Optimization of analgesia for piglet castration under isoflurane anaesthesia with parenteral butorphanol, meloxicam or intratesticular lidocaine.

INTRODUCTION: This blinded prospective study investigated analgesic effects of intramuscular (IM) butorphanol, meloxicam or intratesticular (IT) lidocaine for castration of 7-14 days old piglets under isoflurane anaesthesia. 66 piglets were randomly injected with: meloxicam IM (0.4 mg/kg; group M), butorphanol IM (0.2 mg/kg; group B), or both (group BM) 20 minutes prior to castration, or lidocaine IT (4 mg/kg (group ML4) or 8 mg/kg (group ML8)) together with meloxicam IM (0.4 mg/kg) under anaesthesia with 1.8% end-tidal isoflurane. Heart rate, respiratory rate, mean arterial blood pressure and end-tidal carbon dioxide were recorded. Anaesthesia quality was scored and postoperative behaviour assessed. As butorphanol caused unacceptable side effects, its use was stopped. Group M showed worse anaesthesia quality than ML4 and ML8 (higher incidence of movements: 11/17, 3/18 and 4/17, respectively). There were no significant differences between groups regarding parameters measured during castration. Postoperative behaviour did not differ between groups. For castration of 7-14 days old piglets under isoflurane anaesthesia, IT lidocaine provides an additional side effect free analgesia.