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United States Department of Agriculture

Agricultural Research Service

Research Project: OPTIMIZING THE BIOLOGY OF THE ANIMAL-PLANT INTERFACE FOR IMPROVED SUSTAINABILITY OF FORAGE-BASED ANIMAL ENTERPRISES

Location: Forage-Animal Production Research

Title: What fescue toxicosis is really doing inside your animals

Author
item Aiken, Glen

Submitted to: Kentucky Cattlemen's Association
Publication Type: Proceedings
Publication Acceptance Date: December 9, 2011
Publication Date: January 9, 2012
Citation: Aiken, G.E. 2012. What fescue toxicosis is really doing inside your animals. Kentucky Cattlemen's Association. CD-ROM.

Interpretive Summary: Eighty years have passed since Dr. F.N. Fergus collected seed of tall fescue from that hillside in Menefee County, Kentucky that led to the commercial release of the cultivar ‘Kentucky 31’. Plantings of tall fescue were numerous in the state during the 1940s and 1950s, and its hardiness and adaptability resulted in the grass spreading over much of the middle and upper southeastern USA, eventually covering a region now called the “fescue belt”. It did not take long before cattle producers complained of severe lameness and sloughing of hoofs, tails, and ear tips during cold weather, and poor weight gain and thriftiness during warm weather conditions. Reductions in calving rates and milk production were also of concern. Horse producers also identified serious issues with grazing pregnant mares (prolonged gestation, retained placentas, stillborns, and poor milk production) on Kentucky 31 tall fescue. Ergot alkaloids produced by the endophyte were soon identified as the causal factors of fescue toxicosis. Understanding how ergot alkaloids affect animal tissues has been difficult because the biological processes and the chemistry of alkaloids are extremely complex. However, researchers now have the tools needed to improve our understanding of the causes of toxicosis. Although more research is needed to fully understand the toxicosis syndrome, considerable progress has been made over the last 10 years. A paper will discuss what we understand about the mechanisms used by ergot alkaloids to affect 1) vascular blood flow, 2) hair shedding and growth during the summer, and 3) circulating concentrations of the hormone prolactin.

Technical Abstract: Plantings of tall fescue were numerous in Kentucky during the 1940s and 1950s after the cultivar, ‘Kentucky 31’, was released. Its hardiness and adaptability resulted in the grass spreading over much of the middle and upper southeastern USA. Cases of severe lameness and sloughing of hoofs, tails, and ear tips during cold weather, and poor weight gain and thriftiness during warm weather conditions were soon reported for cattle grazing tall fescue pastures. Reductions in calving rates and milk production were also of concern. Horse producers identified serious issues with grazing pregnant mares (prolonged gestation, retained placentas, stillborns, and poor milk production) on tall fescue. It was determined that ergot alkaloids produced by a fungal endophyte that infects the grass were eventually determined to be the cause of the fescue toxicosis syndrome. Complexities of the biological processes and the chemistry of alkaloids have made it difficult to understand how ergot alkaloids affect animal tissues. However, researchers now have the tools needed to improve our understanding of the causes of toxicosis. The paper will discuss our understanding of the mechanisms by which ergot alkaloids affect 1) vascular blood flow, 2) hair shedding and growth during the summer, and 3) circulating concentrations of prolactin. Although, considerable progress has been made over the last 10 years, more research is needed to fully understand the toxicosis syndrome.

Last Modified: 10/1/2014
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