Vitrified embryo transfer in Merino sheep under extensive conditions

Abstract

The aim was to evaluate pregnancy success after transfer of embryos vitrified in micropipette tips in Merino sheep under extensive conditions. A second objective was to evaluate the influence of embryo stage in such pregnancy rate. One hundred and twenty-seven embryos were rewarmed and transferred into recipient ewes. On rewarming, the embryos were placed into three-step cryoprotectant dilutions. Finally, prior to transfer to recipient females, embryos were maintained in Basic Medium for 5 min at 25ºC and were reevaluated by morphological criteria; all degenerated embryos were eliminated. Recipient ewes (n = 150) were treated for estrus with sponges placed for 14 days and 300 IU of eCG. At embryo transfer, three experimental groups were defined: morulae transferred on Day 7, blastocysts transferred on Day 7 and blastocysts transferred on Day 8 after sponge removal. In all groups, semi-laparoscopic transfer of one rewarmed embryo per recipient was performed. Pregnancy was diagnosed by ultrasonography on day 28 after embryo transfer. The embryo selection rate after rewarming was higher for blastocysts (89.3%-67/75) compared to morulae (65.9%-60/91) (P < 0.05). Pregnancy diagnosis showed a 38.3% (23/60) of success after morula transfer on Day 7 post progestagen removal. The day of transfer showed a significant influence on pregnancy rate after blastocyst transfer (Day 8, 55.9%-19/34 vs Day 7, 21.2%-7/33) (P < 0.05). Blastocysts transfer on Day 8 showed the highest global efficiency (pregnancies/total embryos after rewarming) (47.5%-19/40) (P < 0.05). In conclusion, reproductive efficiency obtained by vitrified embryo transfer allows its recommendation for embryo transfer programs under extensive conditions. The importance of considering the synchrony between the embryo age and the recipient uterus stage is emphasized.

Pregnancy rate after fixed‐time transfer of cryopreserved embryos collected by non‐surgical route in Lacaune sheep

“…The survival rate of in vivo‐derived cryopreserved embryos by vitrification technique described in the existing literature is 32.0%–36.0% (Folch, Olivera Muzante, & Aguilar Gomez, ), 41.2%–50.0% (Gibbons, Cueto, & Pereyra‐Bonnet, ) or 60.1%–75.1% (Dattena et al, ). In the present study, the VT embryo survival rate was 15.9%, which is similar to the 22.6% rate that was recently reported for embryos recovered by laparotomy (Gibbons et al, ). However, our lambing rates (18.8%) were lower than the 62.9% rate observed by Dattena, Ptak, Loi, and Cappai () and the 80.0% rate recorded by Naitana et al, ().…”

“…Embryo morphology was classified according to the IETS. Grade I and II embryos randomly underwent either slow freezing (SF; Fonseca et al, ) or vitrification (VT; Gibbons, Bruno‐Galarraga, Fernandez, Gonzalez‐Bulnes, & Cueto, ). The percentage of morulae and blastocysts transferred did not differ ( p < .05, chi‐square test) in SF (48.4%–30/62 and 51.6%–32/62) and VT (36.4%–16/44 and 63.6–28/44) groups, respectively.…”

Laparoscope Assisted Embryo Transfer and Conception Rate in Farm Rambouillet Ewes

“…5). These results are quite satisfactory and are better than the previous reports of 29% to 65% pregnancies and 46% -80 % lambing after embryo transfer in sheep (Ishwar and Memon, 1996;Gibbons et al, 2019;Folchet et al, 2000;Dattena et al,2000). Brown and Radziewic (1998) reported higher pregnancy rate after transfer of twin (64%) and single (39%) in vitro derived embryos.…”

A study of the factors affecting embryo yields and quality in superovulated Morada Nova ewes that underwent non‐surgical uterine flushing

“…To summarize, the ewes allocated to the G‐12 SOV group produced more blastocysts than those in the G‐9 SOV group. Not only is it important for the transfer of fresh sheep embryos but it can also impinge on the success of embryo cryopreservation and/or biobanking (Fonseca et al., 2018; Gibbons et al., 2019; Morais et al., 2020).…”