Abstract
The objective of this study was to improve culture condition of in vitro produced bovine embryo cultured in CR1aa and to examine the developmental ability of the oocytes from a small number of oocytes per drop culture to blastocyst stage in vitro. Bovine cumulus-oocytes complexes (COCs) were matured, fertilized in a 100 μl-drop (10 presumptive COCs/drop) of medium. After insemination, zygotes were divided into three groups; (1) CR1aa: zygotes were cultured in 100 μl-drop of CR1aa (2) CR1aa+TCM: at 72 h after culture in CR1aa, embryos were cultured in TCM (3) TCM: zygotes were cultured in TCM. The blastocyst production rate was significantly higher (p<0.05, P<0.01) with CR1aa+TCM (42.4%) than those of CR1aa+CR1aa and TCM+TCM (31.3, 22.5%, respectively). To examine the effect of number of oocytes on the IVMFC, zygotes were cultured 2-9 or 10 embryos per 100 μl drop in CR1aa+TCM for 11 days. The proportion of embryos cleaved and blastocysts were not different between embryos derived from 10 embryos/drop and 2-9 embryos/drop (80.9% vs. 13.6% and 65.5% vs. 13.7%, respectively). Four blastocysts developed from 2-9 embryos per drop were transferred into recipients. One of the 4 recipients became pregnant. One male live calf was born at 286 day. These results indicate that CR1aa+TCM are effective media for IVC of a small number of embryos per drop, and embryos from a small number of embryos per drop have the developmental capacity to become calf.
