During digestion, some endogenous protein—such as enzymes and intestinal cells—is lost through manure. Additional protein is required to replace this loss. This fraction is called intestinal digestible Metabolic Fecal Protein (MFP). Since MFP is not available for growth or production, it is subtracted from the Intestinal digestible protein value:
Intestinal digestible protein (DVE) = Intestinal digestible bypass protein + MCP – MFP.
MFP depends on the digestibility of organic matter in the ration. The harder the feed is to digest, the higher the MFP fraction (protein loss) and the lower the intestinal digestible protein content.
In the current Intestinal Digestible Protein (DVE) system (2007), MFP is calculated as:
MFP = 75 g per kg of indigestible dry matter = 0.075 × (D – Digestible Organic Compound – Digestible Crude Ash).