Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Agriculture, Food and Environment


Animal and Food Sciences

First Advisor

Dr. David L. Harmon


Endophyte-infected (E+) tall fescue grass has been associated with fescue toxicosis, a costly syndrome characterized by poor cattle performance and health resulting in significant production losses. The fungal endophyte produces ergot alkaloids, which help the grass thrive in poor conditions but are toxic to mammals. A number of symptoms of fescue toxicosis can be related to vasoconstriction of bovine core, peripheral, and foregut vasculature. The first part of this series of experiments demonstrated ergot alkaloids were also vasoactive in midgut vasculature, with the exception of lysergic acid. Additionally, prior dietary exposure to ergot alkaloids decreased the contractile response of mesenteric vasculature to many of the ergot alkaloids tested. In the second part of this series, a non-invasive method was developed for measuring rumen motility in cannulated cattle. Using this technology without different dietary treatments, it was determined that 8 to 16 h after feeding was the least variable between animals and would provide the best opportunity to measure differences in motility. Application of this technique in the third part of this series investigated the effect of ruminally dosed ergot alkaloids on rumen motility. Treatments were not effective at inducing fescue toxicosis, and no differences in rumen motility variables were detected.