A new protein evaluation system for pig feeds and its practical application

Abstract

The present basis for determining the protein value in pig feeds is discussed and a proposal for a new protein evaluation system is presented. The system proposed includes (i) a quantification of digestible amino acids according to their ileal digestibility, determined using standardized methods; (ii) a characterization of the protein value according to the contribution of digestible amino acids to ideal protein; (iii) a calculation of surplus amino acid‐N; and (iv) a calculation of the physiologically available energy of surplus amino acids.

Practical methods for improving the quantification of digestible amino acids in the actual samples are described. The methods include calculations of (i) total amino acids in feedstuffs from nitrogen analyses by the use of specific factors or regression equations and (ii) standardized digestible amino acids from in vitro digestible nitrogen and correction for the extra endogenous amino acid losses specifically induced by the feedstuff itself. An example calculation for the practical use of the proposed protein evaluation system is given.

Key words:

• amino acids
• crude protein
• ideal protein
• ileal digestibility
• in vitro
• nutritional value
• physiological energy
• standardized digestibility