Study of the n-3 highly unsaturated fatty acids requirement and antioxidant status of Dentex dentex larvae at the Artemia feeding stage

Abstract

This study was designed to investigate the requirements of Dentex dentex larvae for (n-3) highly unsaturated fatty acids (HUFA) at the Artemia feeding stage. Artemia were enriched using mixtures of ICES Experimental Emulsions ICES 50/0.6/C (500 mg/g (n-3) HUFA, 0.6 DHA/EPA ratio, based on ethyl esters) and ICES 0/-/C (based on coconut oil) and to give five dietary treatments which contained different levels of (n-3) HUFA from 0.72 to 6.23 as dry weight percentage. Optimal growth, as evidenced by total length, individual dry weight, specific growth rate and thermal growth coefficient, was achieved when dietary (n-3) HUFA was 3.97 on a dry weight basis. Larvae fed Artemia enriched with apparently super-optimal levels of (n-3) HUFA (5.67-6.23 %) showed significantly lower vitamin E contents and higher malondialdehyde (MDA) levels combined with their eyes having maximum (n-3) HUFA values and DHA/EPA ratios. Poorer performance of larvae was associated with increased dietary and larval MDA and decreased larval vitamin E, indicating increasing oxidation of (n-3) HUFA in Artemia and larval utilization of vitamin E with increasing levels of dietary (n-3) HUFA, particularly at supraoptimal levels of enrichment. The activities of antioxidant enzymes in the larvae was generally not greatly affected by the dietary treatments in this study. A balance is required between growth-promoting essential fatty acid (EFA) qualities of (n-3) HUFA and their potentially growth-inhibiting (prooxidant) qualities which must be counter-balanced with adequate dietary antioxidants.