EFFICACY OF ABSORPTION OF VARIOUS VITAMIN E FORMS BY CAPTIVE ELEPHANTS AND BLACK RHINOCEROSES

A biochemical vitamin E deficiency may exist in captive elephants (Elephas maximus and Loxodonta africana) and black rhinoceroses (Diceros bicornis) because plasma a-tocopherol concentrations apparently are lower in these animals than in their free-ranging counterparts. Analysis of serum or plasma from 35 elephants and 11 black rhinoceroses from 11 zoological institutions and one private owner confirmed common occurrence and persistence of low circulating a-tocopherol levels. Concentrations averaged < 0.3 Mg/ml despite prolonged supplementation with D,L-a-tocopher yl acetate, the most common vitamin E supplement for animal diets. Further experimental work demonstrated that supplementing the diet with d,l- or D-a-tocopheryl acetate or D-a-tocopherol to provide up to 62 IU/kg body weight (BW) in elephants and 23 IU/kg BW in black rhinoceroses increased circulating blood a-tocopherol by <0.2 /?g/ml. Apparently, elephants and black rhinoc eroses absorbed these fat-soluble or water-dispersible forms of vitamin E poorly. In contrast, the water-soluble form, D-a-tocopheryl polyethylene glycol 1,000 succinate (TPGS), was absorbed well, as indicated by rapid increases in circulating blood a-tocopherol (0.3-1.9 /ig/ml) from several-fold lower TPGS doses in the diet (4.8 or 6.6 IU/kg BW in elephants and 1.5 or 3.9 IU/kg BW in black rhinoceroses). There is a marked difference in the bioavailability of TPGS versus other vitamin E forms in captive elephants and black rhinoceroses, suggesting that there are major species differences in the utilization of various forms of vitamin E.