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

Abstract

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.