Behavioural and physiological responses of calves to dehorning by heat cauterization with or without local anaesthesia

Behavioural and physiological reactions to thermal dehorning were studied in separate groups of 4- to 6-week-old calves after injection of a local anaesthetic (A), after saline injection (S), and without any injection (C). To assess the physiological responses, blood was collected from a jugular catheter from each calf of the physiology groups A (n = 8), S (n = 8), and C (n = 7) prior to and for 4 h after injection and dehorning, which occurred 20 min after the injection. Behavioural reactions during dehorning were video-recorded. For the next 4 h thereafter, behavioural data were recorded by visual observations in the behaviour groups (A: n = 10, S: n = 10, C: n = 10). Two days prior to the actual dehorning, the complete procedure was simulated in all calves. Compared to simulation, dehorning C-calves induced increased frequencies of tail wagging (35 +/- 0.5 [mean +/- SEM] vs. 1.5 +/- 0.5; P < 0.05), head moving (5.3 +/- 1.5 vs. 2.9 +/- 0.6; n.s.), tripping (3.1 +/- 0.5 vs. 1 +/- 0.5; P < 0.05), and rearing (1.9 +/- 0.5 vs, 0.4 +/- 0.2; P < 0.05), as well as more frequent abnormal backward-locomotion for 1 h (2.6 +/- 1.0 vs. 0; P < 0.05) and higher frequencies of head shaking (27.4 +/- 5.9 vs. 1.3 +/- 0.6. P < 0.05). The same effects were seen in S-calves. S- and C-calves also entirely avoided head pushing during the 4 h postdehorning and showed clearly reduced feeding behaviour for 2 h. Plasma concentrations of vasopressin, ACTH, and cortisol were increased following dehorning in S- and C-calves. Local anaesthesia eliminated or markedly attenuated all these behavioural and endocrine reactions to dehorning. The saline injection induced some of the above mentioned changes, but these were less pronounced by the injection of the anaesthetic. Behavioural and physiological responses together indicate that dehorning calves by heat cauterization is accompanied by considerable pain and stress, which can be significantly alleviated during and up to 2 h postdehorning by local anaesthesia. (C) 1999 Elsevier Science B.V. All rights reserved.