Ergovaline Recovery From Digested Residues of Grazed Tall Fescue Seedheads.

Ergot alkaloids produced by the endophyte [Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon, and Hanlin] of tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are a common problem faced by livestock producers.  While these toxins are often concentrated within the seedheads, there has been little research done to shown to show the degree at which the alkaloids are released when they are ingested.  The objectives of this study were to determine the extent at which reproductive growth was removed by cattle and the amount of ergovaline that may potentially be released into the rumen.  Reproductive tillers were collected from pastures at the University of Kentucky Animal Research Center (ARC), near Versailles, KY during the summer of 2010.  Also at this time, pastures were monitored for the grazing of reproductive growth by Angus steers.  Samples were digested with two-stage acid-pepsin procedure and the residues, as well as undigested materials, were tested for ergovaline content.  On June 4^th, 60.7% of the seedheads within the pastures had been grazed to some extent.  Before this date removal by animals was minimal (< 5%).  Nearly two weeks after the initial consumption began (June 17^th), removal of seedheads had increased (P < 0.05) to 78.8%% of the culms within the pasture.  The in vitro organic matter digestibility (IVOMD) were significantly higher (P < 0.05) for the seedheads collected on June 11^th and 17^th than those harvested early in the growing season, and is believed to be due to the accumulation of carbohydrate reserves in the developing seed.  Similarly, ergovaline concentrations were higher (P < 0.05) for these dates (3.78 and 4.41 µg g^-1, respectively), and, despite an increase in digestibility, the percentage of ruminally released ergovaline was reduced (P < 0.05) for these samples (97.7% and 95.9%, respectively).  There was no ergovaline detected in the digested residues of seedheads collected before this date, possibly indicating a complete release of the alkaloid from the tissue. It should noted that although there was a decrease in ergovaline release with more mature seedheads, this decrease was relatively small and more total alkaloid was potentially released into the animal due to the large increase in ergovaline concentration for these dates.  Therefore, it may be concluded from this study that a majority (> 96%) of the ergovaline contained within tall fescue seedheads may potentially released into the animal, and that future management strategies should continue to be aimed at controlling reproductive growth of the grass.