Pigs have a strong natural motivation to root and wallow in substrate. In intensive systems without rooting material or wallowing opportunities, this behavioural need goes chronically unmet, causing significant frustration and welfare harm.
Rooting and substrate investigation are not optional extras for pigs — they are core behavioural needs with a strong neurological drive. Frustration of these needs in bare-floor systems leads to redirected oral behaviours that cause injury to pen-mates and are major sources of suffering in commercial pig production. Enrichment provision — even simple items like hanging chains or straw racks — provides partial mitigation, but direct substrate access (deep litter, rooting bays, outdoor paddocks) better meets the full behavioural need. Welfare assessment schemes increasingly prioritise evidence of substrate use as a positive welfare indicator.