Standing sedation in captive zebra (Equus grevyi and Equus burchellii)

Immobilization of captive plains zebras (Equus quagga) with a combination of etorphine hydrochloride, acepromazine, and xylazine hydrochloride

The plains zebra (Equus quagga) is a zebra species commonly kept in zoos around the world. However, they are not tame like their domestic relatives and are difficult to immobilize. We immobilized 30 captive plains zebra with a combination of etorphine hydrochloride (2-4 mg), acepromazine (8 mg), and xylazine hydrochloride (30 or 50 mg) to perform physical examination and blood sample collection for disease diagnostics. Physiological parameters including heart rate, respiratory rate, body temperature, and hemoglobin oxygen saturation were recorded. All zebras exhibited satisfactory anesthesia and fully recovered without re-narcotization. The results suggest that etorphine hydrochloride-acepromazine-xylazine hydrochloride combination for plains zebra immobilization is a safe and sufficient regimen for short procedures such as wellness examinations and sample collection.

DETOMIDINE AND BUTORPHANOL FOR STANDING SEDATION IN A RANGE OF ZOO-KEPT UNGULATE SPECIES

General anesthesia poses risks for larger zoo species, like cardiorespiratory depression, myopathy, and hyperthermia. In ruminants, ruminal bloat and regurgitation of rumen contents with potential aspiration pneumonia are added risks. Thus, the use of sedation to perform minor procedures is justified in zoo animals. A combination of detomidine and butorphanol has been routinely used in domestic animals. This drug combination, administered by remote intramuscular injection, can also be applied for standing sedation in a range of zoo animals, allowing a number of minor procedures. The combination was successfully administered in five species of nondomesticated equids (Przewalski horse [ Equus ferus przewalskii; n = 1], onager [ Equus hemionus onager; n = 4], kiang [ Equus kiang ; n = 3], Grevy's zebra [ Equus grevyi ; n = 4], and Somali wild ass [ Equus africanus somaliensis; n = 7]), with a mean dose range of 0.10-0.17 mg/kg detomidine and 0.07-0.13 mg/kg butorphanol; the white ( Ceratotherium simum simum; n = 12) and greater one-horned rhinoceros ( Rhinoceros unicornis ; n = 4), with a mean dose of 0.015 mg/kg of both detomidine and butorphanol; and Asiatic elephant bulls ( Elephas maximus ; n = 2), with a mean dose of 0.018 mg/kg of both detomidine and butorphanol. In addition, the combination was successfully used for standing sedation in six species of artiodactylids: giraffe ( Giraffa camelopardalis reticulata; n = 3), western bongo ( Tragelaphus eurycerus eurycerus; n = 2), wisent ( Bison bonasus ; n = 5), yak ( Bos grunniens ; n = 1), water buffalo ( Bubalus bubalis ; n = 4) and Bactrian camel ( Camelus bactrianus ; n = 5). The mean dose range for artiodactylid species except bongo was 0.04-0.06 mg/kg detomidine and 0.03-0.06 mg/kg butorphanol. The dose in bongo, 0.15-0.20 mg/kg detomidine and 0.13-0.15 mg/kg butorphanol, was considerably higher. Times to first effect, approach, and recovery after antidote were short. The use of detomidine and butorphanol has been demonstrated to be a reliable, safe alternative to general anesthesia for a number of large ungulate species.

Comparative analyses of tooth wear in free-ranging and captive wild equids

REASONS FOR PERFORMING STUDY

Captive breeding has played a crucial role in the conservation of threatened equid species. Grazing ruminants and rhinoceros in captivity have less abrasion-dominated tooth wear than their free-ranging conspecifics, with potential negative consequences for their health. However, a similar study on wild equids in captivity is missing.

OBJECTIVES

The aim was to establish if different tooth wear patterns are exhibited by free-ranging and captive equids.

STUDY DESIGN

Cross-sectional study of museum specimens comparing free-ranging and captive equids.

METHODS

Dental casts of maxillary cheek teeth of 228 museum specimens (122 from free-ranging and 106 from captive individuals) of 7 wild equid species were analysed using the extended mesowear method. Although teeth showing specific abnormalities were not scored, the presence of focal overgrowths (hooks) of the rostral premolars (106, 206) was recorded.

RESULTS

Captive Equus ferus przewalskii, E. grevyi, E. hemionus, E. quagga boehmi and E. zebra hartmannae have less abrasion-dominated tooth wear on their premolars than their free-ranging conspecifics (P<0.001). Fewer differences were exhibited between populations in the molars. No differences were exhibited in the distal cusp of the molars (110, 210) between populations, except in a small sample of E. kiang. Captive equids exhibited more homogeneous wear along the tooth row whereas free-ranging equids exhibited a tooth wear gradient, with more abrasion on premolars than molars. There were more rostral hooks on the premolars (106, 206) in the captive than the free-ranging population (P = 0.02).

CONCLUSIONS

Captive equids did experience less abrasion-dominated tooth wear than their free-ranging conspecifics, but the differences in tooth wear were less pronounced than those between captive and free-ranging wild ruminant and rhinoceros species. This indicates that feeding regimes for captive equids deviate less from natural diets than those for captive ruminants and rhinoceros but that factors leading to hook formation, in particular feeding height, should receive special attention. The Summary is available in Chinese - see Supporting information.