The Crude Fiber method divides carbohydrates into digestible and indigestible fractions.
It is the reference for the legal measure of fiber in grains and finished feeds, even if it underestimates the real content of the fiber because 50-90% of the lignin, 0-50% of cellulose, and up to 85% of hemicellulose can be solubilized and therefore not measured as crude fiber.
Even though Crude Fiber is not a very useful parameter for quantifying forage fiber where lignin content is substantial, it is a reasonable estimate of the fiber in grains because of their low lignin content.
Thus, it is still commonly used for the analysis of feeds for non-ruminants or monogastric animals.
The crude fiber method uses sequential acid (1,25%) and alkali extraction (1,25%).