Die Bedeutung der Embryonenqualität im Rahmen des Embryotransfers beim Rind – eine Literaturstudie

The aim of this work was to describe the importance of the estimation of the quality of cattle embryos in embryo transfer as well as to discuss the causes of the appearance of the variable embryo qualities after superovulation and the different possibilities to assess the embryo quality. After superovulation there are always variable embryo quality observed. The reasons for this are versatile. An important, the result of a superovulation treatment influencing factor, is the donor cow. Both the individual disposition, the age and as well healthy status and the stressexposition of the animals are playing an important role. The ovary reactions are rather essentially influenced by the existence of a dominant follicle at the moment of introduction of a superovulation treatment. By removal of dominant follicle the results can significant be improved. Another important factor is the sort of a gonadotrophin used for superovulation. The reaction to a superovulation treatment is not just depending on the selection of the gonadotroph hormone, but also on the composition of the preparations, the doses und the way of application. Because the morphological evaluation of embryo quality is subjected to subjective influences, it should attach importance to the training of the evaluating persons, to receive comparable results. The importance of assessment of embryo quality to select embryos is considerable. The results of embryo transfer, the pregnancy rates, are essentially depending on the quality of the transferred embryos. The survival of embryos after kryopreservation is also influenced by the embryo quality. Embryo quality can be evaluated by different approaches: if the selected embryo has to be transferred, the technique to estimate embryo quality must not be invasive. In the practice of the embryo transfer embryo quality is estimated before transfer by gross embryo morphology. However, this method is a rather subjective possibility for assessment of the embryo quality. More accurate date can be obtained by the use of invasive techniques. Metabolic tests to evaluate embryo viability include measurement of nutrient uptake, energy metabolism and oxygen uptake. Enzyme leakage and hormone or growth factor production can also give more details on the quality of embryos. Techniques which might partially are able to affect the embryo are the determination of the freezing resistance and vital staining. With vital staining, membrane integrity, which is critical for embryo survival, can be assessed by means of fluorescent probes. The most common staining methods for evaluating embryo quality are DAPI and FDA. These two fluorescent probes do not alter the embryo, so that you can still transfer the embryo after these examinations. Invasive assessment of the embryo quality mostly involves a kind of fixation or staining of the embryo and so they are not suitable for the practical use of the embryo transfer. Cytogenetic analysis of embryos is an important issue for caryotyping. Chromosomal deviations are known to cause early embryonic mortality in cattle. Determination of the total cell number and the allocation of these cells to the inner cell mass (ICM) and trophectoderm (TE) after differential staining of these cells give more details on the quality of an embryo.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2002

Author dc:creator

• Maag, Sabine

Repository record source_url

https://edoc.ub.uni-muenchen.de/1363/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:1363