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 ofsucrose 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 embryosurvival and post-transfer fertility of goat morulae and blastocysts vitrified by the S-VitriTip protocol. Embryorecovery from donor goats (n = 23) was carried out on Days 8 and 9 after sponge removal. Immediately afterrecovery, morulae and blastocysts were vitrified using the S-VitriTip protocol. Briefly, all embryos were exposedto three different increasing solutions of cryoprotectants (glycerol, ethylene glycol, sucrose), loaded intomicropipette tips and stored in liquid nitrogen. After warming, embryos were transferred in pairs into recipientgoats (n = 47); morulae and blastocysts were transferred on the same day they were recovered, either Day 8 orDay 9 after sponge removal. On day 25 after embryo transfer, ultrasound diagnosis was performed. No significantdifferences were observed on embryo survival nor on post-transfer fertility according to embryo stage or day ofembryo recovery (42 and 50 %, respectively; P > 0.05). Embryo survival and post-transfer fertility of vitrifiedmorulae 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 ofthis innovative vitrification protocol.