IMPROVING THE EFFICIENCY OF BOVINE SOMATIC CELL NUCLEAR TRANSFER PROTOCOL BY ESTABLISHMENT OF CULTURE MEDIUM CHANGING SYSTEM

Bovine cloning is expected as a promising technology for endangered genome conservation and the production of transgenic cloned cows to manufacture human recombinant proteins. However, cloned bovine embryos often resulted in poor development, thus reducing the success of producing cloned offspring. One of the reasons is based on culture medium, which directly relates to the development of cloned bovine embryos. This study aimed to establish culture medium changing system to improve the efficiency of bovine somatic cell nuclear transfer protocol. Our results showed that using the culture medium of Takahashi and First 1992 produced the cloned bovine blastocyst at the highest rate (9.4%, P < 0.05) among different modified synthetic oviduct fluid (mSOF) media. In addition, the rate of embryos developed to the hatching blastocyst was highest in the culture group within transfer embryos to the fresh medium with 5% FBS on day 3 and day 5 (18.5%) compared to the other treatments. Finally, we found that cloned embryos in the group of partial replacement presented significantly higher blastocyst formation rate and quality compared to the group of full replacement (27.6% and 15.6%, respectively, P < 0.05), and it also showed the highest number of cells in blastocyst (about 116 cells). In conclusion, using mSOF and changing the fresh medium supplemented with 5% FBS on day 3 following partial replacement on day 5 improved the preimplantation development of cloned bovine embryos and promoted the blastocyst quality.