The Most Frequently-Used Chemicals for the Immobilization of White-tailed Deer
Managing white-tailed deer (Odocoileus virginianus) often requires the live capture of individual animals, and chemical immobilization often is the most effective method of capture.1 Throughout the modern history of the chemical immobilization of wildlife (which effectively began in the mid-1950s), numerous chemical immobilization agents and classes thereof have been used. With increased scientific and physiological knowledge and the refinement of immobilizing drugs, numerous chemical agents and drug formulations (combinations) are now available.
The selective capture of individual white-tailed deer is sometimes necessary for research (attaching or removing radio-transmitters) translocating nuisance animals, or for the treatment of injured or sick animals.2 For research and wildlife management purposes, many techniques are used to capture white-tailed deer. Among these are live traps, drop nets, drive nets and rocket nets.3 These methods tend to limit researcher and wildlife manager ability to select specific animals for capture however, and once trapped, an animal must still be handled. Thus, chemical immobilization using a remotely-delivered anesthetic agent becomes the preferred capture technique in that it is not only selective, but it reduces the stress of manual capture on the animal. This technique also foregoes the pre-positioning of equipment like traps and nets.
White-tailed Deer Immobilization: Requirements
The ideal attributes of a chemical immobilizing agent include short induction time, minimal physiological distress as well as rapid and complete reversal, whether spontaneous or via a reversal agent (antagonist).1 Large cervids such as white-tailed deer are often startled and attempt to flee after being struck with a dart.2 Thus, long induction times are unacceptable and risky, as they allow an animal to travel a greater distance prior to immobilization. This not only decreases the chance of locating the immobilized deer, but dramatically increases the chance of injury or mortality to the animal.
Even circumventing the use of traps, chemical immobilization does cause physiological stress to deer. Anesthetized animals become at risk of complications such as the cardiovascular or respiratory depression and disruption of the thermoregulatory system. These effects can require supportive treatment by the attending veterinarian or support staff or the initiation of anesthetic reversal prior to completion of the procedure.3
As mentioned above, the effects of many immobilization agents currently in use can be reversed with the administration of an antagonist. Reversal agents decrease recovery time and reduce the risk of complications as well as the amount of time required to monitor and care for the immobilized animal.2 If a management or research protocol requires the immobilization of multiple animals, rapid recovery can facilitate the handling of multiple animals during a set period of time.3
The Evolution of Immobilizing Agents
Today, a variety of compounds are used to immobilize white-tailed deer. One of the most commonly used drugs has been a combination of xylazine and Telazol (zolazopam-tiletamine). Xylazine is an α-2 adrenergic antagonist that is widely used in veterinary medicine, and Telazol is a potent cyclohexane.2 More recently, formulations consisting of medetomidine and ketamine and medetomidine, ketamine and butorphanol (butorphanol tartrate) have emerged as excellent alternatives to drug combinations used in years past, particularly for white-tailed deer, which can present dosing challenges across the age and sex of individuals.2,4 The medetomidine/ketamine combination is widely known as the MK formulation, which was developed to provide veterinarians and wildlife handlers with an immobilization anesthesia option that could be effectively used to immobilize a broad range of exotic animal species.
The MK2 formulation contains higher concentrations of medetomidine and ketamine than the MK formulation and thus provides longer and deeper sedation, extended working time and quick recovery. As such, it is often recommended for larger-bodied white-tailed deer and bucks (as well as other large species). It is also very useful in scenarios where longer working times and/or multiple procedures are required. It should be noted that there is a high risk of hyperthermia in using MK2 when the ambient air temperature exceeds 82 degrees Fahrenheit, so caution should be taken when operating with white-tailed deer in such an environment.
In the MKB formulation, butorphanol is added to the medetomidine/ketamine combination. Butorphanol is an opioid agonist/antagonist that is used in a variety of species as an analgesic, premedication, antitussive, or antiemetic. The MKB formulation allows wildlife handlers to induce a reversible sedation, with inductions times ranging from 3 to 5 minutes and working times of 10 to15 minutes. The benefits of using this sedation is that it provides the ability for the animal to recover on its own if the handler does happen to lose the animal after darting. The MKB formulation offers smooth induction with faster reversal times than the MK formulation due to a lower concentration of ketamine. Veterinarians and wildlife handlers derive the benefits of the MK formulation with better reversal times.
For those who may be new to utilizing premixed formulations, it is important to understand the level of anesthesia being administered with these drug combinations. They bring about a deep sedation that is not to be confused with other (or earlier) sedations which are moderate. The MK, MK2 and MKB formulations are offered by custom veterinary compounding pharmacies, and often are available in kit form, which includes the formulations and reversal agents (typically atipamezole and/or naltrexone) in the appropriate concentrations.
1Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
2Schwertner, T., et. al. Immobilizing Captive White-tailed Deer Using Medetomidine-Ketamine versus Xylazine-Telazol. Proc. Annu. Conf. Southeast. Fish and Wildl. Agencies 56:343–351.
3Schemnitz, S. 1994. Capturing and handling wild animals. Pages 125—139 in T.A. Bookhout, ed. Research and management techniques for wildlife and habitats. The Wildl. Soc., Bethesda, Md. 740pp.
4Monteith, K., et. al. Immobilization of White-Tailed Deer With Telazol, Ketamine, and Xylazine, and Evaluation of Antagonists. The Journal of Wildlife Management 76(7):1412–1419; 201.
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
Disclaimer
The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.
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