The use of nose-rings in pigs: consequences for rooting, other functional activities, and welfare

Commercial pigs kept outdoors are often given nose-rings, to inhibit rooting and minimize pasture damage. If rooting is a 'behavioural need' in the pig, and ringing is effective because it renders rooting painful, nose-ringing may be a threat to welfare. Thirty gestating sows were assigned to one of three conditions: unringed controls (UR); sows ringed with three, wire 'clip' rings through the snout rim (CR); or sows with one, rigid 'bull' ring (BR). They were observed on grass for 7h day(-1) at intervals over 6 months. Ringing almost totally abolished penetration of the ground by rooting during the month after ringing (UR, CR and BR sows respectively spent 5.6%, 0.1% and 0.1 % of scan observations dig-rooting during this month; P < 0.001). These differences in recorded rooting were reflected in a much greater extent of pasture damage in paddocks containing UR sows. Rooting remained largely suppressed throughout the 6 months of observations in BR sows; but substantial recovery of this function occurred in CR sows by the sixth month, although much of this may be attributed to the fact that most sows lost at least some of their rings. Ringing also partially inhibited grazing (which accounted for 26.2% 27.1% and 21.9 % of scans over the whole project in UR, CR and BR sows respectively; P < 0.05), nosing in straw, digging out wallows and stone-chewing (18.3% 9.5% and 9.2 % respectively of all scans in UR, CR and BR sows; P < 0.001). Ringed sows spent more time standing but otherwise inactive than did controls (0.8%, 1.7% and 4.0 % of all scans in UR, CR and BR sows respectively; P < 0.001), and displayed more straw-chewing, vacuum-chewing and digging at soil with the forepaw. We conclude that nose-ringing in pigs inhibited a range of functional activities, as well as rooting, and elicited more behaviours that suggest a degree of reduced welfare. BR sows displayed more of these effects than did CR ones, although these differences may be largely, but not entirely, due to a loss of clip rings over time.