Assessment of different dietary soybean meals and corn fermented protein in practical diets for fingerling channel catfish.

One of the most common difficulties for the aquaculture industry is the farmers' demand for low-cost feeds, which may result in reduced performance of the culture species. This study aimed to evaluate the potential of replacing solvent-extracted soybean meal, one of the primary low-cost protein sources in a practical catfish feeds with improved plant-based proteins. Four open feed formulations were tested which included: basal diet (32 % protein, 6 % lipid) contained 56.4 % soybean meal (SBM); basal modified to include 10 % of a corn-fermented protein (CFP) from the ethanol industry (Basal-CFP); the complete replacement of SBM with either enzyme-treated soybean meal (43 % inclusion, Basal-ET) or low oligosaccharide soybean meal (45 % inclusion, Basal-LO). Diets were evaluated under controlled indoor aquaria conditions (12-weeks) and under production condition over a 70-day culture period using in-pond raceways. Channel catfish reared in aquaria were offered the four test diets as well as a commercial catfish feed. In this trial, catfish demonstrated significantly better growth and fcr when fed the Basal-LO and Basal CFP diets indicating that commercial feed formulations can be improved. In both trials, channel catfish offered the Basal-LO and Basal-CFP diets generally did better than those reared on the Basal diet. Blood parameters were measured in both trials with limited differences in hematology. Gene expression analysis of the liver of fish reared under controlled conditions showed decreased hepatic hexokinase expression in the Basal-LO group and increased intestinal cholecystokinin expression in all diet groups compared to the control. This indicates metabolic alteration of appetite in fish in response to changes in the feed ingredients. These results suggest that newer soybean variants may be beneficial in improving the growth performance of channel catfish. Thus warranting continued work on improved ingredients in practical feed formulations for channel catfish. • Commercial feed formulations have the potential to be improved. • Low Oligosaccharide soybean meal produces improved performance in fingerling catfish. • Corn fermented protein works synergistically with soybean meal. • Enzyme modified soybean meal is an acceptable replacement for SE soybean meal.