In this interview with Engormix, Kurt Rosentrater, Associate Professor at Iowa State University and Executive Director at the Distillers Grains Technology Council, answered questions about several important factors to take into account when using DDGS as a feed ingredient.
Rosentrater deals with these topics and more on the recently released fifth edition of the book Kent’s Technology of Cereals: An Introduction for Students of Food Science and Agriculture. This edition has been thoroughly updated with new sections, including extrusion cooking and the use of cereals for animal feed. In addition, it offers information on statistics, new products, the impact of climate changes and genetics, new economic trends, nutrition regulations and new technologies.
- What are the main differences between grains that can be used as DDGS: barley, corn, wheat, etc.?
Each type of grain contains different quantities and types of starch, which impact fermentability into ethanol. Additionally, each grain contains different levels of proteins and other nutrients, which ultimately will impact the nutrient contents in the DDGS.
- What can you tell us about color as an indicator of quality in DDGS?
DDGS color will certainly be impacted by the type of grain used for fermentation. Corn will result in a bright yellow DDGS; wheat and barley will result in darker DDGS.
But, color is a good indicator of quality over time at a single plant which uses a single type of grain. For example, if the DDGS at your ethanol plant suddenly changes color (i.e., becomes darker) or suddenly black spots appear in your DDGS, this is a sign that something has changed in your processing conditions at your ethanol plant, and must be fixed or adjusted right away.
- Recommendations you can give to guarantee the quality of the final product.
Each coproduct should be sold with a guaranteed nutrient profile. Although the composition of DDGS may vary from ethanol plant to ethanol plant, variability at each plant is quite low over time. So it is important that livestock producers work with ethanol plants and understand the guaranteed analysis of the DDGS that they are purchasing.
- What is the advantage of pelleting in DDGS?
Pelleting of DDGS can result in much better product flowability and much higher bulk density (up to 20% increase). These are both great advantages for livestock producers.
- What is a good percentage of protein content in DDGS?
In the U.S., protein levels in DDGS are commonly about 30% (dry basis). They are often a little higher in DWG (on a dry basis). These protein levels are a little higher than they used to be years ago, due to improved processing efficiencies. There are some ethanol plants who are installing new technologies to produce coproducts with protein levels greater than 40%, 50% or even 60%.
- Which contaminants can be found at DDGS and how to best prevent them?
The most important contaminants for grain-based products are mycotoxins. It is important for ethanol plants to screen incoming grain for mycotoxins, and to reject loads of grain that are above threshold levels. If ethanol plants do this, then the DDGS and DWG should be free of mycotoxins. It is also important for livestock producers to understand what is the mycotoxin levels in the coproducts that they purchase from ethanol plants.