This test method is a procedure used to determine Acid Detergent Fiber (ADF) content in forages, animal feeds, and fibrous materials. ADF represents the portion of plant material composed mainly of cellulose, lignin, and silica, which are less digestible components affecting the nutritional quality of the feed. The feed or forage sample is dried, ground, and weighed. Then the sample is boiled in an acid detergent solution, which removes hemicellulose and soluble components, leaving behind the ADF residue. The insoluble residue is filtered, dried, and weighed. The residue is ashed in a furnace to remove mineral content; the weight loss upon ashing is subtracted to correct the fiber weight.