Insemination of recipient sows improves the survival to term of vitrified and warmed porcine expanded blastocysts transferred non-surgically.

This study was performed to evaluate reproductive performance after non-surgical embryo transfer (Ns-ET) of 10-15 porcine expanded blastocysts (ExBs) that had been vitrified and warmed (V/W) using the micro volume air cooling (MVAC) method. The effect of asynchrony between the donor and recipient estrous cycle was investigated. Ns-ET was conducted in recipients whose estrous cycle was asynchronous to that of donors by a delay of 2, 1, or 0 days. In the 2-day and 1-day groups, the similar farrowing rates (27.3% and 25.0%) and survival rates to term (13.9% and 15.7%) were obtained after Ns-ET of V/W ExBs. None of the recipients in 0-day group farrowed. Artificial insemination (AI) prior to Ns-ET was then evaluated. Ten-15 V/W ExBs were transferred non-surgically to 12 recipients whose estrous cycles were asynchronous to that of donors by a 2-day delay. All of the recipients produced piglets, and all (100.0%) delivered piglets were derived from the transferred V/W ExBs. The survival rate of V/W ExBs to term was 25.2%. These results demonstrate that Ns-ET of V/W ExBs using MVAC can facilitate piglet production, even if 10-15 embryos are transferred. Moreover, piglets were obtained stably when AI was performed prior to Ns-ET.