Complete replacement of fish oil by three microalgal products rich in n-3 long-chain polyunsaturated fatty acids in early weaning microdiets for gilthead sea bream (Sparus aurata)

The aim of the present study was to evaluate the effect of different n-3 LC-PUFA-rich microalgae replacing FO in larval diets, on performance, biochemical composition and health of gilthead sea bream (Sparus aurata). Dietary fish oil (FO) was replaced with oleic acid (OA) or 3 n-3 LC-PUFA-rich algae products (2 commercial products: All G Rich and DHA Gold, and a development product: MO060). The five early weaning microdiets were fed to 20-dah gilthead sea bream larvae for 21 days. Proximate composition and fatty acid profiles of total, neutral and polar lipids of seabream larvae were analysed, as well as hepatocyte morphology and the expression of selected genes related to lipid metabolism. OA diet significantly inhibited larval growth and survival after a stress challenge, whereas FO replacement by DHA Gold and MO60 led to a higher body weight, total length, and stress resistance. Larvae fed the diets containing microalgae had increased DHA content in whole body lipids and showed a down-regulation of expression of fads2, indicating an inhibition of LC-PUFA biosynthesis. Relative expression of genes related to lipid (ppar-α) or eicosanoids (cox-2 and 5-lox) metabolism were unaffected by the replacement of FO by any of the three microalgal products or OA. In conclusion, all the microalgae products tested were effective total replacers of FO in weaning microdiets for gilthead sea bream larvae, providing the necessary dietary n-3 LC-PUFA for optimal growth and survival. •Microalgae products were effective total replacers of FO in the diets of gilthead sea bream larvae.•Microalgae diets raised the DHA content in the whole body of larvae compared to oleic acid or fish oil-based diets.•Microalgal products down-regulated FA synthesis though fads2 associated to the high DHA level.