Factors influencing bacterial attachment to the ruminal epithelium in vitro

Some factors influencing bacterial attachment to the rumen epithelium were studied in vitro using mixed rumen bacteria (upper- or lower-layer bacteria formed at bacterial sediment by centrifugation), isolated from steers fed a roughage diet, and rumen epithelial cells collected from beef cattle given low-concentrate (50%; LC) and high-concentrate (90%; HC) diets. Optimal incubation conditions for bacterial attachment to rumen epithelial cells were 39 degrees C for 30 min. The bacteria isolated from the upper layer had a higher attaching activity to the LC epithelial cells than those of the lower layer. A higher degree of bacterial attachment was observed using the rumen epithelium from steers fed the LC diet rather than the HC diet (p<0.01). Ethylenediamine dihydroiodide (EDDI) added at 10 through 40 &mgr;g/ml increased bacterial attachment to the HC epithelial cells. Ammonia at 50 through 100 &mgr;g/ml positively affected bacterial attachment to both LC and HC epithelial cells. Bacterial attachment to the HC epithelial cells was enhanced (p<0.01) by the addition of a reducing agent (L-cysteine.HCl) but no increase was noted with LC cells. L- or D-lactate, volatile and unsaturated fatty acids markedly decreased bacterial attachment to rumen epithelial cells.