Cryopreservation of in vitro-produced bovine embryos by vitrification: In pursuit of a simplified, standardized procedure that improves pregnancy rates to promote cattle industry use

Van Do,Andrew Taylor-Robinson

doi:10.2298/bah2003251h

Van Do, Andrew Taylor-Robinson

Open Access

https://doi.org/10.2298/bah2003251h

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Abstract

The goal of cryopreservation is to retain the original stage of gametes and embryos after they have endured cooling and warming. Slow freezing is a standard method for in vivo-derived bovine embryo cryopreservation, threefifths of such embryos being frozen by this method globally. However, it is evident that slow freezing is not efficient for cryopreserving in vitro-produced bovine embryos. Hence, only one-third of in vitro-produced bovine embryos are cryopreserved. Vitrification is a preferred method for storage of human embryos; consequently, it has been explored as a novel means to store in vitro-produced bovine embryos, for which it shows considerable promise as an alternative to slow freezing. This is due to several reasons: vitrification is often less time-consuming than slow freezing; it does not need expensive slow rate freezing machines; and it has been proven to have comparatively higher survival rates. Yet, in the cattle industry vitrification continues to present shortcomings, such as possible toxicity of vitrification solutions and failure to standardize methods, which pose a challenge for its application to in vitro-produced bovine embryos. Therefore, determining the most suitable procedure is crucial to make vitrification more practical in commercial settings.

Highlights

In commercial breeding of farmed livestock embryo transfer is an important tool to increase the number of elite animals in a herd or for herd replacement
With the in vivo method, bovine embryos are generated by a superovulation technique in which donors are given exogenous gonadotropin hormones in order to stimulate the activity of their ovaries
While the published literature covers a broad scope of bovine embryo cryopreservation, including the standard slow freezing procedure, this review focuses primarily on vitrification as a method to cryopreserve in vitro-produced bovine embryos

Summary

Introduction

In commercial breeding of farmed livestock embryo transfer is an important tool to increase the number of elite animals in a herd or for herd replacement. The alternative route of embryo production, in vitro to in vivo, involves the aspiration of either mature or immature oocytes from donor ovaries, in vitro fertilization, usually with frozen sperm, and subsequent in vitro culture to the blastocyst stage. This means of embryo production has been established since the 1980s but as late as the early 2000s the great majority of bovine embryos were still generated by the in vivo method (Merton et al, 2009).

Different methods of freezing embryos

Findings

Conclusion