In vitro and in vivo ruminal and physiological responses to endophyte-infected tall fescue.
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.
Westendorf
M L
ML
Department of Animal Science, University of Kentucky, Lexington 40546.
Mitchell
G E
GE
Tucker
R E
RE
Bush
L P
LP
Petroski
R J
RJ
Powell
R G
RG
D000164:Acremonium / Q000254:growth & development; D000470:Alkaloids / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D004032:Diet; D004063:Digestion; D066298:In Vitro Techniques; D006109:Poaceae / Q000378:metabolism / Q000382:microbiology*; D012417:Rumen / Q000378:metabolism*; D012756:Sheep
D000470:Alkaloids; C059478:loline