EVALUATION OF FEEDSTUFFS AND PIG DIETS - ENERGY OR NUTRIENT-BASED EVALUATION SYSTEMS - I - LIMITATIONS OF PRESENT ENERGY EVALUATION SYSTEMS

The present energy evaluation systems of pig feeds are described and e valuated with reference to their scientific basis and practical perfor mance. The different energy evaluation systems are assessed with regar d to (i) the definitions and determinations of nutrient fractions in t he feed, (ii) the methods for determination of digestible nutrient fra ctions, (iii) the expression of energy value, (iv) the methods for det ermination of specific energy coefficients for the different nutrient fractions, and (v) the adequacy of using energy as the sole properly i n the feed value. It is concluded that present feed evaluation might g enerally be imprecise due to limitations in the principles of current energy evaluation systems, which oversimplify the nutritional value of the feed and ignore variations in the actual values.