Identifier

etd-07132005-172811

Degree

Doctor of Philosophy (PhD)

Department

Animal Science (Animal, Dairy, and Poultry Sciences)

Document Type

Dissertation

Abstract

The low survival rates of nuclear transfer fetuses and neonates in goats and cattle have been linked to placental abnormalities. A series of studies was designed to investigate the possibility of supplementing nuclear transfer embryos with electrofused embryos to generate placental tissue in goats and cattle. The initial study was designed to determine if the breeding season of goats could be extended with hCG treatment. Progesterone concentrations in treated does increased but pregnancy rates were unaffected. In the second study, goat embryos were electrofused and combined with nuclear transfer embryos at the 8-cell stage to produce the first offspring as a result of electrofused embryo complementation in goats. The remainder of the studies focused on electrofused embryos in cattle. The method of electrofusion was studied and it was determined that fusion efficiency and developmental rates after two fusogenic pulses were not different from fusion efficiency and developmental rates after a single pulse. The latter study also showed that the time of cleavage following in vitro fertilization affected the cleavage and blastocyst rates of embryos after electrofusion. In the next study, electrofused embryos were aggregated with nuclear transfer embryos at the 8-cell stage. Aggregate embryos developed to the blastocyst stage at the same rate as electrofused and nuclear transfer control embryos. The final study was a series of experiments conducted to characterize the nuclear status of electrofused embryos. In the first and second experiments of the series, embryos were stained following electrofusion and it was found that more embryos were tetraploid and fewer were binucleate when embryos were electrofused later after cleavage. The third and fourth experiments in this series examined the stage of the cell cycle prior to electrofusion. These experiments indicated that the embryos electrofused at 30 hours post-insemination were in the G2 phase of the cell cycle. It was concluded that the stage of the cell cycle would be an important factor in the production of tetraploid embryos via electrofusion and this should be the basis of future research in this area.

Date

2005

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Robert A. Godke

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