Legal minimum enrichment requirements for pigs are often provided as simple chains or ropes, but evidence shows more complex substrates provide significantly better welfare.
Pigs have strong exploratory and rooting motivations that are frustrated in barren slat environments. Chains and hanging ropes provide limited enrichment value and pigs rapidly habituate to them. The European Food Safety Authority has concluded that only substrate materials achievable at floor level adequately address rooting motivation. Providing straw, compost, or other loose manipulable materials significantly reduces tail-biting, stereotypies, and apparent frustration.