Birth of piglets after OPS vitrification and transfer of compacted morula stage embryos with intact zona pellucida

In swine, five to six days post-insemination, morulae and blastocysts are c ollected together after uterine flushing. The purpose of this study was to vitrify zona pellucida-intact morulae with Open Pulled Straw (OPS) technolo gy and obtain piglets after transfer. Morulae (200) were vitrified after a two-step equilibration in ethylene glycol, dimethyl sulfoxide and sucrose i n Hepes-buffered TCM199+20% NBCS medium (TCM). 2-6 morulae were loaded into OPS and plunged into liquid nitrogen. At embryo warming, a three-step dilu tion with decreasing concentrations of sucrose was applied. In each of 10 r ecipients, 20 morulae were transferred surgically. Day 25, gestation rate a nd the farrowing rate were 80% and 70%, respectively. The pregnant recipien ts farrowed from 1 to 8 piglets and the survival of total transferred embry os was 13%. Although survival rates are still compromised, OPS technology i s therefore appropriate to cryopreserve porcine morulae with intact zona pe llucida.