NOMINAL RESPONSE OF PASSAGE RATES TO FIBER PARTICLE-SIZE IN RATS

The influence of wheat bran particle size on the rate of passage of digesta through the rat gut was investigated. Small and large particle size wheat bran-supplemented diets were used in combination with the particulate digestion marker chromium mordanted bran (CrMB) and the soluble digestion marker cobalt-EDTA (Co EDTA). The particle size of CrMB did not significantly affect the estimates of marker residence halftime (t1/2), mean retention time or transit time, when administered to animals fed a large particle bran diet. Utilization of different particle size bran diets and a common small particle CrMB marker tended to result in a longer t1/2 and mean retention time in the smaller particle bran diet. Therefore, the selection of dietary particle size, but not CrMB particle size, tended to influence the estimates of t1/2 and mean retention time. Similarly, the Co EDTA t1/2, mean retention time and transit time tended to be longer in small particle bran-fed animals than in large particle bran-fed animals. In some comparisons the mean retention time of Co EDTA was significantly less (P < 0.05) than that of CrMB, indicating that preferential retention of particles relative to solutes can occur in rats. Nevertheless, the overall movement of the liquid and particles largely corresponded.