Comparison of essential amino acid requirements with A/E ratio among fish species

So far, the dietary requirements of the ten amino acids arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have been proved in fish and the quantitative requirements have been determined in several fishes. However, each essential amino acid requirement determined by different laboratories does not correspond with each other, not only among species but also even within species, because of the differences of experimental conditions. Therefore, some researchers have applied a new method based on the idea that there should be a correlation between whole body amino acid pattern and the dietary amino acid requirement: i.e., only one amino acid requirement is determined by growth data and the other nine are estimated as being proportional to the whole body amino acid pattern. There would be little difference in the patterns of requirement by this new method among species, because body amino acid patterns are almost identical among species. On the other hand, when the A/E ratios of amino acid requirements based on growth assay are compared, close similarities were noted between carp and catla in the family Cyprinidae, and among chinook salmon, chum salmon and coho salmon in the family Salmonidae, suggesting the existence of specificity in requirements among fish species or family.