['To assess the effect of six different enteral diets on the gut barrier.', 'Laboratory study.', 'University hospital, Germany.', '70 Specific pathogen free female Crl:CDR BR rats.', 'For 7 days, 6 groups of rats were fed orally with standard chow (n = 15); total parenteral nutrition solution (oral TPN, n = 15); elemental diet (ED, n = 10); nutrient-defined diet (NDD, n = 10); or the NDD supplemented with uracil (NDD+uracil, n = 10), or fibre (NDD+fibre, n = 10).', 'Bacterial translocation to mesenteric lymph nodes, numbers of Gram negative enterobacteria and total aerobic bacteria in the caecum, and intestinal concentrations of secretory IgA.', 'The incidence of bacterial translocation was significantly increased in the groups given oral TPN, ED, NDD, and NDD+uracil compared with the group given chow. Only NDD+fibre resulted in a similar degree of translocation to that in the chow group. All groups in which there was increased translocation had a highly significant overgrowth of aerobic bacteria in the caecum, mainly by Gram negative enteric organisms. The secretory IgA concentration was reduced in the group that had been given oral TPN, and that in the ED and NDD+uracil groups was similar to that in the chow group. NDD and NDD+fibre were associated with higher intestinal concentrations of secretory IgA than chow.'] Is fibre an essential ingredient of enteral diets to limit bacterial translocation in rats?