ISO 6655:1997

Overview

ISO 6655:1997 specifies an analytical method for determining the soluble nitrogen content of animal feeding stuffs after treatment with pepsin in dilute hydrochloric acid. The procedure measures nitrogen solubilised by in vitro pepsin digestion and reports results as soluble nitrogen (g/kg) or converted to soluble crude protein (factor 6.25). The standard clarifies that results do not distinguish protein nitrogen from non‑protein nitrogen and are not a direct measure of in vivo digestibility.