What to Expect at Embryo Transfer (ET)

The transfer of the embryos is the last step in the IVP process. Most of the work in ensuring the best possible result at transfer focuses on the management of recipients (see also recipient management resource) and the synchronisation process (see also synchronisation resource). However, there are some good tips to ensure that the day runs smoothly and results are optimised.

Embryo transfer procedure

From an outsider’s point of view, the embryo transfer procedure is not too dissimilar to watching artificial insemination. There are however some key differences in the procedure outlined in the process below

Preparing recipients on day of transfer:

• Prior to transfer, the technician will examine the reproductive tract and check for the presence of a corpus luteum (CL), assess its quality and determine which ovary it is located on.
• A CL is a transient endocrine gland that forms on the ovary after ovulation and is an indication that the recipient has ovulated and has a good probability of pregnancy. The location of the CL is also important as the technician will need to deposit the embryo into the horn of the uterus that is on the same side as the ovary with the CL.
• Unfortunately, not all recipients will be suitable for embryo transfer. The technician will draft out any recipients that do not have a CL or have a low-grade CL. Even in well managed herds, generally only up to 80% of recipients will have an embryo transferred into them. For this reason, it is a good idea to synchronise and prepare 20% more recipients than the expected number of embryo transfers.
• If fresh or direct transfer (DT) embryos are being transferred, the technician will then commence the embryo transfer process. If vitrified or frozen embryos are being transferred, the field embryologist will commence the thawing process in batches of embryos according to the number of recipients that have been selected.

Embryo transfer process:

• Once the recipient has been selected, the technician will administer an epidural to limit any straining and thereby enable accurate deposition of the embryo.
• The field embryologist will load a single embryo into a transfer pipette, specifically designed for transfer of embryos.
• The technician will hygienically insert the pipette into the vagina, and then with the aid of rectal palpation guide it through the closed cervix.
• Once the cervix has been traversed, the technician will carefully progress the pipette down the uterine horn that is on the same side as the CL. Once the pipette is in the correct position, the plunger is depressed depositing the embryo.
• The technician then withdraws the pipette completing the embryo transfer process.

Management of recipients before, during and after transfer

It is critical to manage recipients in a low stress manner before, during and after embryo transfer to increase the likelihood of conception. If recipients need to be held in the yards for a duration of time, or overnight, it is recommended that they have full access to hay, water and shade. Ensuring facilities are fit for purpose is also recommended (see also our facilities resource).

After the transfer of embryos, ideally recipients will be given at least 30 mins rest before being walked calmly back to the paddock. A maximum 30 min walk is recommended, minimising the disruption of the social structure of the group as much as possible.

Pregnancy diagnosis can occur any time from 3 weeks after transfer if using transrectal ultrasound. However, if pregnancy diagnosis occurs prior to 12 weeks gestation, it is recommended to re-check these females later to determine if any pregnancy loss has occurred.

Lastly, having experienced, well-prepared and well-trained staff will help optimise the results from a program.  Producers who consistently get good results are those who run best-practise production systems with attention to detail at every stage.