Abstract: Low-quality bovine embryos were co-transplanted with trophoblastic vesicles (TRV). These TRV were prepared by dissection of conceptus that were collected by uterine flushing after culture for seven days in the uterus following transfer of embryos derived by in vitro fertilization (IVF). Pregnancy diagnoses were performed twice, in between day 26th and 43rd, between day 38th and 73rd post-estrus by ultrasonography. The pregnancy rate was significantly increased at first pregnancy diag-noses when low-quality bovine embryos were co-transplanted with TRV (66.7%, 16/24) compared with the control group (34.5%, 10/29) (P<0.05). The final pregnancy rate according to delivered offspring was 41.7% (10/24) and 27.6% (8/29), respectively. There were no statistically significant differences between the two groups. The gestation lengths and birth weight of the offspring were almost the same for the co-transplantation and control group.

Key words: low-quality bovine embryos; trophoblastic vesicles; co-transplantation; pregnancy rate; gestation; birth weigh