Sable Antelope Chemical Immobilization and Sedation

The African sable (Hippotragus niger) is an antelope that inhabits the savannah of East Africa below Kenya and down into South Africa. The sable is included among the subfamily Hippotragus, meaning “horse antelope.”¹ Antelopes within this subfamily are recognized as such because of their compact, powerful build, erect mane and thick necks.

Sable bulls have glossy black coats with white underparts, rump, throat, and facial markings. Females and young are chestnut to brown in color; the pronounced color differences between the sexes make the sable one of the most sexually dimorphic antelope species.² Unlike most antelopes, both males and females have long, scimitar-shaped horns, although the horns of the females are slightly shorter.

The sable’s range extends through the southern savanna from central Tanzania to South Africa. It is considered an “edge” species that prefers the ecotone between wooded savanna and grassland, and is a grazer and a browser. Herds of females and young numbering up to 70 animals, and sometimes even in the hundreds, live in large home ranges with one dominant male in attendance. Female offspring remain in the home range, but subadult males are driven out as they mature. These young males subsequently join bachelor herds until they mature and are ready to compete for a territory.¹

Sable and Chemical Immobilization

Conservation and management programs, research and zoo applications often require the capture and manipulation of sable. Novel non- and minimally invasive procedures that have been developed have allowed researchers and management personnel to obtain certain data without the need to handle animals. Other information, however, can only be obtained by capturing animals.³ Captures are also important for marking individuals for ecological and behavioral studies.

New technological advances such as global positioning system (GPS) collars, heat sensitive transmitters and advanced physiological monitoring equipment now allow detailed research on wildlife species such as sable, but still require the initial capture and manipulation of individual animals.⁴ Live captures are also required in conservation biology for animal translocations, reintroductions or population restocking.

According to the literature, each species of antelope has its own anesthesia recommendations with intra-species variations of dosages because of diverse individual responses to anesthetic agents.^5,6 Captures can involve risk of mortality, reduction in survival probability or injury of individual animals. Mortality is the most important factor when evaluating the safety level of a capture methodology. Mortality occurring during capture is easy to measure, while delayed mortality is much more difficult to determine.

The effects of immobilization may differ according to the capture methodology employed. The relevant published research agrees that captures by remote delivery of immobilizing drugs via darting lower an animal’s stress levels, thus decreasing the subsequent capture effects compared to other techniques.⁵ This is one of the main reasons why chemical immobilization is becoming the preferred capture method, particularly concerning large mammals like antelope.

Drugs Used for Chemical Immobilization of Sable

There are three basic classes of drugs that are used to immobilize sable:

• Opioids
• Cyclohexamines
• Neuroleptics

Opioids

• The most potent drugs available for immobilization
• Widely available antagonists for reversal
• Lower volume of drugs are typically required
• Most practical for remote immobilization of large animals
• Potentially toxic to humans

Cyclohexamines

• AKA “dissociative agents”
• Produce altered consciousness
• Dissociate mental state from environmental stimulation.
• Retain many vital reflexes
• The animal cannot walk, but can move tongue, blink, swallow
• The animal may feel some pain
• Cyclohexamines should not be used alone and are not reversible

Neuroleptics

• Also referred to as tranquilizers
• Produce calmness and relaxation
• Do not cause loss of consciousness or alleviate pain perception
• Can cause death before they cause loss of consciousness
• Best used in conjunction with other drugs

Practical Application

When immobilized in a zoo setting, less stress on sable is likely to occur than in the field, as zoo animals tend to be far more acclimatized to humans and procedures. In some cases, intramuscular hand injection can be used when working with zoo animals that are cooperative, or those that have been cornered in squeeze cages or enclosures. Pole syringes are also widely used in this application; these afford greater distance than approaching an animal for a hand injection without resorting to remote delivery systems.³ Drug delivery by pole syringe requires manual injection follow through to administer the drug, as the handle is usually a direct extension of the plunger. As with hand injection, larger bore needles should be used to ensure complete drug delivery.

Remote chemical immobilization is usually carried out by approaching sable and shooting a dart from a helicopter, an off-road vehicle or from the ground. While this can significantly reduce stress compared to physical capture methods, it still impacts the animal’s stress levels. Frightened sable will have an increased heart rate, higher levels of cortisol and other stress-related biochemicals.⁴ An approach from the ground tends to produce even lower stress levels, because animals are generally less frightened than if a noisy vehicle is used. On the other hand, this is more difficult to accomplish, because it requires a closer approach with animals that are extremely alert, fast and agile.

Analgesia should be provided if a sable’s skin has been breached by anything larger than a hypodermic needle, including biopsy instruments. Invasive surgeries should be conducted using general anesthetics with the animal at a surgical plane; intraoperative analgesia that continues after anesthetic recovery should be provided in some form to every surgical patient.³

Many of the opioid analgesics (e.g., buprenorphine, fentanyl, butorphenol, oxymorphone) administered in the early evening, for example, will not be effective after 12 hours. Longer‐lasting, non‐steroidal anti‐inflammatory analgesics (NSAIDs) such as meloxicam, carprofen, flunixin, ketoprofen, etc. have longer durations of action than opioids, and can be administered in conjunction with opioids to increase potency of effect and duration of action.⁷

Drug Reversal Agents for Sable

Reversal agents are often required to neutralize sedation or anesthetic agents whether general anesthesia or sedation has been used. These drugs allow the animal to completely recover from being anesthetized before being released. This is even more important in the field than in a clinic or zoo setting, because a chemically-compromised animal will be in danger of injury, predation and other hazards.

The duration of anesthesia will be influenced by the drugs used, age, sex, body weight, procedure(s) performed and the amount of stimulus during the procedure. Considering the aggregate of factors that influence duration of anesthesia, the literature maintains that anesthetic drugs should always be titrated to effect. If anesthesia is being maintained by a gas anesthetic (e.g., isoflurane), titration of anesthetic depth can be controlled almost immediately by adjusting the amount of anesthetic gas being administered to the animal. In addition, anesthetic duration can be extended for as long as the anesthetic gas is administered.⁷

Injectable anesthetics and sedatives (which may be used for less invasive or higher-risk procedures) do not have the same flexibility. Once a dose has been administered, it cannot be “un-administered.”⁸ In such cases, reversal drugs can be used to bring about recovery from anesthesia/sedation.

Atipamezole is a synthetic α2-adrenergic antagonist. Developed to reverse the actions of compounds such as medetomidine and dexmedetomidine.

Naltrexone hydrochloride is an opioid receptor antagonist that is used in veterinary medicine to block receptors as a reversal agent for opiate agonists such as butorphanol. The time from administration to Naltrexone taking full effect is reported to be between 1 to 2 hours. The effects of this medication are short-lived, meaning they will stop working within 24 hours, although the benefits may be prolonged if an animal has decreased kidney and/or liver function.⁹

Great care has been taken with chemical immobilization protocols and drug development to keep these within safety margins through the use of novel anesthetics, including combinations of true anesthetics, neuromuscular blockers and tranquilizers.² As a result, modern chemical immobilization techniques have dramatically reduced mortality and the side-effects of drugs. In addition, the use of antagonists to anesthetics is now widely employed, as this avoids the undesirable and potentially harmful effects of drugs and facilitates speedy recovery from chemical immobilization events.^3,4

In recent years, veterinary custom compounding pharmacies have widely expanded the variety, availability and efficacy of immobilizing drugs through the development of custom formulations for wildlife such as sable. One such formulation is the MKBM™ Kit, an original formulation containing:

• Medetomidine hcl 20 mg/ml
• Ketamine hcl 100 mg/ml
• Butorphanol 30 mg/ml
• Midazolam 20mg/ml

The MKBM™ Kit also includes the reversal agents:

• Atipamezole 40mg/ml
• Naltrexone 50 mg/ml

The MKBM™ Kit was developed for the chemical immobilization of numerous large exotic hoofstock species. It is an excellent choice for anesthetizing antelope, bongo, kudu, gazelle, eland, as well as other African hoofstock and certain domestic wildlife species.

The drug formulations currently available for immobilizing sable and other large wildlife species have been refined to a degree that eliminates much of the risk that existed in years past. With the right drug formulations, proper planning and safety precautions in place, experienced personnel can have the expectation of effective and incident-free chemical immobilization of sable.

¹britannica.com.

²awf.org.

³Brivio F, Grignolio S, Sica N, Cerise S, Bassano B (2015) Assessing the Impact of Capture on Wild Animals: The Case Study of Chemical Immobilisation on Alpine Ibex. PLoS ONE 10(6): e0130957.

⁴Powell RA, Proulx G (2003) Trapping and marking terrestrial mammals for research: integrating ethics, performance criteria, techniques, and common sense. ILAR J 44: 259–276.

⁵Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed.

⁶Nielsen, L. Chemical Immobilization of Wild and Exotic Animals. (1999) Ames, Iowa, Iowa State University Press.

⁷Lance, W. Exotic Hoof Stock Anesthesia and Analgesia: Best Practices. In: Proceedings, NAVC Conference 2008, pp. 1914-15.

⁸Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014.

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

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