Crude protein

Crude protein is an estimate of a food's protein content, calculated from its measured total nitrogen multiplied by a conventional factor, usually 6.25, on the assumption that protein averages about 16 percent nitrogen. The word crude is doing a lot of work here, because the figure says nothing about protein quality or digestibility: it measures nitrogen, not whether the amino acids present are usable by a dog or cat (FEDIAF, 2024; AAFCO, 2024). That is its central limitation. Two foods can declare the same crude protein while differing greatly in biological value, because a highly digestible animal protein and a poorly digestible source contribute identical nitrogen to the test. A genuinely cautionary fact is that this method cannot, by itself, distinguish protein from non-protein nitrogen, the vulnerability that was exploited in the 2007 melamine adulteration episode, when a nitrogen-rich contaminant was added to inflate apparent protein and caused widespread pet illness (FDA CVM, 2007). For a premium buyer, the practical response is to read crude protein alongside the [ingredient order](/glossary/ingredient-order), which hints at the protein sources, and to recognise that named animal proteins and reputable [meat meals](/glossary/meat-meal) generally signal better quality than the number alone reveals. As with all analytical values, compare it on a [dry matter basis](/glossary/as-fed-vs-dry-matter), and remember it appears within the [analytical constituents](/glossary/analytical-constituents). For more, see the [Petipedia glossary](/glossary).

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