Twenty suspended l-m3 cages were each stocked with 300 five- to six-inch channel catfish fingerlings to allow for the evaluation of five feeding regimens, each replicated four times. The experiment began April 15 and terminated October 21, providing for a 180-day feeding period. The daily feeding rate was 4% of biomass initially and decreased to 1.5% of biomass during the latter phase of the feeding trial. The experimental feeds were nutritionally complete, low-fiber, expanded (nonsinking) 3/ 16-inch diameter pellets. Treatments (diets) I through 3 contained protein levels of 40,35, and 30%, with 38% of the protein in each diet coming from fishmeal and the remainder from plant sources. Diet 4 was designed to contain the same theoretical amino acid composition as diet I with only 17.5% of the protein coming from fishmeal and the deficient amino acids supplemented in isolated form. The fifth feeding regimen was feeding the 40% protein diet until the fish reached 0.5 Ib then feeding the 30% protein diet for the remainder of the period. Mean responses to treatments I through 5, respectively, were as follows: weight gain per fish (Ib), 1.31, 1.28, 1.24,0.97 and 1.25; feed conversion ratio, 1.26, 1.26, 1.29, 1.36 and 1.31. Based upon diet ingredient costs treatment 3 effected the least cost per pound of gain, followed by treatments 2,5,4, and I, respectively.
