In-straw cryoprotectant dilution for bovine embryos vitrified using Cryotop

Area of Science:

• Veterinary Reproduction
• Embryology
• Cryobiology

Background:

• Vitrification is a key technique for preserving bovine embryos.
• Conventional cryopreservation methods can be complex and require specialized equipment.
• Simplifying the warming and dilution process is crucial for efficient embryo transfer.

Purpose of the Study:

• To develop and validate an in-straw dilution method for Cryotop-vitrified bovine embryos.
• To assess the efficacy of the Cryotop vitrification-straw dilution (CVSD) method compared to other cryopreservation techniques.
• To evaluate the feasibility of a simplified, microscope-free 1-step bovine embryo transfer procedure.

Main Methods:

• In vitro-produced (IVP) and in vivo-produced bovine embryos were cryopreserved using CVSD, in-straw vitrification-dilution (ISVD), and slow freezing outside dilution of straw (SFODS) methods.
• Embryo development to hatched blastocyst stage was assessed after various warming and dilution times.
• Conception and delivery rates were evaluated after embryo transfer to recipient animals.

Main Results:

• Optimal warming and dilution times for CVSD were determined to be 5-10 minutes, yielding high blastocyst development rates (82.4-94.3%).
• CVSD and ISVD methods resulted in significantly higher hatching blastocyst rates compared to SFODS.
• No significant differences in conception or delivery rates were observed between CVSD, ISVD, and fresh embryo transfers in recipient animals.

Conclusions:

• The developed in-straw dilution method (CVSD) is effective for warming Cryotop-vitrified bovine embryos.
• This simplified procedure allows for efficient 1-step bovine embryo transfer without requiring a microscope.
• The CVSD method offers a practical and effective alternative for bovine embryo cryopreservation and transfer.