Author
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Aiken, Glen |
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Submitted to: Cow Country News
Publication Type: Popular Publication Publication Acceptance Date: 4/18/2015 Publication Date: 5/15/2015 Citation: Aiken, G.E. 2015. From the Lab Bench: Season Changes in Ergot Alkaloid Concentrations of Toxic Tall Fescue. Cow Country News. Pgs. 29-30. Interpretive Summary: Cattle grazing toxic endophyte-infected tall fescue may start spending more time under the shade or standing in the ponds and less time grazing as summer air temperatures approach. Body condition may drop even though forage is in ample supply. Rough, winter hair coats on some or most of the herd do not seem to show signs of shedding. These are typical observations in the late spring and summer, but what about the fall months when we most often see the fescue foot malady? To understand why these signs of toxicosis occur when they do, we must first understand growth of the fungal endophyte within the tall fescue plant and the conditions that cause increases in toxic ergot alkaloid production. Trends of ergot alkaloid concentrations in tall fescue follow the same pattern as the growth of the grass plant, with alkaloid concentrations and plant growth being the highest in the late spring and early summer, low in the summer during periods of high air temperatures, high again in the fall, and minimal during the winter months. Management strategies can be developed for cattle producers that manage toxic endophyte-infected tall fescue to reduce the consumption of tall fescue during the late spring to early summer, and fall seasons when ergot alkaloids can be at their highest concentration. Technical Abstract: A column was written to discuss seasonal trends in ergot alkaloids produced by the fungal endophyte that infects most plants of tall fescue. Tall fescue is the predominant grass utilized for forage in the U.S. transition zone between the temperature northeast and subtropical southeast; however, ergot alkaloids produced by the fungal endophyte that infects tall fescue are the causal agents of fescue toxicosis. Cattle undergoing “fescue toxicosis” can exhibit severe heat stress in the late spring and summer and can further be inflicted with the “fescue foot” condition in the fall and winter that causes extreme lameness and sloughing of hoofs, tail switches, and ear tips. Ergot alkaloid concentrations in fescue tissues are seasonal and understanding these trends could be beneficial in developing management strategies to mitigate fescue toxicosis. Trends of ergot alkaloid concentrations in tall fescue follow the same pattern as the growth of the grass plant. Trends in ergot alkaloid concentrations over months of the year are similar to that of the growth distribution of tall fescue: increases in ergot alklaoids with active growth in the spring, low ergot alkaloid production with low fescue growth in the summer, followed by higher ergot alkaloids with fescue growth rates during the fall, and minimal ergot alkaloids in the restricted growth during the winter production. These trends indicate that cattle grazing toxic endophyte-infected tall fescue should be managed to either remove or reduce the consumption of fresh tall fescue in the late spring to early summer and fall seasons. |
