Serum osmolality and effects of water deprivation in captive Asian elephants (Elephas maximus)

Abstract

Serum from 21 healthy, captive Asian elephants (Elephas maximus) was evaluated by measured and calculated osmolality. Serum osmolality results for this population of Asian elephants had a median of 261 mOsm/kg and an interquartile interval of 258–269 mOsm/kg when measured by freezing point osmometry and a median of 264 mOsm/kg and an interquartile interval of 257–269 mOsm/kg when measured by vapor pressure osmometry. These values are significantly lower than values reported in other mammalian species and have important diagnostic and therapeutic implications. Calculated osmolality produced unreliable results and needs further study to determine an appropriate formula and its clinical application in this species. A 16-hr water deprivation test in 16 Asian elephants induced a small, subclinical, but statistically significant increase in measured serum osmolality. Serum osmolality, blood urea nitrogen, and total protein by refractometer were sensitive indicators of hydration status. Serum osmolality measurement by freezing point or vapor pressure osmometry is a useful adjunct to routine clinical tests in the diagnostic evaluation of elephants.

Proboscidea

“…25 Subcutaneous administration into the folds of the neck is a possibility, but very few drugs have been evaluated using this route. Several elephants have sloughed off large portions of their ears because of intravenous drugs leaking extravascularly.…”

“…25 Total protein is usually high, consisting primarily of globulins. Serum osmolarity is significantly lower than in other species.…”

Oncotic pressure and the effects of water deprivation in healthy captive Asian elephants

“…Asian elephants are reported to have low serum osmolality. 5 Elephants have an erythrocyte volume ~3 times that of the horse. 14 African elephants have erythrocytes with increased flexibility and, in healthy states, they have plasma viscosity approaching that seen with advanced renal insufficiency in other species.…”

“…Osmolality by freezing point osmometer (FPO) was also obtained on all samples by methods described previously. 5 In phase 2, 7 mo after the initial blood collection, we performed a water deprivation test. Sixteen elephants were selected from the previously described group based on elephant availability and behavioral compliance for consecutive blood draws under time constraints.…”

“…Osmolality by FPO was also obtained on all samples by methods described previously. 5 Calculations were performed (MATLAB v.R2008b; MathWorks, Natick, MA). All statistical tests were performed at the 95% confidence interval with a p ≤ 0.05 considered significant.…”