Journal of Chemical Ecology

, Volume 32, Issue 1, pp 15–28 | Cite as

Interactions Between Euphorbia esula Toxins and Bovine Ruminal Microbes

  • Scott L. Kronberg
  • Fathi T. Halaweish
  • Mindy B. Hubert
  • Paul J. Weimer


Cattle generally avoid grazing leafy spurge (LS; Euphorbia esula), whereas sheep and goats will often eat it. Understanding metabolism of toxic phytochemicals in LS by bovine rumen microflora may help explain why cattle often develop aversions to LS after initially eating it. Toxicity of LS compounds after in vitro fermentation with normal vs. antibiotic-modified bovine rumen digesta was evaluated at different lengths of fermentation. Levels of toxic and aversion-inducing ingenols were determined for fermented and nonfermented mixtures of LS and bovine rumen digesta, and the toxicity of an aversion-inducing extract of LS to rumen microbial species that are common in cattle, sheep, and goats was evaluated. Fermentation of LS with bovine digesta increased the toxicity of extracted compounds. Introduction of neomycin (an antibiotic that preferentially inhibits gram-negative bacteria) into the LS and bovine rumen digesta mixtures did not appear to affect toxicities regardless of fermentation length. Levels of ingenol were observed in LS and bovine digesta mixtures (both fermented and nonfermented) that were consistent with levels of ingenols reported for LS. Finally, a toxic extract of LS had little or no negative effect on the growth of several common species of rumen bacteria. The results indicate that LS is not generally toxic to the ruminal bacteria, but that microbial activity in the rumen may be responsible for enhancing LS toxicity to cattle.

Key Words

Cattle ingenol leafy spurge ruminal fermentation toxicity 



We thank Kristine Nichols, Douglas Ranynie, Igor Sergeev, and anonymous reviewers for their helpful comments on the manuscript and Kjersten Grong for help with the brine shrimp toxicity assays.


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Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • Scott L. Kronberg
    • 1
  • Fathi T. Halaweish
    • 2
  • Mindy B. Hubert
    • 3
  • Paul J. Weimer
    • 4
  1. 1.Northern Great Plains Research LaboratoryUSDA-Agricultural Research ServiceMandanUSA
  2. 2.Department of Chemistry and BiochemistrySouth Dakota State UniversityBrookingsUSA
  3. 3.West River Agricultural CenterSouth Dakota State UniversityRapid CityUSA
  4. 4.US Dairy Forage Research Center, USDA-Agricultural Research Service, and Department of BacteriologyUniversity of WisconsinMadisonUSA

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