Cattle Breeding: Embryo transfer

Most female breeding cattle produce one calf per year. The use of embryo transfer (ET) allows a producer to quickly multiply the genetics of the top females in the herd in addition to gaining genetic improvement from purchasing the best semen that is available that comes with using artificial insemination (AI). By multiplying the best genetics in females and using semen from bulls with high genetic merit, calves with superior genetics are produced. Females in the herd with less desired genetics can serve as recipients for the embryos and the overall genetic quality of the herd may quickly be drastically improved.

Embryo transfer requires two components: generating and then obtaining (flushing) the embryos from the donor female and transferring each embryo into a different female (recipient) which gestates and give birth to that fetus. These two components do not necessarily have to be done by the same producer. Embryos can be produced and sold as such so that someone else purchases them and transfers them into his or her own recipient females.

Selection of each donor female is one of the most important decisions in embryo transfer. Donor females should be of superior genetic worth and marketability to justify embryo transfer costs. Mating decisions should be made considering the genetic worth and economic value of potential calves. The reproductive potential of a donor female must also be acceptable. The ideal donor female has had regular estrous cycles beginning at a young age, routinely conceives with no more than two breedings, maintains a 365-day or less calving interval, calves without difficulty, is free of reproductive abnormalities and disease, and has no conformational or known genetic defects. Good nutritional management of these females is critical for productivity as embryo donors. This involves managing body condition and providing proper nutrients including minerals important to reproductive function.

Because successful embryo transfer programs require highly trained technicians, be diligent in selection of persons to perform these services. Embryos may not be marketable unless they have proper documentation such as freeze codes. Some breed associations require record reporting of embryo removal dates or other items for calves resulting from embryo transfer to be eligible for registration in the breed registry. Technicians should complete certificates of embryo recovery, freezing, or transfer as appropriate. Many technicians are members of the International Embryo Transfer Society. These embryologists develop reputations for proficiency among producers, so it is useful to visit with other producers using embryo transfer services to locate a desirable technician.

The cost of embryo transfer services is highly variable. There may not be a qualified technician available in the local area or at the particular time needed, so there can be considerable travel distance required for an on-farm visit from a technician. Travel expense is often included in the bill to the producer. Some embryo transfer facilities allow donor females and/or recipient females to be delivered to the facilities for embryo collection and transfer services. Scheduling embryo transfer services several months in advance is advised.