Sows show intense nest-building motivation in the hours before farrowing, and systems that allow this behaviour produce better welfare outcomes for both sows and piglets.
Nest building before farrowing is one of the most strongly motivated behaviours in sow biology, driven by hormonal surges in the final hours before birth. A sow confined in a farrowing crate cannot collect material, push it into position, or create the bedded space that her biology is preparing her to make. The resulting frustration is not abstract — it is a specific, intense, thwarted drive that the sow cannot discharge. Systems that provide straw and space for nest building allow this motivation to be expressed, producing calmer farrowing events, better maternal behaviour, and improved piglet survival in well-managed operations. The argument that crates are necessary for piglet survival in all circumstances is contradicted by growing evidence from well-designed loose farrowing systems.