In vitro embryo production in alpacas (Lama pacos): Blastocyst development from oocytes vitrified by Microdrop or Cryotech technique

We evaluated the use of alpaca oocytes vitrified using the Microdrop or Cryotech technique for in vitro embryo production. Grade I-II COCs (n = 1094) were recovered from slaughterhouse ovaries, and in vitro matured for 36 h. Then, MII oocytes were randomly distributed in groups: a) vitrified using two techniques [Microdrop (VM group; n = 250) or Cryotech (VC group; n = 244)], b) just exposed to the corresponding vitrification/thawing solutions (EM group; n = 200 or EC group; n = 200) or c) non-exposed nor vitrified (i.e. fresh oocytes; control group; n = 200). After treatment administration oocytes from all groups were IVF using epididymal sperm and in vitro cultured for up to 8 days. The vitrification technique and the exposure to vitrification solutions of MII oocytes negatively affected (p < 0.001) the cleavage rate compared to control group. On the other hand, exposure to Microdrop vitrification solution (EM group) and vitrification using the Microdrop technique significantly (p < 0.001) reduced the embryo developmental rate at all stages evaluated. Early blastocysts rate was affected (p < 0.001) by treatment, and it was greatest (p < 0.001) for the EC and VC, intermediate (p < 0.05) for the control, and lowest (p < 0.001) for VM and EM groups. Expanded and hatched blastocyst were not observed in the groups where oocytes were subjected to either Cryotech or Microdrop vitrification technique. We conclude that Cryotech is a more suitable vitrification technique for MII alpaca oocytes than Microdrop, under the conditions used in this study (timing and cryoprotectants concentration), allowing the development of early blastocyst at a rate comparable to control group.