Comparison of total calcium, ionised calcium and albumin concentrations in the plasma of captive tortoises (Testudo species).

Plasma total calcium, ionised calcium and albumin levels in Hermann's tortoises (Testudo hermanni), spur-thighed tortoises (Testudo graeca), marginated tortoises (Testudo marginata) and Horsfield's tortoises (Testudo horsfieldi) were investigated. The animals were captive adults maintained under natural unfiltered sunlight in the UK with no dietary sources of cholecalciferol. Analysis of total calcium data showed statistically significant seasonal elevations in females in August compared with March (P=0.003), and statistically significant elevations in females compared with males at all sampling points (March P=0.036, June P=0.003 and August P<0.0001). These differences in values became more prominent as the summer progressed. Albumin values did not appear significantly affected by season. However, males had significantly higher albumin levels than females in the August samples. A correlation between total calcium and ionised calcium was confirmed but there was no correlation between total calcium and albumin values. Total calcium levels were a poor indication of ionised calcium levels, which constituted between 18 and 57 per cent of the total calcium value.