Alfaxalone

Current intramuscular anaesthesia for piglet castration, involving azaperone and ketamine, is unsatisfactory in terms of anaesthesia and recovery. This study aimed to evaluate different intramuscular drug combinations to achieve anaesthesia without movement or vocalisation during surgery, while maintaining haemoglobin oxygen saturation (SpO2) >90 % and excitation-free induction and recovery, with piglets standing within two hours of drug administration. Alfaxalone and dexmedetomidine were administered to 19 piglets at starting doses of 2 mg/kg and 25 µg/kg, respectively. If two consecutive piglets moved during surgery, the doses were increased based on a predetermined dosage tree, with maximum doses of 6 mg/kg alfaxalone and 40 µg/kg dexmedetomidine. In case of reaction to presurgical nose pinch, 4 mg/kg lidocaine 2 % was injected intratesticulary. Despite local anaesthesia or no reaction to nose pinch indicating sufficient depth of anaesthesia, only one piglet did not react to spermatic cord crushing. Consequently, another 12 piglets, randomly received 40, 50 or 60 µg/kg dexmedetomidine and 5 mg/kg alfaxalone, with or without butorphanol 0,2 mg/kg. Only one piglet, after butorphanol and 40 µg/kg dexmedetomidine, did not move during surgery. Therefore, another eight piglets received 40 µg/kg dexmedetomidine, 5 mg/kg alfaxalone and 4 mg/kg pethidine. However, all piglets reacted to surgery, and SpO2 was below 90 %. No further testing was conducted. In conclusion, none of the tested combinations of alfaxalone and dexmedetomidine, whether with or without an opioid, provided satisfactory anaesthesia for surgical castration in piglets aged between two and eight days.