Hyperaccumulation of selenium in hybrid striped bass: a functional food for aquaculture?

One method of increasing the value of aquacultured product is to produce fillets that are fortified with minerals that are beneficial to human health - that is enhance the functionality of an already healthy product. A good candidate mineral in this regard is selenium (Se) which is of vital importance to normal metabolism in humans. In order to evaluate the dose response and tissue accumulation of supplemental dietary Se, a study was undertaken with hybrid striped bass (HSB). Animals were fed diets supplemented with either organic (0-3.2 mg kg(-1) as SelPlex(R)) or inorganic (0.2 and 0.4 mg kg(-1) as sodium selenite) Se for 6 weeks. Because basal fishmeal-based diets contained 1.22 mg Se kg(-1), doses of Se delivered equated to 1.22-4.42 mg kg(-1). At trial end, greatest weight gain was observed in fish receiving 0.2 mg Se kg(-1), irrespective of form (organic/inorganic). Se accumulation in HSB liver and fillet revealed a classical dose-response once a threshold level of 0.2 mg Se kg(-1) was surpassed. Greatest tissue accumulation of Se was observed in fish fed the 3.2 mg Se kg(-1) level (P > 0.0001). A 100 g portion of Se-enhanced HSB fillet would contain between 33 and 109 mu g Se, amounting to a dietary intake of between 25 and 80 mu g Se; a level that would satisfy present daily intake recommendations. Comparison of tissue Se levels indicated that the muscle provides a more conspicuous gauge of dietary Se dose-response than does liver. Dietary treatments of between 0.4 and 1.6 mg organic Se kg(-1) reduced (P < 0.024) plasma glutathione peroxidase (GSH-Px) activity. No differences were observed in ceruloplasmin, lysozyme or GSH-Px activities between organic and inorganic Se when delivered at the 0.2 mg Se kg(-1) level. Ceruloplasmin, lysozyme and GSH-Px levels were elevated (P >= 0.025) in fish fed the diet containing 0.4 mg inorganic Se kg(-1).