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Embryo Transfer

We specialise in Embryo Transfer at Twemlows – the process of breeding a donor mare (your mare) and transferring the embryo into another mare (the recipient mare). Our expert resident vets can transfer fresh, transported or frozen embryos at stud.

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Why Choose Embryo Transfer?

Embryo Transfer (ET) has transformed modern breeding. It is especially useful for performance mares who are still competing, as it enables you to breed from your mare without pausing her competitive career. It is also valuable for mares with health conditions that make pregnancy risky, or mares you would like to breed from more than once in a season.

What is Embryo Transfer?

ET works by artificially inseminating your mare (the donor mare) and then flushing the embryo 7 to 8 days later. The embryo is then transferred into another mare, the recipient mare, who will carry the pregnancy to term, foal down, and nurse the foal until weaning. It’s an established, non-surgical procedure, performed routinely at Twemlows with outstanding success rates.

The key to successful ET lies in careful synchronisation. Our vets work to ensure that both donor and recipient mares ovulate within a narrow window, allowing for the embryo to be transferred at exactly the right time. Seven days after transfer, the recipient mare is scanned to confirm pregnancy, with further scans over the next four weeks to monitor the embryo development.

Donor Mare, Recipient Mare and Stallion

Consideration does need to be given to the stallion, donor mare and recipient mare. Fresh and chilled semen tends to give higher embryo retrieval rates. We use frozen semen on a regular basis and have good success although it is important to use a stallion with high pregnancy rates. The donor mare, while not carrying the pregnancy to term, does need to ovulate and carry the embryo for its first seven-eight days until it is flushed out. A healthy uterus is important as any infection or fluid retention can have a negative effect on embryo survival. The recipient mare obviously needs to be reproductively sound and in good general health. We usually aim to use a recipient similar in size to the donor mare.

Do I Need to Provide a Recipient Mare?

No. As well as our skill at performing successful ET, a standout feature of Twemlows is our large recipient mare herd. We are home to over 280 recipient mares, meaning you can carry out ET on your own mare, even if you don’t have a recipient mare lined up. Our well-loved herd of recipient mares are diverse in size and breed allowing us to select the ideal mare to match yours.

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Transported Embryo Transfer

If you would prefer to AI and flush your mare at home, we offer transported embryo transfer too – find out more here:

TRANSPORTED EMBRYO SERVICE
ET BOOKING FORM

Embryo Transfer
Charges 2025

Please read our full terms and conditions

T&Cs

Veterinary Package Fees

  • AI Fresh & Chilled Semen: £285 (+ VAT) per AI cycle

  • AI Frozen Semen: £415 (+ VAT) per AI cycle

  • Synchronisation of Recipient mares for ET: £310 (+ VAT) per AI cycle. Recipients may be maiden or barren mares

  • Embryo Transfer flush & search: £315 (+ VAT) per flush

  • Non-surgical transfer to recipient mare: £200 (+ VAT) per transfer

  • ET Recipient Loan Mare Hire: £2350 (+ VAT) for 18 months (or until foal is weaned)

  • ICSI / OPU: Details on application

  • Fetal Sexing Scan: £80 (+ VAT) at 60 to 65 days pregnant

ET in Foal Fee

  • ET Recipient Mares : 
    £255     (+ VAT)

Foaling Fee

  • £435 (+ VAT)
    (Mares must be booked in in advance)

Boarding Fee

  • £10.00 per day at grass (+ VAT)

  • £26.85 per day stabled (+ VAT)

  • £38.85 per day stabled (+ VAT) when requiring an individual paddock and/or the horse walker

  • + £2.70 per day for mares with foal at foot (+ VAT)

Long term boarders & over winter rates available on application

All fees must be paid before the mares leave the stud

Veterinary Contract:

Mares will be accepted with a veterinary package to cover routine veterinary reproduction work at Twemlows Stud Farm. Routine includes reproduction scans, standard reproduction drugs, a pregnancy determination (PD) scan at 14-16 days, a PD scan at 28-30 days and a PD scan at about 42 days.

It does not include swabs, twinning, caslicks, uterine lavage and the treatment of mares with endometritis and other non-routine matters, which if relevant are invoiced separately.

All mares that have been inseminated need to have pregnancy scans at 14 days and 28/30 days to confirm a single viable and healthy pregnancy. If mares leave the stud before the pregnancy scan it is the owner’s responsibility to arrange for this to be carried out.

Charges for a range of miscellaneous items, such as passporting/microchipping, farriery work, worming and any veterinary call-outs are available on request.