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Ethanol-Powered Cows

Most U.S.-based ethanol plants use corn as their main ingredient in making ethanol, and the growth of the industry has provided an abundance of co-products — such as distillers grains — that can be used as high-protein and energy supplements in animal diets.

The ethanol industry is on the fast track for expansion as fuel prices skyrocket. Its production has been expanding at breakneck speed for the past few years, and is expected to continue for several more.

Most U.S.-based plants use corn as their main ingredient in making ethanol, and the growth of the industry has provided an abundance of co-products — such as distillers grains — that can be used as high-protein and energy supplements in animal diets. Supplements fill in the holes left by limited and low-quality forages found in many drought-stressed pastures.

“Including distillers as part of the diet will reduce the amount of forage needed,” says Rick Rasby, University of Nebraska-Lincoln (UNL) beef nutritionist. “Put together a combination of lower-quality hay, or even some straw or baled cornstalks, with distillers. That diet could maintain cows prior to calving; and grass hay and distillers grains could meet the cow's needs after calving as well,” he adds.

Feeding distillers to cows

Distillers grains from ethanol plants generally contain a higher concentration of nutrients than such supplements as corn gluten feed, according to “Ethanol Co-Products For Cattle,” an Iowa State University Extension publication. Distillers grains contain about 30% protein and are high in energy, primarily because of high fat content. Fat content ranges from 9-14% on a dry matter (DM) basis.

Researchers acknowledge little work has been done to specifically measure the effects of adding distillers to cow rations. Most of the research has centered on growing and finishing cattle. But researchers like Rasby are beginning to study the effects of supplementing cows, and liking what they see.

“There don't appear to be any negative interactions with the forage,” Rasby says. “From a digestive standpoint, distillers grains and forage have a complementary effect on each other.”

Distillers, Rasby warns, can be high in phosphorous, so supplementing calcium may be warranted to keep the minerals in balance.

“In most diets I've worked with for cow-calf producers, I've probably included distillers rations at no more than 7 lbs./head/day on a DM basis,” Rasby says. “Because of the fairly high fat content, feeding more could cause a reduction in forage digestion.”

He adds that distillers are often used more as a supplement, fed at 2-4 lbs./head/day.

Feeding wet vs. dry distillers

Rasby adds there isn't much nutritional difference when considering whether to feed wet or dry distillers grains (DDG). Wet distillers grains (WDG) are high in fat, but difficult to store for long periods (65% moisture) due to spoilage concerns.

He reports UNL researchers worked this spring on a solution to the spoilage problem by eliminating oxygen from WDG and storing them like silage for long periods.

“At 65% moisture, distillers don't pack well, though,” Rasby says. “We added forage to the WDG to help pack during bagging and ensiling, and did it successfully.

“If you're going to bag it, use 15% hay, 85% WDG on a DM basis and it bags quite nicely,” he adds.

They also used a bunker silo in the trial, adding about 35% dry forage and 65% WDG to pack the silo.

“In the summer, when prices are low, cow-calf operators with the equipment to feed it can use this method to buy cheap distillers, store it and have it available to feed in the winter,” Rasby says. “As you move from summer into the late fall and winter, price also increases. Feedlot numbers, which are low in the summer, increase in the winter and so does the demand for these feed products.”

Rasby cautions that even with the forage mixed with the distillers, he still wouldn't supplement more than 7 lbs./head/day dry matter of distillers grains.

For more information on storing WDG, visit

Pricing by-products

Costs of distillers grains vary by demand for the product. Galen Erickson, UNL assistant professor of animal science, says, “As a general rule, you can buy WDGs at 90-95% the price of corn on a DM basis.”

He cautions producers to make sure they do the math.

“You might have a price on distillers grains for $35/ton, and think it's a great deal because it's cheap,” Erickson says. “But when you figure it's only 35% DM, $35 on an as-is basis works out to be $100/ton DM.”

Pricing them on a DM basis relative to corn is how to how you want to price any by-product, he says.

Transportation is the other major factor in determining cost. Erickson cautions producers to look at transportation costs in deciding where to buy (see map).

“If you're 200 miles from a plant, that changes your options dramatically compared to if you're only 10 miles away, because of high transportation costs,” he says.

Nebraska currently has 12 plants in operation, with an additional seven scheduled to be built in the next few years.

A 2005 UNL study evaluated the economic costs of feeding distillers in feedlots, including transportation costs of the distillers. For more information on that study, see the 2006 Nebraska Beef Report at

One farmer's story

Kent Pruismann, an Iowa farmer, has been feeding corn by-products to his cow herd for a number of years.

“I started feeding liquid by-products from the liquid corn processor plant in Marshall, MN,” says Pruismann, who keeps his 250 fall-calving cows near Rock Valley, IA.

Pruismann is also on the board of directors for Siouxland Energy and Livestock Coop, a producer-owned ethanol plant near Sioux Center, IA. The coop's 391 farmer-members are required to supply 2,500 bu. of corn/year/share owned. The ethanol plant produces approximately 25 million gals. of ethanol/year.

All of Siouxland's by-products are sold within 100 miles of the plant, Pruismann says. “That's part of the mission of the ethanol plant,” he adds. “It was to fit into the livestock part of it also.”

Feeding corn syrup

Pruismann takes advantage of his close proximity to the plant. “We put corn syrup in everything. It's quite economical and high in protein,” he adds.

Corn syrup, like distillers grains, is a high-energy by-product produced by ethanol plants. Pruismann uses it with baled and ground cornstalks.

“We feed 35% syrup, 64% ground cornstalks with the balance of trace minerals,” he adds. The syrup contains about 10-12% fat and 22% protein.

He rotationally-grazes his cow herd on 100 acres of grass until winter, when they're moved to cornstalks.

“This year, it's been quite dry and the grass didn't regrow. We put the cows on drylot so we could start feeding the cornstalk/corn syrup ration, which we did for 30 days,” Pruismann says. “I was concerned about switching cows back and forth from grass back to fed mixed ration, and then back to grass, but that hasn't been a concern.”