Effects of Varying Levels of High-Protein Distiller's Grains on Growth Performance of Channel Catfish, Ictalurus punctatus, and Post-Extrusion Feed Pellet Characteristics

Channel catfish, Ictalurus punctatus, remains the USA's largest aquaculture industry. However, in recent years, high feed prices have negatively impacted profitability. Production of ethanol as a biofuel has increased dramatically. Companies have modified their processes to enhance ethanol yield and these modified processes also increase the crude protein content of the byproduct. The object of this study was to evaluate this high-protein dried distiller's grains (HP-DDG) for its suitability in catfish diets. A total of 25 full-sibling channel catfish (7.1 +/- 2.3g) were randomly stocked into each of twelve 260-L polyethylene tanks to achieve 25 fish per tank. The control diet was similar to a commercial formulation. Experimental diets contained 20, 40, or 40% HP-DDG with added lysine (1% of total diet). There were three replicate tanks per diet. Fish were fed to apparent satiation twice daily for 9wk. Average harvest weights for fish fed the 40% HP-DDG diet without lysine supplementation (57.0g) were significantly smaller than that for fish fed the control diet (77.7g). Average harvest weights of fish fed 20% HP-DDG (86.8g) were significantly greater than that of fish fed either 40% HP-DDG (57.0g) or 40% HP-DDG+lysine (73.7g). There were no significant differences in feed conversion ratios or survivals among treatments, which overall averaged 1.1 and 99%, respectively. These data indicate that HP-DDG appears to be a suitable ingredient in channel catfish diets up to at least 20% of the total formulation. Data also indicate that inclusion levels of at least 40% HP-DDG are likely limiting in lysine.