Comparing Feed Options: Whole Soybeans, Roasted Soybeans, and Distillers Grains in Silage-Based Growing Cattle Diets

Oct 05, 2026

By Erin Laborie

Corn silage is often used as a primary ingredient in growing cattle diets. The crude protein content of corn silage is approximately 6.5 to 8.5%, which is primarily in the form of rumen degradable protein (RDP).

Rumen degradable protein is digested in the rumen and utilized by the microbes for protein synthesis. Rumen undegradable protein (RUP) escapes rumen degradation and is digested in the small intestine. The true protein that is absorbed in the small intestine as a combination of microbial crude protein and RUP is referred to as metabolizable protein (MP). Cattle use MP to perform metabolic processes involved in maintenance and growth. When MP requirements are not met due to inadequate RUP, growth performance is limited.

Corn silage is low in RUP, with approximately 16% of the crude protein value consisting of RUP (2022 Nebraska Beef Cattle Report). In order to meet the MP requirements of growing cattle, distillers grains is often supplemented due to its high RUP content (63% of crude protein). Previous research has shown improved performance of growing calves fed distillers grains in silage-based diets (2011 Nebraska Beef Cattle Report).

When distillers grains are unavailable or cost prohibitive, soybeans may be a viable alternative protein source. Soybeans are high in crude protein (around 40%). While raw soybeans are relatively low in RUP (20% of crude protein), roasting soybeans can increase the RUP content to 50% or more.

Source : unl.edu

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