Estimation of the potential digestibility and rate of degradation of water-insoluble dietary fiber in the pig cecum with a modified nylon bag technique

Potential digestibility and rate of degradation of water-insoluble material (WIM) prepared from rutabaga, wheat bran and digesta recovered from the terminal ileum of pigs fed bran- or rutabaga-based diets were measured in the cecum of surgically modified pigs. WIM samples recovered from the cecum after fixed incubation times were analyzed and the rate of total disappearance of organic matter, cellulose, uronic acid and noncellulosic neutral sugars was calculated. Maximum degradation of each WIM occurred within 48 h after incubation and was for rutabaga and its ileal digesta 90 and 70%, respectively, and for bran and bran ileal digesta 55 and 45%, respectively. Cellulose and uronic acid in bran samples did not appear to be degraded, material disappearance being attributable to the loss of noncellulosic neutral sugars. Estimation of potential organic matter digestibility showed rutabaga to be 93%, rutabaga digesta 79%, bran 56% and bran digesta 43% digestible. Fractional rates of digestion in rutabaga samples were significantly faster than in corresponding bran samples. When related to the role of fiber in nutrition the results obtained suggest that cereal fiber would be only slightly modified during gut transit, unlike vegetable fiber in which microbial digestion would probably result in the total destruction of the fiber cell wall matrix.