Is a taurine supplement necessary in fishmeal-based feeds for juvenile European sea bass (Dicentrarchus labrax)?

The effect of taurine supplementation of fishmeal-based feeds for juvenile European sea bass ( Dicentrarchus labrax ) was investigated. Fish (initial weight ca. 5 g) were reared for 90 days in 12 concrete tanks (1 m 3 ), with 50 fish in each tank. Four feeds (44% crude protein (CP) and 17% lipids (L)) containing 0 (control (CTRL)), 0.4 (T4), 0.7 (T7) and 1.0 (T10) % taurine were prepared and were fed to apparent visual satiation to triplicate groups of fish. The effects on fish growth, feed utilization, proximate chemical composition, haematology, immune biomarkers and muscle morphometry were examined. An increase in the dietary taurine incorporation resulted in progressive increases in the growth metrics, with the highest values being observed for fish receiving the T10 feed (weight gain 22 vs 18 g/fish in CTRL; protein productive value 31 vs 28% in CTRL). Taurine addition at all levels significantly increased the fish protein percentage, but the percentage lipid was reduced significantly in T4 fish only (7.8% compared with 9.4% in CTRL fish). Taurine supplementation resulted in elevated blood lymphocyte and monocyte counts and increased serum phagocytic and lysozyme activities. Taurine addition at 1% (T10 feed), the suggested level to boost growth, altered the dorsal muscle cellularity and myofibril ultrastructure, suggesting enhanced muscle function and firmness in comparison with that of the fish given the CTRL feed.