Raw whole soybeans contain roughly 20% rumen undegradable protein, while roasting can raise that figure to at least 50%, according to wisconsinagconnection.com reporting on University of Nebraska–Lincoln trials. Protein supplementation plays a critical role in supporting growth when cattle consume corn silage-based diets containing low natural metabolizable protein.
In Plain English: The Clinical Takeaway
- Rumen Undegradable Protein (RUP): Dietary protein that escapes microbial breakdown in the first stomach compartment (rumen) and travels directly to the small intestine for absorption.
- Metabolizable Protein (MP): The total usable protein absorbed by the animal’s body, derived from both rumen microorganisms and dietary RUP to sustain metabolic function and tissue growth.
- Feed Efficiency: The biological ratio measuring how effectively an animal converts ingested feed dry matter into measurable body weight gain.
Protein Dynamics in Corn Silage Rations
Corn silage generally contains between 6.5% and 8.5% crude protein, with the majority categorized as rumen degradable protein utilized by microorganisms. Data from the 2022 Nebraska Beef Cattle Report indicate that approximately 16% of corn silage crude protein escapes as RUP. When the diet fails to supply adequate metabolizable protein, animal growth rates suffer significantly.
Distillers grains traditionally serve as a reliable protein supplement because roughly 63% of their crude protein is RUP. Research reported in the 2011 Nebraska Beef Cattle Report confirmed that adding distillers grains improves performance in growing calves. However, market volatility can make distillers grains expensive or difficult to obtain for producers.
Trial Results Comparing Soybeans and Distillers Grains
Wisconsinagconnection.com reported that a recent University of Nebraska–Lincoln trial evaluated modified distillers grains against raw whole and roasted soybeans in corn silage diets. Each protein source was fed at 7%, 14%, or 21% of diet dry matter over an 84-day period. Modified distillers grains produced the greatest overall feed intake and live weight gain.
Roasted soybeans, conversely, resulted in superior feed efficiency compared to their raw counterparts. Increasing the inclusion rate to 21% generally improved overall gains and feed conversion rates relative to the 14% level. Researchers attribute this positive metabolic response to additional dietary energy since baseline protein requirements were already fully satisfied.
| Protein Source | Crude Protein Content | Rumen Undegradable Protein (RUP) | Observed Trial Performance |
|---|---|---|---|
| Corn Silage | 6.5% – 8.5% | ~16% | Provides baseline forage; low in metabolizable protein. |
| Distillers Grains | Variable | ~63% | Produced highest overall feed intake and weight gain. |
| Raw Whole Soybeans | ~40% | ~20% | Viable alternative dependent on market pricing and availability. |
| Roasted Soybeans | ~40% | At least 50% | Improved feed efficiency via higher RUP concentration and dietary energy. |
Evaluating Future Feed Alternatives
The findings indicate that both raw and roasted soybeans can function as practical alternatives when distillers grains face market scarcity. Roasted soybeans deliver a distinct performance advantage through elevated RUP concentration and added dietary fat. The ultimate selection between these protein sources continues to depend heavily on local market prices and regional supply availability.
References
- University of Nebraska–Lincoln Extension. Nebraska Beef Cattle Report. 2011.
- University of Nebraska–Lincoln Extension. Nebraska Beef Cattle Report. 2022.
- Wisconsin Ag Connection. Roasted Soybeans Show Promise in Cattle Diets. October 2026.
Disclaimer: This article is provided for informational and educational purposes only and does not constitute veterinary medical advice, nutritional prescriptions, or occupational health guidance.
