Development of a semipurified test diet for determining amino acid requirements of Florida pompano Trachinotus carolinus reared under low-salinity conditions

•Pompano can utilize crystalline amino acids.•Coating amino acids prior to dietary incorporation may improve nitrogen retention.•A suitable test diet for determining amino acid requirements was developed.•An ideal reference protein profile for utilization as an A/E ratio was established.

Two trials were conducted to develop a semipurified test diet for determining indispensable amino acid (IAA) requirements for Florida pompano Trachinotus carolinus. The objective of the first trial was to evaluate casein and corn gluten meal as principal intact protein sources, and the ability of Florida pompano to utilize l-crystalline amino acids in the diet. Eight isonitrogenous (42% crude protein) and isoenergetic (22.0 kJ/kg) diets were formulated. A 2 × 4 factorial was employed to evaluate the two intact proteins, each with four amino acid profiles that mimicked the ratio of IAA in pompano whole body, pompano unfertilized eggs, menhaden fish meal, or unsupplemented negative control. Growth and efficiency were significantly better (P < 0.05) for each of the IAA profiles with the casein-based diets.The objective of the second trial was to re-evaluate the same IAA profiles in 46% crude protein and 22.0 kJ/kg casein-based diets to evaluate their performance relative to each other and to a practical type fish meal-based control diet. Growth and feed conversion were significantly better (P < 0.05) in pompano fed the diet supplemented to mimic the ratio of the pompano whole body IAA profile than the other test diets, but not different from the control where they were 94% and 98% of the control diet, respectively. Significantly better growth and efficiency in fish fed the whole body IAA profile diet than the unsupplemented diet suggest that the crystalline amino acids were well utilized. However, a significantly lower (P < 0.05) protein productive value in fish fed the whole body IAA profile diet relative to the fish meal control suggests pompano may benefit from coating the amino acids prior to dietary inclusion, or more frequent feedings. A test diet incorporating casein at 200 g/kg dry diet and supplemented with crystalline amino acids to mimic the IAA ratio of the Florida pompano whole body is suitable for evaluating Florida pompano amino acid requirements.