Local anaesthesia with lidocaine is insufficient for ovine tail docking: A randomised clinical trial

BACKGROUND: Tail docking in sheep is a common management practice associated with significant pain and stress. Local anaesthesia with lidocaine has been reported to provide limited analgesia during this procedure. The present study evaluated whether the addition of xylazine could improve welfare outcomes in lambs undergoing thermal tail docking. METHODS: Thirty Texel lambs (10.1 ± 4.0 kg; 6.4 ± 2.4 weeks old) were randomly assigned to two groups: GX (xylazine 0.1 mg/kg intramuscularly) or GS (saline). Twenty minutes later, both groups received a circumferential block at the tail base with lidocaine 2 mg/kg, followed by tail docking five minutes later. Physiological parameters (heart rate, respiratory rate, rectal temperature), agitation scores and sedation levels were recorded. Postoperative pain was assessed hourly for 5 h using the UNESP-Botucatu pain scale and the McLennan facial expression scale. Plasma cortisol was measured at baseline and 1 h after docking. Rescue analgesia (meloxicam 0.5 mg/kg IM) was administered when pain scores ≥5. RESULTS: Six lambs in GS required rescue analgesia, whereas none in GX did (P = 0.02). Plasma cortisol increased significantly in GS compared to GX and to baseline (P < 0.05). Xylazine induced mild sedation, reduced agitation and attenuated increases in heart rate and rectal temperature observed in GS. Pain scores increased in both groups postoperatively, but only GS animals exceeded the rescue threshold. CONCLUSIONS: Lidocaine alone was insufficient for analgesia during tail docking. The addition of intramuscular xylazine reduced stress responses, decreased the need for rescue analgesia and improved lamb welfare.