The ovum pick up(OPU) technique can be used to produce embryos after in vitro culture of ovarian oocytes, can be used for early securement for effective herd early proliferation and excellent Hanwoo genetic resources, It is attracting attention as a very important technique for establishing technology. In addition to in vitro culture techniques, the number of oocytes retrieved depends on the environment and timing of the OPU. This study was conducted to compare and examine seasonal effect to the differences in the number of recovered oocytes, recovery rate and embryo development rate using Korean cattle kept in animal genetic resource research center by OPU technique. The grade of COCs was evaluated by microscopic examination. Grade A had 3 or more layers of cumulus cell and compact cytoplasm. Grade B had 1~3 layers of cumulus cell and compact cytoplasm. Grade C had 1 layers cumulus cell and compact cytoplasm. Grade D was denuded oocyte and poor cytoplasm. The recovery rate was 47.8±3.4% in summer (June to August) and 51.6±3.8% in autumn (September to October). The number of oocytes was 5.7±0.6 in summer and 5.2±0.7 in autumn. Oocyte grade A and B was 46.2%±6.3% in summer and 51.1±5.0% in autumn. The cleavage rate was 46.1±7.1% in summer and 65.0±11.3% in autumn. Blastocyst development rate was 19.9±9.4% in summer and 29.0±8.7% in autumn. There was no difference the recovery rate of oocytes and the number of embryos between summer and autumn. Cleavage rate and blastocyst rate of autumn was higher than summer. we will investigate to study the appropriate method for the production of Hanwoo embryos and the systematic comparison.

The elevated temperature and high humidity has been known as main reason for heat stress on animals and cause detrimental effects on productivity of organisms and physiological conditions of normal bioactivities. The aims of this study were to evaluate the relationship between time of heat shock simulation during in vitro maturation and developmental competence of subsequent embryo after in vitro fertilization. Heat shocked cumulus-oocyte complexes (COCs) of Korean native cattle were subjected to normal conditions for 22, 21, 18 and 12 h respectively and transferred to heat stress inducing condition at 40.5 °C in other incubator for 0 (control), 1 and 4 h. After maturation for 22 h, the oocytes were fertilized and cultured in mSOF media for 8 d and examined the developmental capacity of embryos. There were no differences in maturation and cleavage rates between 0, 1 and 4 h heat socked oocytes, but blastocysts formation were lower in the 4 h heat stressed oocytes. The apoptotic cells of developed blastocysts were also increased in at day 8 with 4 h heat shocked oocytes. These results indicate that heat shock on oocytes during maturation could cause negative effects on the developmental competence of embryos.

During the ovary preservation in low temperature, the cumulus oocyte complexes(COCs) lose their developmental competences after in vitro fertilization. We used phosphate-buffered saline (PBS) as a basic solutions of at various temperatures (25, 15 or 5 ℃) and supplemented them with 1mM glucose and 0.5mM glutamine as a source of carbohydrate metabolites. After recovery of COCs and in vitro fertilization, a significantly higher number of oocytes developed into blastocysts. The developmental competence of embryos that were originated from ovaries preserved at 15 ℃ was increased compared to those of 25 or 5 ℃. The maturation rate of oocytes was not differed between 24 and 36 h at 15 ℃ but showed lower than control group (71% versus 78%). In vitro-fertilized oocytes from ovaries stored at 25 ℃ for 24 h or at 5 ℃ for 24 h had a significantly decreased developmental potentials, but at 15 ℃ did not (27% versus 29% of blastocysts to develop into day 8). With these results, bovine ovaries can be preserved at 15 ℃ for 36 h without decreasing developmental capacity of in vitro-fertilized oocyte at least to the blastocyst stage. This information provides valuable information of preserving ovaries for embryo transfer or in vitro embryo production.