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Why crude fibre decides the shape of a compound feed recipe

Crude fibre is the parameter buyers quote most often and specify least precisely. In a compound feed recipe it does three separate jobs, and only one of them is nutritional.

Fibre is structure before it is nutrition

In ruminants and horses, the fibre fraction determines chewing time, saliva production and the rate at which material leaves the stomach. A recipe can meet its energy and protein targets perfectly and still fail in practice if the fibre carrier is too finely ground to do this mechanical work.

This is why two materials with the same declared crude fibre value are not interchangeable. Dried apple pomace at around 28 % crude fibre behaves differently as flakes than it does milled to 3 mm, even when the laboratory result is identical.

Crude fibre, NDF and ADF describe different things

Crude fibre is a historical method that underestimates the total cell-wall fraction. NDF captures cellulose, hemicellulose and lignin; ADF captures cellulose and lignin. For apple pomace, typical values are roughly 28 % crude fibre, 44 % NDF and 34 % ADF.

The gap between those numbers is the hemicellulose fraction, and it matters for fermentation in the hindgut. If your formulation model works on NDF, asking a supplier only for crude fibre leaves you guessing.

What to specify when you order

A useful fibre specification names four things:

  • the analytical parameter you actually formulate on, not just crude fibre
  • the physical form: flakes, meal with a defined particle size, or pellets
  • the acceptable range, not a single figure, because natural raw materials vary by crop and origin
  • the method, since results are not comparable across different laboratory procedures

Variation is normal, undocumented variation is not

Fruit and vegetable by-products vary with harvest, variety and processing at the juice plant. That variation is inherent to natural raw materials. What a professional buyer should expect is not the absence of variation but its documentation: a specification with ranges, a certificate of analysis per batch, and a supplier able to explain which direction a given crop year moved.

If you are comparing fibre carriers for a new recipe, request a sample of each in the exact form you intend to use, and ask for the batch documentation alongside it.

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