Year of Publication

2012

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture

Department

Veterinary Science

First Advisor

Dr. Karen McDowell

Abstract

Three experiments were conducted to explore the effect of fescue toxicosis on vasoconstriction and various parameters of the estrous cycle. In the experiment of Chapter 3, a 2x2 crossover experimental design with repeated measures was implemented to test whether the ingestion of endophyte-infected tall fescue seed would alter blood hormone concentrations of prolactin, progesterone, and estradiol, interovulatory intervals, and corpus luteum blood flow. Also, Doppler ultrasonography was used to assess whether palmar artery and palmar vein lumen diameter, area, circumference, and resistivity index could be altered by the ingestion of endophyte-infected tall fescue seed. Ingestion of endophyte-infected tall fescue seed significantly decreased palmar artery resistivity index, area, and circumference, and palmar artery and palmar vein lumen diameter, but did not alter interovulatory intervals, serum concentrations of prolactin, progesterone, estradiol, or corpus luteum blood flow. Experiments 1 and 2 from Chapter 4 profiled the dopaminergic, serotonergic, and α-adrenergic receptor types and subtypes, as expressed within the equine medial palmar artery, medial palmar vein, and uterine artery transcriptomes. Combined results from Chapters 3 & 4 imply that relative quantity of serotonergic receptor subtypes within a vessel may be related to with the severity of that vessel's vasoconstrictive response to endophyte-infected tall fescue.

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