Low temperature preservation of bovine ovaries on in vitro development of oocytes

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 $5^{\circ}C$) 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 $15^{\circ}C$ was increased compared to those of 25 or $5^{\circ}C$. The maturation rate of oocytes was not differed between 24 and 36 h at $15^{\circ}C$ but showed lower than control group (71% versus 78%). In vitro-fertilized oocytes from ovaries stored at $25^{\circ}C$ for 24 h or at $5^{\circ}C$ for 24 h had a significantly decreased developmental potentials, but at $15^{\circ}C$ did not (27% versus 29% of blastocysts to develop into day 8). With these results, bovine ovaries can be preserved at $15^{\circ}C$ 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.

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