Predicting the energy value of pig feeds using in vitro or analytical methods

Abstract

An in vitro method, using ileal digesta or faecal extract as inocula, was used either alone or in combination with chemical composition to predict the content of metabolisable (ME) and digestible energy (DE) of cereals, yellow lupin and rape-seed oilmeal (either singly or in mixed feeds) for pigs. By means of regression analysis, in vitro dry matter solubilisation with ileal digesta (IDMS) and faecal extract (FDMS) as inoculum was found to be correlated to the in vivo ME (IDMS, r 2 = 0.94, cv = 1.13; FDMS, r 2 = 0.67, cv = 2.64 and DE (IDMS, r 2 = 0.90, cv = 1.40; FDMS, r 2 = 0,73, cv = 2.24) content of the feeds, when pure rape-seed oilmeal and yellow lupin were excluded. The correlations were further enhanced by combining IDMS with the starch, crude protein and dietary fibre content in the regression equations (ME, r 2 = 0.98, cv = 0.85; DE, r 2 = 0.97, cv = 0.92). In vivo metabolisable and digestible energy contents could also be predicted from chemical composition, employing either non-nutrients (ash and dietary fibre; ME, r 2 = 0.95, cv = 1.01; DE, r 2 = 0.93, cv = 1.23) or nutrients (starch, crude protein and crude fat; ME, r 2 = 0.93, cv = 1.37; DE, r 2 = 0.91, cv = 1.48). It is suggested that in vitro or appropriate dietary components, i.e. starch, crude protein and dietary fibre, could be employed to predict the nutritive value of feeds for pigs.