Distillers Dried Grains with Solubles as an Alternative Protein Source in Fish Feeds

Distillers dried grains with solubles (DDGS), a co-product of the dry-mill ethanol industry, are the dried residue that remains after the fermentation of corn (or other grains) mash by selected yeasts and enzymes to produce ethanol and carbon dioxide. The nutrient composition of DDGS varies depending on the source of grain and the methods used for ethanol and DDGS production. Generally, corn DDGS contains approximately 29% crude protein, 10% fat, 9% crude fiber and 5% ash. Based on the essential amino acid (EAA) composition, distillers grain products (DGP) from various grain sources are deficient in a few EAA for most fish species, notably in lysine and methionine but does not contain antinutritional factors found in most other plant protein sources. At present, DGP are mainly used in terrestrial animal feeds, and its use in fish feeds is limited. Optimum inclusion levels of DDGS in fish diets appeared to vary depending on the type of ingredient substituted and levels of other protein source, especially fish meal, present in the diets. However, results of previous research have shown that corn DDGS is a promising ingredient for aquaculture diets. A level of 20 to 40% DDGS has been successfully used in channel catfish and tilapia diets. In trout diets, a level of 15% has been suggested. However, inclusion levels of dietary DDGS can be increased by supplementation of limiting EAA such as lysine.