Effect of replacing fish meal with soybean meal and of DL-methionine or lysine supplementation in pelleted diets on growth and nutrient utilization of juvenile golden pompano (Trachinotus ovatus)

The experiment was conducted to determine the effect of dietary DL-methionine addition in fish meal reduction diet for juvenile golden pompano (Trachinotus ovatus). The trial comprises the following of 11 diet treatments. (i) D1 diet as the standard was formulated with fish meal as the main protein source. (ii) D2–D5 diets were formulated to replace fish meal with soybean meal at 60, 120, 180 and 300 g kg−1, respectively, and the amino acid profiles (including methionine and lysine) of D2–D5 were referred to the amino acid profile of D1. (iii) D6-D9 diets were the same as D2–D5, respectively, but without methionine supplementation. (iv) D10 and D11 diets were the same as D3 and D5 diets, respectively, but without lysine supplementation. Each diet was randomly fed to groups of 20 fish (initial average weight about 18 g) per net cage (1.0 × 1.0 × 1.5 m) in triplicate and the feeding experiment lasted for 56 days. Weight gain (WG, %) and final body weight (FBW, g) of fish fed D3 diet were significantly higher than those of fish fed D8 and D9 diets (P   0.05). Feed conversion ratio (FCR) of D3, D4 and D5 diet treatments were significantly lower than that of D11 diet treatment (P   0.05). Whole-body protein contents of fish fed D3–D5 were significantly higher than those of fish fed D7–D9 (P   0.05). In conclusion, the replacement of fish meal by soybean meal could reach 300 g kg−1 without detrimental but profitable effect on growth and survival when enough methionine and lysine were supplemented in the diet; moreover, lysine is not the first-limiting amino acid relative to methionine for juvenile T. ovatus from the present growth and proximate composition results.