DDGS: It’s a new generation
Whether you agree with the energy policy or not, a decade of rapid growth in the use of grains for ethanol production has resulted in several new generation dried distillers grain products for livestock feed.
By P.H. Robinson
High crude oil prices and a desire for “energy security” have more countries in the developed world reaching out for renewable fuels. One of those fuels is corn-based ethanol and, although it will not likely exceed 10% of total automobile “gasoline” in most countries in the foreseeable future, it will impact what dairy cows eat in the next decade.
Corn-based dried distillers grain (DDG) products constitute the bulk of distillation process by-products used as livestock feeds in the United States. The fermentation process uses microorganisms to ferment starch (about 67% of the dry weight of corn grain) to create ethanol. The remaining one-third of the corn’s dry weight becomes a corn distillers by-product of some kind.
Distillers grains from the alcohol beverage industry have long been used as cattle feed. However, feed quality was often variable, due to a mixture of grain types (corn, wheat, rye or barley) prior to fermentation to impart desirable flavors. In addition, the value of the distillers grains was so trivial compared to the value of the beverage that distillers placed little emphasis on proper handling and drying. The result: variable coloration (often dark) due to poor control during drying of the wet distillers grains. The over-drying reduced protein and neutral detergent fiber digestibility, which combined make up about 60% of the dry weight of distillers dried grains with solubles (DDGS).
Most modern ethanol manufacturers depend on not only the value of the ethanol, but also the value of spent grains to remain profitable. This, combined with the more consistent feed stock (virtually 100% of ethanol producers use a single grain) and more consistent control during drying creates a much more consistent DDGS product, with a generally higher nutritive livestock feeding value.
Distillers grains: The new generation
With the increased production of ethanol – and the economic need to tailor by-product characteristics to livestock producers – a number of “new generation” corn-based DDGS products have entered the feed market. These new products vary widely by production facility, production process and the quality of the grain used in the fermentation process. However corn-based DDG products generally fall into one of the following categories:
• Conventional DDGS has been available as an animal feed since the advent of the ethanol industry. A by-product of a conventional ethanol production process using ground corn grain cooked prior to fermentation, this product has generally excellent flowability, and bridging is uncommon. Its dry nature also makes it ideal for long-distance transport by rail or ship, minimizing transportation costs per ton of dry matter (DM). Many companies have created branded DDGS products with high quality control.
• An option to DDGS is wet DGS (WDGS), which is theoretically simply the DDGS without the final drying step. WDGS quality control is often erratic, leading to a somewhat more variable product. WDGS has found substantial markets in situations where food animal production facilities are sited near the ethanol facilities, since WDGS has high transportation costs per ton of DM. Its short shelf life means delivery to farms must be a frequent to prevent spoilage and excess DM losses.
• High protein distillers dried grains (HPDDGS) result when the corn goes through a preliminary process before fermentation, removing much of the seed coat fiber, and continuous grinding to remove corn germ. The resulting DDG has a much higher level of protein, due to lower levels of fiber and fat. In contrast to DDGS, where the solubles are blended with the wet fermentation residue prior to drying, this process blends the solubles with the corn fiber removed in the preliminary step. It creates a fiber/solubles product which is generally sold locally as a wet feedstuff, or dried and pelleted for shipment to markets further away. Overall, HPDDGS has a chemical profile much closer to competing protein meals (especially solvent extracted canola meal) than does DDGS, and it is generally classed as a protein meal.
• Low fat distillers dried grains (LFDDGS) are attractive to dairy producers already feeding high levels of unsaturated oils in lactation diets, which can suppress milk fat synthesis. The corn undergoes a pre-fermentation grinding process to remove much of the corn germ. The resulting DDG has a much lower level of fat, about half that of DDGS, but levels of other nutrients are minimally impacted. In contrast to HPDDGS, where the solubles are not blended with the wet fermentation residue prior to drying, this process blends the solubles with the wet fermentation residue.
Next time: DDG product nutrient profiles and variability will be examined.
• P.H. Robinson is a Cooperative Extension Specialist responsible for dairy cattle nutrition and nutritional management. He can be reached via phone: 530-754-7565; email: email@example.com or visit http://