Effect of butorphanol in combination with xylazine during castration of calves: A randomised trial under field conditions

Background: In horses, cats and dogs, the opioid butorphanol has been proven effective in management of visceral pain and for peri- and postoperative pain relief. The aim of this study was to evaluate physiological responses and indicators of noxious stimuli when adding butorphanol to xylazine for sedation of bull calves during surgical castration. Methods: In total, 54 bull calves were randomly assigned to a control group sedated with only xylazine and a treatment group sedated with the addition of butorphanol prior to castration. Observation of physiological responses by blinded observers from sedation and 1 hour onwards. Results: Apart from significantly more vocalisations in the treatment group prior, during and after the surgical procedure, no adverse effects of butorphanol addition were noted. Also, improved alertness and less drowsiness 1 hour after initiation of sedation were seen in the treatment group possibly associated with improved analgesia. Limitations: A longer follow-up time after sedation and additional measurements of cortisol levels would have given additional valuable information. Conclusion: Addition of butorphanol leads to increased vocalisation during and possibly a shortened recovery time post-sedation.