EVALUATION OF FEEDSTUFFS AND PIG DIETS - ENERGY OR NUTRIENT-BASED EVALUATION SYSTEMS - II - PROPOSAL FOR A NEW NUTRIENT-BASED EVALUATION SYSTEM

A new nutrient-based evaluation system for feedstuffs and pig diets is proposed. The proposed system is based on (i) an identification of th ose organic nutrient fractions that, according to their absorption, me tabolism and utilization, are relevant for determining the value of th e feed, and (ii) 'biochemically-based calculations of the potential ph ysiological value of these fractions. The system is further based on a flexible stepwise evaluation in which the fundamental properties of t he feed are related to its utilization in actual situations. Step 1 is characterized by single feedstuffs according to the digestible amount s of those nutrient fractions which are relevant for feed formulation, i.e. essential amino acids, other N-compounds, ileal digestible carbo hydrates, fermentable carbohydrates, fatty acids and other lipid compo unds. Step 2 involves complete diets with three complementary properti es, measured according to their potential value for the pig: protein v alue (i.e. amount of digestible ideal protein), ''fat value'' (i.e. am ount of digestible triacylglycerols) and the ''complemental energy val ue'' (i.e. potential metabolic energy generated directly from the resi dual digestible nutrient fractions). Step 3 predicts the production va lue, either a standardized value determined by standard mathematical e quations, or the actual value determined by the use of computerized pi g models.