Mixing it Up
Corn stover has been used in small amounts as cattle feed for more than 100 years. Separately, distillers grains has grown in popularity as a cattle feed over the past few decades as ethanol plants have established themselves throughout the Midwest, often in close proximity to feedlots. But now, research is showing that by combining the two feeds, the mixture can be fed in greater percentages as a nutritious, highly palatable and economical alternative to corn.
Archer Daniels Midland Co. has spearheaded much of the research exploring the use of treated stover and distillers grains as a replacement for corn. Its work in that area began more than a decade ago, as company scientists began to recognize the opportunity for getting more value out of the byproducts produced at corn processing plants. The company expanded its work in this area to include crop residues and some energy crops about five years ago, as corn prices continued to climb and demand for economical feed products also increased. A year ago, the company announced early results of the research, which showed that by treating stover with hydrated lime (calcium hydroxide), it could comprise up to 25 percent of cattle rations when combined with wet distillers grains with solubles (WDGS). Traditionally, untreated stover has been fed only in small amounts (approximately 5 percent of the feed ration) and only as a fiber source, rather than an energy source, so the finding that rations could be increased and used in feedlots was considered quite significant by those involved in the project.
“Global agriculture needs to produce more using less water, fertilizer and other inputs, and without bringing vast amounts of new land into production,” Mike Baroni, vice president of economic policy for ADM, said following the company’s February announcement. “Using crop residues and coproducts, rather than higher-value grains, to help feed animals could enable the world to make more of the global harvest and help agriculture expand to meet all needs.”
Mike Cecava, ADM’s director of feed technology, says ADM expects there to be continued pressure on grain prices, so finding an economical alternative to corn as livestock feed is an incentive to explore stover and other coproducts. He stresses that much of the research conducted in recent years on crop residues has its roots in the 1960s and 1970s, with one important difference. “Now we’ve got the opportunity to use more of these ag coproducts like the distillers grains, some of the liquid feed ingredients, and corn gluten feed, to complement the residues,” he says. “The crux of the matter today is we can use combinations of these coproducts and residues to substitute out corn and soybean meal to give producers more flexible combinations. We’ve been able to show that we can substitute out a fair amount of grain, we can reduce ration costs and we can improve the cost of gain. It looks commercially feasible and I think it’s very sustainable.”
One of the researchers involved in the ADM-funded testing of treated corn stover was Jim Russell, professor of animal science at Iowa State University. He says another reason for the latest round of research on using stover as feed sprouted from a desire by cattle producers to identify a low-protein, low-phosphorous energy source that could be added to feedlot diets as a replacement for high-priced corn. Russell and other ISU researchers applied various treatments to stover to increase its digestibility and found that while ammonia—which was the most popular stover treatment method a few decades ago—is effective, it also increases protein content. Because distillers grains already has a high protein levels, as well as sulfur and oil, additional protein from the stover is undesirable. Calcium hydroxide, however, was found to be effective in breaking down the stover to improve digestibility without adding unnecessary protein.
Cattle fed a diet consisting of 20 percent calcium hydroxide-treated stover, 40 percent WDGS and 40 percent corn gained as much weight as cattle fed a control diet containing just 5 percent stover. In fact, the only notable difference between diets containing greater percentages of treated stover and the control diet was that cattle fed higher levels of forage had slightly less marbling, Russell says. Cecava adds that while the ISU test showed reduced marbling, other research has shown no difference in marbling between beef fed mostly corn and beef fed greater percentages of stover and distillers grains. He expects marbling and other effects of livestock diets will vary depending on region, just as livestock diets vary by region. And while reduced marbling usually means a reduced price for beef on the market, when corn prices are high, it could prove to be more profitable to reduce the feed costs rather than suffer the burden of high inputs for prime quality beef.
ISU conducted an economic analysis to evaluate the cost of production and found that a treated stover with modified distillers grains ration is cost comparative with corn as low as $4 per bushel, assuming that the distillers grains is priced at 65 percent of the corn price and bagged, treated stover is $51 per ton. As corn prices were increased to $5 and $6 per bushel, the economic benefits of using any type of stover becomes more attractive, but the analysis found that calcium hydroxide treated stover offered the best returns.
The Right Combination
Researchers will continue to evaluate the best methods of application for the calcium hydroxide, but Russell says research has shown the treatment works best if the stover has a high moisture content because the lime will be added as a dry material. When the ISU project was being conducted in October 2009, half of the approximately 76.5 tons of harvested corn stover was left on a concrete surface after harvest until it could be packed into a silo bag. Before it was packed, the area received nearly 2.5 inches of rain, which increased the moisture content of the stover to about 40 percent. Russell says some feeders may need to add water to the stover when they treat it with calcium hydroxide; others are exploring adding the calcium hydroxide as a slurry.
Another topic of consideration is whether to include wet, dry or modified distillers grains. University of Nebraska-Lincoln researchers have concluded that while any type of distillers grains will work, WDGS is by far the best performer. “Nutritionally, there is no difference,” says Terry Klopfenstein, professor of ruminant nutrition at UNL. “The moisture that’s there is what really enhances the palatability of those residues. The wet distillers is very palatable, so it makes unpalatable things like corn stalks readily consumed by the cattle.”
UNL researchers examined two different scenarios for feeding stover to cattle. The first scenario is one in which the cattle are let out to graze in the stover fields. This allows them to select the most appealing portions of the stover, primarily the leaves and husks. The result is that about half of the stover is left untouched by the cattle and can then be disked into the field by the farmer and serve as soil nutrients. Distillers grains is not directly mixed into the diet in this scenario, but can be fed as a supplement.
In the second scenario, stover is harvested and ground into smaller particles, which is meant to encourage the cattle to consume the less-palatable stalks of the plant. “Still, the cattle are not very enthused about that,” Klopfenstein says. “But if you mix the wet distillers grains with it, they’ll eat it. I can’t emphasize enough that there is tremendous complementarity between these byproducts, especially the wet byproducts and the crop residues, whether it’s treated or not. That’s the key. One could do treatments to the residue and not feed the byproducts, but boy they really work well together.”
For corn farmers who supply ethanol plants and raise cattle, this research presents a closed-loop opportunity to serve all their needs. Farmers can deliver their corn to the ethanol plant, pick up distillers grains at the back end and mix them with stover from their fields to feed their cattle. The stover-WDGS feed combination is also very attractive to feedlots, particularly those located near ethanol facilities, that have felt the pinch of rising grain prices.
In Nebraska, where cattle, corn and ethanol industries are all very strong, the concept is especially appealing. Klopfenstein says he’s noticed tremendous interest from feedlots in the state and while every group has a percentage that will be resistant to change, the overall feedback has been very positive. “Nothing in my 46-year career has had as much impact on the cattle industry as ethanol has,” Klopfenstein says. “I’m not saying that’s bad. It’s just different. One has to be flexible and these byproducts are really interesting.”
Cecava says he’s seen skeptics of the alternative feed quickly become believers once they see it in action. “We have been very pleased with the response so far,” he says.
Russell agrees. “We’ve known how to harvest corn stalks for a long time and have harvested them as cow feed in many cases, but as low-quality, low-value product,” he says. “This is a way to enhance the value.”
One thing many cattle producers may eventually face is the irony that the stover they’re using to replace the corn that is used for ethanol production could very well also become a desirable ethanol feedstock in the future. In fact, much of ADM’s stover research in the past couple of years was conducted as part of a group effort known as the DAM project [John Deere, ADM, Monsanto] that focused on exploring stover as a power or biofuel feedstock. But until commercial-scale cellulosic ethanol facilities come online, harvesting stover for animal feed could provide farmers with a second crop from their corn acres and cattle producers with an economical, nutritious feed alternative. “Fuels are the holy grail,” Cecava says. “But animal feed could also be a very suitable application. The process technologies to use stover as a feed are not nearly as expensive [as ethanol] and it hooks farmers up with a way to get the stover harvest going commercially. We’re interested in this so that people see that biomass can be a new feedstock.”
Author: Kris Bevill
Associate Editor, Ethanol Producer Magazine