Diversity of methanogens in ruminants in Queensland

Methane emissions from ruminant livestock represent a loss of carbon during feed conversion, which has implications for both animal productivity and the environment because this gas is considered to be one of the more potent forms of greenhouses gases contributing to global warming. Many strategies to reduce emissions are targeting the methanogens that inhabit the rumen, but suchanapproachcanonlybe successful if it targets all themajorgroupsof ruminant methanogens. Therefore, a thorough knowledge of the diversity of thesemicrobes in different breeds of cattle and sheep, as well as in response todifferentdiets, is required.Astudywasundertakenusing themolecular techniquesdenaturinggradient gel electrophoresis, DNA cloning and DNA sequence analysis to define the extent of diversity among methanogens in ruminants, particularly Bos indicus cross cattle, on differing forages in Queensland. It was found that the diversity of methanogens in forage-fed cattle in Queensland was greater than in grain-fed cattle but there was little variability in methanogen community composition between cattle fed different forages. The species that dominate the rumen microbial communities of B. indicus cross cattle are from the genusMethanobrevibacter, although rumen-fluid inoculated digestors fed Leucaena leucocephala leaf were populated with Methanosphaera-like strains, with the Methanobrevibacter-like strains displaced. If ruminant methane emissions are to be reduced, then antimethanogen bioactives that target both broad groups of ruminantmethanogens aremost likely to be needed, and as a part of an integrated suite of approaches that redirect rumen fermentation towards other more useful end products. Additional keywords: Archaea, pasture.