Combined effects of dietary n-3 long-chain polyunsaturated fatty acid levels and saturated to monounsaturated fatty acid ratios on growth, fillet composition and blood parameters of European sea bass, Dicentrarchus labrax L.

The aim of this study was the assessment of the combined effects of different dietary n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) levels and saturated (SFA) to monounsaturated fatty acid (MUFA) ratios on European sea bass growth, fillet composition and blood parameters. Two levels of n-3 LC-PUFAwere selected (low at 5% and medium at 7% total identified fatty acids). Within each level, three SFA to MUFA ratios (0.4, 0.6 and 0.9) were achieved by adding alternative lipid source mixtures. A 251-day experimental rearing took place, followed by a 99-day finisher-diet period. From day 188 until day 350, the control group displayed superior growth, with no significant differences among the remaining treatments. Finisher period partially restored fillet fatty acid profile, resulting in an n-3/n-6 ratio > 1. Fish fed on diets L0.4 and L0.6 demonstrated relatively low feed conversion ratio, plasma glucose and liver lipid levels. These diets may be viable selections, when followed by a finisher diet and contribute to fish welfare and quality. In conclusion, for long-term sea bass rearing using diets with fish oil substitution, the interactions among fatty acid groups, seem to regulate growth performance more effectively than their sheer contribution to the fatty acid profile.