title: Natural variation in methane emission of sheep fed on a lucerne pellet diet is unrelated to rumen ciliate community type.
abstract: Only limited information is available on the roles of different rumen ciliate community types, first described by Eadie in 1962, in enteric methane (CH4) formation by their ruminant hosts. If the different types were differentially associated with CH4 formation, then ciliate community typing could be used to identify naturally high and low CH4-emitting animals. Here we measured the CH4 yields [g CH4 (kg feed dry matter intake, DMI)(-1)] of 118 sheep fed a standard pelleted lucerne diet at two different times, at least 2 weeks apart. There were significant differences (P < 2.2 × 10(-16), Wilcoxon rank sum test) in the CH4 yields (± sd) from sheep selected as high [16.7 ± 1.5 g CH4 (kg DMI)(-1)] and low emitters [13.3 ± 1.5 g CH4 (kg DMI)(-1)]. A rumen sample was collected after each of the two measurements, and ciliate composition was analysed using barcoded 454 Titanium pyrosequencing of 18S rRNA genes. The genera found, in order of mean relative abundance, were Epidinium, Entodinium, Dasytricha, Eudiplodinium, Polyplastron, Isotricha and Anoplodinium-Diplodinium, none of which was significantly correlated with the CH4 emissions ranking associated with the rumen sample. Ciliate communities naturally assembled into four types (A, AB, B and O), characterized by the presence and absence of key genera. There was no difference in CH4 yield between sheep that harboured different ciliate community types, suggesting that these did not underlie the natural variation in CH4 yields. Further research is needed to unravel the nature of interactions between ciliate protozoa and other rumen micro-organisms, which may ultimately lead to contrasting CH4 emission phenotypes.
authors.affiliation: AgResearch Ltd, Grasslands Research Centre, Palmerston, North 4442, New Zealand.
authors.forename: Sandra
authors.initials: S
authors.lastname: Kittelmann
authors.affiliation: AgResearch Ltd, Grasslands Research Centre, Palmerston, North 4442, New Zealand.
authors.forename: Cesar S
authors.initials: CS
authors.lastname: Pinares-Patiño
authors.affiliation: AgResearch Ltd, Grasslands Research Centre, Palmerston, North 4442, New Zealand.
authors.forename: Henning
authors.initials: H
authors.lastname: Seedorf
authors.affiliation: AgResearch Ltd, Grasslands Research Centre, Palmerston, North 4442, New Zealand.
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Kirk
authors.affiliation: AgResearch Ltd, Invermay Agricultural Centre, Mosgiel 9053, New Zealand.
authors.forename: John C
authors.initials: JC
authors.lastname: McEwan
authors.affiliation: AgResearch Ltd, Grasslands Research Centre, Palmerston, North 4442, New Zealand.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Janssen
mesh_terms: D000821:Animal Feed; D000818:Animals; D058448:Biota; D016798:Ciliophora / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004032:Diet / Q000379:methods*; D000455:Medicago sativa / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012417:Rumen / Q000469:parasitology*; D017422:Sequence Analysis, DNA; D012756:Sheep
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D008697:Methane