Environmental enrichment for farm animals reduces suffering and stereotypic behavior, with a growing body of evidence on what kinds of enrichment are most effective for different species.
Farm animal enrichment science has advanced to the point where specific recommendations are evidence-based rather than speculative. For pigs: rooting substrate (straw, compost) is far more effective than hanging chains. For chickens: dust bath substrate, perches, and pecking blocks address the most strongly motivated behaviors. For dairy cows: pasture access provides the broadest behavioral benefits. Enrichment works by providing outlets for motivated behaviors that, if blocked, lead to frustration, stereotypy, and sometimes aggression. The challenge is scaling enrichment from research conditions to commercial practice — a challenge that welfare certification schemes and purchasing requirements are beginning to address.