Chemical fiber is not effective fiber

The detergent method measures cell-wall residue. It does not measure particle length, fragility, sorting, or the ration cows actually consume. A fine by-product can contribute NDF without doing the same physical job as forage particles that hold a mat and earn saliva.

On farm, peNDF is commonly estimated from as-fed particles retained on the ≥4 mm Penn State Particle Separator screens, multiplied by NDF — and the number that matters is the diet the cow ate. Grant and related Miner work treat peNDF and uNDF as linked field measures, not interchangeable names. Do not treat chemical NDF as proof of a physical response.

Sister notes on this universe cover same-ndf-different-forage. The physically-effective-fiber universe’s chop-length-is-not-pendf, shake-the-bunk-not-the-memory, and sorting-steals-the-pendf notes are the barn half of this laboratory line. Educational only — not a diagnosis, prescription, or ration formula.