Re-evaluation of protein and amino acid requirements of rainbow trout ( Oncorhynchus mykiss)

Abstract

Work on protein and amino acid requirements of rainbow trout, previously done at the University of Wisconsin, Aquaculture Research Laboratory, was re-evaluated with the view that the requirements are not much different from those of other rapidly growing farm animals. Most fish species are carnivorous and are adapted to use protein as a preferred energy source over carbohydrate, and thus require high levels of dietary protein (30–60%). Rainbow trout were found to utilize a dispensable amino acid (DAA) mixture or alanine alone as effectively as casein as an energy source. When a DAA mixture was used as a substitute for casein in a diet containing 2% gelatin and casein supplemented with arginine and methionine, the level of dietary protein needed to meet the indispensable amino acid (IDAA) requirements was found to be about 24%. This level is not different from that for baby pigs as recommended by the National Research Council. The levels of IDAA in the 24% protein diet exceeded the IDAA requirements of rainbow trout estimated to date. The estimated requirements (vs the contents in the 24% protein diet) for lysine, sulfur amino acids, tryptophan, aromatic amino acids and arginine were 1.3 (1.9), 0.8 (0.98), 0.2 (0.28), 1.5 (2.5) and 1.4 (1.6)% of diet, respectively. These values are comparable to those recommended for baby pigs except for arginine: 1.4, 0.68, 0.2, 1.1 and 0.6%, respectively. Results indicate that the requirements of rainbow trout for protein and amino acids are not much different from those of other rapidly growing farm animals.