Embryo Transfer

By: Ainsley Lovrien

Embryo transfer involves the recovery of embryos, most likely from an elite female or donor and the subsequent transfer to recipient females. The recovery of embryos includes the induction of multiple ovulation by hormonal treatment. Embryo transfer is used to disseminate desirable genes from superior female animals from various species (cattle, pigs, horses, goats, and sheep).

There are many advantages to embryo transfer. The main advantages are: increase in the number of offspring per female, easier and more rapid exchange of genetic material between countries, less transport of live animals, thereby reducing risks of disease transmission, and storage and expansion of rare genetic stock.

Embryo transfer has proved to be a powerful technology in the genetic improvement of farm animals to propagate the genes of females of superior pedigree. In cattle, mainly in the dairy industry, breeding programs have been developed to promote the genetic process by strategic use of conventional methods to produce embryos available for transfer, new technologies that produce embryos after cloning by a somatic cell transfer or transgenesis are available but not widely used commercially.

Embryo transfer protocols have also been extensively used in research critical to understand several areas of biology and medicine, such as maternal-fetal interactions, models of human and animal disease, production of transgenic animals to produce therapeutic proteins for people, etc. This discussion is restricted to the principles and methods currently used in commercial embryo transfer of farm animals. Except in horses, embryo transfer programs in most mammals include the administration of drugs that superovulate females to allow the probability that multiple embryos were collected per producer.

Embryo transfer can be performed after various durations of embryo culture, conferring different stages in embryogenesis. The main stages that embryo transfer takes part in are called cleavage stage (day 2 to 4 after co-incubation) or the blastocyst stage (day 5 to 6 after co-incubation). There are a significantly higher odds of preterm births and congenital anomalies among births having reached the blastocyst stage compared with the cleavage stage. Increased female embryo mortality due to epigenetic modifications induced by extended culture.