Growth Performance and Tissue Fatty Acid Composition of Rainbow Trout Reared on Feeds Containing Fish Oil or Equal Blends of Fish Oil and Traditional or Novel Alternative Lipids

Abstract

Fish oil (FO) sparing is common in aquafeed formulation; however, some alternative lipids have proven to be more successful than others in ensuring adequate growth and maintenance of desirable fillet fatty acid (FA) composition. Depending on the lipids used, grow-out feeds influence the FA composition of the tissues of “lean-fleshed” fishes and their responsiveness to subsequent tailoring during finishing. To address whether different lipid sources similarly influence growth performance and tissue composition of a “fat-fleshed” fish, rainbow trout Oncorhynchus mykiss were reared on feeds containing FO or a 50:50 blend of FO and coconut oil (COCONUT), palm oil (PALM), standard soybean oil (STD-SBO), hydrogenated soybean oil (HYD-SBO), low-18:3(n-3) (alpha-linolenic acid) soybean oil (LO-ALA-SBO), or low-18:3(n-3) canola oil (LO-ALA-CAN). Two saturated FA (SFA)-enriched lipids derived from the processing of cottonseed (SFA-COT) or soybean (SFA-SBO) were also evaluated as 50% FO substitutes. After 7 weeks, growth performance was largely unaffected by dietary lipid source. Fillet levels of long-chain (LC) polyunsaturated FAs (PUFAs) among fish that received the HYD-SBO, LO-ALA-SBO, SFA-SBO, and SFA-COT feeds were equivalent to levels in fish that received the FO feed, despite an approximate 50% reduction in dietary LC-PUFA intake. Our results indicate that feeds containing a blend of FO and novel soy- or cottonseed-derived lipids yielded equivalent growth performance and fillet LC-PUFA content in rainbow trout. The use of STD-SBO, COCONUT, PALM, or LO-ALA-CAN did not impair growth or efficiency but did alter the fillet FA profile. Rainbow trout appeared to differ somewhat from other fishes in terms of dietary influence on tissue FA profile; however, the pattern of greater LC-PUFA retention in fish reared on SFA-rich feeds appears to be largely consistent among the fish taxa we have assessed.

Received January 19, 2010; accepted July 25, 2010

ACKNOWLEDGMENTS

We extend our sincere thanks to the Illinois Soybean Association for supporting this research project under Grant Number 09-ISA-35-409-3. We thank Archer Daniels Midland for providing the alternative soy- and cottonseed-derived lipids evaluated, and we are grateful to Omega Protein, Tate and Lyle, and Darling International for the donation of FO and other feedstuffs used in the experimental feeds. We also thank the many students and staff at the Fisheries and Illinois Aquaculture Center who assisted with data collection.