Long-term feeding of vegetable oils to Senegalese sole until market size: Effects on growth and flesh quality. Recovery of fatty acid profiles by a fish oil finishing diet

•Total fish oil substitution does not impair growth or feed utilization.•Sole selectively retains highly unsaturated fatty acids (ARA and DHA).•Sole fillets fed high VO levels are well accepted by consumers.•Sole fillets fed high VO levels provide 1.5 times the RDI level of EPA + DHA.

The present study evaluates the long term (5 months) effects of feeding vegetable oil-based diets to Senegalese sole (Solea senegalensis) until market size. Extruded isonitrogenous and isoenergetic diets (56% crude protein and 20 kJ/g) were formulated to substitute 0 (CTRL), 50 (VO50) and 100% (VO100) of FO by a VO blend (rapeseed oil, RO, soybean oil, SO, and linseed oil, LO). A concomitant replacement of 50% FM and FO (VO50PP50) by plant protein sources (pea, soybean meal, potato concentrate, corn and wheat gluten) and oils was also evaluated. After the growth trial (140 days), fish were fed a fish oil-based diet (CTRL) over a period of 26 days and growth, flesh quality and organoleptic properties were determined.Results show that it seems possible to substitute up to 100% of FO by a VO blend, as well as concomitantly substituting 50% FO and FM by vegetable sources in on-growing Senegalese sole diets, without compromising growth performance and feed utilization. This species selectively retains highly unsaturated fatty acids (ARA and DHA) and seems to adapt well to a low dietary supply of these FAs. At the end of the growth out experiment fish fed VO50 diet showed a similar n − 3 HUFA profile to the CTRL fed fish. Total FO substitution resulted in a strong reduction of muscle EPA content that was totally recovered after 26 days of re-feeding with a FO based diet. Despite the observed changes in fatty acid composition, sole fillets from fish fed 100% VO are very well accepted by fish consumers and still are good nutritional value end-products for human consumption, providing 1.5 times the RDI level (0.4 g per 100 g of muscle) of EPA + DHA.