2.2. Experimental diets
Four isonitrogenous and isoenergetic (52% crude protein and 11% lipid) experimental diets with high levels of plant protein (only 15% fish meal in the basal diet) were formulated, differing in the supplementation levels of FPH and fish meal (Table 1). The experimental diets were
prepared containing graded levels of FPH (0, 3.1%, 6.2% and 12.4%),meanwhile the fish meal was replaced correspondingly by 0% (Diet FPH-0, control), 5% (Diet FPH-5), 10% (Diet FPH-10) and 20% (Diet FPH-20) of total dietary protein, respectively. The amino acid compositions of the experimental diets were presented in Table 2. The fatty acid composition was constant among the experimental diets (full data not shown).