What is DDGS?

Each bushel of corn (25.4 kg) fermented in a dry mill ethanol plant will produce approximately 10.2 liters of ethanol, 8.2 kg of carbon dioxide, and 8.2 kg of DDGS. Yellow dent corn is most commonly used to produce ethanol and DDGS because it is an excellent source of readily fermentable starch. Corn contains about 62% starch, 3.8% corn oil, 8.0% protein, and 11.2% fiber, and 15% moisture. Because most of the starch is converted to ethanol during fermentation, the resulting nutrient fractions (protein, oil, fiber) are 2 to 3 times more concentrated in DDGS compared to corn. A few ethanol plants use sorghum, barley, and wheat to make ethanol, and as a result, the nutritional composition of the DDGS produced from these grain sources is different than corn DDGS.

Approximately 40% of US fuel ethanol is produced in dry mills, whereas the other 60% is produced in wet mills (Figures 1 and 2). Because the ethanol production processes are different between dry mills and wet mills, the resulting corn co-products are also nutritionally different. Dry mills produce DDGS, but wet mills produce corn gluten feed, corn gluten meal, and corn germ meal. According to Long (1985), wet milling of yellow dent corn involves its separation into the four major products (dry matter basis): corn starch (67.2 %), corn gluten feed (19.6 %), corn gluten meal (60% protein, 5.7 %), and corn germ (50% corn oil, 7.5 %).

The ethanol beverage industry also produces DDGS (<1% of total DDGS production), but it is often dark in color, tends to be more variable in nutrient content (due to the type and source of grain used), and has lower levels of digestible nutrients than DDGS from ‘new generation’ fuel ethanol plants. Brewer’s dried grain is a co-product of the beer manufacturing industry and consists of the dried residue of barley malt and other grains that have been used to provide maltose and dextrins for fermenting. Use of brewer’s dried grains in monogastric diets is limited due to the relatively high fiber level (18 to 19%). A comparison of the nutrient composition of these grain co-products is shown in Table 1.

The primary nutritional advantages of new generation DDGS compared to corn gluten feed, corn gluten meal, and brewer’s dried grains are the high levels of oil and available phosphorus (Table 1). The DE and ME value of new generation DDGS is significantly higher than corn gluten feed and brewer’s dried grains, comparable to corn, but less than corn gluten meal. Amino acid levels of DDGS are lower than corn gluten meal and corn germ meal, but comparable to corn gluten feed and brewer’s dried grains.

How is ‘new generation’ DDGS different from ‘old generation’ DDGS?

Research conducted at the University of Minnesota has shown that DDGS produced in new generation, modern ethanol plants is higher in digestible and metabolizable energy, higher in digestible amino acids, and higher in available phosphorus than DDGS produced in older, more traditional ethanol plants. Although DDGS contains a significant amount of crude fiber (7 to 8%), it also contains a high amount of crude fat (9 to 10% on an as fed basis), which results in DDGS containing an energy value (DE, 3965 kcal/kg; ME, 3592 kcal/kg) about equal to that found in corn (DE, 3961 kcal/kg; ME, 3843 kcal/kg) on a dry matter basis (Table 2).

Additional studies conducted at the University of Minnesota have shown that the ‘golden’ colored DDGS produced in new generation ethanol plants contains significantly higher levels of amino acids (Table 3). Furthermore, the level of apparent digestible amino acids in new generation DDGS is higher than values from dark colored, ‘old generation’ DDGS and values published in NRC (1998) shown in Table 4.

Perhaps the biggest nutritional advantage of feeding DDGS to swine is its high available phosphorus content. It is well known that corn is relatively low in phosphorus (0.28%), and relative phosphorus availability is also low (14%). However, the phosphorus content of new generation DDGS is 0.89% and the relative availability of phosphorus is increased to 90% after the corn has gone through the fermentation process (Table 5).

Why is there so much interest in feeding DDGS to swine?

One of the hottest topics in the feed industry today involves feeding new generation distiller’s dried grains with solubles (DDGS) to swine. Historically, distiller’s dried grains with solubles (DDGS) have not been used extensively in swine diets. The primary reasons for this limited use include variability in quality and nutrient content among sources, poor amino acid digestibility due to overheating during drying, concerns about the high fiber content, and cost competitiveness with corn, soybean meal and dicalcium phosphate.

Although the majority (>80%) of DDGS has historically been fed to cattle, recent research studies conducted at the University of Minnesota have clearly shown that corn DDGS produced by new generation ethanol plants contains significantly higher levels of digestible and metabolizable energy, digestible amino acids, and available phosphorus than found in DDGS produced by older, more traditional ethanol plants. Because of its higher nutrient value, new generation DDGS is well suited for swine and poultry diets, and can be a cost effective partial replacement for corn, soybean meal, and dicalcium phosphate in swine feeding programs.

As a result of recent research conducted at the University of Minnesota, usage of new generation DDGS in US swine feeding programs has increased from about 30,000 tonnes in 2000 to more than 80,000 tonnes in 2002. The production of ethanol and DDGS is increasing at a rapid rate, which is due in part to the banning of MTBE (methyl tertiary butyl ether) as an oxygenation agent in gasoline in 14 states, and the resulting increase in demand for ethanol to be used as a replacement for MTBE.

Currently, the US fuel ethanol industry produces about 3.8 million tonnes of DDGS. By 2005, this amount is projected to be near 5.5 million tonnes. New and undeveloped markets are needed to utilize this increased DDGS supply. The pork industry is a very viable, but underdeveloped DDGS market that could realize substantial economic benefits from using new generation DDGS.

Further Information

To continue reading this article, click here (PDF) Source: University of Minnesota Extension Service - May 2003