Seven fish oil substitutes over a rainbow trout grow-out cycle : II) Effects on final eating quality and a tentative estimation of feed-related production costs

The effects of seven alternative oils on final product quality and production cost was assessed in rainbow trout (Oncorhynchus mykiss). The tested oils were: monola (a high oleic acid canola cultivar; MO), canola (rapeseed; CO), poultry by-product (chicken fat; PbPO), palm (PO), sunflower (SFO), high oleic acid sunflower (HOSFO) and soybean (SBO). Tested oils were included at a 75% substitution level of fish oil, and were compared to a control diet containing 100% fish oil (FO). Fillets of trout fed FO contained a 2.8-fold higher amount of EPA+DHA in comparison to fish fed the alternative oils, whilst the n-6/n-3 ratios varied from 0.2 in FO to 3.67 in SFO. Fillet pigmentation was highly affected by the different dietary treatments, as was the refrigerated product shelf-life. Fillets of trout fed FO recorded significantly higher lipid peroxidation at days 6 and 9 of refrigeration compared to the other treatments. The fillet flavour volatile compounds were significantly affected by the treatments, but no differences were detected by the panellists in the sensorial analysis. A discrepancy between production costs at “feed mill” or “on-farm” was recorded, suggesting that fish oil replacement may result in no real economic benefit.