Investigation of graded-level soybean meal diets in red drum (Sciaenops ocellatus) using NMR-based metabolomics analysis

We investigated changes in the metabolome in juvenile red drum (Sciaenops ocellatus) induced by increasing amounts of soybean meal (0% to 60%) in extruded, fishmeal-free diets using a nuclear magnetic resonance spectroscopy (NMR)-based metabolomics approach in a 12-week feeding trial. All of the diets were composed of 40% total crude protein, approximate to 11% total crude lipid and were energetically balanced. A fishmeal-containing, commercial extruded diet was used as a control diet throughout the trial. Each week, liver, muscle, intestine and plasma samples were collected and analyzed by NMR to provide a snapshot of the metabolome at different time points. Results indicate significant time-dependence of the metabolic profiles in various tissues with stable metabolomic profiles forming after about 9-weeks on the experimental diets. We identify a previously un-exploited biomarker of potential dietary stress (N-formimino-L-glutamate (FIGLU)) in the fish that may prove to be useful for optimization of alternative diet formulations.