Effect of enrichment time and dietary DHA and non-highly unsaturated fatty acid composition on the efficiency of DHA enrichment in phospholipid of rotifer (Brachionus Cayman)

Abstract

Abstract An increasing number of studies suggest that DHA associated with dietary phospholipid (PL) is better metabolically available for fish larvae. Knowledge on how to increase DHA levels in the major PL classes of the live feed is needed. Brachionus Cayman was cultured in conical fibreglass vessels, enriched with commonly used commercial diet Multigain or DHA Selco (DSelco) in flat bottom vessels at 20 °C. The changes of DHA content in the PL of the rotifers through enrichment and through a starvation phase post-enrichment were investigated in order to define an appropriate enrichment time and to test the stability of DHA post-enrichment. The different dietary non-HUFA (non-highly unsaturated fatty acid) composition of DSelco (25.1% SFA, 32.1% MUFA) and Multigain (40.7% SFA, 2.11% MUFA) allowed an evaluation on how SFA and MUFA might affect the efficiency of DHA enrichment of phospholipid in the rotifers. Rotifer samples were collected at 0 h, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h after initiation of enrichment. Total lipid (TL) and the fatty acid composition in TL, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of rotifers and enrichment diets were analysed. The highest DHA levels in PC (23.0%) and PE (16.5%) in Cayman were found after 24 h enrichment with Multigain, and levels were far higher than obtained earlier. The enriched DHA was stable at 10 °C for at least 24 h post-enrichment under starving conditions ( p > 0.05), whereas a significant ( p Statement of relevance The paper is bringing information about fatty acid enrichment of rotifers in questions that are so far quite unclear and could have a strong impact on larviculture of marine fish larvae. This study shows methods to obtain high level of DHA in phospholipids of rotifer. The results could potentially have a significant impact to improve current fatty acid enrichment protocols for rotifers.