Chemical composition of pea fibre isolates and their effect on the endogenous amino acid flow at the ileum of the pig

Pea starch, hulls and cotyledon inner fibres, isolated from pea seeds, were incorporated in N-free diets, on a NDF-content basis, in order to study their effect on the ileal endogenous amino acid (AA) excretion in the growing pig. Maize starch and wood cellulose were selected as references. The inner fibre-containing diet was also supplemented with enzymatically hydrolysed casein (EHC) in order to test the peptide alimentation method on a diet containing a fibre source with a high water-holding capacity (WHC = 10.9 g water g-1 DM). The fibres were also analyzed by different methods (crude fibre, NDF, ADF, enzymatic gravimetric method, Englyst method). The fibre content of the inner fibre fraction varied widely from one method to another and ranged from 109 g crude fibre to 480 g AOAC fibre kg-1 DM. Compared to the 'maize starch + wood cellulose' diet (11.0 g AA excreted kg-1 DM intake), pea starch had no effect on ileal AA losses (9.6 g), whereas pea hulls slightly increased them (14.2 g). The AA excretion dramatically increased with the incorporation of inner fibres (28.0 g), because of their very high WHC. The addition of EHC increased the output (48.0 g) further, at a level that can hardly be explained only by an increase of the endogenous secretions. The results suggest that the NDF content of grain legume products is not indicative of their effect on the ileal endogenous AA losses in pigs and that the physiological effects of fibres along the gastrointestinal tract are due to both their chemical and physical properties