SELECTED INDIGESTIBLE OLIGOSACCHARIDES AFFECT LARGE-BOWEL MASS, CECALAND FECAL SHORT-CHAIN FATTY-ACIDS, PH AND MICROFLORA IN RATS

Certain indigestible oligosaccharides may benefit gastrointestinal tra ct health via fermentation and proliferation of desirable bacterial sp ecies. The purpose of this study was to elucidate effects of selected oligosaccharides on cecal and fecal short-chain fatty acid (SCFA) conc entration, pH, total large bowel wet weight and wall weight, and gut m icrobiota levels in rats. Fifty male Sprague-Dawley rats were randomly assigned to one of five treatments: 1) control diet; 2) control diet + 5% microcrystalline cellulose (5% CC); 3) control diet + 5% CC + 6% fructooligosaccharides; 4) control diet + 5% CC + 6% oligofructose; or 5) control diet + 5% CC + 6% xylooligosaccharides. The control diet c onsisted of (dry matter basis) 20% protein, 65% carbohydrate, 10.5% fa t, vitamin and mineral mixes. The duration of the study was 14 d. The oligofructose- and fructooligosaccharide-containing diets resulted in higher cecal butyrate concentrations compared with the control, cellul ose and xylooligosaccharide diets. Generally, total cecal SCFA pools w ere higher while pH was lower from ingesting oligosaccharide-containin g diets compared with control or cellulose diets. Cecal total weight a nd wall weight were higher from oligosaccharide consumption, whereas c olonic total wet weight was higher for rats consuming xylooligosacchar ides compared with other treatments; colon wall weight was unaffected by treatments. Cecal bifidobacteria and total anaerobes were higher wh ereas total aerobes were lower in rats fed oligosaccharide diets compa red with those fed the control diet. Cecal lactobacilli levels were un affected by treatment. Dietary incorporation of fermentable, indigesti ble oligosaccharides, by providing SCFA, lowering pH, and increasing b ifidobacteria, may be beneficial in improving gastrointestinal health.