Establishing the optimum dietary essential amino acid pattern for silvery‐black porgy (Sparidentex hasta) juveniles by deletion method

A 6‐week feeding trial was conducted to estimate the optimum dietary essential amino acid (EAA) pattern for silvery‐black porgy juvenile based on the AA deletion method. Eleven isonitrogenous and isoenergetic diets were formulated containing 60% of fish meal nitrogen and 40% of crystalline AA nitrogen. In the control diet, the EAA profile was made similar to fish meal protein. Ten other diets were formulated similar to the control diet but replacing 40% of each EAA by a mixture of non‐essential amino acids. Triplicate groups of fish (initial body weight of 4.7 g) were handfed with the experimental diets, three times a day, to visual satiation, for 42 days. At the end of the trial, final body weight of all EAA‐deficient groups was lower than that of control group, ranging from 6.3% of reduction with arginine‐deficient diet to 39.4% of reduction with lysine‐deficient diet, relatively to the control group. Based on the relationship between nitrogen retention and EAA intake of the control and EAA‐deficient diets, the optimal dietary EAA profile for silvery‐black porgy juveniles was estimated to be (g 16/g N): arginine 5.3, lysine 6.0, threonine 5.2, histidine 2.5, isoleucine 4.6, leucine 5.4, methionine + cysteine 4.0 (in a diet containing 0.6 cysteine), phenylalanine + tyrosine 5.6 (in a diet containing 1.9 tyrosine), tryptophan 1.0 and valine 4.6.