Scientific Curiosity Fuels Two Decades of Research by Iowa State Professor on Feeding Corn Milling Co-Products

AMES, Iowa — Count Allen Trenkle among those who think increasing ethanol production in Iowa is a good thing. "I'm enthusiastic about it. We have opportunities in Iowa that other parts of the country don't have, and one of those is to use this increase in ethanol production to increase cattle production," he said. Trenkle is a Charles F. Curtiss Distinguished Professor in Agriculture at Iowa State University. He's retiring this month after 44 years on the animal science faculty. But as an emeritus professor, he said his "scientific curiosity" will lead him to continue his research on how co-products of corn milling operations can be used as feed sources for livestock and poultry. Trenkle's interest in this area started in the 1980s with the expansion of Iowa's corn wet milling industry, producing corn syrup and sweeteners. The Iowa Beef Industry Council and the Iowa Corn Promotion Board funded Trenkle's research on how the by-product of that milling process — corn gluten feed — could be incorporated into cattle rations. In the mid-1990s, the Iowa Corn Promotion Board was planning a series of meetings to promote ethanol production. Trenkle was asked to talk about incorporating the co-products into livestock rations. "We hadn't done any work with distillers grains yet," Trenkle said. "There weren't any plants in production in Iowa, so we hauled wet distillers grains from Minnesota for our trials. We found it makes an excellent feed source, maybe better than the corn gluten feed we had tested earlier." Trenkle presented his research results at the American Society of Animal Science annual meeting in 1996. At the time, he said distillers grains should be considered a co-product, rather than a byproduct, because of its value as a feed. "It is an excellent feed and based on the performance of cattle, has a higher apparent energy value than corn," he said. "I thought we had all the answers," he said in a recent interview. "We had looked at a 40 percent inclusion rate and had success at that level. But producers said they wouldn't feed that much. So we did more experimentation, looking at digestion and other factors at lower inclusion levels. Now we have all these ethanol plants coming on line and producers are asking if they can feed more than 40 percent." So Trenkle's research continues. He's looking at 60 percent inclusion levels, and at the effect of combining dry distillers grains with distillers grains with solubles. "Every plant has a different output," he said. "These excess solubles have value, but you can't feed as much because it's higher in oil." Most research projects involve seeing how much of the corn in a typical ration can be replaced with ethanol plant co-products, and Trenkle has done a number of those types of projects. But his next focus will be the possibility of taking all corn out of a ration and supplementing distillers grains with corn stalks or chopped grass hay. If feeding trials show promise, Trenkle said this alternative might help producers remain profitable despite increasing corn prices. The economics of feeding distillers grains is something Trenkle urges producers to consider. "They must think through the process," he said. "Sometimes distillers grains will be economical but sometimes they can get priced out of the feed ration." Trenkle said each situation is different and producers need to compare the cost of ethanol co-products to the cost of corn, plus work with a nutritionist to determine feed values and proper supplementation, before they make a decision on incorporating distillers grains into livestock rations. Trenkle, who has been a member of the Leopold Center for Sustainable Agriculture advisory board since 1989, and served as the Center's interim director in 2000, sees Iowa's growing ethanol industry as a nutrient recycling system that is good for the environment. Solar energy and Iowa's rich soil and rainfall combine to grow crops, which are transformed into ethanol and co-products fed to livestock. The animals produce fertilizer that is recycled into future crops, thereby reducing the cost and importation of commercial fertilizer. "I want to do an analysis of this nutrient recycling system from an energy balance standpoint," he said. "I think the net energy balance of ethanol production can be greatly improved with the addition of livestock to the system." Trenkle earned a bachelor's degree at the University of Nebraska in 1956, a master's degree at Iowa State in 1958 and a doctorate degree at Iowa State in 1960. He was in a postdoctoral fellowship at University of California, Berkeley for 18 months before joining the Iowa State University animal science faculty in 1962. He was named a distinguished professor in 1983. Additional information available online: Research is Ongoing on Livestock Use of Ethanol By-Products Allen Trenkle, Charles F. Curtiss Distinguished Professor of Agriculture, has been researching the use of corn milling co-products in livestock rations for more than 20 years. Many others at Iowa State University also are working in this area. A sampling of recent research and extension work on the use of distillers grains can also be viewed online.