Repeated ruminal dosing of Ruminococcus spp. does not result in persistence, but changes in other microbial populations occur that can be measured with quantitative 16S-rRNA-based probes

Digestibility of fibre in ruminants may be improved by the introduction of highly fibrolytic strains of ruminal bacteria. This approach may be feasibl e if, for example, strains of Ruminococcus that are significantly more fibr olytic than the normal population of Ruminococcus are used for inoculation purposes. Introduced strains of bacteria, irrespective of ecosystem, often decline after inoculation, and in this study, highly fibrolytic strains of Ruminococcus were continuously dosed to ensure that measurements of fibre d igestion were made in the presence of significant numbers of the introduced bacteria. During dosing the total culturable count increased significantly (P < 0.05), but declined post dosing. The level of dosed Ruminococcus, and total Ruminococcus, Fibrobacter succinogenes and eukaryotes measured by 16 S rRNA probes increased significantly (P < 0.05) during the dosing period, but also declined post-dosing. When in vitro nylon bag digestibility, feed intake or whole-tract digestibility was measured, no improvement could be m easured.