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Effects of pure plant secondary metabolites on methane production, rumen fermentation and rumen bacteria populations in vitro
- Joch, M., Mrázek, J., Skřivanová, E., Čermák, L., Marounek, M.
- Journal of animal physiology and animal nutrition 2018 v.102 no.4 pp. 869-881
- 8-hydroxyquinoline, Lachnospiraceae, Ruminococcaceae, Succinivibrionaceae, alpha-pinene, alpha-terpineol, bacterial communities, bornyl acetate, camphor, community structure, denaturing gradient gel electrophoresis, fermentation, methane, methane production, quinones, rumen, rumen bacteria, rumen fermentation, secondary metabolites, thymol, volatile fatty acids
- In this study, the effects of seven pure plant secondary metabolites (PSMs) on rumen fermentation, methane (CH₄) production and rumen bacterial community composition were determined. Two in vitro trials were conducted. In trial 1, nine concentrations of 8‐hydroxyquinoline, α‐terpineol, camphor, bornyl acetate, α‐pinene, thymoquinone and thymol were incubated on separate days using in vitro 24‐hr batch incubations. All compounds tested demonstrated the ability to alter rumen fermentation parameters and decrease CH₄ production. However, effective concentrations differed among individual PSMs. The lowest concentrations that reduced (p < .05) CH₄ production were as follows: 8 mg/L of 8‐hydroxyquinoline, 120 mg/L of thymoquinone, 240 mg/L of thymol and 480 mg/L of α‐terpineol, camphor, bornyl acetate and α‐pinene. These concentrations were selected for use in trial 2. In trial 2, PSMs were incubated in one run. Methane was decreased (p < .05) by all PSMs at selected concentrations. However, only 8‐hydroxyquinoline, bornyl acetate and thymoquinone decreased (p < .05) CH₄ relative to volatile fatty acids (VFAs). Based on denaturing gradient gel electrophoresis analysis, different PSMs changed the composition of bacterial communities to different extents. As revealed by Ion Torrent sequencing, the effects of PSMs on relative abundance were most pronounced in the predominant families, especially in Lachnospiraceae, Succinivibrionaceae, Prevotellaceae, unclassified Clostridiales and Ruminococcaceae. The CH₄ production was correlated negatively (−.72; p < .05) with relative abundance of Succinivibrionaceae and positively with relative abundance of Ruminococcaceae (.86; p < .05). In summary, this study identified three pure PSMs (8hydroxyquinoline, bornyl acetate and thymoquinone) with potentially promising effects on rumen CH₄ production. The PSMs tested in this study demonstrated considerable impact on rumen bacterial communities even at the lowest concentrations that decreased CH₄ production. The findings from this study may help to elucidate how PSMs affect rumen bacterial fermentation.