NMR-BASED METABOLOMIC EVALUATION OF A FORMULATED FEED IN JUVENILE YELLOWFIN TUNA Thunnus albacares

Nuclear Magnetic Resonance (NMR)-based metabolomics is an emerging analytical technology that allows for the evaluation of potential differences at the molecular level induced by various environmental factors including diet in an organism's tissues and biofluids. Currently, metabolomic studies on tuna are extremely sparse, which limits our understanding of physiological responses of this species to alternative feeds in tuna ranching. A 13-week feeding trial with juvenile yellowfin tuna (YFT) was conducted at the Achotines Laboratory in Panama in two concrete tanks arranged as a semi-closed recirculating system. The effects of an alternative diet on YFT metabolite profiles were evaluated at the conclusion of the trial.

The formulated feed contained ~ 22 % total crude protein and ~ 17 % total crude lipid. A diet composed of baitfish (squid, Loligo opalescens, and Pacific thread herring, Opisthonema spp; 50:50) was used as a control.

Tissues (liver, muscle, intestine) and plasma samples were collected at the end of the feeding trial to evaluate possible differences in metabolite profiles between the experimental group (n=6) and the control group (n = 3). Polar extracts of each tissue were analyzed by NMR spectroscopy. Results from the NMR-based metabolomic analysis of these samples (Fig. 1) indicate a high similarity in metabolite profiles between tuna fed baitfish and those fed the compound (CPD) diet.

Differences between treatments included amino acids, organic acids, TCA cycle intermediates, biogenic amines, metabolites associated with oxidative stress, and other metabolites including feed additives. Some of these metabolites were clearly of dietary origin, since they were also detected at significant levels in feed extracts. However, non-dietary metabolites were also shown to vary according to the specific dietary treatment, possibly indicating significant effects on YFT metabolism.