Analgesic efficacy of preoperative paracetamol administration in piglets undergoing surgical castration under xylazine-ketamine anaesthesia

Surgical castration in piglets causes significant pain and distress, yet standardized analgesic protocols remain inadequately established for commercial settings. This study evaluated whether preoperative paracetamol administration provides effective analgesia for piglets undergoing castration under xylazine-ketamine anaesthesia. Twelve large white piglets (3-5 weeks old) with weights between 2.5 and 5.0 kg were randomly allocated into two groups. Piglets in group A were treated with 15mg/kg paracetamol injection two hours before anaesthesia induction with 2% xylazine (2 mg/kg) and 5% ketamine (20 mg/kg) administered intramuscularly, while piglets in group B were administered saline of equal volume. Physiological parameters (heart rate, respiratory rate, and rectal temperature) were recorded at baseline and ten-minute intervals post-induction. Pain was assessed using the UNESP-Botucatu composite scale and behavioural observations at 0-, 6-, 24-, and 48-hours post-surgery. No significant differences were observed in respiratory rates or rectal temperatures between groups at any time point (p>0.05). Heart rates were significantly lower (p<0.05) in the paracetamol group throughout the 30-minute observation period, with values at anaesthesia induction of 128.00±13.72 bpm compared to control 169.00±31.62 bpm. No significant differences were detected in standardized pain scores or pain-associated behaviours between groups throughout the 48-hour observation period. The findings of this study reveal that preoperative administration of paracetamol injection at a dosage of 15 mg/kg did not significantly improve overall pain outcomes in piglets undergoing surgical castration under xylazine-ketamine anaesthesia, despite producing sustained cardiovascular effects throughout the observation period. Thus, evaluation of alternative analgesic approaches, including repeated-dose paracetamol protocols and other analgesic agents, is necessary for effectively managing castration-associated pain in piglets.