Preliminary Data for Comparison of Carfentanil-Xylazine and Thiafentanil-Medetomidine in Electroejaculation of Captive Gaur (Bos frontalis gaurus)
American Association of Zoo Veterinarians Conference 2007
Julia E. Napier, DVM; Naida M. Loskutoff, PhD; Sarah M. Dankof; Lee G. Simmons, DVM; Douglas L. Armstrong, DVM
Omaha’s Henry Doorly Zoo, Omaha, NE, USA


Carfentanil citrate and thiafentanil oxalate have been used successfully to immobilize captive and free-ranging ungulates.1-3,5,7 The objective of this study was to compare the efficacy and certain physiologic parameters of protocols using the two opioids in gaur (Bos frontalis gaurus).

Seven adult gaur bulls were immobilized for electroejaculation at Omaha’s Henry Doorly Zoo. An estimated weight of 1000kg4,6) was used for all bulls. Each animal was immobilized twice using two protocols:

1.  10 mg carfentanil combined with 100 mg xylazine (CX), reversed with 1000 mg naltrexone and 24 mg yohimbine.

2.  12 mg thiafentanil combined with 20 mg medetomidine (TM), reversed with 120 mg naltrexone and 100 mg atipamezole.

Both combinations were delivered IM in the shoulder area via pole syringe. Electroejaculation was carried out by a standardized protocol to duplicate procedural stimulation on each animal. Induction and recovery times, initial rectal temperatures, heart rate, respiratory rate, anesthetic depth, oxygen saturation, indirect blood pressure and arterial blood gases were recorded at time of initial “hands on,” then at 10-min intervals pre-ejaculation and once post-ejaculation. Antagonists were administered ¼ IV and ¾ SC.

Both protocols require a very small amount of drug for a large ungulate, provide smooth inductions, and adequate anesthesia. Animals on CX showed better blood gas values (based on lower CO2) and lower blood pressure values. Animals on TM had better muscle relaxation and smoother recoveries with no renarcotization noticed during this study. Additional immobilizations need to take place to further compare these two combinations in this species.


The authors would like to thank veterinary technicians Nicole Linafelter and Amanda Mohn and the keeper staffs at the Lee G. Simmons Wildlife Safari Park and Omaha’s Henry Doorly Zoo for their participation and support in this research.

Literature Cited

1.  Allen, J.L. 1989. Renarcotization following carfentanil immobilization of nondomestic ungulates. J. Zoo Wildl. Med. 20:423–426.

2.  Caulkett, N., J. Paterson, J C. Haigh and L. Siefert. 2006. Comparative physiologic effects of thiafentanil-azaperone and thiafentanil-medetomidine-ketamine in free-ranging Uganda kob (Kobus kob thomasi). Proc. Am. Assoc. Zoo Vet. Pp. 216–218.

3.  Citino, S.B.., M. Bush, W. Lance, M. Hofmeyer and D. Grobler. 2006. Use of thiafentanil (A3080) medetomidine and ketamine for anesthesia of captive and free-ranging giraffe (Giraffe camelopardalis). Proc. Am. Assoc. Zoo Vet. Pp. 211–213.

4.  Grzimek, B. 1972. Animal Life Encyclopedia. Van Nostrand Reinhold Co. New York, N.Y. Pp. 360–364.

5.  Howard, L.L., K.S. Kearns, T.L. Clippinger, R.S. Larsen and P.J. Morris. 2004. Chemical immobilization of rhebok (Pelea capreolus) with carfentanil-xylazine or etorphine-xylazine. J. Zoo Wildl. Med. 35:312–319.

6.  Nowak, R.M. 1964. Walker’s Mammals of the World. Johns Hopkins University Press, Baltimore MD. Pp. 1424–1430.

7.  Smith, K.M., B.L. Raphael, P.P. Calle, S. James, R. Moore, H. Zurawka and S. Goscilo. 2005. Immobilization of axis deer (Axis axis): evaluation of thiafentanil, medetomidine and ketamine vs. medetomidine and ketamine. Proc. Am. Assoc. Zoo Vet. Pp. 264–265.


Speaker Information
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Julia E. Napier, DVM
Omaha’s Henry Doorly Zoo
Omaha, NE, USA

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