Embryo Transfer (ET)

Every superior ram has the ability through AI to sire many thousands of lambs annually but an elite ewe usually raises only one or maybe two lambs per year. Using ET a ewe can produce an average of 5 lambs per embryo flush or a lifetime of lambs in one mating. It is possible for a ewe to be flushed successfully several times per year for many years as long as she continues to produce.

Some donor ewes have many more than 5 lambs from an ET program but equally other ewes produce less. The average reflects the combined results achieved over many thousands of donor ewes since the late 1980ís. We suggest 3 donor ewes as being a minimum number to program.

Donor ewes can be programmed and flushed at WESTBREED in Northam and the embryos transported to your farm for implanting into recipients ewes. For more than 6 donors, the whole ET procedure including surgery and transfer can be done on farm with donors and recipients prepared by the breeder. We have experienced no difference in results achieved by either method.

Programming the donor ewe begins 3 weeks before the ET day. Around day 10 the ewes receive a series of daily injections to ensure they have multiple ovulations and are then inseminated with either freshly collected or frozen thawed semen.


About 5 days later the donors are flushed under general anaesthesia and the embryos transferred. Usually 10 recipient ewes are prepared for each donor in the ET program but some recipient ewes prove unsuitable so about 80% of recipient ewes actually receive embryos and of these an average of 65% will have lambs from a donor ewe.

Quality recipient or surrogate ewes, proven to be good mothers, are essential for embryo and lamb survival.

Management of recipient ewes is just as important as the selection of donor ewes.


Stages of Embryo development from fertilization to Day 6-7.