PREDICTION OF THE DIGESTIBLE AND METABOLISABLE ENERGY CONTENT OF PIG DIETS FROM THEIR FIBRE CONTENT

Abstract

Digestible energy (DE) and metabolisable energy (ME) values were determined for 22 pig diets, 14 from commercial sources, with pigs of between 30 and 90 kg liveweight, DE values ranged from 2680 to 3780 k cal/kg of feed dry matter. Similar and highly significant regression equations were found relating DE and ME in k cal/kg of feed dry matter to crude fibre (CF), cellulose (CEL) and acid detergent fibre (ADF) determined by the modification of Clancy and Wilson. The best prediction of DE was given by the modified acid detergent fibre assay: DE ? 4102.97 - 84.99 (ADF): rsd = ?140.4: r = -0.916*** ME and DE values were very closely related. ME = 0.98 DE - 78.98: rsd = ?20.38: r = 0.998*** The mean ME of commercial rations was 95.5% of the DE with sd = ?0.60%. The decline in DE as a percentage of gross energy (GE) with increase in fibre was found to be: DE% = 91.48 - 2.22 (CF): rsd = ?2.21: r = 0.946*** Fibre results were closely related to one another, the equation for ADF and CF being ADF = 0.39 + 1.217 (CF): rsd = ?0.81: r = 0.974*** The practical implications of these relationships are discussed.