Crude protein Calculator

Crude protein is an estimate for total protein. A crude protein contains nitrogen from not only protein but non-protein sources as well.

Crude protein is used for energy and helps build tissue. Crude Protein (CP) is based on a laboratory nitrogen analysis, from which the total protein content in a feedstuff can be calculated by multiplying the nitrogen figure by 100/16 or 6.25. This is from the assumption that nitrogen is derived from protein containing 16 % nitrogen (AOAC, 1984). However, some portion of the N in most feeds is found as non-protein nitrogen (NPN) and, therefore, the value calculated by multiplying N x 6.25 is referred to as crude rather than true protein. Protein is made up of amino acids.

A mixture of true protein and non protein nitrogen in a food is called crude protein. It indicates the capacity of a feed to meet an animal's protein needs. The approximate amount of protein in foods that is calculated from the determined nitrogen content by multiplying by a factor (as 6.25 for many foods and 5.7 for wheat) derived from the average percentage of nitrogen in the food proteins and that may contain an appreciable error if the nitrogen is derived from non protein material or from a protein of unusual composition.

How to calculate crude protein in feed?

Example:
Calculate the estimated percentage of crude protein.
Blank titre value = 25
Titre value = 5
Normality of NaOH = 10
Sample weight = 15

Solution:
Apply Formula:
Percentage of crude protein = (blank-titre value) * 1.401 * 6.25 * 20 * Normality of NaOHSample Weight
Percentage of crude protein = 2335