Abstract

Numerous protocols have been described for immobilization of captive exotic suid species at zoological institutions.^1,3-5 A commercially available tiletamine-zolazepam combination (Telazol®; Fort Dodge, Inc., Fort Dodge, Iowa, USA) has been used extensively, and is adequate for immobilization of most exotic suids.¹ Its usage offers the advantages of being relatively inexpensive and readily available. However, prolonged and rough recoveries are seen with tiletamine-zolazepam^1,5, and adverse effects are most commonly noted at doses exceeding 3 mg/kg¹. In some cases, rough recoveries have resulted in death.⁵ The use of adjunct anesthetic agents facilitates the usage of lower doses of Telazol®, and therefore minimizes secondary, drug-dependent adverse effects.¹ Most documented anesthetic combinations used in suids contain an alpha₂-adrenergic agonist, and some require a large volume for successful induction.⁴ Alpha₂-adrenergic agonist combinations may cause bradycardia, which is likely a physiologic response to changes in peripheral vascular resistance induced by this class of drugs. Physiologic parameters seen in response to various anesthetic combinations have been well documented in domestic swine.^3,6 Species-specific variations in sensitivity to drug effects have been reported in some exotic swine,⁷ although not extensively characterized for all species.

The purpose of this prospective clinical trial was to develop a reliable anesthetic protocol to be used in babirusa (Babyrousa babyrussa) as an alternative to the use of alpha₂-adrenergic agonists. A combination of tiletamine-zolazepam (Telazol®, combined dose of 1.26±0.3 mg/kg) and butorphanol (Torbugesic® 10 mg/ml, Fort Dodge Laboratories, Fort Dodge, Iowa, USA; 0.37±0.04 mg/kg) administered intramuscularly by blowdart was used in a total of 16 immobilizations performed on animals undergoing elective medical procedures. This combination of butorphanol-tiletamine-zolazepam (BuTZ) resulted in a smooth induction and a stable plane of anesthesia to facilitate minor elective procedures. Mean time to anesthetic induction was 8.1±5.6 min, and was inversely correlated to drug dose, with higher doses resulting in shorter induction times. A light plane of anesthesia or heavy sedation was achieved in all cases, and was sufficient for non-invasive procedures (transport, hoof trims, relocation, venipuncture, examination, ultrasonography, radiography). Heart rate values ranged from 80 to 120 bpm, which was higher than values reported in a xylazine-Telazol® combination previously reported in this species.² Neither respiratory depression nor hypoxemia was observed when BuTZ was used. Pulse oximetry saturation values ranged from 92 to 100% without oxygen supplementation. Indirect mean blood pressure readings ranged from 100–150 mm Hg, and were consistent throughout all immobilization events.

Partial antagonism with intramuscular naltrexone (Trexonil, Wildlife Pharmaceuticals, Inc.; 0.34±0.2 mg/kg) was used to decrease recovery times, with most individuals ambulating voluntarily within 60 min of induction. The BuTZ protocol was adequate for elective, non-invasive medical procedures, and offers the advantages of a low volume for induction, relatively low cost, and stable cardiorespiratory function. Anesthetic recoveries can be prolonged with this protocol, but are shorter than combinations that rely on higher doses of tiletamine-zolazepam. This protocol offers a reliable, safe alternative to the use of alpha-2 based protocols in babirusa, and should be useful in the clinical management of cases where this class of drugs would be contraindicated.

Acknowledgments

The author acknowledges the efforts of the Saint Louis Zoo’s keepers and technicians who assisted during immobilization events. Special thanks go to Martha Fischer, Diane Wilson, Randy Junge and R. Eric Miller for providing logistic support and feedback during this project.

Literature Cited

1.  Calle PP, PJ Morris. Anesthesia of non-domestic suids. In: Fowler ME, RE Miller, eds. Zoo and Wildlife Medicine: Current Therapy. 4th edition. W.B. Saunders Co., Philadelphia, Pennsylvania. U.S.A. Pp: 639–645.

2.  James SB, RA Cook, BL Raphael, MD Stetter, P Kalk, K Maclaughlin, PP Calle. 1999. Immobilization of babirusa (Babyrousa babyrussa) with xylazine and tiletamine/zolazepam and reversal with yohimbine and flumazenil. J. Zoo Wildl. Med. 30: 521–525.

3.  Moon PF, LJ Smith. 1996. General anesthetic techniques in swine. Vet. Clin. North Am. Food Anim. Pract. 12: 663–691.

4.  Morris PJ, B Bicknese, DL Janssen, M Sutherland-Smith, L Young. 1999. Chemical immobilization of exotic swine at the San Diego Zoo. Proc. Am. Assoc. Zoo Vet. 150–153.

5.  Morris PJ, AL Shima. 2003. Suidae and Tayassuidae (wild pigs, peccaries). In: Fowler ME, RE Miller, eds. Zoo and Wildlife Medicine. 5th edition. Saunders, Saint Louis, Missouri. U.S.A. Pp: 586–602.

6.  Sakaguchi M, R Nishimura, N Sasaki, T Ishiguro, H Tamura, A Takeuchi. 1996. Anesthesia induced in pigs by use of a combination of medetomidine, butorphanol, and ketamine and its reversal by administration of atipamezole. Am. J. Vet. Res. 57: 529–34.

7.  Selmi AL, GM Mendes, JP Figueiredo, FB Guimarães, GRB Selmi, FEM Bernal, C McMannus, GR Paludo. 2003. Chemical restraint of peccaries with tiletamine/zolazepam and xylazine or tiletamine/zolazepam and butorphanol. Vet. Anaesth. Analg. 30: 24.