Bovine Embryo Transfer (ET)
Commercial bovine embryo transfer has become a large international business with a well established technology and logistics.
In 2006 world wide annual production of embryos from superovulated cows exceeds 500,000.
Reasons for using ET
- Faster genetic progress
- more calves from a valuable cow its lifetime
- increased rate of genetic improvement of a herd
- faster evaluation of bulls in the AI centres
- Epidemiological safety
- international movement of genetic material free from the epidemiological concerns associated with the movement of animals
- reduced quarantine costs
- Biotechnology – generation of transgenic animals
- improvement of the efficiency of meat or milk production
- modification of milk composition e.g. to produce certain substances of medicinal properties
- improved resistance to disease
At present embryo transfer can be divided into two categories based on embryo origin:
- Direct transfer of embryos from donor cows to synchronised recipients
- Transfer of embryos preserved in low temperatures (liquid nitrogen) to synchronised recipients
a) embryos produced in vivo (as in point 1)
b) embryos produced in vitro
- oocytes harvested from ovaries from slaughterhouses
- oocytes harvested via ovum pick-up procedures in vivo
The International Embryo Transfer Society issues a series of carefully defined procedures, especially in respect of the zoo-sanitary and epidemiological aspects of embryo production and transfer. Infectious factors such as BVD and IBR were identified as potentially transferable with embryos, which led to the adoption of specific procedures to ensure the safety of ET in respect of these pathogens. Bovine embryos with intact zonae pellucidae can be specified pathogen-free through washing procedures.