Effect of Vitrification and Cryostorage Length on Viability of Rabbit Embryos after Thawing

The effects of vitrification and cryostorage length in liquid nitrogen (LN2) on in vitro survival of rabbit embryos were examined. A total of 374 morphological normal embryos collected from 20 superovulated multiparous New Zealand White rabbit were divided into two groups. The first group (n=94) was non-vitrified used as a fresh control group and the second group (n=280) was vitrified and storage in liquid nitrogen at three different times (2 days, 6 months or one year). Regardless the cryostorage length in LN2, post thawing morphological normal appearance rates of cryopreserved rabbit embryos were significantly affected by vitrification procedure. Only 62.1-67.4% from embryo vitrified-thawed appears undamaged. Blastocyst and hatching rates were decreased (P<0.05) in vitrified group compared to the control group, whilst no difference was observed among different storage time in liquid nitrogen. Blastocyst and hatching rates ranged between 51.7-58.9 and 39.847.4% in vitrified-thawed embryos groups compared to 94.7 and 90.4% in control group. Significance difference was observed in embryo diameter between vitrified groups and control group (123-124 vs. 129 μm). Blastocyst and hatching rates did not vary according to the cryostorage length from 2 days until 1 year in LN2. In a same way, no significant differences were found in diameter of warmed embryos when the cryostorage increases. Our results indicate that compared to the control group, the vitrification process decreases the in vitro embryo development. In contrast, the cryostorage length in liquid nitrogen did not affect the in vitro development of rabbit embryos (≥16-cells stage).