through vacuum behavior. This is not a preference being inconvenienced but a fundamental biological drive being blocked. The welfare case for allowing nest-building - through free farrowing pens with appropriate material - is therefore among the strongest in pig welfare science. It is also one of the clearest examples of how welfare science can identify and address the most significant welfare compromises in production systems.

What You Can Do

Support pig welfare campaigns advocating for free-farrowing systems that allow nest building
Choose pork from producers using alternative farrowing systems that enable nest-building behavior
Advocate for farrowing crate bans with realistic transition timelines for pig producers
Support research into nest material provision that best satisfies nest building motivation in confined sows
Learn about sow nest building research to understand the strength of behavioral motivation being denied by crates