Distillers grains are a byproduct of ethanol production, created from the leftover grain after the sugars have been fermented into alcohol. They’re nutrient-dense, high in protein and fat, and primarily used as livestock feed for cattle, pigs, and poultry. The U.S. alone produces roughly 1.6 million tons of dried distillers grains in a single month, making them one of the most widely available and economical feed ingredients in modern agriculture.
How Distillers Grains Are Made
Most distillers grains come from corn-based ethanol plants that use a process called dry milling. The corn is ground into flour, mixed with water and enzymes, then fermented with yeast. The yeast converts the starch into ethanol and carbon dioxide. Everything left behind after the alcohol is removed, the protein, fat, fiber, and minerals, becomes distillers grains.
Because the starch is consumed during fermentation, the remaining nutrients become concentrated. A bushel of corn that started at about 9% protein yields a byproduct closer to 27-30% protein. This concentration effect is what makes distillers grains valuable as feed rather than waste.
Wet vs. Dried: The Two Main Forms
Distillers grains leave the ethanol plant in a wet form containing about 65% moisture. From there, they’re sold as either wet distillers grains (WDG) or dried down into distillers dried grains with solubles (DDGS). The “solubles” part refers to the thin liquid fraction that’s often condensed back into a syrup and mixed with the grains before drying.
Wet distillers grains are cheaper per unit of nutrition because drying is expensive and energy-intensive. But they spoil fast: 3 to 4 days in summer temperatures, and 7 to 10 days in winter. That short window limits their use to farms within trucking distance of an ethanol plant. Propionic acid-based preservatives are the most common way to extend that shelf life, though ensiling (packing the material in airtight storage like silage) also works. Experimental techniques combining cold plasma treatment with carbon dioxide storage have pushed shelf life to 21-28 days, but these aren’t yet standard practice.
DDGS, by contrast, store and ship like any dry grain product. They dominate the market and are traded internationally. In April 2025, U.S. dry mills produced 1.63 million tons of DDGS alongside 1.26 million tons of wet grains.
Nutritional Profile
Conventional corn-based DDGS typically contain about 27-28% crude protein, with individual batches ranging from 24% to 31%. Fat content runs around 9% or higher, and phosphorus averages 0.70% on a dry matter basis. Fiber content varies, with neutral detergent fiber (a measure of total cell wall material) averaging around 25% and acid detergent fiber (the less digestible portion) around 10%.
These numbers make DDGS a solid mid-range protein source that also delivers meaningful energy from its fat content. The phosphorus is notably more available to animals than the phosphorus locked up in whole corn, which reduces the need for supplemental mineral sources in some rations.
Newer High-Protein Varieties
Modern ethanol plants have moved beyond producing a single, uniform byproduct. Some facilities now use fractionation technology to separate fiber from the grain before fermentation, extract oil after fermentation, or both. The result is a high-protein DDGS that contains 37-44% crude protein compared to the conventional 27-29%. These high-protein versions also contain less fiber: roughly 32% neutral detergent fiber versus 37% in conventional DDGS, and about 15% acid detergent fiber versus 17%.
Low-oil DDGS are another variant, produced when plants extract corn oil from the solubles before mixing them back with the grains. The extracted oil is sold separately for biodiesel or cooking use. These products have less energy density than traditional DDGS but are still nutritionally useful. The variety of products now available means buyers need to check nutrient specs carefully rather than assuming all DDGS are the same.
How They’re Used in Livestock Diets
Beef and dairy cattle get the most benefit from distillers grains. Ruminants can handle the fiber content well, and DDGS can typically make up about 20% of the total diet on a dry matter basis. For cattle near ethanol plants, wet distillers grains are often the most cost-effective feed option available, sometimes replacing a significant portion of the corn that would otherwise go into the ration.
Pigs can handle DDGS at around 10% of the diet, while poultry rations traditionally cap inclusion at about 5%. Those lower limits reflect the higher fiber content relative to what monogastric animals (those with simple, single-chambered stomachs) can efficiently digest. However, recent research has pushed those boundaries. One study fed broiler chickens diets containing 30% wheat-based DDGS for the full 42-day growing period and found no loss in growth performance, carcass weight, or meat quality when the diet was properly formulated to meet nutritional requirements. The breast meat’s chemical composition, including protein, fat, and moisture, stayed the same across treatment groups. The only measurable difference was a slight change in meat color: birds fed DDGS produced less yellow breast meat.
The Sulfur Problem in Cattle
The biggest nutritional risk with distillers grains is sulfur. Sulfur content in DDGS varies significantly from batch to batch, and when cattle consume too much, the consequences can be serious. In the rumen, excess sulfur gets converted into hydrogen sulfide gas. The animal belches this gas up, inhales it, and it enters the bloodstream through the lungs. At high enough concentrations, hydrogen sulfide reaches the brain and disrupts cellular energy production.
The result is a neurological condition called sulfur-induced polioencephalomalacia, characterized by brain tissue death in the outer layer of the brain. Affected cattle may press their heads against walls, go blind, have seizures, or become unable to stand. Finishing cattle on high-grain diets are the most vulnerable because they eat less forage fiber, and that fiber normally helps buffer the rumen against hydrogen sulfide buildup.
The recommended maximum total dietary sulfur is 0.4% of dry matter for growing cattle and 0.3% for finishing cattle. Research on Texas beef operations found that rations in many regions exceeded these thresholds, largely because DDGS sulfur content is so inconsistent. Producers feeding significant amounts of distillers grains need to monitor sulfur levels in each batch and balance the total ration accordingly, especially during finishing when cattle are most at risk.
Why Distillers Grains Matter Economically
Distillers grains turn what would be an industrial waste stream into a revenue source for ethanol plants and an affordable feed ingredient for livestock producers. For every gallon of ethanol produced, roughly a third of the original corn kernel’s weight ends up as distillers grains. That steady, large-volume supply keeps prices competitive with other protein and energy sources like soybean meal and whole corn, particularly in the Midwest where ethanol plants and cattle feedlots overlap geographically.
The export market is also substantial. DDGS ship worldwide to feed operations in Asia, Latin America, and Europe. Their relatively standardized nutrient profile and long shelf life in dried form make them a practical commodity for international trade, though the variability in sulfur and other components means quality specifications matter more than they once did as the product has evolved from a simple byproduct into a diverse category of feed ingredients.