Total aromatic amino acid requirement of Indian major carp Labeo rohita (Hamilton) fry

An 8-week growth trial was conducted to quantify the total aromatic amino acid (phenylalanine + tyrosine) requirement of Indian major carp Labeo rohita fry (3.5 ± 0.2 cm; 0.18 ± 0.04 g) by feeding isonitrogenous (40% crude protein) and isocaloric (17.90 kJ g− 1 gross energy) amino acid test diets containing casein, gelatin and l-crystalline amino acids with graded levels of phenylalanine (0.40, 0.65, 0.9, 1.15, 1.4 and 1.65% dry diet, with 1% tyrosine fixed in each diet) to apparent satiation in triplicate groups, twice a day at 07.00 and 17.30 h. Specific growth rate (SGR) 2.53%, feed conversion ratio (FCR) 1.41, protein efficiency ratio (PER) 1.77 and body protein deposition (BPD) 33.69 were significantly (P < 0.05) higher in fish fed the diet containing 1.15% phenylalanine. Second-degree polynomial regression analysis of SGR, FCR, PER and BPD data indicated the dietary phenylalanine requirement at 1.21, 1.22, 1.22 and 1.16% of the dry diet, corresponding to 3.02, 3.05, 3.05 and 2.90% of the dietary protein, respectively. On the basis of the quadratic regression analysis of SGR, FCR, PER and BPD data, it is recommended that the inclusion of total aromatic amino acid (phenylalanine + tyrosine) in the range of 2.16% (1.16% phenylalanine + 1.0% tyrosine) of the dry diet, corresponding to 5.40% (2.9% phenylalanine + 2.5% tyrosine) of protein to 2.22% (1.22% phenylalanine + 1.0% tyrosine) of the dry diet, corresponding to 5.55% (3.05% phenylalanine + 2.5% tyrosine) of the dietary protein is essential in developing total aromatic amino acid balanced diets for intensive culture of fry L. rohita.