Dehydration in Sable Antelope During Capture and Chemical Immobilization
The sable (Hippotragus niger) is considered one of Africa’s most visually striking antelopes. Its build, mane and gain has led to its inclusion in the “horse antelope” genus (Hippotragini).1
There are four subspecies of sable:
- Black sable (also Mastitis sable)—This is the most widespread sable. Its habitat covers south of the Zambezi River through Zimbabwe and Botswana into South Africa.
- Giant Sable (also Royal sable)—These have the longest horns of any sable subspecies.
- Common (also southern sable)—This antelope is sometimes called the West Zambian sable.
- Eastern sable—This is the smallest of the sable family, with a range that includes the costal lands of southern Kenya, eastern Tanzania and into Mozambique.2
Both male and female sable have scimitar-shaped horns, although those of the females are shorter and less curved. Sable bulls have glossy black coats with white undersides, rump, throat and facial markings. The females and young are chestnut in color. Females of some subspecies can appear much darker.
The range of the sable includes the southern savanna from central Tanzania to South Africa.2 They inhabit the ecotone between wooded savannas and grasslands. During the dry season, sable come out onto grasslands where it grazes on green plants that emerge after the annual fires. During the rainy season from September to April, they forage grasses and foliage of the woodlands.
Sable are territorial but sociable, with herds of females and young of over 50 animals congregating in ranges of 4 to more than 20 square miles. In some areas, herds can be much larger. Dominant males will defend the herd vigorously with their formidable horns, even against dangerous predators. Female offspring usually remain in their home ranges, but adult males drive out subadult males as they mature. The banished males will join bachelor herds until they are ready to compete for their own territory.2
Chemical Immobilization of Sable
The field immobilization of sable can be required for transportation, medical examination, sample collection and identification, and the importance of performing such procedures for research and conservation projects is widely acknowledged.3 As these activities have become more common, the need to assess their negative effects has increased. Research in this area itself has revealed that the physiological and behavioral effects of capture are as important as the direct risks of injury or death of an animal.4
There are a number of common stressors related to the chemical immobilization of antelope that can, in some cases, lead to complications during or after an anesthetic event. The overall health of an individual animal (which might be poor, and in some cases the very reason for its capture) is also a factor affecting the potential for complications during and after anesthesia.
These stressors fall into four categories:
- Physiological: Heavy exercise, hemorrhage, hyperthermia, shock, pain, infection
- Physical: Trauma/surgery, intense heat/cold
- Chemical: Hypoxemia, acid-base imbalance, anesthetic drugs
- Emotional: Anxiety, fear5
Chemical immobilization agents are represented by the third category, although elements of the other three are often included in immobilization events. The physical stress of capture and/or attempts to escape during capture on the part of an animal certainly constitute physiological stress; surgical and even environmental conditions can bring about physical stress, and anxiety and fear are nearly always a component to some degree in a capture scenario.
Acute stress during capture can also bring about spikes in adrenaline, cortisol levels, heart rate, blood pressure, respiration, metabolic rate, blood glucose, lactic acid and body temperature, while bringing about a decrease in pH and a redistribution of blood within the organs. The effects of capture and anesthesia can activate the fight-or-flight response, HPA-axis activation, hyperthermia, respiratory depression (hypoxemia), lactid acid build-up and acidosis. In severe cases, this can lead to neurological/myocardial dysfunction, multi-organ failure, capture myopathy and death.6
Dehydration in Sable Antelope
Dehydration may seem like a minor concern compared to other complications, but inasmuch as it can lead directly to cardiac arrest, dehydration (a reduction of the body’s water content) is potentially quite dangerous. All animals require water to ensure their bodies are working properly, and it is so important that all bodily functions require it to remain operative. If an animal loses more water and electrolytes than it is taking in, it will begin to dehydrate and its health will quickly deteriorate.
Electrolytes are minerals that naturally occur in all animals, and they are essential for proper health. Electrolytes are comprised of sodium, chloride, and potassium, and facilitate the movement of nutrients into cells, aid in muscle function, and help regulate nerve activities.5,6 An animal’s natural activities—breathing, urinating, and defecating, as well as simple evaporation—can all cause it to lose fluids. When an animal eats and drinks, the lost water and electrolytes are replaced. If the animal’s fluid intake becomes less than what they are losing, dehydration will occur. This causes a reduction in bodily fluids that reduces blood flow and the delivery of oxygen to organs and tissues.
Understanding Dehydration
Understanding the distribution of fluid and water in the body is the first step to understanding dehydration. Total body water (TBW) comprises approximately 60% of an animal’s body weight. Approximately 67% of TBW is found inside the body’s cells; this is referred to as intracellular fluid (ICF). The remaining 33% of TBW is the extracellular fluid (ECF), which is made up of:
- Interstitial fluid, which bathes cells and tissues (~24% of TBW)
- Plasma, the liquid portion of blood, which constitutes most of intravascular volume (~8%–10% of TBW)
- Transcellular fluid, which comprises synovial joint fluid, cerebrospinal fluid, bile, and the fluid in the linings of the peritoneal cavity, pericardium, and pleural space (~2% of TBW)4
A simple approximate formula for the distribution of fluids in the body is the 60:40:20 rule: 60% of an animal’s body weight is water, 40% of body weight is ICF, and 20% of body weight is ECF.4,5
Dehydration in sable can be caused by hyperthermia, chronic vomiting or diarrhea, excessive urination or wound drainage. In both human and veterinary medicine, IV fluids are usually administered prophylactically dueing surgeries, depending on the nature of the procedure. Veterinarians often provide fluid therapy to patients for many reasons, including correction of dehydration, expansion and support of intravascular volume, correction of electrolyte disturbances, and encouragement of appropriate redistribution of fluids that may be in the wrong compartment (e.g., peritoneal effusion).4
Treating Dehydration in Sable
During the chemical immobilization of sable, monitoring core body temperature is essential,5 as hyperthermia and subsequent capture myopathy are commonly-encountered problems with antelope anesthesia. Intubation has been widely recommended for any anesthetized antelope that needs to be transported or anesthetized for greater than one hour.
During immobilization events, hydration status can be assessed using various tests. One of the easiest to perform is a skin tent test to check the turgor (moisture level) of the skin. To do this, the skin over the thorax or lumbar region is pulled away from the back. In a well-hydrated animal, the skin immediately returns to its normal resting position. If the tent formed remains standing, it is a likely indication of dehydration. If there is evidence of dehydration in an antelope during a procedure, all administration of immobilizing drugs must be immediately suspended. Fluid therapy should begin in the form of lactated Ringer’s solution or 0.9% saline, IV, SQ or IP.5
Perioperative IV fluid therapy is very common in veterinary medicine and allows practitioners to restore intravascular volume, correct dehydration, and administer IV medications quickly.6 While perioperative fluid therapy under many field conditions may be impractical, fluids should always be available in the case of dehydration when chemically immobilizing sable or other antelope.
3Laricchiuta P, De Monte V, Campolo M, Grano F, Iarussi F, Crovace A, Staffieri F. Evaluation of a butorphanol, detomidine, and midazolam combination for immobilization of captive Nile lechwe antelopes (Kobus magaceros). J Wildl Dis. 2012 Jul;48(3):739-46.
4Brivio 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.
5Kreeger T., Arnemo, J., Raath, J. Handbook of Wildlife Chemical Immobilization, International Edition, Wildlife Pharmaceuticals, Inc., Fort Collins, CO. (2002).
6Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014,
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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.
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