Internal parasites including liver fluke and roundworms cause chronic welfare harm in pigs. Understanding and managing these parasites is an important welfare priority in outdoor and extensive pig systems.
Internal parasites are a significant but often invisible welfare problem in pig production, particularly in outdoor systems. Liver fluke migration through hepatic tissue causes pain, chronic inflammation, and progressive liver damage. Affected pigs grow more slowly, are more susceptible to secondary infections, and in severe cases become significantly debilitated. Because the welfare impact is chronic and gradual rather than acute and visible, parasite burdens often go unrecognised until slaughter examination reveals liver damage. Effective parasite management in outdoor systems requires a combination of targeted anthelmintic treatment, pasture management to reduce contamination, and monitoring of slaughter data to inform flock-level risk assessment. The development of anthelmintic resistance makes management approaches that reduce reliance on treatment particularly important.