Improvement of embryo, cryopreservation and embryo transfer methods in small ruminants

In small ruminants, the costs of embryo transfer is a main limiting factor to the use of this method. The use of ultra rapid techniques such as embryo vitrification and direct transfer may contributed to reduce a part of the costs and increase the use of embryo transfer in sheep and goats. In order to evaluate the efficiency of these techniques, two experiments were performed. In a first experiment the viability of vitrified/thawed embryos was compared to results obtained after transfer of fresh embryos in ewes or frozen embryos (with slow freezing method) in goats. The pregnancy rate at term as well as embryo survival rate did not differ significantly according to embryo treatment (in ewes : 72% and 60% for fresh embryos vs 72% and 50% for vitrified embryos; in goats : 69% and 55% for frozen embryos vs 48% and 39% for vitrified embryos). In a second experiment, the possibility to transfer the vitrified embryos or frozen embryos directly after thawing (without cryo-protectant removal and evaluation of the morphological status of the embryos) was tested by comparison with the standard technique of transfer of vitrified or frozen/thawed embryos (removal of cryoprotectant and morphological evaluation). No significant effect of the transfer method was observed on the pregnancy rate at term and embryo survival rate (in ewes/vitrified embryos : 67% and 49% for traditional transfer vs 75% and 53% for direct transfer; in goats/ vitrified embryos : 23% and 15% for traditional transfer vs 38% and 26% for direct transfer; in goats/frozen embryos : 74% and 45% for traditional transfer vs 71% and 57% for direct transfer).