Growth Response and Resistance to Edwardsiella ictaluri of Channel Catfish, Ictalurus punctatus, Fed Diets Containing Distiller’s Dried Grains with Solubles

A study was conducted to examine the effect of dietary levels of distiller’s dried grains with solubles (DDGS) on growth, body composition, hematology, immune response, and resistance of channel catfish, Ictalurus punctatus, to Edwardsiella ictaluri challenge. Five diets containing 0, 10, 20, 30, and 40% DDGS with supplemental lysine (Diets 1–5) as partial replacements of a combination of soybean meal and cornmeal on an equal protein basis were fed to juvenile catfish (13.33 6 0.25 g) for 12 wk. Growth performance and feed utilization efficiency were similar for fish in all treatments. Body lipid and moisture increased and decreased, respectively, in fish feed DDGS-containing diets relative to the control group. Dietary treatment had no effect on red and white blood cell counts. Hemoglobin and hematocrit were significantly higher in fish fed diets containing DDGS than in those fed the control diet. Fish fed 20–40% DDGS diets had increased serum total immunoglobulin, and those fed the 30% DDGS diet had significantly increased antibody titers 21 d following E. ictaluri challenge. Other immune variables evaluated were not affected by dietary treatments. Preliminary results on bacterial challenge showedan increased resistance againstE. ictaluri in fish fedDDGS-containingdiets (Diets 2–5). Feed cost is the single largest expenditure in channel catfish culture operations, and protein is the most expensive component in catfish feeds. Efforts by nutritionists to reduce feed costs have resulted in increased use of alternative plant proteins in diet formulations as replacements of more expensive animal proteins. Soybean meal (SBM), because of its low cost, consistent quality and availability, and high nutritional value, is the most commonly used plant ingredient in fish feeds. Currently, SBM comprises 35 to more than 45% commercial grow-out feeds for catfish (NRC 1993; Robinson and Li 2005). Replacement of SBM with less expensive protein sources would be beneficial in reducing feed costs. Distiller’s dried grains with solubles (DDGS), a corn coproduct obtained after fermentation of corn for ethanol production, is highly palatable to fish and less expensive than SBM and other protein sources on a per unit protein basis. According to Buchheit (2002), approximately 98% of the DDGS in North America is from plants that produced ethanol for fuel, while the remaining 1–2% is produced by the alcohol beverage industry. In 2001, the USA produced about 3.1 million tons of DDGS. As a result of the recent interest in increasing ethanol production for fuels to reduce the shortage and dependency on petroleum-based fuel, the DDGS production in the USA has been estimated to increase to approximately 8 million tons in 2006 (Shurson 2006). Thus, increased and new uses are needed to use these abundant DDGS supplies. DDGS has a relatively high protein content (;30% crude protein) without the presence of antinutritional factors commonly found in most plant protein sources. At present, DDGS is widely used as a protein supplement in terrestrial animal feeds, but its use in fish feed is limited because of its low content of essential amino acids, especially lysine that is only about 40% of that found in SBM (NRC 1993). According to Webster et al. (1995), research to evaluate the nutritional value of DDGS in fish diets began as early as the 1940. More recent research has shown that DDGS is a promising 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 40, No. 2