EFFECTS OF WHEAT-FLOUR AND OAT MILL FRACTIONS ON JEJUNAL FLOW, STARCHDEGRADATION AND ABSORPTION OF GLUCOSE OVER AN ISOLATED LOOP OF JEJUNUM IN PIGS

The effect of cereal-based diets varying in dietary fibre (DF) on gast ric emptying and glucose absorption over an isolated loop of jejunum w as studied in four pigs fitted with two sets of re-entrant cannulas. T he pigs were fed on either a wheat-hour diet or three diets based on o at flour (endosperm), rolled oats or oat bran containing different amo unts of soluble DF. Mean transit time (MTT) of liquid estimated from t he output from the first jejunal cannula was significantly higher with the two diets having the highest DP content, but MTT of dry matter (D M), starch, xylose and neutral non-starch polysaccharides (nNSP) was n ot correlated directly to the DF content of the diet. DP had a stimula tory effect on secretion of gastrointestinal juices, but the effect wa s not linearly correlated with the DP content of the diet. Starch was significantly degraded in digesta collected within 30 min after feedin g with maltooligosaccharides accounting for 140-147 g/kg total starch. The degradation was more extensive with higher DF and lower starch co ntent of the diet. However, taking into account the differences in jej unal how, the amount of malto-oligosaccharides available for absorptio n in the first 0.5 h decreased with higher levels of DF in the oat-bas ed diets. The absorption of glucose from the isolated loop was 18-34 g /m intestine over an 8 h period with no significant differences betwee n diets. This corresponded to a non-significant decrease in recovery o f starch from 0.91 to 0.82 with increasing levels of DF and decreasing levels of starch in the diet. This suggests that the capacity for abs orption of large doses of starch entering the proximal small intestine after ingestion of a carbohydrate-rich cereal-based diet has a major influence on the absorption at this site. Consequently any effect of D P on glucose absorption may be exerted either through the rate of gast ric emptying or by impaired rate of absorption more distal in the smal l intestine and not by displacement of the site for starch absorption.