MICHAEL HOELKER1, URBAN BESENFELDER2, VITA HAVLICEK1, FRANCA RINGS1, DAWIT TESFAYE1, DANYEL JENNEN1, KARL SCHELLANDER1
1University of Bonn, Institute of Animal Science, Animal Breeding and Husbandry Group, Germany
2University of Veterinary Sciences, Institute of Animal Breeding and Genetics, Austria
In vitro production (IVP) of bovine embryos offers enormous potential both for agriculture and animal breeding. However, its widespread use is still fraught with problems, since in vitro produced embryos do not reach the quality of in vivo derived embryos. Thereby the aim of the present work was to explore whether a temporary culture in the bovine oviduct enhances the quantity and quality in vitro produced embryos. A total of 758 in vitro produced embryos at 8-cell stage were endoscopically transferred to the oviduct of 15 synchronised recipient heifers (43-59 per recipient) and were flushed back at day 7. As a control we produced 547 embryos parallel and cultured them until day 7 completely in vitro (CR1, 5% CO2, 20% O2). In a second experiment we incubated 646 cumulus oocyte complexes together with frozen-thawed spermatozoa and transferred both into the fallopian tube of the oviducts of 12 synchronised recipient heifers (50-77 cumulus oocyte complexes per recipient) and flushed embryos back at day 7. As a control we cultured 441 cumulus oocyte complexes which had been incubated with spermatozoa parallel to the transferred cumulus oocytes complexes completely in vitro. Embryos transferred into the ovicuct at 8-cell stage did not reach higher blastocyst rates at day 7 than completely in vitro cultured embryos (23.7% vs. 24.7%). Contrary, cumulus oocyte complexes transferred together with spermatozoa into the bovine oviduct at day 0 reached significant higher blastocyst rates (p < 0.05) at day 7 (16.31% vs. 6.89%), day 8 (28.34% vs. 19.72%) and day 9 (31.1% vs. 24.31%) than completely in vitro cultured complexes. Moreover, blastocyst development (day 7/day 9) was faster in the in vivo cultured embryos (52.5% vs. 33.6%). Collectively, we were able to show that in vivo culture from fertilisation up to day 7 can enhance embryonic preimplantative development while in vivo culture from 8-cell to day 7 stage does not. That suggests that microenvironment in the period from fertilisation up to 8-cell stage has superior impact on bovine embryo development in terms of blastocyst quantity and quality than culture condition after 8-cell stage.
Keywords: Bovine, embryo transfer, in vitro, in vivo, oviduct