The effect of artificial insemination prior to transfer of a limited number of vitrified and warmed porcine embryos by open pulled straw (OPS) method on their survival ability for farrowing

Embryo transfer (ET) of 20 porcine expanded blastocysts (ExBs) vitrified and warmed (VW) by open pulled straw (OPS) to a recipient allows stable piglet production. The efficiency of artificial insemination (AI) prior to ET of 10 VW ExBs for piglet production was investigated. For one trial, 10-15 VW ExBs from single donor were assigned, 10 were used for ET and the remains were assessed for their in vitro viability. In the non-AI/ET group, 10 were transferred to each of five recipients. As AI/ET group, 10 were transferred to each of five recipients after AI. In AI/non-ET group, only AI was performed to seven gilts. In the non-AI/ET group, the pregnancy rate was 40%, but none of them farrowed. In the AI/ET group, all recipients produced piglets. Four (80.0%) delivered piglets from transferred VW ExBs. The survival rate of VW ExBs to term was 20.0% (10/50). In the AI/non- ET group, six of the seven gilts farrowed. There was no difference in in vitro viability between the non-AI/ET and AI/ET groups (62.5% and 68.3%, respectively). AI prior to ET can be an appropriate way to maintain pregnancy and assist the development of a low number of VW ExBs to term.