Cardiorespiratory and neurological effects of morphine and butorphanol in Bos taurus

Abstract

Spanish fighting bulls (Bos taurus) are ruminants whose temperament necessitates chemical restraint for safe handling. Each of 10 animals was anaesthetised with each of 4 different protocols, which were administered in random order with a washout period of 10 days. The control protocol (C) consisted of tiletamine (0.5 mg/kg), zolazepam (0.5 mg/kg), and xylazine (1 mg/kg) administered intramuscularly. The experimental protocols included an analgesic agent, either butorphanol (0.1 mg/kg) (B) or morphine [(0.2 mg/kg) (M2) or (0.4 mg/kg) (M4)], in addition to the control protocol. Atipamezole (25 μg/kg) was administered intravenously 30 min after induction. During anaesthesia, heart rate (HR), respiratory rate (RR), temperature, direct arterial pressure (BP), the bispectral index (BIS), electromyography (EMG) results, arterial blood gas parameters, and the induction and recovery times were recorded. Protocol C yielded the highest RR, BP, BIS, and EMG values. Protocol M4 significantly reduced HR and PaCO2 relative to the control values. All protocols produced hypoxaemia. Protocol C produced the longest induction time and protocol M4 the longest recovery time. In conclusion, butorphanol and morphine are both effective additives to the tiletamine–zolazepam–xylazine protocol for immobilising Spanish fighting bulls. However, oxygen supplementation is strongly recommended.