The effect of indigestible particles on digestive transit time and colonic motility in dogs and pigs.

The myoelectric activity of the colon was examined in three dogs and three pigs when they were given a basal diet or a basal diet plus indigestible particles (IP), 2 mm in diameter, at 100 g/kg dry matter. The mean retention time was determined using coloured discs as a marker added to the daily meal. Colonic electromyograms of dogs and pigs given IP revealed a 30% reduction in the number of long spike bursts (LSB) when compared with controls. The other components, propulsive migrating spike bursts (MSB) or non-propulsive short spike bursts (SSB), were unchanged. Mean retention time was decreased from 28.6 h to 17.6 h in dogs and from 129 h to 94.2 h in pigs. These changes developed progressively during 3-4 d in both species, suggesting that the reduction in motor activity was an adaptation to the changes in bulk contents. From the decreased motility of the colon linked to the reduction of LSB and paralleled by an increased transit time, it was concluded that one of the functions of the LSB is to impede the passage of digesta.