Prediction of the digestible energy in pig diets from analyses of fibre contents

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Abstract
SUMMARY Digestible energy (DE) values were determined for 15 pig diets with pigs 8 to 18 weeks old by standard digestibility procedures. The 15 diets contained 4360 to 4920 kcal gross energy (GE)/kg dry matter (DM), 2750 to 4070 kcal DE/kg DM, 2·8 to 15·8% crude fibre (CF), 2·4 to 21·1% acid-detergent fibre (ADF), and 7·3 to 33·8% neutraldetergent fibre (NDF). The prediction equations obtained were all highly significant. DE was most accurately predicted when the fibre value used was NDF, the regression equation being: DE = 4314·37·22 NDF (residual SD + 265). The inclusion of GE in the regression equation considerably improved its accuracy: DE = 1·510 GE-2579·39·37 NDF (residual SD ±127). However, the greater digestibility by pigs of NDF in diets containing sweet lupin seed meal (SLSM) resulted in these diets being more efficiently digested than diets containing other common protein supplements. Omitting the four diets containing SLSM from the regression analysis resulted in an even more accurate prediction equation: DE = 1·177 GE-1085·40·22 NDF (residual SD±107). It is suggested that this equation may be used to predict DE of pig diets compounded from commonly used constituents.