Evaluation of the In Vitro Embryo Production of Farm Animals Under the Circumstances of Embryo Transfer Technology

"Embryo transfer" technology is one of the deterministic techniques related to the production of in vitro or in vivo produced embryos. This technique controls to a large extent the integrity of the developmental component of early embryos and their ability to develop later until birth. Pregnancy rates resulting from the transferred embryos were widely dispersed and associated with many variables and factors. The developmental stage of early embryos had a significant impact on pregnancy rates, as most studies agreed to transfer embryos in the blastocyst and morula stages due to the high rates of pregnancy (40%-100%) compared to the blastomeres. Embryo cryopreservation technology (rapid and slow) competed to a large extent with fresh embryos in pregnancy rates, even surpassing the latter in some cases, as the percentage approached 100%. The resulting pregnancy rates varied greatly (up to 95%) according to the method of transferring and hormonal induction. The results were mainly based on the size and type of the animal on the one hand and on the nature of the biological activity and the specific function of the hormones (progesterone, prostaglandin F2α, gonadotropin - releasing hormone and follicle - stimulating hormone, etc.) involved in regulating estrus in donors and recipients on the other hand. This review concluded that the embryo transfer technology has given many scenarios that cannot lead to an inevitable result in judging the efficacy of the technology of in vitro embryo production, but the results are encouraging and require further efforts.