Dietary Natural Plant Extracts Modulate Growth Performance and Antioxidant Status of Senegalese Sole Postlarvae

Abstract

Oxidative stress has a direct impact on fish production, affecting both growth and health status. Plant based extracts, such as those from green tea, curcumin and grape seeds, are known for their abundant content and diversity of polyphenols. These bioactive compounds have a high antioxidant capacity making such extracts good additives to include in fish diets potentially improving the oxidative status of fish, and therefore enhancing growth and stress resistance of farmed fish. A growth trial with Senegalese sole postlarvae (45 DAH) fed with four experimental diets, a control (CTRL) and three supplemented with natural antioxidants, namely curcumin (CC), green tea (GT) and grape seed (GS) extracts, was performed during 25 days to check if these supplements could improve growth performance and fish oxidative status. Moreover, a thermal stress was applied at the end of the growth trial, to assess the effect of these supplemented diets in stress resistance of sole juveniles.Sole growth was improved by the dietary inclusion of CC and GS compared to CTRL. Juveniles from CC and CTRL present the lowest values of oxidative damage (lipid peroxidation (LPO) and protein carbonylation (PC)). Moreover, the fish fed CC showed a decrease in stress related biomarkers (heat shock protein 70 (HSP70) and glutathione-S-transferase (GST)) compare to CTRL, which might be due to direct antioxidant capacity. In contrast the supplementation of GT and GS increased the content of oxidative damage in sole reared in standard conditions. However, after a thermal stress exposure both GT and GS treatment seem to prevent the increase of PC and decrease of antioxidant glutathione (GSH) in sole and depending on the time of exposure. In conclusion, dietary supplementation with these natural extracts modulates oxidative status and stress response after a short/long term temperature increase. The incorporation of curcumin seems to be a safe additive to include in sole diets, enhancing growth and oxidative status. The supplementation of the studied doses of green tea and grape seed extracts in fish diets needs further research as they may act as pro-oxidant depending of the culture conditions.