In Vitro and In Vivo Ruminal and Physiological Responses to Endophyte-Infected Tall Fescue

M. L. Westendorf, G. E. Mitchell, R. E. Tucker, L. P. Bush, R. J. Petroski, R. G. Powell

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42 Scopus citations


Relationships between alkaloid compounds in endophyte-infected tall fescue and ruminal metabolism were studied in two experiments. In the first experiment, different combinations of the pyrrolizidine alkaloids, N-formyl and N-acetyl loline, were incubated with ruminal fluid for 0, 24, or 48 h. Rate of disappearance of N-formyl and N-acetyl loline increased over time. After 48 h, disappearance of N-formyl loline and combinations of N-formyl and N-acetyl loline was greater than N-acetyl loline. Significant amounts of N-formyl and N-acetyl loline were metabolized and converted to loline. In the second experiment, abomasally cannulated sheep were fed increasing amounts of endophyte-infected feed to compare diet digestibility, alkaloid metabolism, and physiological responses. Total tract DM digestibility was greatest for the endophyte-free diet, as were ruminal and total tract ADF, ruminal NDF, and total tract CP digestibilities. N-Formyl and N-acetyl loline recoveries averaged 5% from abomasal contents and 0% in feces. Sixty-eight percent of the pyrrolizidine alkaloids recovered in abomasal contents had been metabolizable to loline. Ergot alkaloids administered in the diet were recovered (50 to 60%) in the abomasal contents, but recovery was only 5% in fecal collections. No significant differences occurred in the physiological parameters measured. Results indicate that response to endophyte-infected tall fescue may be influenced by ruminal metabolism.

Original languageEnglish (US)
Pages (from-to)555-563
Number of pages9
JournalJournal of Dairy Science
Issue number2
StatePublished - 1993
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Food Science
  • Animal Science and Zoology
  • Genetics


  • AL
  • EF
  • EI
  • FL
  • N-acetyl loline
  • N-formyl loline
  • endophyte-free
  • endophyte-infected (945 and 2346 mg)
  • ruminal, tall fescue, endophyte, alkaloid


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