Effects of new microalgae and macroalgae products on live prey and fish performance
Algae are rich in valuable compounds such as vitamins, minerals, proteins, phenolic compounds, sterols and other lipids including n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA). They also have high contents of pigments that exert antioxidant activity, being considered as good candidates to be used in human and animal nutrition and for pharmacological and nutraceutical purposes. In the present study, new Isochrysis galbana and Navicula salinicola microalgae formats in aquaculture live prey (rotifer and Artemia) enrichment protocols are assayed, being spray-dried I. galbana the best format to enhance the preys n-3 LC-PUFA content, their phospholipid retention and oxidative status protection. On the other hand, lipid characterization of seaweeds regularly present in beach casts from the Macaronesian region is assessed, in order to discuss their potential use for animal and human nutrition and health. The low n-6/n-3 PUFA ratio, and their content in some beneficial lipids such as phytosterols make the algae analysed interesting from both a nutritional and health perspective. Finally, a 7% inclusion of a multispecific or two monospecific (Lobophora sp. and Dictyota sp.) macroalgal wracks in grass carp (Ctenopharyngodon idella) and gilthead seabream (Sparus aurata) diets is assayed, with any negative effect in the culture performance of C. idella and S. aurata juveniles being found. In fact, the multispecific wrack displayed less fat deposition in C. idella, while both multispecific and monospecific (Lobophora sp.) wracks caused some protective effects by enhancing the antioxidant capacity in the fish liver. S. aurata also showed a higher capacity to mold the glutathione metabolism when feeding the monospecific Dictyota sp. wrack. Furthermore, S. aurata showed some altered patterns in the digestive enzymes activities with respect to the control fish, without effecting the fish performance.