Ethanol Plants and Distillers Grains: How Will This Impact Nutrient Management?

Feeding distiller's grains to dairy cattle is nothing new. This ingredient has been included at levels of 25-35 percent in grain mixes and up to 10 percent of the total ration dry matter for as long as rations have been formulated. So why is there renewed interest in distiller's grains?

Background:
According to the National Corn Growers Association, the continued rapid expansion of the ethanol industry in the United States will mean increased volume of distiller's grains. In 1999, 1.47 billion gallons of ethanol was produced compared to 3.41 billion in 2004, and 4 billion in 2005. During the 2004/2005 crop year, 1.325 billion bushels of corn went to ethanol production and approximately 1.5 billion bushels of corn will be used in the 2005/2006 crop year. As a result the byproduct of ethanol production, distiller's grain, has gone from 7.3 million tons produced in 2004, to 8.89 million tons in 2005/2006 with an expected production of 10 millions tons in 2006/2007. The first question: What is going to happen to the increasing volume of distiller's grain produced?

New generation of distiller's grains (NGDG):
With advancing technology, today's ethanol plants are producing a slightly different product compared to previous analyses reported in the 1989 and 2001 NRC Nutrient Requirements of Dairy Cattle. The average crude protein of NGDG is around 30 percent with a range between 27 to 35 percent on a dry matter basis. Recent research on NGDG shows rumen undegradable protein higher (63.5 percent to 78 percent of crude protein) compared to previous reports of 47 percent to 57 percent of crude protein. The fiber fractions in NGDG can be quite variable and they tend to be lower compared to values reported in the 1989 and 2001 NRC. Based on recent research, the neutral detergent fiber value is on the low end of the range (27 percent on a dry matter basis) compared to the NRC values of 39 percent to 44 percent. Other nutrients that should be evaluated with NGDG are fat and phosphorus. Distiller's grains contain high levels of unsaturated oil and fat can range from 10-15 percent on a dry matter basis. The range for phosphorus can be 0.65 to 0.95 percent on a dry matter basis. Another difference with advancing technology in ethanol plants, is improving the complete fermentation of starch. NGDG contain 5 percent or less starch compared to earlier analyses of 10 to 15 percent on a dry matter basis. The analyses of NGDG can vary substantially among ethanol plants. The second question: What affect will NGDG have on precision feeding?

Nutrient Management Considerations (Precision Feeding):
The dairy industry has made significant improvements in lowering phosphorus content in dairy rations and recently, working on fine-tuning nitrogen intakes to help improve water and air quality. With the increased volume of distiller's grains on the market (question 1), the logical assumption is that it will go to livestock feeding. There have been several research papers evaluating feeding 20 to 25 percent of the ration dry matter with distiller's grain for lactating dairy cows. This equates to 10 to 13 pounds of dried distiller's grain per cow daily. This is very different from the 4 to 5 pounds commonly fed. Add to the volume of distiller's grain fed, the higher level of protein and phosphorus along with the variability in nutrients, the potential to over feed phosphorus and nitrogen is great (question 2). There is also the issue of feeding high levels of fat and rumen undegradable protein and the effect on production and components.

If the industry moves towards feeding higher levels of distiller's grains, the issue is not only excess nutrients fed and excreted, but the impact on production and components. Before higher inclusion levels of NGDG are even considered, pay attention to ration costs (best cost ration vs. least cost), potential impacts on animal performance and profitability, and don't overlook the environmental impact. Constant attention to regular feed analysis will be critical with the NGDG. There is a lot to consider before incorporating NGDG into rations, especially at the higher inclusion levels.

References:

Distiller's Grain Feeding Recommendations for Beef, Dairy, Swine and Poultry. 2006. Compiled by the National Corn Grower's Association. www.ncga.com
Using Distillers Grains in Dairy Cattle Diets. 2006. Penn State Dairy Cattle Nutrition Workshop Proceedings. Pg 79. http://www.das.psu.edu/dairynutrition/education/workshop2006/

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Virginia A. Ishler, Extension Associate, Nutrient Management and Penn State Dairy Unit Manager

Penn State Dairy Alliance, a Penn State Cooperative Extension Initiative