Effects of dietary iron supplementation on growth performance, fatty acid composition and fatty acid metabolism in rainbow trout (Oncorhynchus mykiss) fed vegetable oil based diets

The complete and successful replacement of fish oil in aquafeed without compromising fillet omega-3 long chain polyunsaturated fatty acid (n − 3 LC-PUFA) concentrations has yet to be achieved. As means of overcoming this issue, the potential of in vivo n − 3 LC-PUFA biosynthesis in cultured fish has been widely investigated and may permit the future economical and sustainable development of aquaculture. Two of the key enzymes involved in this process include the fatty acid Δ-6 and Δ-5 desaturases, where, in the terminal protein of each complex, iron is present in the active di-iron centres. To the best of authors' knowledge, no investigations have thus far been attempted to elucidate the potential roles of dietary iron on the fatty acid metabolism of cultured fish. In this study, graded inclusions of dietary iron were tested in rainbow trout fed vegetable oil based diets. This study generated preliminary evidence suggesting that dietary iron concentration can have a positive effect on LC-PUFA biosynthesis in fish and data are herein reported. In particular, dietary iron level was shown to affect the final n − 3 LC-PUFA content of fish tissues and also to modulate the activity of fatty acid desaturase enzymes. This activity was insufficient to compensate for a diet lacking in LC-PUFA but does highlight potential strategies to maximise this activity in cultured fish fed fish oil free diets.

► Iron plays an important role in the active centres of fatty acid desaturase enzymes.
► Is dietary iron affecting LC-PUFA biosynthesis in fish fed fish oil free diets?
► Dietary iron level affected the final n − 3 LC-PUFA content of fish tissues.
► Preliminary evidence that iron modulates the activity of desaturases was reported.
► This increased activity was insufficient to compensate for diets lacking in LC-PUFA.