Outdoor farrowing systems allow sows to express natural nesting behavior and produce piglets in environments that improve welfare compared to indoor crates.
Sows in conventional indoor farrowing crates cannot perform the nesting behavior that is biologically compelling for them around parturition. The frustration of this behavioral drive is a significant welfare deprivation. Sows given access to nest building materials show persistent nesting behavior in the days before farrowing, and being able to build a nest reduces parturition duration and piglet mortality in some studies. Outdoor farrowing provides genuine welfare improvements for sows but requires management skill to prevent elevated piglet mortality from crushing and exposure. The welfare tradeoffs between indoor and outdoor farrowing are real and nuanced.