REVIEW: The rumen microbiome: Composition, abundance, diversity, and new investigative tools

Ruminants are able to degrade and use fibrous feed as a source of energy and nutrients because of the presence of complex anaerobic microbiota in the rumen, composed mainly of bacteria, fungi, and ciliate protozoa. Ruminal microorganisms play different roles in feed digestion and act synergistically to ferment plant structural and nonstructural carbohydrates and proteins. This review reports the latest assessment of microbiota diversity in the rumen ecosystem and summarizes the molecular techniques and the newly available “omic” technologies, based on DNA and RNA sequence analysis, which allow for new insights into the structure and functions of these complex microbial communities.