Nose ringing in pigs is used to prevent rooting behaviour in outdoor systems, but it causes pain and prevents expression of one of pigs' most fundamental natural behaviours.
Nose ringing inflicts acute pain during insertion and causes ongoing discomfort whenever pigs attempt to root - a behaviour driven by intense motivation equivalent to hunger. Preventing rooting does not eliminate the drive; it simply prevents satisfaction, creating a state of chronic frustration. The welfare cost of ringing is significant: pigs spend considerably less time performing natural foraging behaviour, and show elevated stress indicators. Pasture management alternatives that allow some rooting while managing land damage are being developed.