Evaluating conditioned place preference in calves 0 and 20 days after hot-iron disbudding

Abstract Hot-iron disbudding, a routine procedure that prevents horn bud growth through cauterization, is painful for calves. The resulting burns remain sensitive to touch for weeks, but it is unclear whether calves experience ongoing, non-evoked pain during healing. We evaluated conditioned place preference for analgesia in 44 calves disbudded or sham-disbudded 6 h (Day 0) or 20 days (Day 20) before testing (n = 11/treatment). Calves were conditioned to associate the effects of a lidocaine cornual nerve block with the location (left or right side of the home pen) and pattern of a visual stimulus (solid black or black-and-white striped board), and a control injection of saline with the contrasting stimulus. Calves received 6 conditioning trials over 3 days, alternating between lidocaine- and saline-paired stimuli. On the fourth day, calves were provided both stimuli for 5 min and preference was assessed. Contrary to our predictions, we found no evidence of a preference for either stimulus at 0 or 20 days after disbudding or sham-disbudding. Given that pain is well established in the hours after disbudding and some studies report behavioral changes weeks later, we suggest the conditioned place preference paradigm, as applied in this study, would benefit from further refinement.