Pain Assessment in Pigs: Tools for Better Welfare Decision-Making

Accurate pain assessment in pigs enables timely treatment and humane endpoint decisions — validated tools are increasingly available for farm use.

Key Facts

• Pigs show subtle behavioral pain indicators that require training to recognize
• Grimace scales developed for mice and rats have been adapted for pig pain assessment
• Ear position, orbital tightening, nose buldge, and cheek tension are validated pig grimace scale indicators
• Pigs modulate pain behavior in the presence of humans — assessment should include unobserved behavior
• Validated locomotion scoring translates objectively to pain and welfare status in lame pigs

Welfare Considerations

Pain assessment in pigs is complicated by their tendency to mask pain in the presence of humans — as prey animals, displaying vulnerability to potential predators (including humans) is selected against. This masking behavior means that welfare-relevant pain is systematically underestimated in farm settings where assessments are made only during human presence. Remote camera assessment of pen behavior, combined with the Pig Grimace Scale — validated facial expression indicators of acute pain — improves pain detection. Lameness scoring provides a validated, objective measure of pain-related mobility compromise. Better pain assessment tools enable timely treatment, appropriate analgesic prescription, and compassionate humane endpoint decisions for severely affected individuals.

What You Can Do

• Train farm staff to recognize subtle pig pain indicators including ear position and facial expression changes
• Implement the Pig Grimace Scale for acute pain assessment in post-procedural and ill pigs
• Use remote camera observation to assess unobserved pain behavior in pigs with suspected chronic pain
• Combine locomotion scoring with facial expression assessment for comprehensive welfare evaluation
• Establish clear treatment and humane endpoint criteria based on pain assessment thresholds