Transit bacterien dans le tube digestive de la truite arc-en-ciel

The present study concerns bacterial transit in the digestive tract of rainbow trout at 13 degree C and compares fecal excretion of 4 tracers in the alimentary bolus, an inert bacterial tracer: spores of Bacillus stearothermophilus , a bacterial marker capable of multiplying in the digestive organs: Citrobacter freundii ; a tracer of the liquid phase: polyethylene glycol (PEG), a tracer of the solid phase: Cr sub(2)O sub(3). Two peaks of fecal excretion of bacterial bodies are indicated in the results, the first one taking place within the first 4 h following ingestion of the traced meal, the second peak, a hundred times more important, occurring 10 h after the meal. This two-phase mode of excretion corroborates the observations previously made. The physical tracers (PEG and Cr sub(2)O sub(3)) utilized seem to follow the same pattern of excretion, in spite of a lesser sensitivity. They show the existence of an early faecal excretion. A high number of pyloric caeca does not seem to involve modifications of the digestive transit speed. These results show interest in bacteria as markers of liquid and solid phases in the alimentary bolus.