The control diet was formulated to be representative of commercial feeds typically used for gibel carp in southern China (without amino acids supplementation) [Gibel carp feed No. XII from Haid Com., Ltd (Guangzhou, China)]. The test diets were supplemented with a combination of L-lysine·H2SO4 and DL-methionine hydroxy analogue calcium (MHA-Ca) to match the EAA profile of the control diet, respectively. The formulation and composition of the test diets were presented in Table 3, and the EAA composition of the diets and juvenile gibel carp carcass (without viscera) was
shown in Table 4. The EAA content of these diets was similar to the control. The essential amino acid (A/E) ratio of the experimental diets and juvenile gibel carp (initial body weight 13.5 g fish−1) carcass was presented in Table 5