[Application of modern molecular biology techniques to study micro-ecosystem in the rumen].

The microbial community inhabiting in the rumen is characterized by its high population density, wide diversity and interactive complexity. However, until recently our knowledge of rumen microbiology was primarily based on classical culture based techniques (isolation, enumeration and nutritional characterization) which probably only account for 10% to 20% of the rumen microbial population. Modem molecular biology techniques provide effective methods to study the micro-ecosystem in the rumen. The use of molecular techniques based on nucleic acid probes is likely to revolutionize the approach to microbial ecology in the rumen and provide, not simply a refinement or increased understanding but a complete description of rumen community for the first time. Modem molecular techniques based on sequence comparisons of nucleic acids may be used to explore molecular characterization and provide a classification scheme which predicts natural evolutionary relationships. Genetic fingerprinting techniques that provide a pattern or profile of genetic diversity have been applied in a variety of environmental studies for the analysis of microbial communities. Whole-cell hybridization is a powerful technique which may be used to study the structure and function of microbial communities in situ and describe the expression of key enzymes. Real-time quantitative PCR technique may be conducted to accurately quantify the target microorganisms in the rumen. Development of these procedures and techniques will result in greater insights into community structure and activity of rumen microbial communities in relation to functional interactions, spatial and temporal relationships between different microorganisms and between microorganisms and feed particles. The successful development and application of these methods promise to provide the first opportunity to link distribution and identity of rumen microbes in their natural environment with their genetic potential and in situ activities.

Tea saponins affect in vitro fermentation and methanogenesis in faunated and defaunated rumen fluid.

The effect of tea saponins (TS) on rumen fermentation and methane emission was examined using an in vitro gas production technique named Reading Pressure Technique. Three levels of TS addition (0, 0.2, 0.4 mg/ml) were evaluated in the faunated and defaunated rumen fluid. Compared to the control, TS addition decreased the 24 h gas production in the faunated rumen fluid, but had a minor effect on gas yield in the defaunated rumen fluid. The TS significantly reduced methane production in vitro. In the faunated rumen fluid, 0.2 or 0.4 mg/ml TS decreased the 24 h methane emission by 12.7% or 14.0%, respectively. Rumen fluid pH value was affected neither by TS addition nor by defaunation. The TS addition had only minor effects on volatile fatty acids, but the yield and pattern of volatile fatty acids were greatly affected by defaunation. While the molar proportion of acetate was not affected by defaunation, the propionate was significantly increased and the butyrate significantly decreased. Ammonia-N concentration and microbial protein yield were influenced by TS inclusion and defaunation. Inclusion of 0.4 mg/ml TS increased the microbial protein mass by 18.4% and 13.8% and decreased the ammonia-N concentration by 8.3% and 19.6% in the faunated and defaunated rumen fluid, respectively. Protozoa counts were significantly reduced by TS inclusion. The current study demonstrated the beneficial effect of TS on methane production and rumen fermentation, and indicated that this may be due to the effect of the associated depression on protozoa counts.

[Methanogens and manipulation of methane production in the rumen].

Methanogens belong to the kingdom of Euryarchaeota in the domain of Archaea. They are characterized by their ability to produce methane under anaerobic conditions. Methane production in the rumen represents a loss of energy for the host animal, and, in addition, methane eructated by ruminants may contribute to a greenhouse effect or global warming. Reduction or elimination of methanogenesis in the rumen has been touted as a way of improving animal production and may marginally benefit to control of anthropogenic release of methane. More and more scientists focus on ruminal methanogens and methanogenesis recently. Authors summarized the manipulation of methanogenesis in the rumen, including defaunation, feed formulation, adding electron acceptors and stimulation of acetogens. The characteristics of methanogenic Archaea and the recent knowledge of the methanogenesis in the rumen were also reviewed in this article.