Distillers Dried Grains with Solubles: useful, but not a balanced equine feed

Distillers Dried Grains with Solubles (DDGS) have generated a great deal of interest as a feed ingredient as the ethanol industry has grown in the U.S. DDGS are defined by the American Association of Feed Control Officials (AAFCO) as "The product obtained after the removal of ethyl alcohol by distillation from the yeast fermentation of a grain or grain mixture." DDGS can come from a number of different grains, with corn being the most common in the U.S. Industry estimates suggest that over 22 million tons of DDGS will be produced in 2008 in the U.S. and will be used both domestically and for export as a feed ingredient.

Because of the processing involved, DDGS contain substantially less starch and sugar (Non-Structural Carbohydrates or NSC) than the base or starting grain (corn). Other nutrients may be concentrated as the starch and sugar are removed. Although the remaining nutrients are concentrate, the energy value (DE Mcal/kg) is lower.

Table 1 lists the National Research Council's (NRC) nutritional values for Corn and Corn DDGS expressed on a dry matter basis. What the NRC and Table 1 do not show is the change in the Non-Structural Carbohydrate (NSC) content of the two ingredients or the variability. Equi-Analytical Laboratory data gives average NSC value on a dry matter basis for corn of 73.13% and for DDGS of 10.4%. The large drop in NSC demonstrates the amount of starch and sugar that is fermented to produce alcohol.

Table 1. The NRC nutritional values for Corn and Corn DDGS

Ingredient	DM % (dry matter)	CP % (protein)	Lysine %	DE Mcal/kg	NDF %	Fat %	Ash %	Ca %	P %
Corn	88.1	9.4	0.27	3.88	9.5	4.2	1.5	0.04	0.3
Corn DDGS	90.2	29.7	0.67	2.99	38.8	10.0	5.2	0.22	0.83

Probably the most significant nutritional problem with DDGS is that the Ca:P ratio (recommended ratio for the mature horse is 2:1) is inverted (Table 1). The inverted Ca:P ratio, if not corrected, may contribute to bone development problems, particularly in young animals.

Another challenge with DDGS is the variability of the product in nutrient content and value (Figure 1). Different distiller plants have different processing techniques and different drying systems. The normal range for protein reported by Equi-Analytical is 26 to 34%. Perhaps more importantly, there is a wide range in lysine digestibility depending on the level of heating during drying. There is also a wide range in aroma due to processing techniques.

Figure 1. Color variation in Corn DGGS

DDGS can be used effectively as an ingredient in horse feeds and in a wide range of livestock feeds to deliver balanced diets (feed companies test each batch of feed and compensate for the variability with additional additives or products). If owners choose to purchase DDGS to feed straight to animals, they need to be aware of the inverted Ca:P ratio, the risk of nutrient variability and the potential presence of mycotoxins (from moldy corn) which may be detrimental to the animals.

By R. Johnson and J. Shelton, PhD, Cargill
University of Minnesota Extension Horse Newsletter

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Distillers Dried Grains with Solubles: useful, but not a balanced equine feed