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Crude fiber analysis

WEENDE METHOD (CRUDE FIBER)

The universally used method is Weende.  This method was developed by Henneberg and Strohmann during the 1860s at the Weende Experiment Station in Germany and is often referred to as the Weende System of proximate analysis.

The method is based on the differentiation of carbohydrates into digestible and indigestible fractions.

It is the reference for the legal measure of fiber grains, meals, flours, and feeds, even if it 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).

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 determination can be summed up in 5 steps:
  1. ACID DIGESTION (BOILING & FILTERING): the feed sample is boiled in sulfuric acid 1,25 % for the extraction of sugar and starch
  2. WASHING: the residues in the crucibles are washed with water to remove acid residues and neutralize the pH
  3. ALKALY DIGESTION: the second digestion with 1.25 % sodium or potassium hydroxide removes proteins, some hemicellulose and lignin.
  4. WASHING: is performed again in order to remove the alkali residues into the crucibles with water and neutralize the pH
  5. DEFATTING: the final step, where the last washes are performed with acetone
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