Productive Results, Oxidative Stress and Contaminant Markers in European Sea Bass: Conventional vs. Organic Feeding

SIMPLE SUMMARY: Over the years, aquaculture moved to organic production given the rising interest of consumers towards healthy and ecologically friendly food. Among the cultured species, European sea bass (Dicentrarchus labrax) is one of the leading farmed fish products in the Mediterranean area and thus one of the most economically important. For these reasons, further investigations on the effects of organic feeding on this species are of primary interest. In the present study, European sea bass were fed two different diets, organic and conventional, and growing performances, oxidative stress, and contaminant markers were determined. Although conventional diet gave the best results in terms of production, groups fed with the organic one also showed a positive growth trend and importantly no negative effects on fish welfare were observed, demonstrating the feasibility of this diet. This work represents an insight into the emerging aquaculture organic production. ABSTRACT: In the present study European sea bass (Dicentrarchus labrax) subjected to two different diets (organic vs. conventional) were evaluated in terms of growing performances, oxidative stress, and contaminant markers. Growing performances were evaluated using biometric measures and condition factor (K), whereas insulin-like growth factor (IGF-I and IGF-II) levels were assessed trough Real-Time PCR analysis. For oxidative stress, immunohistochemical staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE) was performed, whereas total glutathione (GSH) in blood serum was determined by an enzymatic method adapted. Cytochrome P4501A (CYP1A) and melanomacrophage centers (MMCs) were evaluated as contaminant markers trough immunohistochemical and histochemical approaches, respectively. The growing performances showed a positive trend in both groups but a greater productivity in conventional fed fish compared to the organic ones. A significant higher expression of MMCs was observed in organic vs. conventional diet fed fish. Fillet analysis showed a higher MUFA content and a lower PUFAs n-6 content in organically fed sea bass indicating that diets with a content in fatty acids closer to that of wild fish will definitely affect the fatty acid profile of the fish flesh. On the other hand, the diet composition did not seem to affect neither the oxidative stress parameters (GSH, 8-OHdG, HNE) nor the CYP1A expression.