title: Effect of progressive inoculation of fauna-free sheep with holotrich protozoa and total-fauna on rumen fermentation, microbial diversity and methane emissions.
abstract: Rumen methanogenesis represents an energy waste for the ruminant and an important source of greenhouse gas; thus, integrated studies are needed to fully understand this process. Eight fauna-free sheep were used to investigate the effect of successive inoculation with holotrich protozoa then with total fauna on rumen methanogenesis. Holotrichs inoculation neither altered rumen fermentation rate nor diet digestibility, but increased concentrations of acetate (+15%), butyrate (+57%), anaerobic fungi (+0.82 log), methanogens (+0.41 log) and methanogenesis (+54%). Further inoculation with total fauna increased rumen concentrations of protozoa (+1.0 log), bacteria (+0.29 log), anaerobic fungi (+0.78 log), VFA (+8%), ammonia and fibre digestibility (+17%) without affecting levels of methanogens or methanogenesis. Rumen methanogens population was fairly stable in terms of structure and diversity, while the bacterial community was highly affected by the treatments. Inoculation with holotrich protozoa increased bacterial diversity. Further inoculation with total fauna lowered bacterial diversity but increased concentrations of certain propionate and lactate-producing bacteria, suggesting that alternative H2 sinks could be relevant. This experiment suggests that holotrich protozoa have a greater impact on rumen methanogenesis than entodiniomorphids. Thus, further research is warranted to understand the effect of holotrich protozoa on methane formation and evaluate their elimination from the rumen as a potential methane mitigation strategy.
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion SY23 3DB, UK.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Belanche
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion SY23 3DB, UK.
authors.forename: Gabriel
authors.initials: G
authors.lastname: de la Fuente
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, Ceredigion SY23 3DB, UK cjn@aber.ac.uk.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Newbold
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000818:Animals; D016798:Ciliophora / Q000378:metabolism; D004043:Dietary Fiber; D019605:Euryarchaeota / Q000378:metabolism; D005285:Fermentation / Q000502:physiology*; D005658:Fungi / Q000378:metabolism; D006790:Host-Parasite Interactions / Q000502:physiology*; D019344:Lactic Acid / Q000096:biosynthesis / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis / Q000378:metabolism*; D012150:Polymorphism, Restriction Fragment Length; D011422:Propionates / Q000378:metabolism; D012417:Rumen / Q000382:microbiology* / Q000469:parasitology*; D012756:Sheep / Q000382:microbiology / Q000469:parasitology
chemical_list: D004043:Dietary Fiber; D011422:Propionates; D019344:Lactic Acid; D000641:Ammonia; C029658:propionic acid; D008697:Methane
keywords: entodiniomorphids; fermentation; holotrichs; methanogenesis; methanogens; rumen protozoa