EFFECTS OF FIBER LAXATIVES AND CALCIUM DOCUSATE ON REGIONAL WATER-CONTENT AND VISCOSITY OF DIGESTS IN THE LARGE-INTESTINE OF THE PIG

The aim of this study was to determine how bulk fibers and calcium doc usate affect regional dehydration and digesta viscosity throughout the large intestine. Fifty-two pigs were fed a chow diet supplemented wit h a bulk laxative, placebo, or calcium docusate for three days, after which the pigs were sacrificed and the contents of the large bowel wer e analyzed. Digesta occurred as a continuum from liquid (cecum, 91.2% water content) to solid (rectum, 70.5% water content). The observed 20 .7% difference in water content resulted in a 240-fold increase in vis cosity. Half of this water is reabsorbed in the first 18% of the large bowel length where viscosity remains relatively low. Compared to plac ebo, calcium docusate and calcium polycarbophil had no significant eff ect on digesta water content or viscosity, polycarbophil exhibited sig nificantly (P < 0.05) lower digesta viscosity in three bowel segments, and psyllium exhibited significantly (P < 0.01) lower viscosity in si x bowel segments and higher water content in nine bowel segments. In c onclusion, the majority of digesta dehydration occurs early in the pro ximal large bowel, while the greatest increases in viscosity occur in the distal bowel. Relatively small decreases in digesta water content result in large increases in digesta viscosity. Psyllium, and to a les ser extent polycarbophil, are able to resist dehydration, resulting in a softer digesta.