The science of pig environmental enrichment has advanced significantly, identifying effective materials, management approaches, and welfare indicators that demonstrate enrichment benefit.
Pig enrichment science has moved from the simple provision of any manipulable object to a nuanced understanding of what makes enrichment effective. The key variables are manipulability (can the pig change it?), novelty (is it new?), and biological relevance (does it engage rooting motivation?). Straw consistently outperforms inorganic hanging objects because it is manipulable, novel when renewed, and engages the rooting behaviour that pigs are most strongly motivated to perform. The management implication is clear: providing a single chain and calling it enrichment is insufficient. Regular renewal of genuinely manipulable, biologically relevant materials is required to maintain the welfare benefit of enrichment programmes.