Interferon tau (IFNT), has known as a key signal molecule for a period of pregnancy in ruminants owing to the need on maternal recognition of pregnancy. It is generated in trophectoderm cells of the elongation bovine conceptus at day 13-21 and a peak output is at day 15-17 of pregnancy period. Moreover, other studies indicated that it can be effective in the embryonic development and quality. In previous study, there were 8 bovine IFNT, but only 2 forms of IFNTs, IFNT2 and IFN-tau-c1, were expressed by the conceptuses during the peri-implantation. In this study, we target the one between the two, IFN-tau-c1 and then the effect of IFNT knockout in donor cells to bovine cloned embryonic development by somatic cell nuclear transfer (SCNT) was investigated. In order to proceed this study, the immature oocytes from the ovaries at local slaughterhouse have been matured in vitro for 22 hours. For preparing the donor cell that have a mutation on IFNT gene, somatic cells were transiently transfected with Cas9 protein and single guide RNA targeting IFNT, and various single derived colonies with high proliferation were isolated and confirm the mutation by PCR. Finally, one colony had mono-allelic mutation (4bps deletion) was picked out and applied as the donor cell to SCNT. A donor cell was injected into an oocyte that nucleus was removed. Reconstructed oocytes with the donor cell were fused by electrical shock, activated by chemical stimulation and cultured for 7 days in chemically defined medium. In this study, control (n=199) and IFNT knockout-group (n=219) were compared with four replications. As results, there was no significant difference between control-and IFNT-knockout group not only in cleavage rate, but also blastocyst formation rate (Control: 12.3% ± 9.2, IFNT knockout-group: 20.1 ± 11%). In addition, the number of blastocyst cell was not different between control (91.7 ± 26.2) and IFNT knockout group (83.5 ± 21.3). Some IFNT mutated blastocysts from SCNT were randomly selected for confirmation of the deletion of IFNT and all samples were positive for mutation. In conclusion, these data indicated that the interruption of IFNT did not influence the embryonic development. In future study, we will transfer these mutated embryos toto test the effect of IFNT for pregnancy period. This work was supported by BK21 PLUS Program for Creative Veterinary Science, the National Research Foundation of Korea (2017R1A2B3004972) and the Technology Development Program (S2566872) by MSS.