SUMMER AND WINTER VITAMIN D3 LEVELS IN FOUR LEMUR SPECIES HOUSED AT A BRITISH ZOO, WITH REFERENCE TO UVB LEVELS

A case of rickets in an artificially raised white-tailed eagle (Haliaeetus albicilla) chick at a zoo

A two-week-old white-tailed eagle presented with an inability to stand and flex its limbs. Despite hatching naturally and owing to lack of parental attention, the bird was raised indoors by zookeepers with no access to sunlight. Palpation and radiographic examination of the bilateral tibiotarsus and femur bone revealed pronounced deformation and curvature, and bilateral decreased bone densities, respectively. The reduced calcium concentration in the blood was treated with calcium gluconate injections and calcium-supplemented feeds. Chopped mouse tails were fed directly, and whole pink-skinned nude mice were fed weekly. The zookeeper also gently massaged the bird and dressed it with a bandage. Sunlight exposure was provided daily. Saliva containing chicken feed was obtained from the mother. The bird could stand properly after four weeks of treatment, and the blood calcium concentration was restored to normal levels.

THE VITAMIN D STATUS OF ASIAN ELEPHANTS (ELEPHAS MAXIMUS) MANAGED IN A NORTHERN TEMPERATE CLIMATE

Knowledge about the normal metabolism and involvement of vitamin D in elephant calcium homeostasis is essential to understanding the possible role of vitamin D in Asian elephant (Elephas maximus) health, as well as to informing accurate diet formulation. This study provides an evaluation of analytes involved in vitamin D metabolism, in conjunction with dietary intake and ultraviolet light (UV) exposure, in Asian elephants managed in a northern temperate climate. Once monthly, for a total of 12 mo, serum from six adult Asian elephants was analyzed for 25-hydroxyvitamin D [25(OH)D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], 1,25-dihydroxyvitamin D [1,25(OH)₂D], parathyroid hormone (PTH), total calcium (Ca), ionized calcium (iCa), phosphorus (P), and magnesium (Mg). The diet was analyzed monthly for vitamin D, Ca, and P. Monthly average vitamin D-weighted UV daily sums were determined to gauge average UV light exposure within the vitamin D action spectrum. No serum or diet parameters were affected by time or season. Average serum 25(OH)D₂ was 7.02 ± 0.85 ng/ml. 25(OH)D₃ levels were nondetectable in all samples despite supplementation of the diet with recommended levels of vitamin D₃, and UV exposure was at sufficient levels for cutaneous vitamin D synthesis for 6 mo of the year. Levels of 24,25(OH)₂D averaged 31.7% higher than 25(OH)D, and average 1,25(OH)₂D₂ was 11.24 ± 1.04 pg/ml. Values for PTH, Ca, iCa, P, and Mg were within expected ranges for Asian elephants. The information gained from this research expands the knowledge base for these analytes, evaluates 24,25-dihydroxyvitamin D for the first time, and provides new information regarding vitamin D metabolism and test interpretation in the Asian elephant.

EVALUATION OF 25-HYDROXYVITAMIN D IN HOFFMANN'S TWO-TOED SLOTHS (CHOLOEPUS HOFFMANNI) USING DRIED BLOOD SPOTS ANALYZED BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Although biochemical analytes have typically been measured using serum or whole blood samples, an increasing number of assays are validated for measurement of analytes from dried blood spots (DBS) on filter paper. DBS techniques are minimally invasive, require only a small sample volume, and simplify processing, storage, and shipment of samples. These qualities make DBS-based assays ideal for sampling of wildlife species in both captive and field settings. In this study, a liquid chromatography-tandem mass spectrometry assay was evaluated for measurement of 25-hydroxyvitamin D in sloths. Paired serum and DBS samples were collected from nine healthy captive Hoffmann's two-toed sloths (Choloepus hoffmanni). Statistical analysis using Passing-Bablok regression analysis, Bland-Altman plots, and the Wilcoxon signed-rank tests found good agreement between 25-hydroxyvitamin D3 measurements in serum and DBS samples. Constant and proportional bias were absent. Results from this study support the use of DBS samples for the evaluation of vitamin D status in Hoffmann's two-toed sloths and provide a foundation for further studies to validate this technique.

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.

SUMMER AND WINTER VITAMIN D3 LEVELS IN SEVEN PLATYRRHINE SPECIES HOUSED AT A BRITISH ZOO, WITH REFERENCE TO NATURAL UVB LEVELS

Serum samples were collected from 24 platyrrhines of seven diurnal species housed with outdoor access at Bristol Zoo Gardens (United Kingdom) to test 25-hydroxyvitamin D₃ (25OHD₃) levels as part of the veterinary department's preventative health care program. Samples were collected in August 2008 (summer) and January 2009 (winter) to examine the effect of season on 25OHD₃ levels. Dietary levels of vitamin D₃ remained the same throughout the study period and fell within the range of 2000-4000 IU/kg dry matter, in accordance with current primate guidelines. Statistical analysis showed that there was no significant difference between the platyrrhines' summer 25OHD₃ values (range, <4.0->150.0 μg/L) and winter 25OHD₃ values (range, <4.0-80.1 μg/L). However, ultraviolet B (UVB) measurements taken at the zoo during the study period confirmed that UVB levels were significantly higher in summer (mean reading for 1200-1300 hours GMT time period, 153.8 μW/cm²) compared with winter (mean reading for 1200-1300 hours GMT time period, 19.4 μW/cm²). The 25OHD₃ levels measured were generally found to be low compared with previously published values from healthy captive and wild platyrrhines.

25-OH-vitamin D, parathyroid hormone, and calcium serum levels in captive common marmosets (Callithrix jacchus): Reference values and effect of age, sex, season, and closure of long bone epiphyses

BACKGROUND

To date, reference values for 25-OH-vitamin D, parathyroid hormone (PTH), and calcium in serum of common marmosets (Callithrix jacchus) based on a large sample size are not available.

METHODS

Serum reference values for these parameters were determined and correlated with sex, age, season of sampling, and time of long bone epiphyseal closure in captive-housed marmosets.

RESULTS AND CONCLUSIONS

The 90% reference range for serum 25-OH-vitamin D is 47.40-370.4 nmol/L, for PTH 2.10-30.51 pmol/L, and for calcium 2.08-2.63 mmol/L. Lower levels of vitamin D were measured in fall compared with the other seasons. Levels of PTH were higher in males than in females, and calcium levels were lower in younger animals compared with older marmosets. No other effects of age, sex, season, or timing of growth plate closure were found.