Comparison of three anaesthetic protocols in Bennett's wallabies (Macropus rufogriseus)

Investigate physiological and sedative/anaesthetic effects of xylazine, medetomidine or dexmedetomidine combined with ketamine in free-ranging Bennett's wallabies.

Prospective clinical trial.

Twenty-six adult free-ranging Bennett's wallabies.

Animals were darted intramuscularly with one of three treatments: xylazine and ketamine, 2.0 and 15.0 mg kg(-1), respectively (XK): medetomidine and ketamine 0.1 and 5.0 mg kg(-1) (MK) and dexmedetomidine and ketamine 0.05 and 5.0 mg kg(-1) (DMK). Body weights were estimated. If the animal was still laterally recumbent after 45 minutes of anaesthesia, then an alpha-2 adrenoceptor antagonist, atipamezole, was administered (XK: 0.4 mg kg(-1), MK: 5 mg kg(-1), DMK: 2.5 mg kg(-1)). Heart rate (HR) and respiratory rate (f(R)) were recorded at 5-minute intervals and temperature at 10-minute intervals. Venous blood was taken 30 minutes after initial injection. Statistical analysis utilized anova. p < 0.05 was considered significant.

Animals became recumbent rapidly in all groups. XK animals had muscle twitches, responded to external stimuli, and three animals required additional dosing; this was not observed in the MK and DMK groups. HR (mean +/- SD beats minute(-1)) in XK (81 +/- 4) was significantly higher than MK (74 +/- 2) and DMK (67 +/- 4). There were no differences in f(R), temperature, blood-gas and biochemical values between groups. More animals in MK (9/10) and DMK (5/6) needed antagonism of anaesthesia compared with XK (1/10). There were no adverse effects after anaesthesia.

Cardio-respiratory effects were similar in all groups. There were fewer muscle twitches and reactions to external stimuli in MK and DMK. Duration of anaesthesia was shorter in XK; most animals in MK and DMK needed atipamezole to assist recovery. All three treatments provided satisfactory sedation/anaesthesia and are suitable for use in Bennett's wallabies.