Diet-induced differences in the essential fatty acid (EFA) compositions of larval Atlantic cod (Gadus morhua L.) with reference to possible effects of dietary EFAs on larval performance

Abstract

We studied the performance of cod rearing in which live feed was given under three different essential fatty acid (EFA) enrichment regimes, using commercially available live-feed enrichments. We assessed the fatty acid profile [docosahexaenoic (DHA), eicosapentaenoic (EPA), and arachidonic acid (AA)] in larval somatic tissue, relative to its amounts in both rotifers and Artemia as well as to larval performance. Overall, percentage lipid level of each experimental diet for the trial was approximately 50%. Further, there were no significant differences in total fatty acid levels of larvae from each treatment at the end of the trial (mean = 444.76 μg fatty acid per mg lipid). However, during the rotifer phase, larvae from each treatment were able to incorporate comparable levels of %DHA, irrespective of levels in the diet. Despite this, the rotifer diet with more %DHA still promoted better larval growth than other treatments. Conversely, larvae from two of the treatments did not exhibit any accumulation of AA, reflecting levels found in the diet instead. However, between-tank differences in larval %AA showed improved growth during the rotifer period when larval %AA was high. Low ratios of EPA had no effect. During the Artemia phase, percentage levels of larval DHA decreased; there was no accumulation of DHA relative to dietary levels, which in Artemia were significantly lower than in rotifers (6 cf. 20–30%). However, DHA levels in larvae at the end of the experiment correlated positively with survival. Artemia contained lower levels of AA than rotifers (1.5 cf. 3.0%), yet comparable levels of AA were found in rotifer-fed and Artemia-fed larvae. This also differed significantly between treatments, and correlated positively with survival.

Growth and lipid composition of Atlantic cod (Gadus morhua) larvae in response to differently enriched Artemia franciscana

“…Larval AA levels seemed to be more conservative, with only larvae from the AlgaMac treatment having higher levels of AA at 59 dph than at the start of the experiment. Cutts et al (2006) observed similar trends in Atlantic cod larvae fed rotifers and Artemia enriched differently. Despite the different enrichments, Atlantic cod DHA levels were approximately six times lower at 50 dph in all treatments, when compared to the period where the larvae were still feeding on rotifers (at 10 or 22 dph).…”

“…Despite the different enrichments, Atlantic cod DHA levels were approximately six times lower at 50 dph in all treatments, when compared to the period where the larvae were still feeding on rotifers (at 10 or 22 dph). Atlantic cod AA levels were more stable, with larvae from all treatments exhibiting similar levels throughout the entire trial (Cutts et al 2006). Preferential accumulation of AA and reduction of DHA levels have also been observed in Atlantic halibut, Hippoglossus hippoglossus (Hamre et al 2002), and Senegal sole, Solea senegalensis, larvae (Villalta et al 2005) fed Artemia.…”

“…However, the enrichment process is poorly understood in terms of the mechanisms of lipid assimilation and efficiency, and it is now known that the Artemia nauplii do not act as a mere capsule, but rather can actively change the lipid composition of the diet (Navarro et al 1999). To date, we only know of a few studies that tested different livefeed enrichments for Atlantic cod larvae during the Artemia phase (Zheng et al 1996;Galloway et al 1998;Cutts et al 2006). In the study performed by Cutts et al (2006), the three enrichments tested differed in their proximate composition, however, there were no differences in survival, growth, and larval fatty-acid content of lipids during the Artemia feeding stage.…”

“…To date, we only know of a few studies that tested different livefeed enrichments for Atlantic cod larvae during the Artemia phase (Zheng et al 1996;Galloway et al 1998;Cutts et al 2006). In the study performed by Cutts et al (2006), the three enrichments tested differed in their proximate composition, however, there were no differences in survival, growth, and larval fatty-acid content of lipids during the Artemia feeding stage.…”

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)

“…The conclusion might then be that the percentage fraction of DHA in the diet determined the enrichment levels of DHA in PL of the rotifers. An alternative explanation might be that a lipid emulsion, which constitutes mainly lipids, is more poorly assimilated and therefore metabolically less efficient for transferring DHA to rotifer PL than a slightly more complete enrichment feed, with some proteins added (13%, Table 1) and with high DHA level (Cutts et al, 2006). The enhanced efficiency might be a combination of these effects, and a Multigain-type diet would then in all events be most efficient for PL enrichment of DHA and HUFA.…”