Effects of fish oil substitution by hazelnut oil on growth performance, whole-body fatty acid composition and enzymes of intermediary metabolism of juvenile meagre (Argyrosomus regius Asso, 1801)

The need for new alternative oil sources in the ever-increasing aquaculture of carnivorous species is imperative. We substituted fish oil (FO) with hazelnut oil (HO) in meagre diet at 20, 40, 60, 80 and 100%. Triplicate groups of 40 fish/tank juvenile meagre (ca 15 g) were used. For the reduction of FO level in meagre diet, a 40% substitution by HO is attainable without affecting growth performance. However, higher substitutions appear to have a negative effect on growth performance and feed efficiency, although daily feed intake seems to remain unaffected by the reduction in FO. No effects on whole-body protein and lipid concentration were observed for fish fed the experimental diets. Whole-body fatty acid composition reflected the dietary fatty acid composition in all dietary groups. Diets with higher than 40% levels of FO substitution significantly reduce highly unsaturated omega-3 fatty acids in the fish. Although the metabolic relationship between carbohydrate and fatty acid exploitation is extremely versatile, and thus it is difficult to reach a safe conclusion, it seems that FO substitution by HO activates fish carbohydrate, rather than fatty acids, exploitation machinery. These results support the use of HO in meagre diets up to 40% FO substitution with a future thought for more efficient use of 30% FO substitution by HO.