In vivo vs. in vitro Continuous Culture of Ruminal Microbial Populations

Two continuous culture fermentors were inoculated with rumen contents from a steer. Steer and fermentors were “fed” the same diet and samples were removed after 3, 7 and 14 days of continuous culture to compare the bacterial population between systems. Four hundred and fifty-one strains were isolated from diluted rumen and fermentor contents and studied for possible presumptive identification. Of these, about 51% were presumptively identified as belonging to known genera of rumen bacteria. The same bacterial groups were predominant in the steer and in the fermentors during the 14-day comparison, although a smaller percentage (P<.05) of the bacteria in the fermentors was identified. There were no differences (P<.05) in the proportion of cellulolytic, amylolytic or acid producers from glucose among the bacterial strains isolated from the steer and fermentor cultures. The protozoal numbers were lower and the viable bacterial numbers slightly higher in the fermentors than in the steer. Similar changes in the numbers of certain bacteria were noted in the steer and fermentors.