Effects of a topically applied anaesthetic on the behaviour, pain sensitivity and weight gain of dairy calves following thermocautery disbudding with a local anaesthetic.

Aims: To compare the effect of a topically applied anaesthetic to no pain relief or meloxicam on the behavioural responses, pain sensitivity and weight gain of calves following disbudding with or without sedation. Methods: A total of 364, 2-6 week-old calves from three commercial farms were systematically allocated to one of six treatment groups. All calves received a cornual nerve block prior to disbudding, with half restrained in a crate and half sedated with xylazine. Within these groups one third received no further treatment (control), one third were treated with meloxicam >10 minutes prior to disbudding and one third received a topical anaesthetic applied to the horn bud wounds following disbudding. The frequency of ear flicks, head shakes, head scratches and pain sensitivity of the wound were recorded on up to eight occasions over 24 hours after disbudding. Calves were weighed before, and 7 and 28 days after, disbudding to determine average daily weight gain (ADG). Results: Compared to calves in the crate-control group, all other groups had reduced ear flicks at all times following disbudding (p < 0.01). Treatment with meloxicam and topical anaesthesia in addition to sedation reduced head scratches compared to calves in the crate-control group (p ≤ 0.013). At 22 hours after disbudding head shakes were reduced in sedated calves treated with topical anaesthetic compared to calves in the crate-control group (p < 0.001). Pain sensitivity was lower in all sedated calves than unsedated calves (p < 0.001). The ADG between Days 0-7 was 0.14 (95% CI = 0.015-0.274) kg/day greater in sedated calves treated with meloxicam than calves in the crate-control group (p = 0.03), and the ADG between Days 0-28 tended to be 0.06 (95% CI=-0.01-0.13) kg/day greater in sedated calves treated with topical anaesthetic than calves in the crate-control group (p = 0.09). Conclusion and clinical relevance: Sedation of calves for disbudding reduced the pain experienced in the following 24 hours. There was a benefit to providing calves with topical anaesthetic following disbudding on behavioural responses and pain sensitivity, which was similar to that of treating calves with meloxicam.