EFFECT OF A REDUCTION IN FIBER CONTENT ON THE RATE OF PASSAGE THROUGHTHE DIGESTIVE-TRACT OF THE RABBIT - COMPARISON OF MODELS FOR THE FECAL KINETICS OF 2 MARKERS

Effect of a reduction in fibre content on the rate of passage through the digestive tract of the rabbit. Comparison of models for the fecal kinetics of 2 markers. The rate of passage (RP) in several digestive c ompartments was studied in 4 adult female rabbits cannulated at ileum, and receiving ad libitum 3 diets with decreasing fibre content (40, 3 0 and 22% NDF). The RP values in the whole digestive tract and between ileum and rectum were simultaneously measured by following the fecal kinetics of 2 markers (Yb-169 and Ce-141 adsorbed on the NDF fraction of the diets) given as single doses. The mean retention time (MRT) in the whole tract provided by modelling methods (models: Grovum and Will iams or Ellis) were similar to those obtained by reference method (num eric integration). MRT values in the caecum and the stomach were provi ded by models and were in good agreement with those deduced from refer ence measurements. Compared with the Ellis model, the Grovum and Willi ams model estimated more precisely the RP in tubular compartments (ie small intestine and distal colon); but the increasing part of the kine tics was better fitted using the Ellis model, particularly for low-fib re diets. The decrease in fibre intake (-50%) led to a 12 h increase ( +72%) of the whole tract MRT, originating mainly from a 2-fold increas e of ileo-rectal MRT. The MRT in the stomach decreased from 3 to 1 h, whereas the RP in the small intestine increased. Therefore, the oro-il eal MRT (mean 5 h) was not affected A low dietary fibre induces a long er cecal MRT of large particles, without significant change for fine p articles.