Sustainable Aquaculture Digital - October 2014

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Fish oil is a high quality source of energy and long-chain polyunsaturated fatty acids (LC- PUFAs; C20 or C22 fatty acids with three or more double bonds), but it is increasingly costly, and aquafeed prices must be man- aged by sparing fish oil with less expensive plant and animal-derived oils and fats. Assuming essential fatty acid requirements are met (NRC 2011), fish fed reduced fish oil feeds generally exhibit equivalent growth per- formance. However, sparing LC-PUFA-rich fish oil with alternative lipids typically results in a marked decrease in levels of LC-PUFAs in the edible tissues. Retention of these fatty acids is important for consumer acceptance due to the known benefits of LC-PUFA consumption on infant development, cancer, cardiovascular dis- eases, and mental illnesses. Previous research by our lab and others has demonstrated that feeding diets containing high levels of medium-chain polyunsaturated fatty acids (MC-PUFAs; C18 fatty acids with two or more double bonds) results in sub- stantial tissue fatty acid profile change and LC-PUFA loss, but that these effects are less dramatic among fish fed diets containing pri- marily saturated fatty acids (SFA; fatty acids with no double bonds) and monounsaturated fatty acids (MUFAs; fatty acids with one dou- ble bond). Giovanni Turchini's group at Deakin University, Warrnambool, Australia, dubbed this the "omega-3 sparing effect" of SFAs and MUFAs. Using these types of alternative lipids has been suggested as one approach, along with the use of finishing feeds, to counter LC-PUFA loss among fish fed re- duced fish oil feeds.

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