Vitrification of farmed blue fox oocytes in ethylene glycol and DMSO-based solutions using open-pulled straw (OPS)

Farmed blue fox was used as a model to develop cryopreservation protocol for nondomestic canine species. We report here the developmental potential of farmed blue fox oocytes after vitrification with a two-step OPS method. Oocytes were collected and pre-cultured for 0, 24, 48, 72 hours respectively before cryopreservation. Vitrification of oocytes was achieved by a 30 sec treatment in 10% ethylene glycol (EG) or 10% EG + 10% dimethyl sulfoxide (DMSO) at 25 degree C followed by a 25 sec equilibration in EFS30 (30% (v/v) EG +21% (w/v) Ficoll +0.35M sucrose) or EDFS30 (15% (v/v) EG +15% (v/v) DMSO +21% (w/v) Ficoll +0.35M sucrose), before plunging into liquid nitrogen. The survival of oocytes after vitrification was assessed morphologically immediately after warming, and cultured for in vitro maturation. For comparison, control oocytes were cultured for in vitro maturation for 96 hours. The best result was obtained when oocytes were pre-cultured for 72 hours, first exposed to 10 percent EG + 10% DMSO and vitrified in EDFS30. The survival percentage of oocytes under these conditions was not significantly different (P > 0.05) from that of the control.