Distillers' grains is one of the main co-products of the dry milling process in which corn starch is extracted to produce ethanol. Because starch makes up approximately 67 percent of the kernel, the remaining nutrients: corn bran, oil and protein, and minerals, are concentrated at three times the amount found in corn.
Therefore, distillers'grains is an excellent source of protein and energy (Table 1), although phosphorus, and other elements such as sulfur, are also concentrated.
Depending on the region of the country where the ethanol plant is located, nearness to cattle feeding or dairy operations, plants typically offer one of two types of distillers' grains: dry distillers' grains which result from the process of drying the combined streams of distillers' grains and thin stillage to 10 percent moisture content, and wet distillers' grains, which results either from not drying the combined streams (distillers' grains and thin stillage) or drying these streams, and adding back additional thin stillage.
The moisture concentration of wet distillers' grains is from 50 percent (modified wet distillers' grains) to 70 percent (wet distillers' grains). In either case, because thin stillage (also known as corn syrup or condensed distillers' solubles) is added to the distillers' grains (or mash), the end product is collectively known as distillers' grains with solubles (DGS).
Increased ethanol processing capacity in the upper Midwest has led to greater supplies of dry milling co-products than was originally imagined. This boom in ethanol production has brought some opportunities for cattlemen, but opportunities bring on the challenge of ensuring that co-products are fed in a manner consistent with proper nutrition and management practices.
Producers interested in utilizing distillers' grains in beef cattle diets must understand and manage fluctuations in nutrient content of distillers' grains, issues of storage and handling, and diet formulation.
When feeding lactating cows or growing cattle (replacement heifers or backgrounding calves), DGS make excellent choices to substitute corn grain because for every pound of corn displaced by one pound of DGS (dry basis), energy is fully substituted, and 1/3 more protein than feeding corn is added.
Therefore, many lactating and growing cattle diets do not require additional protein supplementation. Under most feeding conditions when using hay as the base forage, from 6 to 7 lb dry DGS (10 percent moisture) or 21 to 24 lb wet DGS (at 70 percent moisture) meet requirements of lactating cows and growing replacement heifers. Similarly, when using corn silage as the base forage, 3 to 5 lb dry DGS (10 percent moisture) or 7 to 16 lb (at 70 percent moisture) meet requirements of lactating cows and growing replacement heifers.
When evaluating the price relationships between corn, soybean meal and dry DGS, the price of dry DGS tracks the price of corn and soybean meal quite closely. This means that in many situations, producers buy dry DGS at prices that are par with corn price on an energy basis.
The par price for dry DGS with corn price on an energy basis can be determined by multiplying the price of corn ($/bu) by a factor of 36. Thus, if corn is selling for $3.50/bu, then the highest price we can pay for dry DGS is $126/ton, when only taking into consideration the energy derived from dry DGS. Remember, there is an additional 1/3 protein added for every lb dry DGS that substitutes corn.
During the late summer and early fall months of the years 2002 through 2006, dry DGS sold at prices that were well below par with corn (as little as 25 times the price of corn). This may be a trend that producers may wish to evaluate every year, and take advantage of an early opportunity to contract or purchase their yearly supply of dry DGS.
Buying wet DGS is a bit trickier because of issues with transporting as much as 70 percent water, and needing to find suitable long-term storage methods. Typically, wet DGS have a shelf-life of fewer than 7 days.
Ensiling wet co-products will help preserve them. However, investments in silo structures or bags need to be evaluated carefully to prevent excessive storage costs that will offset advantages of using co-products. Researchers recommend mixing 15 percent grass hay, 23 percent alfalfa hay or 13 percent wheat straw when filling bags of wet DGS (available at http://www.animalscience.unl.edu/
Silage wedges made within walls made up of large bales may reduce investment; however, mixing up to 40 percent grass hay may be needed to prevent spoilage, and care must be taken to ensure that the wedge is firmly packed. Other authors (Durham, 2001) indicate that wet DGS can be stored by spreading two 50-lb bags of livestock salt on top of the wedge left behind by the semi-trailer as it delivers the load.
Lastly, one of the greatest issues preventing cow-calf or feedlot producers from using DGS may be excessive concentrations of sulfur. Sulfuric acid is used in the process of fermenting corn starch into ethanol to manipulate the quality of the fermentation process. The result is that many DGS sources contain concentrations of sulfur that are greater than three times the amount found in corn (0.36 percent).
At 0.40 percent sulfur in the diet, cattle may be reaching toxic levels that will result in polyoencephalomalacia (“brainers”) or other disruptions of the immune system caused by tying down mineral co-factors such as copper or zinc. Compounding this issue is the fact the in western Minnesota and the Dakotas, concentrations of sulfate in the water may prohibit inclusion of additional sulfur in the diet.
At average concentrations of dry DGS of 0.43 percent, in a lactating cow consuming 6 lb dry DGS and 12 gallons of water, the maximum permissible amount of sulfate in water would be 2,000 ppm (this calculation does not take into account other sulfur sources such as forage, other grains and mineral supplements in the diet).
Therefore, when DGS contain near 1 percent sulfur, the maximum amount of sulfate in the water may be as low as 700 ppm, or producers will be forced to limit the amount of DGS to less than 3 lb (dry basis).