ABSTRACT
Disbudding and dehorning (DD) calves are common management procedures performed on almost all dairy farms. A general review concerning DD has been published by a task force of the American Veterinary Medical Association (AVMA Animal Welfare Division, 2014). Appropriate DD practices are important for the welfare of the calf, as well as for public perception of the dairy industry. In particular, minimizing pain associated with DD is important to limiting the pain-stress-distress cascade that creates altered behavioural and physiologic states. Pre-emptive analgesia can be accomplished with sedation, general anaesthesia, local anaesthesia, as well as with pre-and postoperative administration of NSAIDs. A summary of currently available research on pain assessment and management following DD has also been published (Stock et al., 2013). Evidence of pain associated with DD include behavioural responses (head shakes, ear flicking; Faulkner and Weary, 2000) and increases in cortisol responses (Petrie et al., 1996) in calves dehorned without pain management. Behavioural responses to pain are reduced using both short-lived local anaesthetic (Stafford and Mellor, 2005) and longer-lasting analgesics (Faulkner and Weary, 2000). While behavioural and physiological changes associated with painful procedures can provide indications of arousal reflecting changes in affective state, novel research in this area has advanced our understanding of affective state. Neave et al. (2013) reported that dairy calves, trained to associate a visual stimulus with a milk reward, were less likely to judge ambiguous stimuli as rewarding after they had been disbudded than they had been before the procedure. These results indicate a negative cognitive bias in calves experiencing pain.
