Rumen microbes use the fermentable organic matter from the diet to produce microbial protein. The microbial protein usually forms the largest part of the protein that arrives in the intestines (DVE) and has a favourable amino acid pattern, well suited to the synthesis of milk protein .
In the old DVE system (1991), it was assumed that the production of microbial protein was constant : 150 g of microbial protein / kg FOS (fermentable organic matter) . In the current DVE - system (2007) the calculation of the microbial protein depends on the amount of organic matter that has actually been fermented ( FOSp ) in the rumen. The amount of energy released by rumen degradation, and thus available for production of microbial protein is different for different carbohydrate fractions. It also takes into account the efficiency with which the microorganisms are capable of producing microbial protein. This is dependent in which form the product is present in the rumen is: dissolved in the rumen fluid or present in coarser particles.