This is the most unsatisfactory principle of the Proximate Analysis. Cellulose too is partially lost. Hence, crude fiber underestimates true fiber. The number or value obtained in this procedure, therefore, is practically meaningless. NFE supposedly represents the soluble carbohydrate of the feed, such as starch and sugar.
Crude fiber represents insoluble carbohydrate.
Hemicellulose, cellulose and lignin are indigestible in non-ruminants, while Hemicellulose and Cellulose are partially digestible in ruminants. By using this method we can better predict the digestibility of forages to animals. Nowadays, most laboratories use ADF analysis instead of crude fiber.