Development in vivo of rabbit compacted morulae after freezing using a two-step cooling method and then thawing was evaluated. Embryos were exposed during 2.5 min at room temperature to the freezing medium composed by dimethylsulphoxide (DMSO, 3.5 mol/1) and sucrose (0.25 mol/1). The embryos, placed into plastic straws, were maintained at -27°C for 30-45 min and were then plunged into liquid nitrogen. After rapid thawing, frozen-thawed embryos were transferred into both oviducts of recipient does (single transfer) or into one of the oviducts when fresh embryos (control) were transferred into the opposite one (combined transfer). Embryo viability was evaluated by the ability of the embryo to develop to sites of implantation on day 17 of gestation, for all embryos, and to fullterm fetuses on day 28 of gestation or young rabbits at birth, for combined or single transfer, respectively. A total of 98 (90.7%) frozen-thawed embryos were considered morphologically normal after applying the procedure of cryopreservation and 80 of these, together with 28 control embryos, were transferred to recipient does. The survival rate at day 17 of gestation for the frozen-thawed embryos was 29% (23/80), or 43% (23/54) for the embryos developed in the pregnant does. The survival rate at term (full-term fetuses or young rabbits) for the frozenthawed embryos was 25% (20/80), or 37% (20/54) for the embryos developed in the pregnant does. Overall, survival rates of the frozen-thawed embryos were significantly lower than those of the control embryos. To summarize, rabbit embryos frozen using a two-step cooling method can continue their development in vivo, but they have about half the chance of survival compared to the fresh embryos. © 1996 Blackwell Wissenschafts-Verlag,.
|Journal||Reproduction in Domestic Animals|
|Publication status||Published - 1 Dec 1996|