Our Animal Breeding Europe (AB Europe) technical team answer your questions about Embryo Transfer (ET) ...

What is embryo transfer?

Embryo transfer is the process by which fertilised embryos are flushed (removed) from a donor ewe and then transplanted into suitably synchronised recipient ewes to establish a surrogate pregnancy. The donor ewe is super-ovulated using hormones so that she produces more eggs than usual at a synchronised mating. This programme usually lasts 20 days with the ewe being artificial inseminated (AI) on day 14, and the six-day-old embryos being flushed from her on day 20. Embryos are then either transferred into prepared surrogate recipient ewes, or frozen for future use.

If the embryos are being transferred fresh on day 2, the recipient ewes must be programmed alongside the embryo donor ewe so that they are ready to receive the embryos.

What does an embryo transfer programme involve?

An embryo transfer programme is split into two parts; synchronisation of embryo donors and synchronisation of embryo recipients. A typical embryo transfer programme lasts 20 days:

Day 0
Insert sponges in donors and recipients

Day 10
Super-ovulating hormone injections begin (donors)

Day 12
Sponge removal from donors and recipients

Day 13
Donor and recipient heat detection

Day 14
Artificial insemination (AI) of donors

Day 10
Embryos flushed from donors and either transferred into recipients or frozen

Day 24
Donor ewe back on heat for natural services or re-programming

Why do I need to synchronise my ewes?

The timing for artificial insemination and embryo transfer in sheep is crucial, so donor ewes must be synchronised to be on heat at the time of AI and recipient programmed so they are ready to receive the developing embryos. Ewes are synchronised using intra-vaginal sponges and PMSG may also be used depending on the breed of sheep and season. Organic sheep breeders can use teasers (vasectomised males) to help synchronise their ewes.

Which ewes should I use as embryo donors for ET?

Donor ewes should be proven and regular breeders in their prime reproductive years and will ideally have responded well to super-ovulation in the past. Donor ewes should be fit and healthy and on a rising plane or nutrition.

Which ewes should I use as embryo recipients?

Recipient ewes are surrogate mothers and so they should be mature ewes with a sound breeding history and will ideally have good mothering and milking qualities. Embryo recipients should also be in good health and on a rising plane of nutrition.

How many recipient ewes should I prepare?

On average, about 7 embryos are collected per super-ovulated flush during the breeding season so 5-6 embryo recipients should be prepared for each embryo donor in your programme.

Are all embryos used?

Not all embryos will be suitable for transfer or freezing. Embryos are graded and only grade 1 and 2 embryos are frozen.

What care do my sheep need after embryo transfer?

The embryo begins to implant about 10 days after surgery so the three weeks following ET are crucial and you should avoid any unnecessary stress (including handling). Ewes should be allowed good quality hay and water for 24 hours after surgery and should then be moved back to similar grazing to that they were on during the four weeks pre-surgery. Beware of overfeeding ewes during these first 3 weeks - overfeeding or access to rich pastures can have a negative effect on embryo development.

How much does embryo transfer for sheep cost?

For further information on costs, and to get a specific quote for your circumstances, please contact your local AB Europe centre:

AB Europe - Malvern centre
01531 651 210

AB Europe - Edinburgh centre
01875 614 500

Terms and conditions of sale apply.

We have a full range of information, technical factsheets and support available for sheep breeders who want to take advantage of our services and expertise, topics include:

  • Laparoscopic insemination in sheep
  • Checklist for AI/ET - the ideal set up
  • Getting your ewes into shape for AI
  • Improving Lap AI and ET conception rates
  • Why use a teaser of vasectomised ram in your flock?
  • Ram preparation guidelines
  • Regulin - its use in AI programmes

Our Centres

AB Europe - Malvern centre
01531 651 210

AB Europe - Edinburgh centre
01875 614 500

AB Europe - Northern Ireland
07967 764 132

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We can be contacted by e-mail at enquiries@abreeds.co.uk or by completing our contact form

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