The Bovine Ruminal Fluid Metabolome

The rumen is a unique organ that serves as the primary site for microbial fermentation of ingested plant material for domestic livestock such as cattle, sheep and goats. The chemical composition of ruminal fluid is thought to closely reflect the healthy/unhealthy interaction between rumen microflora and diet. Just as diet and feed quality is important for livestock production, rumen health is also critical to the growth and production of high quality milk and meat. Therefore a detailed understanding of the chemical composition of ruminal fluid and the influence of diet on its composition could help improve the efficiency and effectiveness of farming and veterinary practices. Consequently we have undertaken an effort to comprehensively characterize the bovine ruminal fluid metabolome. In doing so, we combined NMR spectroscopy, inductively coupled plasma mass-spectroscopy (ICP-MS), gas chromatography-mass spectrometry (GC-MS), direct flow injection (DFI) mass spectrometry and lipidomics with computer-aided literature mining to identify and quantify essentially all of the metabolites in bovine ruminal fluid that can be routinely detected (with today's technology). The use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these techniques. Tables containing the set of 246 ruminal fluid metabolites or metabolite species, their concentrations, related literature reference and links to their known diet associations for the bovine rumen metabolome are freely available at http://www.rumendb.ca.