Welfare outcome indicators (WOIs) measure the actual state of pigs rather than the inputs provided, offering a more direct and reliable assessment of whether management translates into genuine welfare improvements.
Pig welfare outcome indicators represent the maturation of welfare science from assumption to evidence. Early welfare regulations specified inputs — minimum space, enrichment requirements — on the assumption that compliant inputs would produce good welfare. Outcome measurement reveals that compliance with input standards is neither necessary nor sufficient for good welfare: farms that technically comply may have poor outcomes due to management failures, while farms with innovative management may achieve good outcomes with different inputs. Slaughter plant data is particularly valuable because it provides an objective, systematic, and population-level welfare assessment that cannot be manipulated by prior knowledge of inspection: lung lesions indicate chronic respiratory disease, liver condemnation indicates parasite burden, and skin lesions indicate pen-mate aggression. These retrospective indicators allow welfare auditors to identify farms with systematic welfare problems that on-farm input inspection might miss. Integrating WOI data into food company supply chain management creates accountability that drives genuine improvement.