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Ergot alkaloids from endophyte-infected tall fescue decrease reticuloruminal epithelial blood flow and volatile fatty
A P Foote1, N B Kristensen, J L Klotz
1Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
Journal of Animal Science
|August 31, 2013
Summary
Ergot alkaloids from endophyte-infected tall fescue seed reduced rumen epithelial blood flow and volatile fatty acid absorption in steers. These effects, particularly under heat stress, may contribute to fescue toxicosis symptoms like reduced growth.
Area of Science:
- Animal Science
- Ruminant Physiology
- Toxicology
Background:
- Endophyte-infected tall fescue (E+) produces ergot alkaloids, which can cause fescue toxicosis in livestock.
- Fescue toxicosis is associated with reduced feed intake, growth, and thermoregulation, but the impact on rumen function is not fully understood.
- Ergot alkaloids are known vasoconstrictors, potentially affecting blood flow to vital organs.
Purpose of the Study:
- To investigate the effect of ergot alkaloids from E+ tall fescue seed on reticuloruminal epithelial blood flow in steers.
- To determine if heat stress exacerbates the effects of ergot alkaloids on rumen blood flow and volatile fatty acid (VFA) flux.
- To assess the direct impact of ergovaline on rumen epithelial blood flow and VFA absorption.
Main Methods:
- Eight steers were fed alfalfa and dosed with either E+ or endophyte-free (E-) tall fescue seed for 7 days under thermoneutral (TN) or heat stress (HS) conditions.
- Rumen epithelial blood flow was measured using deuterium oxide (D2O) clearance after infusing buffers containing different concentrations of ergovaline extract (CON, 1xEXT, 3xEXT).
- Volatile fatty acid (VFA) flux was also measured, and serum prolactin levels were monitored.
Main Results:
- E+ seed consumption reduced feed intake under HS but not TN conditions.
- Ergovaline extract in the buffer significantly reduced rumen epithelial blood flow by at least 50% at TN, with a larger reduction observed in steers fed E- seed under HS.
- VFA flux was reduced by ergovaline extract, and ergot alkaloid dosing decreased serum prolactin at TN.
Conclusions:
- Ergot alkaloids directly impair rumen epithelial blood flow and reduce VFA absorption.
- Heat stress may interact with ergot alkaloid toxicity, potentially worsening effects on rumen function.
- Reduced VFA absorption due to ergot alkaloids could be a significant factor contributing to the poor performance observed in fescue toxicosis.
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