How to calculate the Net Protein Utilization (NPU)?

Mitchell (1922) introduced the term 'Net Utilization of Dietary Protein' which is a product of digestibility coefficient and biological value divided by 100, as shown herewith.

NPU = Digestible coefficient * Biological Value / 100

A direct method of estimating Net Protein Utilization (NPU) was developed by Miller and Berzder (1955). Groups of albino rats 28 days old were used. One group was fed on a non-protein diet while the other groups were fed on the test diets containing different proteins at 10 percent level for a period of 10 days. The food intakes of the animals were measured. The animals were killed at the end of 10 days and the body nitrogen was determined by Kjeldahl method on a sample of dried and powdered carcass. The NPU is calculated according to the formula:

The main advantage of determining NPU of a food or diet is that it helps in the calculation of the net available protein of the diet. Studies have shown that there is a good correlation between the values for PER, NPU and chemical score.