Soluble crude protein %

Total crude protein can be divided into several classes depending on the breakdown rate in the rumen. These classes are soluble protein, rumen degradable protein and rumen ungradable protein (this fraction escapes breakdown in the rumen). Soluble protein is the fraction which is broken down into ammonia very quickly in the rumen and has a close relationship with RDP and RDP 2h. The higher the solubility of crude protein, the more protein becomes available at rumen level within two hours of feeding.

In grass silage, as much as 40-60% of total protein ends up in this soluble fraction. The time of mowing, fertilization, dry matter content and weather conditions affect the percentage of soluble crude protein. Young mowing and high N-doses result in higher percentages of soluble crude protein.

In the ration, there is a minimum need for fast protein so that the fast fermentable carbohydrates can be utilized for bacterial growth. This index is widely used in ration optimization to properly coordinate protein breakdown and carbohydrate breakdown (rate) at the rumen level. If too much soluble protein is present in the ration, this protein is not utilized but ultimately excreted as urea in urine and milk.