The farrowing period — birth and early nursing — is one of the highest-mortality periods in pig production, with welfare costs to both sows and piglets from intensive confinement systems.
Farrowing system welfare involves competing welfare interests of sows and piglets. Farrowing crates prevent overlying deaths but cause severe frustration in sows unable to perform nesting behavior or move freely during a period of intense behavioral motivation. Free farrowing systems — pens where sows can nest, move, and express maternal behavior — reduce sow frustration significantly. With appropriate nest box design and management, piglet mortality from overlying in free farrowing systems can be comparable to crated systems. The welfare case for free farrowing is strong when management quality is high. Several countries have demonstrated commercial viability, removing the argument that crates are economically necessary.