Impact of Microalgal-Based Diets on Growth, Proximate, Fatty Acid, and Amino Acid Profiles in Daphnia magna

Water flea (Daphnia magna) is an important live prey species for feeding larvae and juvenile fish and is also used as a feed ingredient in aquaculture. The growth performance and nutritional content of D. magna can be enhanced by diets. In this study, one freshwater microalgae Euglena gracilis (EG), one marine microalgae Pavlova lutheri (PL), and four commercial dried microalgal-based diets (Algome [dried Schizochytrium sp.], Naturiga [dried Spirulina platensis], ProteinPlus [PP] and AlgomeGrow [dried Chlorella sp.]) were evaluated for Daphnia production. Higher survival (68%) was supported by the PP diet, and total length was improved by using fresh microalgae EG. Algome (8.91%) and PP (8.77%) diets had resulted in higher crude lipid content, whereas the highest crude protein was obtained by the Naturiga diet (55.66%) in D. magna. D.magna fed Algome diet showed the highest docosahexaenoic acid (DHA; C22:6n-3) accumulation, whereas eicosapentaenoic acid (EPA; C20:5n-3) level was enhanced by PP and arachidonic acid (ARA) level was only supported by Naturiga diet. A strong correlation was observed between certain fatty acid groups (Oleic acid, Ʃ n-3, and Ʃ n-3 highly unsaturated fatty acids [HUFAs]) in the D. magna body and diets. In terms of essential amino acid contents of D. magna, the AlgomeGrow diet had the best performance at the end of the experiment.