Vertical Distribution of Ergot Alkaloids in the Vegetative Canopy of Tall Fescue

• Published in: Crop science 2018-03, Vol.58 (2), p.925-931
• Main Authors: Kenyon, Sarah L., Roberts, Craig A., Kallenbach, Robert L., Lory, John A., Kerley, Monty S., Rottinghaus, George E., Hill, Nicholas S., Ellersieck, Mark R.
• Format: Article
• Language: English
• ISSN: 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2017.03.0202

Ergot alkaloids are toxins produced by Epichloë coenophiala (Morgan‐Jones & W. Gams) C.W. Bacon & Schardl, a fungal endophyte that infects tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] and causes fescue toxicosis in livestock. Previous studies have reported the distribution of ergovaline among anatomical parts during reproductive development. This study was conducted to determine the vertical distribution of ergovaline and total ergot alkaloids throughout the vegetative canopy of tall fescue. Between October 2012 and April 2014, whole tillers were harvested four times from a stand of Epichloë‐infected ‘Kentucky 31’ tall fescue near Alton, MO. Harvests occurred in April before boot stage and in October before killing frost. Tillers were sliced into four segments: 0 to 5, 5 to 10, 10 to 15, and >15 cm, where 0 cm was the soil level, and >15 cm was the top of the canopy. Segments were analyzed for ergovaline and total ergot alkaloids. For tillers harvested in April, ergovaline concentration averaged 272 μg kg−1 dry matter (DM) in the 0‐ to 5‐cm segment and decreased linearly upward through the canopy. In October, break‐point regression indicated that ergovaline concentration averaged 1121 μg kg−1 DM in the 0‐ to 5‐cm segment and ≥70% less above 5 cm. Total ergot alkaloid distribution patterns resembled ergovaline distribution in October; total ergot alkaloids averaged 2585 μg kg−1 DM in the 0‐ to 5‐cm segment and >60% less in the upper portion of the canopy. These findings should encourage field advisors to consider variation of toxicity within the canopy of tall fescue when formulating grazing recommendations.