XYLAZINE IMMOBILIZATION OF MOOSE WITH YOHIMBINE OR TOLAZOLINE AS AN ANTAGONIST; A COMPARISON TO CARFENTANIL AND NALTREXONE

Abstract

When moose (Alces alces) are kept in captivity, it is often necessary to immobilize them for research purposes or animal care. Carfentanil, a very potent narcotic, used in combination with xylazine hydrochloride is the preferred drug mixture when immobilizing moose in the wild. However, carfentanil is both expensive and potentially dangerous to the handler. We evaluated the use of xylazine hydrochloride, an alpha₂ adrenergic sedative and analgesic, used alone, or in combination with either carfentanil citrate or ketamine hydrochloride to immobilize moose at the Moose Research Center. Mean downtime for xylazine alone was not different from xylazine:ketamine and carfentanil:xylazine mixtures. Drugged animals could be approached and handled immediately when given carfentanil:xylazine. Xylazine or xylazine:ketamine drugged animals often lay down 8-12 minutes before completely immobilized. The antagonist yohimbine had no apparent effect on reversal of xylazine - immobilized moose, and recovery times averaged 3:38 ± 2:01 hours. The antagonist tolazoline hydrochloride reduced recovery times significantly (P<0.0001), and animals reversed with this drug were standing within 4 to 31 minutes (x̄ = 21 minutes). Animals immobilized with a mixture of carfentanil:xylazine and reversed with naltrexone were usually standing within 7 minutes with a range from 3 to 21 minutes after administration of the antagonist. Comparison of individual drugs, mixtures and antagonists are discussed relative to cost, efficiency, effectiveness, safety, and reliability of a mobilizing moose.