Heat pretreatment can be an attractive method of improving the digestibility of whole stillage, and hence DDGS, for pigs because heat pretreatment is cheap.
By Casey Zangaro and Tofuko Woyengo, South Dakota State University Department of Animal Science, Rob Patterson, Canadian Bio-Systems Inc.; and William Gibbons, South Dakota State University Department of Biology & Microbiology
Corn distiller’s dried grains with solubles is one of the most widely used feedstuff in formulating swine diets. Corn DDGS has a higher content of amino acids than corn, however, it also has a high fiber content. Since pigs digest fiber poorly, the use of dietary fiber degrading enzymes has been shown to alleviate the negative effects of dietary fiber. However, the use of exogenous enzyme supplementation has been variable with respect to improving the digestibility of DDGS for pigs.
Pretreatment of whole stillage (slurry material that remains after ethanol extraction from grain, and which is dried into DDGS) with heat, diluted acids or alkalis may improve the nutritive value of DDGS by disrupting fiber structures, thereby increasing the susceptibility of said fiber fraction to subsequent enzymatic hydrolysis. Thus, the pretreatment of WS instead of DDGS could be an attractive technology for improving the nutritive value of DDGS as this technology can be integrated into currently existing corn ethanol production facilities with minimal cost.
Recent research at South Dakota State University looked at the effect of pretreating WS with heat, diluted acids or alkalis; and of predigesting the untreated and pretreated WS with a blend of fiber-degrading enzymes (multi-enzyme) on digestion and fermentation characteristics of the WS using an in vitro (laboratory) porcine method that simulates digestion and fermentation of feed within the gastrointestinal tract of pigs.
The WS was obtained from a local ethanol plant. A portion of the WS was pretreated with heat, diluted citric acid, diluted sulfuric acid or diluted ammonia at 160 degrees C and 70 psi for 20 minutes. Half amounts of untreated and pretreated WS were predigested with multi-enzyme (1%) at 38 degrees C for 24 hours. The multi-enzyme used was from Canadian Bio-Systems Inc. in Calgary, Alberta, Canada, and contained a combination of xylanase, glucanase, cellulase, invertase, amylase, mannanase and protease activities. The predigested samples together with untreated sample and pretreated but not predigested samples were subjected to porcine in vitro digestion. Undigested residues were subjected to porcine in vitro fermentation.
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