This older proximate method was used to divide carbohydrates into digestible and indigestible fractions. When CF content is higher, the energy content of the feed is lower because crude fiber is considered indigestible. Measuring crude fiber was one part of the original system of analysing the “digestible” fraction in feedstuffs. This method uses sequential acid and alkali extraction. It was developed by Henneberg and Sttohmann during the 1860s at the Weende Experiment Station in Germany, and is often referred to as the Weende System of proximate analysis. The CF extract was once used as a standard analysis for fibrous parts or the indigestible portion of carbohydrates in feeds. However, some of these substances are partially digestible by microorganisms in the rumen. Crude fiber accounts for most of the cellulose but only a portion of the lignin and no ash, so it underestimates true fiber and is less than acid detergent fiber (ADF). Thus, CF is not a good indicator of digestibility in ruminant animals, and the use of this parameter in feeds for ruminants is declining.
Even though CF is not a very useful parameter for quantifying forage fiber where lignin content is substantial, the CF is a reasonable estimate of the fiber in grains because of their low lignin content. Thus, it is still commonly used for analysis of feeds for non-ruminants or monogastric animals (i.e., those that do not have a chambered stomach or rumen; for example, horses and pigs). Crude fiber is still used today as the
UGA Cooperative Extension Bulletin 1367 • Common Terms Used in Animal Feeding and Nutrition
legal measurement of fiber in grains and finished feeds. 7« Back to Glossary Index