Essential amino acid balance in channel catfish Ictalurus punctatus diets
Type of DegreeMaster's Thesis
School of Fisheries, Aquaculture, and Aquatic Sciences
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Channel catfish are among the top cultured aquaculture species in the U.S. Protein is an important factor in catfish feeds to allow for proper health and development and accounts for 50%-60% of the total feed cost. Due to the high cost of protein associated with feeds, cheaper alternatives are being explored both through ingredient replacement and the optimization of proteins. This study sought to examine reduced protein diets in channel catfish using a better-balanced amino acid profile and the evaluation of possible limiting amino acids. Towards this goal, a 12-week experimental growth trial was conducted to investigate the effects that dietary protein reduction and amino acid balance have on the growth performance of fingerling channel catfish. A total of nine diets were formulated to contain varying amounts of protein (30% and 24%) and amino acid supplements. In general fish maintained on diets containing 30% (B30) or 24% (B24) protein showed no significant differences in growth. Lysine was confirmed to be the first limiting amino acid in the B24 diet. To further optimize the 24% protein diets, the indispensable amino acid requirements (100%) were raised to 140% to further reduce the amount of dispensable amino acids relative to indispensable. Additionally, for the diets containing 24% protein at 140% of the requirement select amino acids including arginine, tyrosine, isoleucine, tryptophan and threonine were omitted. There was no response to the removal of most of these amino acids; however, the removal of arginine resulted in a significant improvement in growth and feed conversion ratio. Overall, this study found that protein levels in catfish feeds can be reduced to 24% without inhibiting growth or feed utilization. Raising the amino acid requirements to 140% in the 24% protein diets showed no significant difference in growth or protein conversion efficiency when compared to fish fed the 24% protein diet at 100% of the requirement.