ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

CHEMICAL EVALUATION

• The level of individual essential amino acids in the test materials are assessed and the results are interpreted as follows:

Chemical score:

• In this concept it is considered that the quality of a protein is decided by that essential amino acid which occurs in greatest deficit when compared with a standard.
• The standard generally used is egg protein.
• The content of each of the essential amino acid of the protein is expressed as a proportion to that of the standard protein.
• The lowest proportion is taken as the score of the protein.
• Eg. In wheat protein the essential amino acid in greatest deficit is lysine.
• The lysine content of egg and wheat protein is 72 and 27g/kg DM respectively, and the chemical score for wheat protein is 27/72=0.37.
• Disadvantage: No account is taken of the deficiencies of acids other than the amino acid in greatest deficit.

Essential amino acid Index : (EAAI)

•  Is defined as the geometric mean of the egg ratios of essential amino acids.
• Advantage : Predicting the effect of supplementation in combination of proteins.
• Disadvantage: Protein having different amino acid profile may have same or a very similar index.