Effects of dietary taurine supplementation to a casein-based diet on growth performance and taurine distribution in two sizes of juvenile turbot (Scophthalmus maximus L.)

Feeding trials were conducted to investigate the effects of dietary taurine on feeding, growth, feed utilization and taurine distribution in tissues of juvenile turbot (Scophthalmus maximus L.) with initial average weight of 6.3 ± 0.01 g (Trial 1) and 165.9 ± 5.01 g (Trial 2). The basal diet was supplemented with 0.0% (control), 0.5%, 1.0% and 1.5% taurine to formulate four isonitrogenous and isolipidic diets (Diet 1 (0.0%), Diet 2 (0.5%), Diet 3 (1.0%) and Diet 4 (1.5%)). The analyzed taurine concentrations were 0.16%, 0.64%, 1.15%, 1.66%, respectively. Each diet was randomly assigned to triplicate groups of 30 fish (6.3 g) in 200 L tank and 15 fish (165.9 g) in 500 L tank. Fish were fed twice daily (06:30 and 18:30) to apparent satiation for 10 weeks. With the increase of dietary taurine, growth, feed efficiency ratio (FER) in fish with initial body weight of 6.3 g first increased (0.0% to 1.0%) (P = 0.000, P = 0.000) and thereafter reached a plateau, while growth in fish with initial body weight of 165.9 g first increased (0.0% to 0.5%) (P = 0.006) and then gradually decreased. Feed intake (FI) in fish with both body weights (6.3 g; 165.9 g) increased with increasing dietary taurine (P = 0.000; P = 0.001) and thereafter gradually declined. With increasing dietary taurine, crude protein contents in fish of both body weights increased (P = 0.049; P = 0.000) and then reached a plateau, while the crude lipid content in fish with 165.9 g weight increased with increasing dietary taurine (P = 0.000). The contents of taurine in body, muscle, eye, liver and brain of turbot were correlated with consumed taurine, and the correlated coefficients in fish with 6.3 g body weight were separately 0.955 (P = 0.000), 0.945 (P = 0.000), 0.881 (P = 0.001), 0.947 (P = 0.000) and 0.924 (P = 0.002) while those fish with 165.9 g body weight were 0.967 (P = 0.000), 0.964 (P = 0.000), 0.977 (P = 0.000), 0.946 (P = 0.000) and 0.997 (P = 0.000). This result suggested that 1.0% taurine in diet of turbot with 6.3 ± 0.01 g weight and 0.5% taurine in diet of turbot with 165.9 ± 5.01 g weight are probably optimal.

► Dietary 1.0% taurine was optimal for growth of turbot with 6.3 g initial weight.
► Dietary 0.5% taurine was optimal for growth of turbot with 165.9 g initial weight.
► Dietary high taurine inclusion had inhibitory effects on turbot.
► Consumed taurine was well correlated with taurine in body and tissues.