Week 8: Protein Systems

Question 1

How to calculate crude protein?

Answer 1

CP = N x 6.25

• most of N requirements of animals is used for protein synthesis, and most N in plants present as protein

Question 2

What to assume when calculating CP?

Answer 2

All food N part of protein

All food protein contains 16%N

Question 3

What is digestible crude protein determined by?

Answer 3

Digestibility trials

Question 4

What does endogenous N include?

Answer 4

saliva N 
bile N 
gastric secretion N 
pancreatic N 
sloughed gut mucous membrane cells
bacterial N

Question 5

How do you determine endogenous N ?

Answer 5

Using labelled 15N in feed

• non radioactive stable isotypes
• known concentration of 15N in diet
• proportiong of 15N in diet
• difference = endogenous N

Question 6

What also affects amount of endogenous N?

Answer 6

fibre in diet and protein status of animal