The use of silages prepared from fish neural tissues as enrichers for rotifers (Brachionus plicatilis) and Artemia in the nutrition of larval marine fish

Abstract

Marine fish larvae have a requirement for large quantities of n − 3 highly unsaturated fatty acids (HUFA), particularly docosahexaenoic acid (DHA; 22:6n − 3), and dietary deficiencies of these induce a range of pathologies in fish including behavioural abnormalities. Therefore, there is a growing demand for natural lipids highly enriched in DHA as nutritional supplements during larval development. In the present study, DHA-rich products were obtained from fish neural tissues by a procedure involving ensiling in organic acids followed by neutralisation, drying, milling and sieving to produce the final paniculate, crumbed products. Lipid content varied in the neural tissue silages from 5.5% to 46.5% but all lipid contained high percentages of DHA and high DHA:EPA (eicosapentaenoic acid; 20:5n − 3) ratios ranging from 3.5 to 5.4. Tuna eye silage was a high lipid, high triacylglycerol (90.6% of total lipid) product and was particularly effective in increasing DHA content, outperforming a commercial product, in rotifer (Brachionus plicatilis) enrichment. Cod brain/eye silage had an intermediate content (18.2%) of lipid, which contained almost 50% as phospholipid, and proved as effective as a commercial enricher in increasing DHA content in Artemia nauplii. Moreover, Artemia nauplii, enriched with the cod brain/eye silage were more effective than nauplii enriched with a commercial enricher in increasing the DHA content of larval turbot brain. In conclusion, tuna eye and cod brain/eye silages are useful as enrichers of Artemia nauplii and rotifers for feeding marine fish larvae prior to weaning onto pelleted formulated diets.