RRR-α-Tocopheryl succinate is a less bioavailable source of vitamin E than all-rac-α-tocopheryl acetate for red drum, Sciaenops ocellatus

Bioavailability of the succinate ester of α-tocopherol has never been investigated with aquatic animals to date. Therefore, a 12-week feeding trial was conducted to compare bioavailability of α-tocopheryl acetate and α-tocopheryl succinate by slope ratio analysis. The semi-purified diets were supplemented with either 0 (basal), 10, 20 and 40 IU vitamin E/kg as all-rac-α-tocopheryl acetate or 10, 20, or 40 IU vitamin E/kg as RRR-α-tocopheryl succinate. Red drum juveniles were conditioned by feeding the basal diet for 8 weeks prior to the experimental period to reduce whole-body tocopherols. Fish initially averaging 12.2 ± 0.4 g/fish (mean ± SD) were fed experimental diets at a rate approaching apparent satiation for 12 weeks. Weight gain and feed efficiency responses of fish fed diets were not significantly altered by the type or level of vitamin E supplemented. However, α-tocopherol levels in liver and plasma were significantly (P < 0.01) influenced by dietary vitamin E level and ester form. The liver retention of α-tocopheryl acetate was 14 times higher than α-tocopheryl succinate, while thiobarbituric acid reactive substances (TBARS) in liver of fish fed α-tocopheryl acetate tended to be (P < 0.1) lower than that of fish fed α-tocopheryl succinate. In addition, plasma ascorbic acid in fish fed graded levels of α-tocopheryl acetate was significantly higher than fish fed graded levels of α-tocopheryl succinate. Fish fed the basal diet and 10 IU α-tocopheryl succinate/kg showed edema in the heart, while fish fed all other diets did not exhibit this pathology. Within the dose range of 0-40 IU/kg diet, hematocrit, neutrophil oxidative radical production and intracellular superoxide anion production of head kidney macrophages were not significantly influenced by α-tocopherol ester or dietary supplementation level. In conclusion, α-tocopheryl succinate is not readily available to juvenile red drum compared to the widely used α-tocopheryl acetate.