Bloat in Sable Antelope During Capture and Chemical Immobilization
The sable (Hippotragus niger) is an African antelope of stout build, short neck, long face, and dark a mane. Both males and females have long, ringed horns that rise and curve backward. They are members of the Hippotraginae family, due to their horse-like build.1 This designation is characterized by the behavioral penchant for sable arching their necks and standing with their heads held high and tails outstretched, where they bear a strong resemblance to horses. This makes sable appear larger than they really are, and males display this stance as a manifestation of dominance.2
Source 1: Discount African Hunts (discountafricanhunts.com)
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
The range of the sable includes the southern savanna from central Tanzania to South Africa.2 Sable herds typically congregate near water, in areas with good drainage and grazing opportunities. They eat mostly grass, but will also eat herbs and leaves from shrubs and trees.
The sable’s social structure consists of small female herds with territorial males. Herds have home ranges that encompass several male territories. Dominant males are known to forcefully defend their territories, particularly from predators, using their scimitar-shaped horns.
Bloat and How it Occurs
Bloat is a distention of the rumenoreticulum with the gases of fermentation.3 In veterinary medicine, it is frequently seen in large dogs and is known as gastric dilatation-volvulus, or GDV, and can occur spontaneously. Bloat occurs when an animal's stomach fills with gas, food, or fluid and subsequently twists. Stomach distension alone is often referred to as dilatation, or “simple bloat,” that can occur spontaneously and can resolve on its own.4 It is known to spontaneously occur in cattle and other ruminants, and in some cases, it is attributable to dietary changes.
Bloat as a complication of capture and chemical immobilization is a serious condition that is fatal if left untreated. Bloat without twisting (GDV) can be life threatening, but the risk is predicated upon the severity and duration. Bloat is a condition that has been reported in many species of antelope; it has been known to occur spontaneously, but is most closely associated with capture and chemical immobilization events.
When bloat occurs, it is the twisting and flipping of the stomach that creates a life-threatening condition. When the stomach becomes severely distended with gas, fluid or food, it puts pressure on the surrounding organs and decreases blood flow to and from these organs. Twisting of the stomach is more severe, as this completely obstructs blood supply to major organs and can impact blood flow throughout the whole body, resulting in shock.3
As the stomach expands, it exerts pressure on the large abdominal arteries and veins. The blood supply is cut off to the stomach; subsequently, toxic products build up and tissues begin to die. Sable (or any other animal experiencing bloat) can go into shock very quickly, and extended periods without treatment increase the risk of further damage and death.3,4
Sable and Chemical Immobilization
The management and research of sable sometimes requires chemical immobilization. Unfortunately, these animals tend to be prone to a variety of capture‐induced risks while immobilized, including bloat.5 The available literature states that each species of antelope has its own anesthesia recommendations, with intra-species variations of dosages because of diverse individual responses to anesthetic agents.4-6 These variations are factors in the risk of bloat and other potential complications. Stress, venue, individual animal and field conditions must also be taken into account.
Source 2: Discount African Hunts (discountafricanhunts.com)
Every anesthetic event carries risk, since anesthesia represents a controlled intoxication of the central nervous system. Since anesthetic drugs are never completely devoid of toxicity, the induction of anesthesia invariably carries a risk even to the life of healthy animals.6 When performing procedures in chemically-immobilized sable, a sternal recumbency position is vital whenever possible, as bloat can more readily occur with animals in lateral recumbency. Other causes of bloat include the use of immobilization drugs such as the α-2-agonists, which can result in a ruminal atony and subsequently, bloat.3
Alpha-2-agonists and opioids used together have a synergistic effect. These drugs inhibit the norepinephrine release by binding with the α-2-adrenoreceptors. Activity in the Sympathetic Nervous System (SNS) is reduced and it results in a decreased heart rate and blood pressure. They induce muscle relaxation, sedation and analgesia, and reduce the stress response. In higher doses, they can induce vomiting because of the activation of the chemoreceptor trigger zone, hypothermia, miosis and hypoxemia. Via inhibition of antidiuretic hormones, an animal usually has an increase of urine production and a decrease of gastrointestinal motility which is thought to result in bloat and colic problems, mainly in herbivores.3
Xylazine was probably the first α-2-agonist to be used in veterinary medicine. It is used in many species, is easily available and inexpensive. It promotes good muscle relaxation, sedation and a short period of analgesia. It can, however, cause hyper salivation, muscle tremors in some species and GIT motility suppression.3-5
Resolving Bloat in Sable Antelope
If an immobilized sable starts to bloat, all administration of immobilizing drugs should be suspended. The animal should be re-positioned into sternal recumbency with the neck extended and the head with the nose pointing down. Intubation of the animal to relieve gases inside may be done; in some cases, trocharization of the rumen is recommended.1 If the veterinarian has high confidence that the bloat is being caused by the anesthetic agents, he or she may employ the available reversal agents to antagonize their effect.3,6
Reversal drugs (e.g., diprenorphine, naltrexone, naloxone) should be given as quickly as possible to avoid the side effects of the immobilizing agents, which may include respiratory depression and cardiovascular issues, among others. Intravenous catheters should be placed and fluid therapy begun, as bloat can cause the heart rate to race at a rate sufficient to cause heart failure. Medication for shock and electrolytes are all essential in stabilizing the animal. Premature ventricular contraction (PVC) is often associated with bloat. If this arises, intravenous medications will also be needed to stabilize the heart rhythm. If the disturbed heart rhythm is noted early on, the animal’s prognosis for recovery is generally good.3
In the event of an animal’s death, post-mortem gas formation in the alimentary tract, especially in ruminants, should be distinguished from ante-mortem bloating, which itself can be a cause of death. In the latter case, there are likely to be signs of asphyxiation.4,6
3Wolfe, B. (2015). Bovidae (except sheep and goats) and antilocapridae. In Miller, R. E., Fowler, M. E. (eds) Zoo and Wild Animal Medicine. (Volume 8). St Louis, Missouri: Elsevier Saunders, 626-644.
4Lance, W. Exotic Hoof Stock Anesthesia and Analgesia: Best Practices. In: Proceedings, NAVC Conference 2008, pp. 1914-15.
5Ball, L. Antelope Anesthesia. Wiley Online Library, 25 July 2014,
6Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
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.
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.
NexGen Pharmaceuticals, LLC does not recommend, endorse or make any representation about the efficacy, appropriateness or suitability of any specific dosing, products, procedures, treatments, services, opinions, veterinary care providers or other information that may be contained in this blog post. NEXGEN PHARMACEUTICALS, LLC IS NOT RESPONSIBLE NOR LIABLE FOR ANY ADVICE, COURSE OF TREATMENT, DIAGNOSIS OR ANY OTHER INFORMATION, SERVICES OR PRODUCTS THAT YOU OBTAIN THROUGH THIS BLOG POST