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UBC Theses and Dissertations

Studies on the mycotoxin zearalenone -- Barley zearalenone contamination survey and In Vitro effects of zearalenone on oocytes and pre-implatation embryos Wallace, Christa Jeanne


The mycotoxin zearalenone is known for its harmful effects on livestock reproduction. Animal exposure occurs through feed sources colonized by Fusarium species which produce the mycotoxin. Since regular screening procedures for zearalenone are not conducted on Western Canadian barley, a survey was carried out to test for possible significant levels of contamination. All samples were found to be negative at a detection level of 500 ppb; therefore, feeds formulated from the barley samples sources would not likely cause zearalenone toxicosis problems in livestock. Also, an ELISA method, Agri-Screen™, developed by Neogen Corporation (Lansing, Michigan) was tested and found to be a simple and economical method for pre-screening of feed samples in the field. To study direct toxicological effects of zearalenone on in vitro murine blastocyst development, murine embryos were cultured in medium (Ham's F-10 + estrous cow serum) containing various levels of the mycotoxin. The critical concentration range for zearalenone to cause detrimental effects on blastocyst development was determined to be between 70-160 μg/ml medium. Additionally, a concentration effect on the length of time required to exert deleterious actions was demonstrated. At mycotoxin concentrations of 500 μg/ml medium and above, blastocysts degenerated after 6 h of culture. At a lower concentration level of 160 μg/ml, blastocysts were not affected until 28 h of culture. In order to investigate the direct toxicological effects of zearalenone on in vitro porcine pre-implantation embryo development, attempts were made to develop a successful culture system. Since a suitable system was not developed, toxicological studies were not possible. Possibly, steps in the recovery process could have resulted in detrimental effects before the embryos were placed in culture. Alternatively, the media chosen (Ham's F-10 + estrous cow serum; Minimum essential medium + fetal calf serum) may not be suitable for in vitro culture of porcine pre-implantation embryos. Finally, at a zearalenone concentration level (250 μg/ml medium) found to cause degeneration of murine blastocysts, the in vitro maturation of bovine oocytes in Tissue Culture Medium 199 was not affected. It was suggested that the surrounding cumulus layer acts as a barrier to prevent the mycotoxin from directly acting on the oocyte.

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