INTRODUCTIONIn the rabbit, the technique most frequently used for embryo transfer involves cryopreservation by slow freezing of morulae, followed by surgical implantation of thawed embryos. This method has the advantage of being well controlled and validated: It helps to maintain mitochondrial genomes, preserves the genetic integrity of biological material under sanitary conditions, and allows for such material to be passed along beyond the normal reproductive lifespan of a given animal, which can be advantageous in the case of rare or valuable strains. Furthermore, because litters of pups can be obtained 1 mo after embryo transfer without the need for additional backcrossings, genotyping is rapid and simple. However, the technique is not without its drawbacks: It requires expensive equipment (e.g., specialized programmable freezers), and producing large numbers of stored embryos requires the sacrifice of many donor females. Although alternative methods of embryo recovery (e.g., surgical or vaginal collection) are possible, such procedures produce fewer embryos.