Differential effects of monensin and a blend of essential oils on rumen microbiota composition of transition dairy cows.
In response to oral application, monensin alters the rumen microbiota, increasing ruminal propionate production and energy availability in the animal. Data from different studies indicate that the susceptibility of rumen bacteria to monensin is mainly cell-wall dependent but tracing its activity to specific microbial groups has been challenging. Several studies have shown a similar effect for essential oils but results are inconsistent. To investigate the influence of monensin and a blend of essential oils (BEO, containing thymol, guaiacol, eugenol, vanillin, salicylaldehyde, and limonene) on the rumen microbiome, rumen liquid samples were collected orally on d 56 postpartum from cows that had either received a monensin controlled-release capsule 3 wk antepartum, a diet containing a BEO from 3 wk antepartum onward, or a control diet (n = 12). The samples were analyzed for pH, volatile fatty acid, ammonia, and lipopolysaccharide concentrations and protozoal counts. A 16S rRNA gene fingerprinting analysis (PCR-single-strand conformation polymorphism) and sequencing revealed that the BEO treatment had no effect on the rumen microbiota, whereas monensin decreased bacterial diversity. Twenty-three bacterial species-level operational taxonomic units were identified for which monensin caused a significant decrease in their relative abundance, all belonging to the phyla Bacteroidetes (uncultured BS11 gut group and BS9 gut group) and Firmicutes (Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae). Ten bacterial operational taxonomic units belonging to the phyla Actinobacteria (Coriobacteriaceae), Bacteroidetes (Prevotella), Cyanobacteria (SHA-109), and Firmicutes (Lachnospiraceae and Ruminococcaceae) increased in relative abundance due to the monensin treatment. These results confirm the hypothesis that varying effects depending on cell-wall constitution and thickness might apply for monensin sensitivity rather than a clear-cut difference between gram-negative and gram-positive bacteria. No effect of monensin on the archaea population was observed, confirming the assumption that reported inhibition of methanogenesis is most likely caused through a decrease in substrate availability, rather than by a direct effect on the methanogens. The data support the hypothesis that the observed increase in ruminal molar propionate proportions due to monensin may be caused by a decrease in abundance of non-producers and moderate producers of propionate and an increase in abundance of succinate and propionate producers.
Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Bundesallee 50, 38116 Brunswick, Germany.
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Schären
Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Bundesallee 50, 38116 Brunswick, Germany.
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Drong
Department of Physiology, University of Veterinary Medicine Hanover, Bischofsholer Damm 15, 30173 Hanover, Germany.
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Kiri
Department of Physiology, University of Veterinary Medicine Hanover, Bischofsholer Damm 15, 30173 Hanover, Germany.
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Riede
Environment, Earth and Ecosystems, The Open University, Milton Keynes, MK7 6AA, United Kingdom.
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Gardener
Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Bundesallee 50, 38116 Brunswick, Germany. Electronic address: Ulrich.Meyer@fli.de.
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Meyer
Ruminant Nutrition, Department of Animal Sciences, Faculty of Agricultural Sciences, Georg-August University Göttingen, Kellnerweg 6, 37077 Göttingen, Germany.
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Hummel
Institute of Microbiology, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 15, 17489 Greifswald, Germany.
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Urich
Department of Physiology, University of Veterinary Medicine Hanover, Bischofsholer Damm 15, 30173 Hanover, Germany.
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Breves
Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Bundesallee 50, 38116 Brunswick, Germany.
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Dänicke
D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary; D005260:Female; D005285:Fermentation; D064307:Microbiota / Q000187:drug effects; D008985:Monensin / Q000494:pharmacology*; D009822:Oils, Volatile / Q000494:pharmacology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012417:Rumen / Q000378:metabolism*
D009822:Oils, Volatile; D012336:RNA, Ribosomal, 16S; D008985:Monensin
essential oils; monensin; rumen microbiota; sequencing