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

SEASONAL VARIATION OF SERUM 25-HYDROXY-VITAMIN D IN TWO CAPTIVE EASTERN BLACK RHINOCEROS ( DICEROS BICORNIS MICHAELI) HOUSED IN A NORTH AMERICAN ZOO

Black rhinoceros ( Diceros bicornis spp.) are critically endangered species, with less than 65 individual animals housed in captivity within Association of Zoos and Aquariums-accredited zoos within the United States, and an estimated 5,500 individual animals of all subspecies surviving in the wild. Previously published reference values for circulating vitamin D₃ (25OHD₃; 55.7 ± 34.2 ng/ml) were based upon samples from free-ranging black rhinoceros in Africa. Recent research in human medicine has highlighted the importance of subclinical vitamin D deficiency, with links to increased risks for developing various health conditions. Serum samples collected opportunistically from two captive Eastern black rhinoceros ( Diceros bicornis michaeli) housed with seasonal access outdoors in a North American zoo were tested for 25-hydroxy-vitamin D (25OHD) levels over a 3-yr period. A commercially prepared pelleted diet containing vitamin D₃ was fed to both rhinos. This study correlates environmental ultraviolet (UV) index, dietary supplementation, and seasonal serum 25OHD levels to compare with known 25OHD₃ levels in free-ranging African black rhinoceros. Results in these two individuals suggest that D. bicornis spp. are dependent upon sunlight or UVB for measurable circulating 25OHD, and that current vitamin D₃ supplementation levels may have little effect for Diceros spp. in human care housed in northern latitudes.

SERUM FERRITIN CONCENTRATION IS NOT A RELIABLE BIOMARKER OF IRON OVERLOAD DISORDER PROGRESSION OR HEMOCHROMATOSIS IN THE SUMATRAN RHINOCEROS (DICERORHINUS SUMATRENSIS)

The aim of this study was to determine if ferritin is a reliable biomarker of iron overload disorder (IOD) progression and hemochromatosis in the Sumatran rhinoceros (Dicerorhinus sumatrensis) by developing a species-specific ferritin assay and testing historically banked samples collected from rhinos that did and did not die of hemochromatosis. Ferritin extracted from Sumatran rhino liver tissue was used to generate antibodies for the Enzyme Immunoassay. Historically banked Sumatran rhino serum samples (n = 298) obtained from six rhinos in US zoos (n = 290); five rhinos at the Sumatran Rhino Conservation Centre in Sungai Dusun, Malaysia (n = 5); and two rhinos in Sabah, Malaysia (n = 3) were analyzed for ferritin concentrations. Across all US zoo samples, serum ferritin concentrations ranged from 348 to 7,071 ng/ml, with individual means ranging from 1,267 (n = 25) to 2,604 ng/ml (n = 36). The ferritin profiles were dynamic, and all rhinos exhibited spikes in ferritin above baseline during the sampling period. The rhino with the highest mean ferritin concentration did not die of hemochromatosis and exhibited only mild hemosiderosis postmortem. A reproductive female exhibited decreases and increases in serum ferritin concurrent with pregnant and nonpregnant states, respectively. Mean (±SD) serum ferritin concentration for Sumatran rhinos in Malaysia was high (4,904 ± 4,828 ng/ml) compared to that for US zoo rhinos (1,835 ± 495 ng/ml). However, those in Sabah had lower ferritin concentrations (1,025 ± 52.7 ng/ml) compared to those in Sungai Dusun (6,456 ± 4,941 ng/ml). In conclusion, Sumatran rhino serum ferritin concentrations are dynamic, and increases often are not associated with illness or hemochromatosis. Neither a specific pattern nor the individual's overall mean ferritin concentration can be used to accurately assess IOD progression or diagnose hemochromatosis in this rhino species.

Evaluation of season-related dietary changes on the serum profiles of fat-soluble vitamins, mineral, fatty acids, and lipids in the captive greater one-horned rhinoceros (Rhinoceros unicornis)

Circulating concentrations of fat-soluble vitamins A, D, and E, minerals, fatty acids, and lipids were quantified in five captive greater one-horned rhinoceroses (Rhinoceros unicornis) throughout two time periods, during which two diets were offered. Animals were fed mixed-grass hay and concentrate pellets while managed in barns for winter housing (April sampling, winter diet). During the spring and summer, animals were fed the same amount of concentrate pellet but had free access to North American browse and grasses instead of dried forage (November sampling, summer diet). Levels of 25-hydroxyvitamin D and α-tocopherol were statistically higher in summer diet samples than in winter diet samples. Retinol was not statistically different between seasons, and β-carotene concentrations were undetectable at both time periods. Cholesterol, triglycerides, and non-esterified fatty acids were all significantly elevated following access to unlimited fresh forages in summer. Serum electrolytes were not different between the two time periods but differences in circulating minerals were noted (cobalt, inorganic iodine, and magnesium elevated in winter diet samples; selenium and zinc elevated in summer diet). Access to non-native fresh green forages resulted in improvement of several nutritional parameters in greater one-horned rhinoceroses, implying a benefit when fresh browse and access to grass is provided.

Black rhinoceros (Diceros bicornis) natural diets: comparing iron levels across seasons and geographical locations

Although excessive iron storage in black rhinoceros (Diceros bicornis) has been a cause for continuous concern over the last four decades and differences in the iron content of diet items fed in captivity and in the wild have been documented, no reports exist on the iron content of the total diet ingested by free-ranging animals. Here, the results of field studies using backtracking to record the ingested diets of black rhinoceros from three habitats across three seasons are reported. Levels of iron and of condensed tannins, which might reduce iron availability, averaged at 91 +/- 41 ppm dry matter and 3.0 +/- 1.0% dry matter, respectively, across all habitats and seasons. Although geographic and seasonal variation was significant, these differences are of a much lower magnitude than differences between the averages of these diets and those fed to black rhinoceros in captivity. The results can provide guidelines for the iron content of diets designed for black rhinoceros and suggest that the effect of tannins in these species should be further investigated.

Serum concentrations of calcium, phosphorus, and 25-hydroxyvitamin d in captive African elephants (Loxodonta africana)

Seventy-two serum samples were collected from 14 healthy African elephants (Loxodonta africana), including three calves, to test for 25-hydroxyvitamin D [25(OH)D] as well as for performing biochemical panels. Samples were collected between July 1997 and January 2008 to establish normal 25(OH)D values for the species and to examine the relationship of season and time on these values. Although the number of samples from the calves was small (n = 7), there was no statistically significant difference in the mean 25(OH)D levels between adults and calves (15.7 +/- 7.7 ng/ml versus 17.1 +/- 5.8 ng/ml, P > 0.05, respectively). The comparison of mean and individual values among seasons showed some variation, but was not statistically different; therefore, all values were combined for further analyses. The mean value of 25(OH)D for all samples was 15.8 +/- 7.5 ng/ml (n = 72), with a 95% confidence interval of 14.0-17.6 ng/ml. There did not appear to be a direct correlation between 25(OH)D levels and calcium (Ca), phosphorus (P), or calcium:phosphorus ratio (Ca:P) based on regression analyses (P < 0.05). Values measured approximated normal distributions. Mean calcium value was 10.5 +/- 0.6 mg/dl (n = 61); mean phosphorus value was 5.2 +/- 0.8 mg/dl (n = 50); and mean Ca:P was 2.06 +/- 0.34. Since all animals appeared healthy during the course of sample collection, and bone density on foot radiographs was assessed as good, the results are considered to be normal for this herd. With the incidence of joint disease in older elephants, and metabolic bone disease in hand-reared calves, these values will provide a basis for further studies of calcium metabolism in elephants.

Antioxidant Status of Faeces of Captive Black Rhinoceros (Diceros bicornis) in Relation to Dietary Tannin Supplementation

In context with the frequent observations of excessive iron (Fe) storage in captive black rhinoceroses (Diceros bicornis), it has been suggested that both an excessive dietary Fe content and a lack of dietary Fe-chelating substances, such as tannins, is the underlying cause. Therefore, studies on the effects of tannin supplementation to captive diet are warranted. Six captive rhinoceroses were fed their normal zoo diet (N), and a similar diet supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins), and the total antioxidant capacity (TAC) was measured as mmol Trolox equivalents per kg fresh faeces. The TAC values on diets N (1.24 +/- 0.39 mmol/kg fresh faeces) and T (1.34 +/- 0.33 mmol/kg fresh faeces) were similar, but significantly higher on diet Q (2.32 +/- 0.61 mmol/kg fresh faeces). In contrast to expectations, faecal TAC increased with increasing faecal Fe, possibly as a result of the fact that the faecal Fe content was positively correlated to the proportion of concentrate feeds in the diet, which also contain antioxidants, such as vitamin E, in addition to Fe. Increased antioxidant status caused by the use of tannin substances could have a beneficial effect on animal health, but if tannins should be incorporated in designed diets, other tannin sources, such as grape pomace should be tested.

Reproductive soundness of captive southern and northern white rhinoceroses (Ceratotherium simum simum, C.s. cottoni): evaluation of male genital tract morphology and semen quality before and after cryopreservation

White rhinoceroses suffer from a low rate of reproduction in captivity. This study examines the role of male reproductive function as a contributing factor. We used ultrasonography to image accessory sex glands, testis and epididymis. Electroejaculation provided 36 ejaculates from 21 rhinoceroses. Based on the percentage of progressively motile spermatozoa, semen was categorized in three groups, high (I: >75%), intermediate (II: 50-70%) or low (III: <50%) quality. Only 52% of the males showed high semen quality. Ejaculates in the high motility category also had the highest proportion of morphologically intact spermatozoa. Both semen parameters, sperm motility and morphology, were found to positively correlate with size of the accessory sex glands. The semen category was associated with group size suggesting that the social status influenced functional reproductive parameters. Change of territorial status (n = 1) improved semen quality. Testicular fibrosis was characterized as a sign of reproductive ageing in all males older than 15 years of age (n = 13); although, this ageing process did not notably affect semen parameters. Furthermore, for the benefit of assisted-reproduction and genetic banking programs protocols for the storage of cooled semen and the cryopreservation of spermatozoa were designed using different cryodiluents. This report provides basic data for the evaluation of reproductive components and of breeding management in male rhinoceros. Our results indicate that low rate of reproduction in captivity can be attributed to reduced male reproductive fitness. Changes in management of white rhinoceroses may positively affect male reproductive function.