Evaluation of post-transfer fertility of vitrified goat morulae and blastocysts using an innovative protocol in micropipette tips

Abstract

In 2022, we developed an innovative protocol consisting of three vitrification solutions with the addition of sucrose to vitrify goat embryos in micropipette tips (S-VitriTip) and obtained promising in vitro results. However, to date, this protocol has not been tested in vivo in recipient females. The study aimed to evaluate the embryo survival and post-transfer fertility of goat morulae and blastocysts vitrified by the S-VitriTip protocol. Embryo recovery from donor goats (n = 23) was carried out on Days 8 and 9 after sponge removal. Immediately after recovery, morulae and blastocysts were vitrified using the S-VitriTip protocol. Briefly, all embryos were exposed to three different increasing solutions of cryoprotectants (glycerol, ethylene glycol, sucrose), loaded into micropipette tips and stored in liquid nitrogen. After warming, embryos were transferred in pairs into recipient goats (n = 47); morulae and blastocysts were transferred on the same day they were recovered, either Day 8 or Day 9 after sponge removal. On day 25 after embryo transfer, ultrasound diagnosis was performed. No significant differences were observed on embryo survival nor on post-transfer fertility according to embryo stage or day of embryo recovery (42 and 50 %, respectively; P > 0.05). Embryo survival and post-transfer fertility of vitrified morulae of 30 % and 40 % were obtained, highlighting our study as one of the first to report efficient reproductive rates through the in vivo transfer of cryopreserved goat morulae, thus demonstrating the effectiveness of this innovative vitrification protocol.