Cat blastocysts produced in vitro from oocytes vitrified using the cryoloop technique and cryopreserved electroejaculated semen

Oocyte preservation is still a challenge in the cat. The aim of this study was to evaluate the efficiency of oocyte vitrification in cryoloop in the domestic cat and to assess the embryonic development after IVF with cryopreserved semen. In vitro matured cat oocytes were vitrified in cryoloop after exposure to 10% ethylene glycol (EG, 0.9 M) in hepes synthetic oviductal fluid (HSOF) for 1 min, 20% EG (1.8 M) in HSOF for 1 min, and 40% EG (3.6 M), 10 mg/ml Ficoll 70 and 0.3 M sucrose in HSOF for 20 s. Warmed oocytes were fertilized in vitro with frozen–thawed semen collected by electroejaculation and presumptive zygote were cultured in vitro for 10 days. Results showed that percentage of degenerated oocytes was higher (P < 0.01), while cleavage rate and morulae blastocysts rate on day 6 were significantly lower (P < 0.01) for vitrified oocytes than control. Blastocyst rate on day 8 was higher (P < 0.01) for control oocytes than vitrified counterparts, and also developmental ability was higher (P < 0.05) for non-vitrified oocytes, while the hatched blastocyst rate on day 10 was higher (P < 0.05) for vitrified oocytes than control. In conclusion cat oocytes can be vitrified in cryoloop with a fairly good survival rate, cleavage rate and embryo development until pre-implantation stage.