Increasing flexibility of ethanol co-product as animal feed is focus of ISU research

AMES, Iowa - Iowa State University researchers are working to safely increase feed use by cattle and poultry producers of a co-product made during ethanol production.
The co-product, dry distiller's grains with solubles (DDGS), is rich in protein, oil and fiber.

Because of the comparatively large number of ethanol plants in Iowa, DDGS are a relatively inexpensive feed source for livestock and are already used as a feed supplement in some livestock diets.

The research by Mike Persia, Stephanie Hansen, assistant professors of animal science, and Dong Ahn, professor of animal science, is funded by the Iowa Power Fund

"Currently people in the poultry industry will feed 5 or 6 and maybe 8 percent of the overall diet as distiller's grains," said Persia, whose research focuses on egg-laying hens. "What we're trying to do with the research is look at ways to safely increase that percentage of DDGS in the diets."

Part of the research includes looking closely at any impact feeding higher levels of DDGS will have on egg quality.

"The biggest area where there might be a change is in the yolk," he said. "DDGS is high in lutein and unsaturated fatty acids, which might change the yolk composition of fatty acids."

Another area Persia is focused on is how the DDGS will affect the waste products of poultry. DDGS are high in amino acids, which can break down into nitrogen in the chickens' digestive system and can be excreted. Excess nitrogen in the waste can led to increased evaporation of ammonia and can be an irritant that affects bird safety, human safety and the environment, according to Persia.

"It's not as simple as putting DDGS in front of birds and saying 'Go at it,' because you might run into production and environmental impacts," said Persia. "It's about working it (DDGS) into a balanced ration and finding out where that maximum is without affecting performance, environment, product quality, and human and bird safety."

Hansen, who is researching DDGS in cattle diets, says they already comprise about 20 to 30 percent of many feedlot cattle diets. Last year, when corn prices were increasing and DDGS prices were still low, that percentage went up to as much as 40 percent or more, she said.

Producers don't use more of this low-cost supplement due to its sulfur content. Too much sulfur in a bovine diet can be toxic.

"The problem in cattle is that DDGS have a lot of sulfur in them because ethanol producers use sulfuric acid in processing ethanol," she said. "We are looking into how much we can get into the diet without running into problems."

Hansen says the industry is still trying to find the best mix for the best result and safety is one of the most important factors.

Because of the risk to the animals, Hansen's research is first focused on developing methods to monitor sulfur levels in cattle. Her goal is to develop an easy-to-use, mobile test to determine when an animal is getting too much sulfur.

"We are looking for things that a veterinarian could do out in the field to actually determine if an animal is having problems with sulfur or having some other problem," said Hansen.

"Sometimes it is hard to distinguish sulfur toxicity from other problems that might be wrong with the animal. We are trying to do a better job of diagnosing."

Once the health issues are better understood, Hansen believes a safe increase in the amount of DDGS included in cattle diets can be reached.

"We want to maximize the inclusion rates of DDGS so it can be most economical for the producer and still produce their best product," she said.

Increasing the use, and potentially the price, of DDGS as a feed source could help ethanol producers realize better profits.

Since the ethanol industry is still fairly new, Persia says that feeding cattle and poultry the ethanol co-product DDGS is still not a science as they learn more and more about the feed ratios.

The researchers say one of the biggest hurdles is the variability in DDGS. The makeup of the DDGS varies in the percentage of fiber, oil, protein and sulfur from ethanol plant to ethanol plant and even within the same plant on different days.