Gastrointestinal implications in the rat of wheat bran, oat bran, and pea fibre

The gastrointestinal (GI) effects of three different dietary fibre (DF) sources: wheat bran (WB), oat bran (OB) and pea fibre (PF), were compared with a low-fibre diet in a 4-week trial with rats (initial body-weight 210 g). The DF sources varied widely in chemical composition, solubility and water-holding properties, and particle size. The DF sources were mixed into diets to comprise the same amount of non-starch polysaccharides (NSP; 135 g/kg dry matter (DM)). Compared with the control diet, all fibre-containing diets reduced apparent digestibility of DM, energy, and protein significantly but to different extents. The ranking order of faecal DM bulking followed that of NSP recovery in the faeces: WB > OB > PF > control. The elongating effect of the diets on the GI tract was most pronounced in the rats fed on the OB diet. The mean transit time (MTT) of the OB diet was similar to that of the control diet (approximately 37 h). which was significantly slower than the MTT of the WB and PF diets (approximately 23 h). The study confirms that no simple cause and effect relationship exists between chemical composition, physical properties, and physiological effects of dietary fibre and their effects along the GI tract.