Production performance and tissue fatty acid composition of rainbow trout fed diets containing traditional and novel lipids

So long as essential fatty acid (FA) requirements are met, most fishes tolerate a wide range of alternative lipids.  However, grow-out feed FA composition influences beneficial long-chain polyunsaturated FA (LC-PUFA) retention within the fillet.  To address whether different lipid sources influence rainbow trout (RBT) production performance and tissue composition, we fed juveniles feeds containing fish oil (FISH), or a 50:50 blend of fish and coconut, palm, standard soybean, hydrogenated soybean (HYD-SBO), low linolenic acid soybean (LO-ALA-SBO), or low linolenic acid canola oils.  Two SFA-enriched lipids derived from cottonseed (SFA-COT) and soybean (SFA-SBO) processing were also evaluated as fish oil substitutes. 

Production performance was largely unaffected by feed composition.  Fillet FA composition generally mirrored the feeds, however, feeding certain of the SFA-rich lipids resulted in greater retention of LC-PUFA.  Fillet levels of LC-PUFA among fish fed the HYD-SBO, LO-ALA-SBO, SFA-SBO, and SFA-COT feeds were equivalent to those fed the FISH feed, despite a ~50% reduction in dietary LC-PUFA intake.  Our results indicate a variety of alternative lipids are effectively utilized by RBT when used to replace 50% of dietary fish oil.  However, alternative lipids rich in certain SFA may provide strategic advantage in terms of maintaining a beneficial fillet FA.