Abstract:The aim of the current study was to assess the effect of oral calcium and cholecalciferol supplementation on several parameters of calcium status in plasma and urine of captive Asian (Elephas maximus; n ¼ 10) and African elephants (Loxodonta africana; n ¼ 6) and to detect potential species differences. Calcium and cholecalciferol supplementation were investigated in a feeding trial using a crossover design consisting of five periods of 28 days each in summer. From days 28-56 (period 2), elephants were fed the Ca-supplemented diet and from days 84-112, elephants were fed the cholecalciferol-supplemented diet (period 4). The control diet was fed during the other periods and was based on their regular ration, and the study was repeated similarly during winter. Periods 1, 3, and 5 were regarded as washout periods. This study revealed species-specific differences with reference to calcium and cholecalciferol supplementation. Asian elephants showed a significant increase in mean plasma total calcium concentration following calcium supplementation during summer, suggesting summerassociated subclinical hypocalcemia in Western Europe. During winter, no effect was seen after oral calcium supplementation, but a significant increase was seen both in mean plasma, total, and ionized calcium concentrations after cholecalciferol supplementation in Asian elephants. In contrast, evidence of subclinical hypocalcemia could be demonstrated neither in summer nor in winter in African elephants, although 28 days of cholecalciferol supplementation during winter reversed the decrease in plasma 1,25(OH)2-cholecalciferol and was followed by a significant increase in mean plasma total calcium concentration. Preliminary findings indicate that the advisable permanent daily intake for calcium in Asian elephants and cholecalciferol in both elephant species at least during winter might be higher than current guidelines. It is strongly recommended to monitor blood calcium concentrations and, if available, blood parathyroid hormone levels to adjust the nutritional supplementation for each individual elephant.

To study calcium metabolism in elephants, it is important to use validated assays, as these might be prone to specific matrix effects in elephant blood. The same might be true for matrix effects in urine. The aim of the current study was to conduct preliminary work for validation of various parameters that play a role in calcium metabolism in both blood and urine of captive elephants. Several basal parameters were compared between Asian elephants (Elephas maximus) and African elephants (Loxodonta africana). The reason for undertaking this study is the occurrence of dystocia in captive elephants. The exact cause of dystocia is unknown, but it may be related to hypocalcemia. 6,19 To the authors' knowledge, no validation studies are available for analyzing parameters of calcium metabolism in elephants. However, there are biochemical studies regarding calcium metabolism, including calcium, phosphorus, creatinine, and pH assessments, and one study described the use of bone markers. [1][2][3][4][5][7][8][9][10][11][12][13][14][15][16]18 The preliminary testing was performed using samples predominantly obtained from 2 healthy female Asian elephants (a 48-year-old nonpregnant elephant and a 22-year-old pregnant elephant weighing approximately 3,800 and 3,000 kg, respectively) belonging to the Rotterdam Zoo, The Netherlands. In addition, basal values of various parameters of calcium metabolism were assessed in 10 female captive Asian and 6 African elephants from 4 different zoos (Hannover Zoo, Germany; Antwerp Zoo, Belgium; Hilvarenbeek Zoo, The Netherlands, and Rhenen Zoo, The Netherlands). The female Asian elephants were 24.7 ± 12.9 years of age (range: 5-47 years) and weighed 3,028 ± 860 kg (range: 1,400-4,444 kg). The female African elephants were 22.2 ± 7.6 years of age (range: 11-37 years) and weighed 3,167 ± 236 kg (range: 3,000-3,500 kg). Water was provided ad libitum, and it was not possible to estimate individual water intake.The estimated mean daily intake of calcium and phosphorus were 94 ± 31 and 45 ± 19 mg/kg body weight (BW), respectively, in Asian elephants, and 59 ± 17 mg/kg BW and 45 ± 16 mg/kg BW, respectively, in African elephants. The estimated daily cholecalciferol intake was 0-2 IU/kg BW for both species. Abstract. Hypocalcemia is a well-known cause of dystocia in animals, including elephants in captivity. In order to study calcium metabolism in elephants, it is of utmost importance to use properly validated assays, as these might be prone to specific matrix effects in elephant blood. The aim of the current study was to conduct preliminary work for validation of various parameters involved in calcium metabolism in both blood and urine of captive elephants. Basal values of these parameters were compared between Asian elephants (Elephas maximus) and African elephants (Loxodonta africana). Preliminary testing of total calcium, inorganic phosphorus, and creatinine appeared valid for use in plasma and creatinine in urine in both species. Furthermore, measurements of bone alkaline phosphatase and N-te...