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A touch of glass: cryopreservation of equine embryos by vitrification

02 November 2023
13 mins read
Volume 7 · Issue 6
Figure 3. a) A minimal vitrification device used as the carrier for vitrifying embryos. This one is a Cryolock (FujiFilm, Irving Scientific, California, USA). b) Embryos are loaded onto the tip (arrowed) in a 2 µl volume of vitrification solution. The excess solution is removed before plunging into liquid nitrogen.
Figure 3. a) A minimal vitrification device used as the carrier for vitrifying embryos. This one is a Cryolock (FujiFilm, Irving Scientific, California, USA). b) Embryos are loaded onto the tip (arrowed) in a 2 µl volume of vitrification solution. The excess solution is removed before plunging into liquid nitrogen.

Abstract

The cryopreservation of equine embryos larger than 300 µm in diameter has proved problematic for many decades. However, there now exist protocols to undertake vitrification of such embryos with good pregnancy rates following their subsequent warming and transfer to recipient mares. This article discusses the reasons why equine embryos have proved so difficult to cryopreserve, and looks at cryopreservation methods before focusing on embryo vitrification. It also provides a historical perspective on the development of vitrification and details the latest techniques and emerging methodologies aimed at making embryo cryopreservation more accessible for practitioners.

Cryopreservation is the process by which cells, tissues or organs are cooled and stored at very low or freezing temperatures to save them for future use. The cryopreservation of equine embryos has always been a desirable addition to modern breeding technologies because it provides breeders with the option to bank embryos of known or potential genetic merit. Hence, young mares who have not yet proven themselves can have embryos cryopreserved for future transfer when the donor mare shows value, or older stock of merit can produce offspring from banked embryos beyond their reproductive lifespan. The technique of cryopreservation also acts as a management tool by allowing embryos to be kept and transferred when a suitable recipient is available or to transfer them at a time of the year that will ensure foalings occur at the desired time. In addition, cryopreserved embryos can be moved internationally, increasing both the availability of bloodlines and worldwide trade between breeders.

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