Efficacy of High-Protein “Finishing” Diets on Growth, Fattiness, and Processing Yield of Channel Catfish, Ictalurus punctatus

Abstract

Three experiments were conducted to evaluate the use of “finishing” diets in channel catfish, Ictalurus punctatusproduction. Fingerling channel catfish weighing 107, 129, and 103 g for Experiments 1, 2, and 3, respectively, were stocked in 0.04-ha earthen ponds at a rate of 14,820 fish per ha and grown to harvestable size in a single growing season. Four replicate ponds were used for each treatment. In Experiment 1, fish were fed either a 28%- or 32%-protein diet for the entire growing season (controls), or fed the 28%- and 32%-protein diets for part of the growing season and then switched to a 36%-protein “finishing” diet either 30 days or 60 days before harvest. In Experiment 2, fish were fed either a 24%- or 32%-protein diet for the entire growing season (controls), or fed a 24%-protein diet for part of the growing season and then switched to a 32%- or a 35%-protein “finishing” diet for either 30 days or 45 days before harvest. In Experiment 3, fish were fed either a 28%-protein diet for the entire growing season or a 28%-protein diet for part of the growing season, and then switched to a 35%-protein “finishing” diet for either 30, 45, or 60 days before harvest. The data show that a 24%-protein diet is sufficient for maximum growth and feed efficiency of catfish but processing yield is reduced. Further, it appears that feeding fish a 24%-protein diet for most of the growing season and then changing to a 32%- or 35%-protein “finishing” diet for 30 days before harvest, improves carcass yield. Fillet yield also appeared to be improved, but the improvement was slight. The data did not show that “finishing” fish fed a 28%-protein diet on higher protein diets was beneficial in improving processing yield. However, evaluating pooled data from across all of our previous studies, there does appear to be about a 0.4% to 0.5% decrease in processing yield of fish fed a 28%-protein diet. Presently, we do not recommend the use of “finishing” diets, because available data are not consistent, and their benefit is questionable. Also, because of various factors (such as off flavor), one cannot predict with certainty when fish will be harvested.