Preliminary observations on the use of a combination of xylazine and ketamine hydrochloride in calves

A combination of xylazine (0.2 mg/kg intramuscularly) and ketamine (5 mg/kg intravenously or 10 mg/kg intramuscularly) was used to anaesthetise 30 calves. The calves were divided into three groups. In group A, ketamine administered intravenously 10 minutes after xylazine gave approximately 20 minutes' anaesthesia. Anaesthesia was prolonged by halothane inhalation and recovery was rapid. The calves stood for 37.0 +/- 7.5 minutes (mean +/- sem) after the cessation of halothane administration. Ketamine was administered intramuscularly either 10 minutes after xylazine (group B) or simultaneously with the xylazine (group C). The duration of anaesthesia in group B was 23.5 +/- 1.8 minutes and in group C 37.0 +/- 3.4 minutes. Anaesthesia was prolonged in these animals by further injections of ketamine (5 mg/kg intramuscularly) when necessary. Recovery was slower in these calves with animals standing 85.0 +/- 10.8 minutes after the last injection of ketamine in group B and after 107.6 +/- 10.5 minutes in group C. Respiratory rates and pulse rates decreased after xylazine administration and then rose again once ketamine was given. The initial bradycardia was absent when the ketamine and xylazine were administered simultaneously. The duration of anaesthesia induced by the initial injection of ketamine in the calves in groups B and C appeared to be related to the age of the calf with duration decreasing with increasing age in calves from one to 10 weeks of age. Thereafter duration of anaesthesia appeared to be constant at about 23 minutes. The drug combination gave good muscle relaxation and recovery was smooth and uncomplicated.