Captive Black Rhinoceroses Research Articles

Oral, nasal, and cutaneous eosinophilic granulomas in the black rhinoceros (Diceros bicornis): a lesion distinct from superficial necrolytic dermatitis.

Oral, nasal, and cutaneous lesions resembling eosinophilic granulomas (EGs) were observed in eight captive black rhinoceroses (Diceros bicornis). Oral lesions were observed in all affected animals and occurred most often behind the prehensile lip. The typical clinical history of affected animals included oral bleeding or epistaxis from multilobulated, fungating, proliferative masses with areas of ulceration. Histologically, lesions were characterized by prominent infiltrates of eosinophils and rare foci of collagen degeneration on a background of marked submucosal or dermal neovascularization. Mucosal or epidermal hyperplasia was also present sometimes in association with distinctive epithelial degenerative changes consistent with superficial necrolytic dermatopathy of black rhinoceroses. Lesions of EG and superficial necrolytic dermatopathy were interpreted as being concurrently manifested in these cases. EG lesions spontaneously resolved over periods of 30 days-7 mo and were recurrent in three animals. Lesions were responsive to treatment with corticosteroids or to local cryotherapy with liquid nitrogen. Two animals treated with systemic corticosteroids died of disseminated fungal infections, emphasizing that corticosteroids should be used cautiously in black rhinoceroses.

Fat soluble vitamins in blood and tissues of free-ranging and captive rhinoceros.

Several disease syndromes in captive rhinoceroses have been linked to low vitamin status. Blood samples from captive and free-ranging black (Diceros bicornis) and white rhinoceros (Ceratotherium simum) and tissue samples of captive individuals from four rhinoceros species were analysed for vitamins A and E. Circulating vitamin A levels measured as retinol for free-ranging versus captive black and white rhinoceros were 0.04 (+/- 0.03 SD) vs. 0.08 (+/- 0.08) and 0.07 (+/- 0.04) vs. 0.06 (+/- 0.02) microgram/ml, respectively. Circulating vitamin E levels measured as alpha-tocopherol were 0.58 (+/- 0.30) vs. 0.84 (+/- 0.96) and 0.62 (+/- 0.48) vs. 0.77 (+/- 0.32) microgram/ml, respectively. In contrast to earlier findings, there was no significant difference in vitamin E concentration between captive and free-ranging black rhinoceros. When the samples of captive black rhinoceros were grouped into those taken before 1990 and after 1990, however, those collected before 1990 had significantly lower (P < 0.001) vitamin E levels (0.46 +/- 0.83 microgram/ml) and those collected in 1990 or later significantly higher (P < 0.001) vitamin E levels (1.03 +/- 1.04 micrograms/ml) than the captive population as a whole. This is probably due to increased dietary supplementation. There were significant differences in circulating vitamin concentrations in black rhinoceroses from different regions in the wild. Serum 25-hydroxy (OH) vitamin D3 averaged 55.7 ng/ml in free-ranging rhinoceroses; no carotenoids were detected in any blood samples. Captive black and white rhinoceroses appear to be adequately supplemented in vitamin A and E. Captive Indian rhinoceroses (Rhinoceros unicornis) had significantly lower vitamin A concentrations in blood (P < 0.001) and higher vitamin A concentrations in liver tissue samples (P < 0.001) than other rhinoceros species. Equine requirements are not recommended as a model for rhinoceros vitamin requirements.

Essential fatty acid profiles differ across diets and browse of black rhinoceros.

In captivity, black rhinoceros (Diceros bicornis) suffer from idiopathic skin lesions that may be linked to dietary deficiencies, in particular essential fatty acid deficiency (EFAD). Therefore, a study was undertaken from July 1995 to May 1997 to characterize the diet of captive D. bicornis in North American zoos and measure fat and fatty acid composition in zoo diet, and African and North American browses. Descriptions of all dietary items offered to black rhinos on a daily basis were compiled from 20 North American zoos; zoo diet contained (mean +/- SE) 61 +/- 2% hay, 28 +/- 2% grain pellets, 6 +/- 1% produce, and 5 +/- 1% fresh browse, with hay and grain pellets together comprising nearly 90% of items offered. Gas chromatography-mass spectrometry analysis (GC-MS) was used to measure triacylglycerol equivalent (TAG), total fatty acids (TFA), and essential fatty acids (EFA) in zoo diet, and African and North American browses. North American browse contained more TAG and TFA than did zoo diet or African browse. Zoo diet contained more linoleic acid (18:2n6) and less linolenic acid (18:3n3) than either African browse corrected for degradation losses or North American browse, whether measured as weight percentage of dry sample or as weight percentage of TFA. In addition, the ratio of 18:2n6 to 18:3n3 was significantly lower in both browses than in zoo diet. There are significant nutritional differences between the major dietary components of North American captive black rhinoceros diets and native African browses that warrant further exploration given the health problems associated with this animal in captivity.

Role of excessive maternal iron in the pathogenesis of congenital leukoencephalomalacia in captive black rhinoceroses (Diceros bicornis).

To investigate the possibility that excessive maternal iron (overload) may contribute to development of congenital leukoencephalomalacia in captive black rhinoceroses. Tissue specimens and serum samples from 18 rhinoceroses in 2 kindreds harboring 4 (possibly 5) affected female calves. Fresh and archival sera and necropsy tissue specimens were evaluated to determine the nature and extent of iron overload in captive and wild black rhinoceroses as well as other rhinoceros species. Quantitative serum and tissue assays of iron and iron analytes, corroborated by histopathologic findings, indicated that these kindreds carried the greatest body burdens of iron yet found among captive black rhinoceroses. Fourteen of 18 rhinoceroses had the highest serum ferritin concentrations measured among 64 black rhinoceroses in captivity in the United States. Dams of affected calves had serum ferritin concentrations 2 orders of magnitude higher than clinically normal humans, equids, or free-ranging rhinoceroses. A neonatal serum sample from 1 affected female calf had a high ferritin concentration (approx 100-fold increase), but a male sibling of another affected female did not, suggesting a possible sex disparity in fetal response to maternal iron overload. Morphologic hallmarks of hemochromatosis were prominent in dams and grandams of affected calves. Excessive maternal iron may affect female fetuses more than males, possibly inducing leukoencephalomalacia by catalyzing production of highly toxic hydroxyl free radicals during crucial periods of in utero development. Reduction of maternal iron overload may decrease the probability of developing leukoencephalomalacia and some other disorders commonly affecting rhinoceroses in captivity.

Nutrient composition of plants most favoured by black rhinoceros ( Diceros bicornis) in the wild

1. 1. The nutrient composition of plants that are most preferred by the black rhinoceros ( Diceros bicomis) in Laikipia, Kenya, was studied. 2. 2. Mean zinc and selenium concentrations of the plants from Laikipia were higher than those of control (clover and rye, 1:1) material from the U.K. 3. 3. Except in Tinnea aethiopica, palmitic (16:0), linoleic (18:2n-6) and linolenic (18:3n-3) were the major fatty acids. 4. 4. The mean RRR-alpha-tocopherol content of the plants was 73.6 μg/g DM, and 2.2 g/d were estimated to be consumed by free-living rhinoceros in the area. 5. 5. The results suggest that the quantitative vitamin E intake of supplemented captive black rhinoceros was comparable with that of their counterparts in the wild. 6. 6. The lack of any obvious relationship between plasma alpha-tocopherol and orally administered racemic alpha-tocopherol and its ester form in captive black rhinos may be due to an insufficiency of emulsifiers.

Beta-globin chain hemoglobin polymorphism and hemoglobin stability in black rhinoceroses (Diceros bicornis)

Summary To evaluate the syndrome of acute intravascular hemolytic anemia in black rhinoceroses (Diceros bicornis), the hemoglobin of this species was evaluated by use of isopropanol- and heat-stability tests and was further characterized by electrophoretic studies. Samples were obtained from 22 apparently healthy captive North American black rhinoceroses, though 3 of the study animals had survived previous hemolytic events, and 3 others were parents of 3 offspring that had suffered hemolysis. The eastern African (Diceros bicornis michaeli) and the southern African subspecies (D b minor) were represented. Comparative samples were also obtained from 2 white (Ceratotherium simum) and 1 Indian (Rhinoceros unicornis) rhinoceroses. The hemoglobin of all 3 species appeared stable when tested by use of the heat and isopropanol methods. Thus, an unstable hemoglobin does not appear to be involved in the hemolytic crises of captive black rhinoceroses. Black rhinoceros hemoglobin had a striking polymorphism. Thirteen of the samples from black rhinoceroses had a single hemoglobin band, based on results of alkaline electrophoresis. Nine had, in addition to this major band, a slow (more cathodic) minor band that comprised about 10% of the total hemoglobin. Further studies indicated that the major band and the slower minor band may contain globin chains analogous to human β- and δ-chains respectively; these bands have been tentatively designated B and C. Phenotypes B and BC are common, in a ratio of 4:3. A genetic mechanism is proposed that assumes βb, and βc, gene loci and that βc-locus-expressed (βc+) and βc,-locus-inhibited (βc°) are common alleles for the βc-locus. The polymorphism of rhinoceros hemoglobins appears to be unrelated to the acute hemolytic anemia that occurs in this species.

Serum alpha-tocopherol, all-trans retinol, total lipids and cholesterol in the black rhinoceros ( diceros bicornis)

1. 1. Mean concentration of serum alpha-tocopherol (Vitamin E) in 28 free-living black rhinoceroses sedated during translocation in Zimbabwe was 1.92 (SD, 0.43) mg/1. 2. 2. Alpha-tocopherol was not detectable (<0.15 mg/1) in five captive black rhinoceroses held at London Zoo. 3. 3. Circulating levels of all-trans retinol (Vitamin A) were not different between the two groups. 4. 4. The low level of alpha-tocopherol in captive rhinoceroses suggests a risk of acute haemolytic anaemia.