Advancements in cryopreservation of domestic animal embryos.

The development of embryo freezing technologies revolutionized cattle breeding. Since then, advancements in cryobiology, cell biology, and domestic animal embryology have enabled the development of embryo preservation methodologies for our other domestic animal species, including sheep and goats. Recently, technologies have been developed to cryopreserve pig embryos, notorious for their extreme sensitivity to cooling; horse embryo cryopreservation is in its infancy. While cryopreservation can enhance the utilization of in vitro embryo production technologies, cryosurvival of in vitro-produced (IVP) or micromanipulated embryos is less than that of in vivo-derived embryos. This review outlines recent efforts in livestock embryo cryopreservation. In the near future, use of preserved embryos could be a routine breeding alternative for all livestock producers providing 1) preservation methods for maternal germplasm, 2) global genetic transport, 3) increased selection pressure within herds, 4) breeding line regeneration or proliferation, and 5) methodology for genetic rescue.