The ethanol industry is the fastest growing segment of American agriculture, and it’s a major consumer of the annual corn crop. According to estimates, 14 percent to 16 percent of the 11-billion-bushel 2005 corn crop will be used for ethanol production this year. About 23 percent of this year’s crop will head in that direction.
U.S. livestock and poultry industries consume about 5 billion bushels of corn annually, which means the competition for corn will heat up. It’s natural to be concerned about what it will mean to future corn prices and availability.
Of course, the ethanol industry produces a growing byproduct supply that can be used as alternative ingredients to corn and soybean meal in livestock and poultry feeds. Approximately 70 percent of total byproducts from dry-grind ethanol plants are available as distillers' dried grains with solubles-- DDGS.
On a dry basis, the North American ethanol industry will produce about 10 million metric tones of distillers’ byproducts in 2006. That’s projected to increase to 14 million metric tones in 2007. Historically, 97 percent of distillers’ byproducts produced in the United States were fed to cattle. Due to DDGS’ growing supply and improved quality, researchers have shown that DDGS can successfully be used in swine diets. The U.S. pork industry now feeds about 16 percent of all DDGS produced, which will continue to climb as the supply grows.
What do we know about feeding DDGS?
Nutrient composition, digestibility and physical characteristics vary among DDGS sources. Its energy value is equal to or greater than corn, making it a good partial substitute in swine diets. Recent studies show that DDGS sources with a light, golden color are preferred for swine feeds because the color indicates less heat damage to protein during drying and results in high lysine digestibility.
DDGS’ phosphorus is highly digestible for swine and much higher than from corn or soybean meal. This means that DDGS can replace most of the inorganic phosphorus supplements added to swine diets, reduce cost and manure phosphorus excretion while supporting optimal performance. Therefore, DDGS is an economical partial replacement for corn, soybean meal and dicalcium phosphate in swine diets.
However, nutrient content and digestibility variability is high among DDGS sources compared to soybean meal sources. But this can be managed. (See accompanying sidebar for tips.)
As for maximum DDGS diet-inclusions, the initial findings are:
Nursery pigs (> 7 kg), up to 25 percent.
Grow/finish pigs, up to 20 percent. (If you use higher levels it may reduce pork-fat quality.)
Gestating sows, up to 50 percent.
Lactating sows, up to 30 percent.
Of course, there are assumptions to those diet inclusion rates. For example, that the DDGS carry no mycotoxins, and that diets are formulated on the basis of digestible amino acids and available phosphorus.
Naturally, there are limitations.
Up to 10 percent DDGS can be added to swine diets with excellent results even if diets are formulated on a total-lysine basis. However, if higher dietary inclusion rates are used, diets should be formulated on a digestible-amino-acid basis to achieve satisfactory performance.
Feeding diets containing DDGS affects manure nutrient content and output. DDGS’ relatively high fiber content reduces the dry matter digestibility, which results in a slight increase in manure output. The high protein-to-lysine ratio increases the nitrogen excretion, but it will reduce the phosphorus concentration in manure if formulations are based on available phosphorus.
Corn DDGS contains approximately 10 percent corn oil. As higher DDGS levels (greater than 20 percent) are added to growing-swine diets, pork-fat quality and belly firmness decline. University of Minnesota researchers are evaluating the effects of DDGS feeding levels and feeding length on fat quality.
A few studies suggest that diet palatability, feed intake and growth rate may decline as DDGS levels increase in corn/soybean meal diets. However, other studies show that DDGS can be added to swine diets at levels up to 50 percent without negative effects on feed intake. It’s unclear why the different responses occurred, but it may be due to differences in DDGS quality and methods used in formulating the diets.
But DDGS does offer unique, value-added attributes. Adding it to grow/finish diets may improve the pigs’ gut health. A University of Minnesota study shows that adding 10 percent DDGS to a finishing diet reduced the length, severity and prevalence of intestinal-tract lesions caused by Lawsonia intracellularis.
Feeding diets containing DDGS to sows has produced positive effects as well. Minnesota researchers conducted a sow study to evaluate diets containing high DDGS levels (50 percent in gestation, 20 percent in lactation), and its effects on reproductive performance over a series of sow reproductive cycles. It showed an increase in the litter size weaned for sows fed DDGS diets during the second reproductive cycle. In a subsequent study, pig weaning weights increased as DDGS levels in the lactation diet increased (up to 30 percent DDGS).
So what’s preventing widespread use?
Variability in nutrient content and digestibility.
Low particle size and flowability problems of some sources.
Perceived risk of mycotoxins—primarily for sows.
Ability to pellet DDGS diets.
Understanding and managing the effects of corn oil in DDGS on pork-fat quality.
Controversy over palatability issues, and negative effects on feed intake at high dietary inclusion rates.
Fast, accurate and inexpensive in vitro methods to estimate amino acid digestibility among sources.
Net energy values of DDGS sources need to be determined.
So, the challenges continue. But we all need to discover answers on how to best use ethanol byproducts, because that industry is here to stay.
Jerry Shurson, is a swine nutritionist at the University of Minnesota. He has been researching DDGS for the past nine years. You will find more information on DDGS at www.ddgs.umn.edu.