Arginine and phenylalanine requirement of juvenile silver perch Bidyanus bidyanus and validation of the use of body amino acid composition for estimating individual amino acid requirements
1999
Ngamsnae, P. | De Silva, S.S. | Gunasekera, R.M.
An experiment was conducted in a closed system to quantify the arginine requirement of juvenile silver perch Bidyanus bidyanus. Five experimental diets were formulated to contain 40% crude protein with five graded levels of arginine. The diets contained casein and gelatine as protein sources supplemented with crystalline L-amino acids to simulate the reference amino acid profile (except for arginine) of silver perch tissue protein. The experiment lasted 12 weeks and, based on growth data using broken-line analysis, the arginine requirement of juvenile silver perch was found to be 2.7 g 100 g-1 dry diet (or 6.8% of protein). Based on whole-body amino acid composition, A/E ratios (essential amino acid/total essential amino acids + (cystine + tyrosine) X 1000) were estimated. Using the experimentally determined requirement for arginine and A/E ratios, the phenylalanine requirement of silver perch was predicted to be 5.5 g 100 g-1 protein. Another feeding trial was conducted to determine the phenylalanine requirement of silver perch using a series of diets with various amounts of phenylalanine and a protocol similar to the previous one. It was found that the experimentally determined phenylalanine requirement of juvenile perch was similar to that predicted. The A/E ratios have been hitherto utilized for the estimation of essential amino acid requirements in three salmonids, common carp and channel catfish: the present findings extend the validity of the method to other fish species.
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