Rho-associated coiled-coil containing kinase inhibitor improves outcomes of direct-transfer slow-cooled bovine blastocysts

Direct-transfer slow-cooling cryopreservation is a widely used method for bovine embryo cryopreservation. However, the transfer of cryopreserved embryos is associated with reduced pregnancy rates. Rho-associated coiled-coil containing kinase inhibitor (ROCKi) has shown promise in improving the viability of post-warmed vitrified bovine embryos. Our objective was to investigate the effects of ROCKi treatment prior to slow-cooling or after cryopreservation on embryo viability. In vitro produced bovine embryos (n = 571) were randomly assigned to one of five groups: No-cryopreservation control group (NC–C), C–C group were cryopreserved by slow-rate cooling without ROCKi at any point, R–C group were incubated with ROCKi for 2 h before cryopreservation, C–R group were not exposed to ROCKi prior to cryopreservation but were cultured with ROCKi after cryopreservation, and R–R group were exposed to ROCKi before and after cryopreservation. Treatment group was significantly associated with blastocoel re-expansion, hatching, and degeneration (P