Livestock Feeding Opportunities with Ethanol By‑Products: Distillers Grains and Thin Stillage
Overview
Ethanol fuel production allows for the availability of distillers grains and related by‑products. Distillers dried grains (DDG), wet distillers grains (WDG), and thin stillage represent valuable feed resources, particularly for ruminants. These by‑products supply high levels of protein and energy and differ physiologically from traditional cereal grains, as starch is removed through enzymatic hydrolysis and fermentation during ethanol production.
In western Canada, wheat is the primary grain used for ethanol, with variable inclusion of barley, rye, and triticale depending on availability and pricing.
Chemical Composition of Distillers Grains
Nutrient Characteristics
As starch is removed during fermentation, nutrient concentrations—particularly protein, fibre, and minerals—become more concentrated.
- Carbohydrates: 50–75% of DM
- ~70% structural carbohydrates (cellulose, hemicellulose)
- ~30% non‑structural (starch, sugars)
- Protein: 15–30% CP
- High proportion of rumen‑insoluble (bypass) protein
- Lower acidosis risk due to reduced starch levels
- High energy value comparable to cereal grains
Table 1. Typical Composition of Distillers Grains (DM basis)
Nutrient |
Wheat DDG (%) |
Corn DDG (%) |
Dry Matter |
93 |
94 |
Crude Protein |
30.5 |
23 |
Crude Fat |
3.75 |
2.86 |
Acid Detergent Fibre |
11.08 |
16.0 |
Total Digestible Nutrients |
86.5 |
86 |
Calcium |
0.20 |
0.11 |
Phosphorus |
1.15 |
0.43 |
Carbohydrate and Protein Degradability
Distillers grains are characterized by slowly degradable carbohydrates and high proportions of rumen‑escape protein.
Carbohydrate and Protein Fractions of Distillers Grains
- Corn DDG: More non‑structural carbohydrates, lower fibre
- Wheat and Barley DDG: Higher fibre content (NDF), lower rapidly degradable carbohydrate
- Protein Fractions:
- B3 (slowly degradable/bypass protein) comprises the largest share across all grain types
- Wheat and barley DDG contain particularly high B3 fractions
These characteristics reduce digestive disturbance risks and increase the value of distillers grains as sources of slowly degradable protein.
Feeding Distillers Grains to Dairy Cattle
Distillers grains supply:
- High energy
- High bypass protein
- Low rapidly fermentable starch
Key Considerations
- Heat damage risk: Over‑drying increases acid detergent insoluble protein (ADIP) and reduces digestibility of protein and energy.
- Milk production:
- Up to 20% of total ration DM is considered effective.
- Potential for reduced milk protein % due to lysine deficiency; rumen‑protected lysine supplementation may be needed.
Feeding Distillers Grains to Beef Cattle
Beef cattle—particularly growing calves—are less sensitive to bypass protein imbalances compared to dairy cows.
Key Findings
- Protein use efficiency: No differences observed between wet vs. dried distillers grains.
- Performance:
- U.S. studies show corn distillers grains support gain efficiencies similar to corn grain.
- Inclusion rates of up to 40% diet DM have been used successfully in beef diets.
- Wheat distillers grains:
- Limited data, but research found no differences in intake, gain, or feed efficiency when wheat WDG were fed at 13.3% (backgrounding) and 4.7% (finishing).
Conclusions
- Distillers grains are a high‑quality, concentrated source of energy and protein for ruminants.
- Their composition—high fibre, low starch, and high bypass protein—supports improved rumen health when replacing cereal grains in high‑energy diets.
- Corn DDG are well‑researched and often equal or superior to corn grain for beef cattle performance.
- Wheat DDG have fewer data but follow similar nutritional principles.
- Energy content is comparable to cereal grains, but protein levels are substantially higher (typically 25–28%).
