Comparison of the Efficacy and Safety of Medetomidine-Ketamine to a Novel Medetomidine-Azaperone-Alfaxalone Combination in Wild Rocky Mountain Bighorn Sheep (Ovis canadensis)
Seventy-four wild, free-ranging Rocky Mountain bighorn sheep (Ovis canadensis) in Canada were darted intramuscularly (IM) with medetomidinea (0.15±0.04 mg/kg) and ketamineb (4.0±1.4 mg/kg) (MK, n=37), or medetomidinea (0.14±0.06 mg/kg), azaperonec (0.21±0.11 mg/kg), and alfaxaloned (0.45±0.21 mg/kg) (MAA, n=37). Arterial blood samples were taken and analyzed immediately with a portable analyzer. Parameters evaluated were pH, PaCO2, PaO2, base excess, bicarbonate, oxygen saturation, and lactate. Rectal temperature, heart rate (HR), and respiratory rate were monitored upon recumbency and throughout anesthesia. Animals were reversed by IM injection of atipamezolee at five times the medetomidine dose. Induction times of animals darted once (8.7±3.2 min, 7.3±3.9 min) and recovery times of all animals (3.4±1.5 min, 3.9±1.6 min) were not significantly different between MK and MAA groups, respectively; however, MK animals had significantly longer downtimes (79.2±10.5 min versus 52.2±14.8 min, p<0.0001). Both groups experienced severe hypoxemia (PaO2 41±9 mm Hg, 40±9 mm Hg). PaCO2 was significantly higher in the MK group than in the MAA group (median 53 [range 52–56] mm Hg versus 48 [48–54] mm Hg, p=0.0248), with a correspondingly lower pH (7.40 versus 7.42, p=0.07). Initially, MK animals had significantly higher HR (49 versus 40 bpm, p=0.0002), which decreased over time. In bighorn sheep, both MK and MAA produced reliable, reversible immobilization with rapid, smooth inductions and recoveries. MAA caused less respiratory depression than MK and is a promising wildlife capture protocol.
a. Medetomidine 30 mg/ml, Bow Valley Research, Inc., Calgary, AB, Canada
b. Vetalar® 100 mg/ml, Bioniche Animal Health, Inc., Belleview, ON, Canada
c. Stresnil® 40 mg/ml, Elanco, Division of Eli Lilly Canada, Inc., Guelph, ON, Canada
d. Alfaxan® 10 mg/ml, Jurox Pty Ltd, Rutherford, Australia
e. Atipamezole 10 mg/ml, Bow Valley Research, Inc., Calgary, AB, Canada
This study was supported in part by the Faculty of Veterinary Medicine, University of Calgary, Canada; a Morris Animal Foundation First Award (Grant ID # D13ZO-317) to Åsa Fahlman; and a Natural Sciences and Engineering Research Council of Canada grant to Kathreen Ruckstuhl, University of Calgary. The authors also thank the University of Calgary R.B. Miller Field Station and volunteers assisting during field work.