Not All DDGS Created Equal

The current boom in U.S. ethanol production means more distiller's dried grains with solubles (DDGS) available for pigs.

In fact, the swine industry is the fastest-growing sector utilizing the feedstuff.

Knowing the nutrient content and amino acid digestibility of the by-product is the biggest challenge to feeding DDGS, according to Jerry Shurson, a University of Minnesota animal scientist who has done much of the research on DDGS for pigs.

High-quality corn DDGS has a metabolizable energy (ME) value equal to corn (Table 1). And, like corn, it is low in lysine relative to crude protein. Threonine is the second-limiting amino acid, and should be monitored when more than 10% corn DDGS is added to swine diets.

Only light-colored, golden sources should be used for pigs, Shurson says. But even among golden corn sources, dryer temperature and length of heating can cause a wide range in digestible lysine.

What distinguishes high-quality corn DDGS from other by-products is fat content and high phosphorus availability, which makes it an attractive, partial replacement for supplemental inorganic phosphorus. About half the savings when feeding DDGS is replacement of dicalcium phosphate, he adds.

Whiskey distilleries produce a different type of DDGS because of the mixture of grains they use. And some products labeled as DDGS are really corn gluten by-products or blends of by-products.

The university offers a web site to assist producers in identifying U.S. corn DDGS sources to nutrient profiles. Obviously, plants that produce the type of DDGS with a nutrient profile and color that matches the feeding application are most desired.

Processes Impact Quality

Several ethanol companies are modifying processes to boost yield and change the end by-product, notes Shurson. The most widely discussed processes involve new enzyme technology to increase the crude protein content of DDGS, remove the germ and/or bran from corn prior to fermentation, and remove the phosphorus prior to producing DDGS. This would not enhance the feeding value for pigs.

Dakota Gold is offering a high-protein DDGS that has 34% more protein than typical Dakota Gold DDGS. The increase is at the expense of fat, a 59% reduction, and phosphorus, a 42% reduction. The proportion of nutrients in the high-protein DDGS is similar to distiller's dried grains (without solubles), Shurson points out. Solubles are what carry fat and phosphorus.

Metabolizable energy estimates provided in nutrient specification sheets for the higher-protein product indicate an energy value that is the same as typical DDGS. This is unlikely, he says. The large reduction in phosphorus content also makes the high protein product less appealing.

Glutenol and corn protein concentrate (CPC) are two other examples of corn-based by-products resulting from a modified ethanol process. These products come post-fermentation, after the germ and primary fiber components are physically removed prior to fermentation. Both are substantially higher in protein than typical DDGS, but lysine and other amino acids are not increased proportionately.

Diet Formulations

Shurson formulated a typical DDGS diet, and diets containing new distiller's by-products, in an effort to compare economic value.

Diets were formulated using different nutrient specifications and amounts of synthetic amino acids. Different diets at a DDGS inclusion rate of 10% affected opportunity cost significantly. A diet using synthetic lysine, methionine and threonine had an opportunity cost of $78/ton, and a diet using synthetic lysine HCL was worth $80/ton due to differences in lysine, sulfur amino acids and threonine levels.

Phosphorus (P) is the third most expensive nutrient in swine diets, and the lower phosphorus content of high-protein DDGS adversely affects its economic value, since more dicalcium phosphate must be added to get the desired level of available P. In fact, using the price for DDGS at $80/ton, and the nutrient content assumptions for high-protein DDGS, one could afford to pay only $51/ton for high-protein DDGS.

CPC and glutenol are higher in crude protein, but estimated energy value and poor protein quality means minimal reductions in corn and soybean meal, compared to adding the same level of DDGS. A slightly higher phosphorus content of CPC compared to DDGS is an economic advantage, but not for glutenol. The economic value or opportunity cost of CPC and glutenol is $61.60/ton and $63.40/ton, respectively, which is much less than typical DDGS, according to Shurson.

If the price is right, swine nutritionist Gregg Sample, of LeRoy, MN, adds DDGS at 10-15% of the diet in the grow-finish phase at Next Generation Pork, an operation that markets over 100,000 pigs.

Sample uses the spreadsheet shown in Figure 1 to determine opportunity cost. When DDGS is cheaper than corn, soybean meal and dicalcium phosphate, they substitute it. Currently, both corn and soybean meal prices are too low to use DDGS, he says.

They also use phytase in all diets, so when DDGS is used, dietary phosphorus is substantially reduced, which in turn reduces phosphorus output in the manure. Most of their DDGS comes from Pro Corn in Preston, MN.

More than 7 million (metric) tonnes (7.7 tons) of distiller's dried grains with solubles were produced in 2005, and some industry experts predict production will reach 10 to 14 million tonnes (11 to 15.4 tons) in three years.

The bottom line: know the source of DDGS. Processes that reduce the fat content of distiller's by-products significantly reduce energy value, which make them more difficult to economically fit into least-cost formulations.

*Acid Detergent Fiber

*Metabolizable Energy