INVESTIGATION OF THE SUBCLINICAL TOXICOLOGICAL EFFECTS OF ERGOT ALKALOID MYCOTOXIN (Claviceps purpurea) EXPOSURE IN BEEF COWS AND BULLS
Date
2020-10-05
Authors
Journal Title
Journal ISSN
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Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
In my dissertation, I examine the effects of ergot alkaloid mycotoxins on vascular and reproductive systems in beef cows and bulls. Ergot alkaloids are toxic secondary metabolites produced by the pathogenic plant fungus Claviceps purpurea. Ergot alkaloids are commonly occurring adulterating toxins in livestock feed and constitute a great concern for the health of animals that consume such feeds. Consumption of these toxins can cause a broad suite of pathophysiological effects. Relevant and up-to-date scientific information on ergotism in livestock is largely unavailable to address this growing issue. The purpose of this research was to better characterize and understand the effects of ergot alkaloids in Canadian beef cattle and to ascertain concentrations at which these effects may occur.
In my first two chapters, beef cows were fed increasing concentrations of ergot alkaloids over a short-term (Chapter 2) and long-term (Chapter 3) basis. As ergot alkaloids have a well-known vasoactive effect, hemodynamics of different arteries were evaluated with ultrasonography (B-mode and Doppler). In both studies, concentration-dependent, subclinical physiological changes in hemodynamics were observed in the caudal artery. These results are significant as a common end-stage manifestation of ergot alkaloid mycotoxicosis is the ischemic necrosis of the tail of exposed cattle. Further, these results indicate that subclinical changes occur at concentrations below current Canadian permissible values. Therefore, vascular changes appear to be the more sensitive indicator of ergot exposure than plasma prolactin changes in cows. Plasma or serum prolactin concentration is an accepted biomarker of ergot alkaloid exposure in livestock.
To address the lack of pharmacokinetic information available on ergot alkaloids in cattle, I conducted two oral pharmacokinetics studies and attempted to develop an analytical method to detect ergot alkaloids in bovine plasma (Chapter 4). Although the method was promising for spiked plasma, ergot alkaloids were not detected in plasma samples collected from ergot-exposed cows. Likely, low oral bioavailability explained the lack of detection of ergot alkaloids in plasma from ergot-exposed cattle. An important practical conclusion of this work is that blood samples from suspected poisoning cases will not be clinically useful.
In my last research chapter (Chapter 5), adult beef bulls were fed diets containing ergot alkaloids for one spermatogenic cycle (i.e., 61 days) to assess the potential negative effects of ergot exposure on sperm production or function. Results of this study indicated that ergot exposure had, at most, a subtle effect on bull sperm endpoints. However, plasma prolactin was affected by treatment. Spermatogenesis is not a sensitive endpoint for ergot exposure in adult bulls. Overall, this work answered questions related to ergot alkaloid exposure that are practically important. This work will enable policy makers to make scientifically-based decisions on guidelines for ergot alkaloids in cattle feed; will bolster the working knowledge of clinicians diagnosing and treating ergot-exposed cattle in the field; and will provide the much sought after information for producers working with ergot-contaminated grain or ergot exposed animals.
Description
Keywords
ergot alkaloids, mycotoxin, bull, cow, vasoconstriction, breeding soundness, LC-MS/MS, Claviceps purpurea
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Toxicology Centre
Program
Toxicology