Calves disbudded with local nerve block and analgesic show conditioned place aversion two days later but not in the hours post-disbudding

Hot-iron disbudding is a very common, painful procedure performed in dairy farms. One of the gold standard practices recommends combining the use of a local anaesthetic (e.g. procaine) and analgesic (e.g. meloxicam) to control pain. However, it is unknown if calves still experience pain during and after the procedure when using multi-modal pain relief. Here, we explored the affective consequence of disbudding using a conditioned place aversion paradigm where inferences are based on learnt aversion to places associated with negative experiences. We conducted two experiments: (1) calves were disbudded in their home-pen and then conditioned immediately afterwards for 6 h so that conditioning involved post-operative pain only; and (2) calves were disbudded in the conditioning compartment and remained there for the following 6 h so that conditioning included the potential pain and fear from the procedure and any post-operative pain. All calves were conditioned in the other (control) conditioning compartment either 2 days before or after disbudding. In both experiments, calves who were disbudded on the second conditioning (control conditioning happening 2 days before the procedure) showed no aversion to the compartment associated with disbudding, suggesting that pain was minimal in the 6 h post-disbudding. However, in Experiment 2, calves displayed a preference for the disbudding compartment when disbudding occurred first (control conditioning happened 2 days later) suggesting they were in more pain on day 2 than in the hours following the procedure. These results show that calves may experience pain for days after hot-iron disbudding, calling for more work on long-lasting pain following disbudding.