INFLUENCE OF DIET COMPOSITION ON THE MICROBIAL ACTIVITY IN THE GASTROINTESTINAL-TRACT OF DOGS .2. EFFECTS ON THE MICROFLORA IN THE ILEUM CHYME

The composition and metabolic activities of gut bacteria were investigated in the ileum chyme of four dogs with ileum fistulae (T-Type) and four intact dogs in relation to the dietary protein intake. Greaves, soya protein (hydrolysate) or corn gluten were fed as pure products (not corn gluten) only supplemented with minerals and vitamins, or as part of a mixed diet (55 % of the protein source plus rice, soya oil, cellulose, and vitamin/mineral supplement). Among the total bacterial counts (aerobic and anaerobic bacteria) 2, 4, 6 hours after feeding (ppr.), the major bacterial genera in the ileum chyme were differentiated (6 h ppr.). The metabolic activities of the microflora were estimated from the concentrations of volatile fatty acids in the ileum chyme and H-2-breath tests. In the ileum chyme, the bacterial numbers were fairly stable, independent of the dietary protein source or the sampling time (2-6 h) after feed intake. When mixed diets with 55 % of the respective test protein were offered, no definite change in the bacterial composition of the ileum flora was observed. Feeding greaves, in particular if offered exclusively, led to an increase in CI. perfringens in the ileum chyme (8.7 log/g) compared with the diets based on plant proteins (7.0-7.2 log/g). Enterotoxin production by Clostridium perfringens was not detected in the ileum chyme. The concentrations of volatile fatty acids in the ileum chyme were between 24 and 44 mu mol/g. Higher values occurred if greaves (isolated) or corn gluten (as pan of a mixed dry diet) were ingested. Greaves enhanced the production of butyric acid, which may reflect changes in the microbial colonization of the small intestine (clostridia, fusobacteria). Greaves, fed pure, enhanced the H-2-exhalation. Soya protein induced a delayed, but long-lasting increase in H-2-concentrations in the expired air, but levels were lower if soya protein was fed as part of the mixed diet. Corn gluten had similar effects. It can be concluded that changes in the composition of the intestinal microflora are more likely with unbalanced rations, while dogs fed on mixed diets seem to have a stable intestinal micro-ecology. For investigations into interactions between the diet and the small intestinal bacteria, the H-2-breath rest may be used as diagnostic tool. Higher postprandial H-2-excretion seems to be linked to an increase in the numbers of CI. perfringens in the intestine.