IRON METABOLISM IN CAPTIVE BLACK (DICEROS BICORNIS) AND WHITE (CERATOTHERIUM SIMUM) RHINOCEROSES

Abstract

Black rhinoceroses that are kept in captivity have increased amounts of hemosiderosis as determined microscopically. The objective of the present study was to measure various iron analytes in captive black (Diceros bicornis) and white (Ceratotherium simum) rhinoceroses. Nonheme iron was measured in liver samples, and iron, total iron binding capacity, percentage of transferrin saturation, and haptoglobin were measured in serum samples. Black rhinoceroses (n = 16), but not white rhinoceroses (n = 9), accumulated iron in the liver during captivity. Serum iron concentration and percentage of transferrin saturation were increased in black (n = 40) compared to white rhi noceroses (n = 13). An enzyme-linked immunoabsorbent assay used to measure ferritin in equine sera was adapted to measure ferritin in rhinoceros sera. Serum ferritin concentration of black rhinoceroses was significantly higher (t = 4.75, P < 0.001) than that of white rhinoceroses and increased significantly (r = 0.43, P = 0.0134) with time in captivity. Because haptoglobin levels did not differ significantly between black (n = 20) and white (n = 10) rhinoceroses, the hypothesis that iron accumulates as a result of a hemolytic anemia is less likely. Alternatively, the hypothesis that a dietary change increases iron absorption may explain these results.