Effects of dietary use of two lipid extracts from the microalga Nannochloropsis gaditana (Lubián, 1982) alone and in combination on growth and muscle composition in juvenile gilthead seabream, Sparus aurata

Abstract

Microalgae are a source of diverse high-value compounds, such as carotenoids and fatty acids, which have a potential application in aquafeeds. Some microalgae species present complex cell wall structures, which make them poorly digestible, thus limiting their use as a feed ingredient. Consequently, applying extracted compounds to aquafeeds instead of using the whole algal biomass is advantageous as this is expected to increase the bioavailability of these nutrients. The aim of this study was to evaluate the effect of the dietary inclusion (2%) of two extracts obtained from the microalga Nannochloropsis gaditana (one composed of saponifiable lipids and the other of non-saponifiable lipids), alone or in combination, on growth, muscle composition, skin color and lipid oxidation in juvenile gilthead seabream, Sparus aurata, following a 39-day trial. Overall, the inclusion of 2% of the saponifiable lipid extract did not affect the growth performance but fish muscle presented a lower percentage of docosahexaenoic acid (DHA) and a higher eicosapentaenoic acid (EPA) than that of the fish fed the diets lacking this lipidic fraction. Despite no effect being observed in fish growth performance, the inclusion of 2% of the non-saponifiable lipid extract enhanced the carotenoid content of the fish muscle, which prevented lipid oxidation, and modulated the skin pigmentation towards a yellow-greenish color. The present study confirms the success of applying both high-value microalgae lipidic extracts, alone or in combination, as feed additives for practical diets in juvenile gilthead seabream.