Taurine requirement for juvenile white seabass (Atractoscion nobilis) fed soy-based diets

• Two growth trials were conducted with diets containing graded taurine levels.
• Cystine supplementation did not result in an improvement in growth.
• This suggests that cysteine decarboxylation is inadequate in this species.
• Taurine requirement was estimated at 0.99% of the diet.

Two growth trials were designed to evaluate varying levels of taurine in diets for white seabass (WSB), Atractoscion nobilis. All diets were formulated to contain 40% protein and 10% lipid with a fixed level of fish meal (FM) and soybean meal (SBM). Trial A tested a series of six practical diets with 0.0, 0.1, 0.2, 0.3, 0.4, 0.5% taurine supplementation at the expense of glutamic acid, and a seventh diet with 0.5% cystine supplementation instead of taurine. Trial B was designed to test higher inclusion levels (0.2–1.6%) of taurine over six diets, while a seventh diet contained 1.6% taurine but no methionine supplement. In Trial A, the increased inclusion of taurine resulted in significantly improved final weight ranging from 14.6 to 26.6 g, TGC ranging from 0.074 to 0.120, and feed efficiency from 68.2 to 111.9%. The supplementation of cystine to the diet did not result in an improvement in growth, indicating the synthesis of taurine from cysteine decarboxylation is inadequate in WSB. Similarly, in Trial B significant improvements in performance were observed with increasing taurine supplements, albeit variation in the data was higher. Final weight ranged from 23.6 to 29.7 g, TGC ranging from 0.111 to 0.130 and feed efficiency from 75.6 to 81.4%. The diet with taurine supplement but without methionine showed a decrease in growth, suggesting that methionine was then limiting. Datasets from both trials were combined, and a saturation kinetics model was used to determine a dietary requirement of 0.99% of the diet (R2 = 0.8770). Based on these results, white seabass have a dietary requirement for taurine presumably due to a limited ability to synthesize it.