RESEARCHERS:

Dr. Marcus Clauss	M. Llechner-Doll
Ellen S. Dierenfeld	Jean-Michael Hatt
Tim Woodfine

PROJECT SUMMARY:
Iron overload and susceptibility to oxidative stressors are recognized to be major problems in the health of captive black rhinoceros. This study aims to evaluate whether tannins, which occur in the natural diet of the animals, and to which they have adapted through evolution, have positive effects for the species - specifically, if a reduction in iron availability and an improvement of antioxidant status can be achieved by adding tannins to captive diets.

Diets without tannins are hypothesized to cause increased iron absorption and an insufficient antioxidant status, and therefore to contribute to several disease symptoms observed in captive black rhinoceros. Iron parameters in blood samples, and iron absorption as measured by conventional digestibility trials and by the use of stable isotope-labeled iron, will be determined for diets before and after the addition of commercially available tannins (tannic acid and quebracho tannins), and tannin-containing browse. Antioxidant as well as mineral status will be determined simultaneously from blood samples.

The fatty acid composition of red blood cells and plasma lipids will receive special attention as parameters of oxidative stress and dietary provision. Animals trained for blood sampling will be fed a consistent diet for at least two months; during the last 2 weeks of each feeding period, intake will be recorded, labeled iron will be dose-fed, and blood and feces will be sampled.

Apart from a facilities' baseline diet, two diets containing tannic acid (a hydrolysable tannin) and quebracho tannin (a condensed tannin), each at 5 % level, and a diet with a high proportion of fresh browse, will be used. The results of this study will allow to decide whether the deliberate inclusion of tannin-containing compounds into captive diets for black rhinoceros should receive further attention for mitigation of iron-mediated toxicity and oxidative stress.