Liver fluke infection in outdoor pigs causes chronic welfare impacts including pain, reduced growth and immune suppression that are frequently underdiagnosed because clinical signs are subtle.
Liver fluke in outdoor pigs represents a genuine but hidden welfare cost. The absence of obvious clinical signs does not reflect the absence of suffering — chronic liver damage, immune suppression and pain associated with tissue migration occur beneath a surface of apparently normal behaviour. The welfare trade-off between the behavioural benefits of outdoor pig keeping and the parasite burden it entails requires proactive management rather than ignoring fluke risk in outdoor systems. Regular treatment, strategic grazing management and monitoring through slaughter data provide the information needed to manage fluke burden while maintaining the welfare benefits of outdoor production.