Total versus standardised ileal digestible
Total amino acids are what the laboratory finds; standardised ileal digestible (SID) amino acids are what the animal absorbs. Two cargoes with identical total lysine can differ materially in SID lysine after over-toasting, and only the SID value predicts performance.
Heat damage indicators
Reactive (available) lysine, KOH protein solubility, protein dispersibility index and urease activity are practical proxies for processing intensity. Specifying at least one of them protects against under- and over-processing, which crude protein cannot detect.
Typical industrial reference values
| Soybean meal lysine | 2.7–2.9% | Reference plant protein |
| Fish meal lysine | 4.5–5.2% | |
| Rapeseed meal lysine | 1.8–2.1% | |
| SID lysine (poultry, SBM) | ≈ 89–91% | Falls with heat damage |
Indicative industry reference values for orientation only — always contract against the delivered lot.
What to verify
- —Digestible, not only total, amino-acid values with the species basis stated
- —A heat-damage proxy appropriate to the ingredient
- —Consistency of the amino-acid to crude-protein ratio across shipments
Typical risks
- —Silent loss of digestible lysine through over-processing
- —Under-processing leaving anti-nutritional factors active
- —Formulation shortfalls that only appear as performance loss weeks later
Common mistakes
- —Buying protein meals on crude protein alone
- —Applying one origin's SID coefficients to a different process route
Frequently asked questions
Which amino acid should be specified first?
Lysine for most monogastric protein sources, because it is usually first limiting and the most sensitive to heat damage. Methionine, threonine and tryptophan follow depending on species and diet stage.
Where this matters most
Related topics
Crude protein is nitrogen content multiplied by a conversion factor (usually 6.25); it estimates total protein but says nothing about amino-acid quality or digestibility.
Digestibility expresses the proportion of a nutrient the animal can actually absorb; it converts an analytical composition into a nutritional value.
A certificate of analysis is a lot-specific record of tested parameters, methods and results; a generic or typical-values sheet is a marketing document, not a certificate.
Build a structured RFQ with the parameters, tolerances and verification steps written in — free for buyers.
Start your RFQTechnical parameter names and analytical method references are kept in English because they are quoted verbatim in contracts, certificates and international standards.
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