Disbudding pain in calves: mitigating short-term effects and exploring long-term consequences

Abstract

In modern cattle production, the presence of horns is often seen as an inconvenience, leading to the practice of disbudding, which involves the destruction of horn-originating tissue in non-hornless cattle during their early days of life. This dissertation addresses knowledge gaps related to this painful procedure. While there is a common belief among farmers and veterinarians that caustic disbudding is less painful than heatcautery disbudding, the scientific community lacks consensus on the extent of pain associated with each method. We explored this issue in Chapter II. A systematic review was undertaken to gather the experimental literature comparing these two methods, and studies were comprehensively examined from an animal welfare perspective, a synthesis of their findings and limitations was provided. We have found 6 studies that somehow compared the two methods. Despite all studies reporting differences between the disbudding method, there were few agreements across the seven types of reported outcomes, and many studies had severe limitations compromising their findings. Consequently, the current scientific literature does not provide sufficient evidence to determine the less detrimental disbudding method. However, caustic disbudding is a painful procedure, and its pain control is often overlooked, especially the use of local anesthetic block, which efficiency is still a subject of debate. Thus, we also investigate the effectiveness of different pharmacological approaches in mitigating pain following caustic disbudding. To address this issue, articles that examined different pharmacological approaches were also included in the systematic review presented in Chapter II. The main findings were narratively reported, but we also build more on this using a meta-analytical approach to summarize the overall intervention's effects on blood cortisol. Our results indicate that lidocaine anesthetic block, either alone or combined with analgesics, effectively controls raises in cortisol levels and reduces pain behavior in the short time after caustic disbudding, while analgesics given alone do not. In Chapter III we seek the answer to whether a painful procedure early in life (e.g., caustic disbudding) could induce long-term threshold changes, despite the implementation of best practices in pain control. To address this question, a randomized controlled trial was conducted where one group of calves had one of the horn buds removed at 10 days of life through caustic disbudding, while another group of calves underwent a sham disbudding. Thirty days later, both groups had the contralateral horn removed through heat-cautery disbudding. We measured pain sensitivity before and after both disbudding procedures using an algometer. Our findings suggest that calves previously exposed to pain may be less sensitive following subsequent painful procedures. In summary, this dissertation pointed out that it is not possible yet to determine whether caustic or heatcautery disbudding is the less detrimental method for calves’ welfare, however, we provided evidence that using lidocaine anesthetic block in combination with nonsteroidal anti-inflammatory drugs is a relatively efficient way to mitigate caustic disbudding pain. Moreover, this dissertation also highlights the need to consider the long-term consequences of painful procedures.