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Subclinical hypocalcaemia in captive Asian elephants (Elephas maximus)
  1. J. H. van der Kolk, DVM, PhD, DipECEIM1,
  2. J. P. T. M. van Leeuwen, PhD3,
  3. A. J. M. van den Belt, DVM, PhD2,
  4. R. H. N. van Schaik, PhD4 and
  5. W. Schaftenaar, DVM5
  1. 1 Department of Equine Sciences, Medicine Section
  2. 2 Department of Diagnostic Imaging, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
  3. 3 Department of Internal Medicine
  4. 4 Department of Clinical Chemistry, Erasmus University Medical Centre, Rotterdam, The Netherlands
  5. 5 Rotterdam Zoo, PO Box 532, 3000 AM, Rotterdam, The Netherlands
  1. Correspondence to Dr Schaftenaar

Abstract

The hypothesis that hypocalcaemia may play a role in dystocia in captive Asian elephants (Elephas maximus) was investigated. The objectives of the study were to measure the total calcium concentration in elephant plasma; assess the changes in parameters of calcium metabolism during a feeding trial; investigate a possible relationship between calcium metabolism and dystocia; and assess bone mineralisation in captive Asian elephants in vivo. The following parameters were measured: total and ionised calcium, inorganic phosphorous and magnesium, the fractional excretions of these minerals, intact parathyroid hormone, 25-OH-D3 and 1,25-OH-D3. Radiographs were taken from tail vertebrae for assessment of bone mineralisation. The mean (sd) heparinised plasma total calcium concentration was 2·7 (0·33) mmol/l (n=43) ranging from 0·84 to 3·08 mmol/l in 11 Asian elephants. There was no significant correlation between plasma total calcium concentration and age. Following feeding of a calcium rich ration to four captive Asian elephant cows, plasma total and ionised calcium peaked at 3·6 (0·24) mmol/l (range 3·4 to 3·9 mmol/l) and 1·25 (0·07) mmol/l (range 1·17 to 1·32 mmol/l), respectively. Plasma ionised calcium concentrations around parturition in four Asian elephant cows ranged from 0·37 to 1·1 mmol/l only. The present study indicates that captive Asian elephants might be hypocalcaemic, and that, in captive Asian elephants, the normal plasma concentration of total calcium should actually be around 3·6 mmol/l and normal plasma concentration of ionised calcium around 1·25 mmol/l. Given the fact that elephants absorb dietary calcium mainly from the intestine, it could be concluded that elephants should be fed calcium-rich diets at all times, and particularly around parturition. In addition, normal values for ionised calcium in captive Asian elephants should be reassessed.

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