December 5, 2006


US study shows nutrient content of distillers grains can vary



Dried distillers grains with solubles (DDGS), which are by-products of ethanol production, are good low-cost sources of protein and energy for swine but they can have variable nutrient profiles depending on the manufacturer and the type of grain raw material used, an analyst said Monday.


Gerald Shurson, professor of swine nutrition and management at the University of Minnesota in Minneapolis, presented research information on the use of DDGS in swine rations at the National Grain and Feed Association's Country Elevator/Feed Industry conference in Kansas City, Missouri.


Shurson said lighter coloured or "golden" corn DDGS have shown over time in research studies to have higher protein digestibility than do the darker DDGS products. He said the darker products are the result of overheating the materials to a point that results in the protein being "bound," which makes them indigestible.


It is important for livestock producers, feed manufacturers and others who purchase DDGS as feed ingredients to know the nutrient makeup of the products, Shurson said. His data on samples of DDGS taken from 32 different ethanol production sites showed a range in dry matter from 87.3 percent to 92.4 percent, a difference of 5.1 percent from low to high. The crude protein content varied from 28.7 percent to 32.9 percent. Other categories, including lysine and phosphorus, also showed wide variations.


Given that lysine is considered the most important amino acid in swine rations and can be a limiting factor for performance if it is too low, the producer or feed manufacturer needs to know how much lysine is in the DDGS being used to determine how much lysine from other sources needs to be added, he said.


A 2005 study showed that the lysine digestibility coefficient from 10 different producers of golden corn DDGS ranged from 40 percent up to 68 percent, he said.


Other characteristics of DDGS such as particle size also can be quite variable depending on the source, Shurson said. Particle size can affect digestibility and flow of the product from transport vehicles such as trucks and railcars.


Samples of the DDGS need to be taken and analysed in order to blend the DDGS with other feed materials to provide a ration that contains the proper amount of each nutrient.


He said there needs to be more standardisation or consistency of the DDGS products but added that with the development of new products and rapid growth of the ethanol industry, it is likely that there will be even more variability in DDGS and other ethanol by-products in the near term.


For example, there are some new high-protein products called HP DDGS, and while the protein content is higher, the amount of fat is lower, so the overall energy value is less, he said.


Another area that must be monitored, Shurson said, is the mycotoxin content. Mycotoxin levels in the grain used to produce ethanol can be increased in the DDGS by a factor of three, so the grain going in needs to be tested.


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