Small intestinal motility and transit by electromyography and radiology in the fasted and fed pig.

The pattern of small intestinal digesta transit was studied in six young pigs (20-30 kg) by simultaneous electromyography and radiology. Pigs showed migrating myoelectric complexes (m.m.c.s) in the small intestine both when fasted and after feeding. The m.m.c.s were modified by feeding; quiescence was much reduced in duration and irregular spiking activity (i.s.a.) was prolonged; m.m.c.s were not disrupted and phases of regular spiking activity (r.s.a.) were still seen after feeding. The r.s.a. phase could be recognized on the screen and in spot films from both fasting and fed pigs as a band of intense rhythmic contractions pinching off the intestine and propelling all intestinal contents ahead of it. The r.s.a. moved caudad clearing the small intestine of digesta and leaving an empty quiescent intestine behind it. It was particularly characteristic in the fasted pig where it was usually associated with the progression of a gas bubble. The pattern of m.m.c.s in both fasted and fed animals along with the intermittent nature of stomach emptying, divided digesta into batches which progressed through the small intestine. Each batch--propelled by a m.m.c.--normally took 180-190 min to pass through the small intestine. M.m.c.s had a cycle length of 70-115 min in different parts of the small intestine. Usually two or three m.m.c.s and batches of intestinal contents were present in the small intestine at any one time. 22-33% of the m.m.c.s faded out in the proximal ileum. Batches of digesta propelled by these m.m.c.s had transit times increased by one m.m.c. duration and fused with the subsequent batch. Sometimes new m.m.c.s were generated in the terminal ileum. Two patterns of transport into the large intestine were seen. Usually digesta was transported by peristaltic rushes starting 100-200 cm from the ileo-caecal junction. The rush then continued through 1-1 1/2 turns of the spiral colon; occasionally the terminal ileum emptied by slow peristalsis. In this case there was no colonic rush and digesta went into the caecum.