Substrate enrichment including straw, compost, and other organic materials provides the most naturalistic enrichment for pigs. Practical implementation challenges are solvable.
Pigs denied substrate enrichment cannot perform the rooting behavior that is fundamental to their nature. The motivational strength of rooting is such that pigs deprived of substrate redirect the behavior to pen-mates' tails, causing tail biting. Straw and other substrate enrichment that satisfies rooting motivation prevents this redirected behavior and meets a fundamental welfare need.