How is crude protein generally calculated in feed analysis?

• A. N × 6.0
• B. N × 5.25
• C. N × 6.25
• D. N × 6.50

Answer: (C)

Nitrogen content is used to estimate crude protein by applying a fixed conversion factor that reflects how much nitrogen is typically found in protein. On average, protein contains about 16% nitrogen, so 100 divided by 16 equals 6.25. That means when you measure the nitrogen percentage in a feed, you multiply it by 6.25 to get the crude protein percentage. For example, if a feed has 2.5% nitrogen, its crude protein is about 2.5 × 6.25 = 15.6%. This method provides a quick, practical estimate, though it can overestimate protein in feeds with non-protein nitrogen or unusual amino acid composition.