DIETARY FIBER VISCOSITY AND AMINO-ACID DIGESTIBILITY, PROTEOLYTIC DIGESTIVE ENZYME-ACTIVITY AND DIGESTIVE ORGAN WEIGHTS IN GROWING RATS

The effect of dietary fiber viscosity on apparent ileal nitrogen and a mino acid digestibility, proteolytic enzyme activity and digestive org an weights was investigated. Eighteen growing rats were fed for 21 d p urified casein-based diets containing carboxymethylcellulose (50 g/kg) of low (20 cP), medium (800 cP) and high (2000 cP) viscosity (LV, MV and HV treatment groups, respectively). Dietary fiber viscosity did no t significantly affect apparent ileal (terminal 15 cm of the iIeum) ni trogen or amino acid digestibility, trypsin or chymotrypsin activity i n the small intestinal contents and pancreatic tissue, aminopeptidase- N activity in the small intestinal contents and tissue, or the weights of the stomach, pancreas, small or large intestines. Intragastric pep sin activity in LV rats was significantly higher than in MV or HV rats (P < 0.01), but fiber viscosity did not affect pepsin activity in the stomach tissue. The intragastric pH of the HV and MV rats was signifi cantly higher than that for the LV rats (P < 0.01). The stomach conten ts (dry matter) of MV and HV rats were greater than in LV rats (P < 0. 05). Delayed passage rate of the more viscous digesta may have resulte d in greater absorption of amino acids, because the HV rats had a high er estimated true ileal digestibility than the LV animals for threonin e, serine, aspartic acid, glutamic acid, histidine, tyrosine and pheny lalanine.