In vitro modulation of rumen microbiota and fermentation by native microorganisms isolated from the rumen of a fed-exclusively-on-pasture bovine

Abstract

In order to increase productive yields, modulation of rumen fermentation has been a concern in economically relevant species. The ban of antibiotics has driven attention into alternative strategies to modulate ruminal fermentation. Among these, the use of probiotics appears as an interesting approach. The objective of this work was to assess the potential of native bacteria isolated from the rumen of a fed-on-template-pasture cow to modulate fermentation in vitro and to influence the microbiota structure. Seven native ruminal bacteria strains were used in an in vitro gas production experiment. Fermentation dynamics were evaluated, and volatile fatty acids (VFA) and methane were quantified by high-performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Microbiota structure was assessed by pyrosequencing and methanogens were quantified by quantitative PCR (qPCR). Added strains modulated fermentation dynamics and VFA synthesis. Neither the general structure of the fermenters microbiota, numbers of methanogenic microorganisms nor methane production were altered by added bacteria. However, addition of two strains reduced the volume of gas produced from soluble carbohydrates, while one of them reduced the ratio of gas production in this phase; this was supported by a VFA concentration diminution (4 h incubation) in almost every treatment. Gas produced by fermentation of non-soluble carbohydrates and its fermentation ratio were enhanced by several strains. Also, the abundances of Lachnospiraceae, Veillonellaceae, Rikenellaceae and Succinivibrionaceae were affected by strain supplementation. Modulation of fermentation by selected ruminal native bacteria was achieved, probably enhancing the fermentation of non-soluble carbohydrates. This study represents a new approach in the knowledge related to the use of probiotics in ruminants.