Replacement of Soybean Meal in Channel Catfish, Ictalurus punctatus, Diets with Cottonseed Meal and Distiller’s Dried Grains with Solubles

Two pond experiments were conducted to evaluate cottonseed meal (CSM), distiller’s dried grains with solubles (DDGS), and supplemental lysine as replacements for soybean meal (SBM) in channel catfish diets. In Experiment 1, fish fed diets in which SBM was totally replaced with CSM gained similar weight as fish fed control diet, but fish fed CSM diet in Experiment 2 had 9.5% lower weight gain than fish fed control diet. In both experiments, feed conversion increased significantly for fish fed CSM diet. There were no consistent trends in body composition of fish fed CSM diet versus control diet. Fish fed the DDGS + SMB diet had higher (Experiment 1) or similar (Experiment 2) weight gain than fish fed control diet. Feed conversion ratio was significantly lower in both experiments for fish fed SBM + DDGS diet than that of fish fed control diet. Body fat tended to be higher in fish fed SBM + DDGS diet compared to fish fed control diet. It appears that about 50% of SBM can be replaced with CSM + lysine in catfish diets without negatively affecting fish performance. Further, DDGS can be used up to at least 30% when the diet is supplemented with lysine. Channel catfish, Ictalurus punctatus, are typically fed a diet comprised primarily of soybean meal (SBM), corn, and wheat middlings plus a small amount of fish meal, fat, and nutrient supplements (Robinson et al. 2001). Because SBM is a relatively expensive protein source, it would be advantageous to replace all or part of the SBM with more economical protein sources. Two products that we are interested in are cottonseed meal (CSM) and distiller’s dried grains with solubles (DDGS). CSM is a locally available product that is generally priced competitively (on a protein basis) with SBM. It is highly palatable to catfish and can be used at levels of 10–15% or higher if supplemental lysine is used without detrimental effects on fish performance (Robinson and Brent 1989; Robinson 1991; Robinson and Li 1993, 1994a, 1994b; Li and Robinson 2006). Also, the use of CSM is not limited by direct toxic affects of gossypol, a compound present in CSM (Dorsa et al. 1982; Li and Robinson 2006). Rather, the factor limiting the use of high levels of CSM in catfish feeds is lysine. That is, gossypol binds to lysine making part of the total lysine inherent in the seed biologically unavailable; thus, if high levels of CSM are used in catfish diets, supplemental lysine must be used. DDGS, although currently not locally available, may become abundant as ethanol plants come on line as a result of new energy policies and an abundant corn crop in the Southern United States. The product has been successfully used in commercial catfish feeds and experimental diets at levels of 15–30% as a replacement for animal proteins and SBM (Webster et al. 1991; Robinson et al. 2001). DDGS are highly palatable to catfish but contain about 45% of the lysine found in SBM, and therefore, as with CSM, their use at high levels in catfish feeds would require the use of supplemental lysine. Research has shown that all the animal protein in catfish diets can be replaced with SBM, and a portion of the SBM can be replaced by other plant proteins. However, how much of the SBM can be replaced by other plant protein sources is unknown. Therefore, we evaluated a series of diets to replace part or all of the SBM in catfish feeds with CSM and/or DDGS along with supplemental lysine. 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 39, No. 4