Transforming bioethanol production coproducts into valuable nutrition for dairy cattle through advanced energy prediction methods
In the global push for renewable energy, billions of gallons of bioethanol are produced annually from crops like corn and sugarcane. But what happens to the plant material left after the fuel is extracted? Rather than becoming waste, these coproducts are embarking on a second life as nutritious feed for dairy cows.
The challenge lies in accurately predicting their energy value—a complex scientific puzzle that directly impacts both the profitability of dairy farms and the sustainability of biofuel production. Welcome to the intersection of renewable energy and animal nutrition, where sophisticated chemical and biological approaches are helping transform bioethanol's leftovers into a valuable dietary component for the dairy industry.
Bioethanol production focuses primarily on fermenting the starch content of grains, but this represents only part of the agricultural material. In the United States, where corn is the primary feedstock for ethanol, approximately 1.3 units of energy are gained for every unit of energy used in the production process 1 .
As the starch is converted to ethanol, the remaining components—proteins, fats, and fibers—become concentrated in what the industry calls dried distillers grains with solubles (DDGS).
This coproduct isn't merely a footnote in the ethanol story—it's a significant economic contributor. The global ethanol industry produces approximately 44 million metric tonnes of high-quality feed annually .
For every bushel of corn processed, ethanol plants generate about 2.7-2.8 gallons of ethanol alongside 17-18 pounds of DDGS 3 .
DDGS contains concentrated proteins, fats, and fibers that can provide valuable nutrition for livestock, particularly dairy cattle.
For dairy farmers, the central question is simple: How much usable energy does DDGS provide to their cows? The answer, however, is complex. The energy value varies significantly depending on whether the original feedstock was corn, wheat, or a blend of both 2 . Furthermore, different ethanol plants use slightly different processing methods, creating additional variation in the final product.
Nutritionists need to determine the digestible energy (DE), metabolizable energy (ME), and net energy for lactation (NEL) values—key measurements that predict how effectively a cow can convert feed into milk.
Historically, researchers used a "chemical approach"—analyzing the protein, fat, and fiber content, then applying mathematical equations to estimate energy values 2 .
Biological methods measure actual digestion in live animals, providing more accurate predictions of how feeds perform in actual dairy operations.
While the chemical method is relatively quick and inexpensive, it doesn't fully capture how the feed will interact with a cow's complex digestive system.
To bridge this gap between chemical composition and biological reality, researchers conducted a crucial experiment comparing different types of DDGS using a more sophisticated biological approach 2 .
Researchers gathered multiple batches of three types of DDGS—wheat-based, corn-based, and a blended variety (70% wheat, 30% corn)—from commercial ethanol plants in Western Canada 2 .
They placed small nylon bags filled with each DDGS type into the rumens of live, specially-fitted dairy cows. These bags remained in place for 48 hours 2 .
After retrieval, the researchers measured what remained in the bags to determine exactly how much of each nutrient component had been digested.
Finally, they compared these biologically-derived energy values against those generated by traditional chemical prediction equations.
The findings revealed significant differences between DDGS types that simple chemical analysis couldn't fully capture. Corn DDGS consistently delivered higher energy values than both wheat and blended DDGS, establishing it as the superior energy source for dairy diets 2 .
Perhaps more importantly, the experiment demonstrated the superiority of biological evaluation methods. The in situ approach provided a more accurate prediction of how the feeds would perform in actual dairy operations because it accounted for the complex microbial fermentation that occurs in a cow's rumen 2 .
| DDGS Type | Digestible Energy (DE3×) | Metabolizable Energy (ME3×) | Net Energy for Lactation (NEL3×) |
|---|---|---|---|
| Corn DDGS | Highest value | Highest value | Highest value |
| Wheat DDGS | Intermediate value | Intermediate value | Intermediate value |
| Blended DDGS | Lowest value | Lowest value | Lowest value |
| Method | Advantages | Limitations |
|---|---|---|
| Chemical Approach | Quick, inexpensive, doesn't require animals | May not fully capture biological availability of nutrients |
| Biological Approach (In Situ) | More accurate, accounts for ruminal fermentation | More time-consuming, requires animal facilities |
This research proved particularly valuable for dairy farmers in Western Canada, where fluctuations in wheat and corn prices have led ethanol plants to use blended feedstocks 2 . The study provided these farmers with reliable data showing that blended DDGS offered different energy values than pure wheat or corn versions—critical information for formulating cost-effective rations.
Conducting such sophisticated feed evaluation requires specific tools and methods. Here are the key components researchers use to unlock the secrets of feed energy values:
| Tool/Method | Function in Research |
|---|---|
| In Situ Incubation | The primary biological method that involves placing feed samples in porous bags within the cow's rumen to measure real-world digestibility 2 . |
| Shotgun Metagenomics | Advanced genetic sequencing technique that identifies microbial populations in the digestive system; recently used to study contaminants in ethanol production that affect fermentation efficiency 4 . |
| Chemical Analysis | Standard laboratory techniques to determine crude protein (CP), ether extract (EE), acid detergent fiber (ADF), and neutral detergent fiber (NDF) content 2 . |
| Prediction Equations | Mathematical formulas developed through previous research that estimate energy values based on chemical composition 2 . |
| Metabolism Trials | Comprehensive studies measuring both input (feed consumed) and output (manure, milk, gases) to determine nutrient utilization 7 . |
Chemical composition analysis forms the foundation of feed evaluation.
In vivo trials provide the most accurate assessment of feed digestibility.
Genomic techniques help understand microbial interactions with feed.
The implications of accurately predicting the energy values of bioethanol coproducts extend far beyond the laboratory. When nutritionists can precisely formulate rations using DDGS, dairy farmers can reduce feed costs without compromising milk production. Meanwhile, ethanol plants gain an important additional revenue stream from their coproducts, improving the overall economics of biofuel production.
The environmental benefits are equally significant. By returning these coproducts to the feed market, the agricultural system effectively reduces the net land use required for cultivation by 11% to 40% . What appears to be simply a feed valuation issue actually represents an important sustainability solution, creating a circular economy where little is wasted.
The scientific journey to transform bioethanol production leftovers into valuable dairy feed represents a remarkable convergence of energy policy, agricultural economics, and nutritional science. Through sophisticated biological approaches like in situ incubation, researchers can now accurately predict the energy values of these coproducts, enabling dairy farmers to make informed decisions that benefit both their operations and the broader environment.
As bioethanol production continues to evolve, with emerging technologies focusing on lignocellulosic biomass and other advanced feedstocks 6 8 , the science of feed evaluation will likewise advance. This ongoing research ensures that agriculture's renewable energy future will include sustainable solutions for both fuel and food production—a win-win for our energy needs and our dairy cows.
Bioethanol production demonstrates how agricultural systems can maximize resource utilization, creating value from what would otherwise be waste products.