Embryo Transfer Guidelines

Selecting a Donor Ewe

Donor ewes should:

  • Be in good health, no history of reproductive disorders, good bodyily condition (fit but NOT fat) and in a rising plane of nutrition.
  • Lie within the prime productive years (1.5 – 5.5 years) of their life.
  • Be proven and regular breeders. We have successfully flushed ewe lambs that have had at least two natural cycles before being programmed, through to ewes aged 8 years of age.
  • Have superr ovulated well in the past. Donors that have failed to super ovulate well in the past will often continue to fail.
  • Be treated for any trace element/ vitamin deficiency.
  • Be dewormed and vaccinated.
  • Lambs should be weaned off the ewes at least four weeks before the program starts.
  • Be correctly ear marked/ identified.
  • Flushing old ewes (over 6 years of age). Please notify us if you intend flushing any old ewes. While many old ewes will respond well to superovulation the best candidates are those that have had a regular lambing history. Very thin/ arthritic ewes are poor candidates.
  • Use teaser rams to heat detect donor ewes. Knowing when donor ewes come into oestrus following CIDR removal can improve fertilisation rates.

Choice of Ram

Using very young ram lambs or rams with a recent history of chronic infertility as sires can place the ET programme at risk as semen from these rams whilst having good motility may not be capable of efficient fertilisation.

Freshly collected semen and laparoscopic AI offers the best method of fertilisation. Lap AI with frozen-thawed semen may also be used, however, there may be a corresponding decrease in the overall success of the ET programme. Please inform us if frozen semen is to be used in your ET program.

Choice of recipients

The recipients act as surrogate mothers for the donors’ offspring. Good management and synchronization of recipients is essential for a successful ET programme.

Recipients should be:

  • In Premier Health:
    • Trace element and vitamin deficiencies corrected (Selenium deficiency in recipients can result in poor embryo pregnancy rate. If in doubt, speak to our vet and treat recipients with a long acting selenium 4-6 weeks before the ET programme.
    • They should be dewormed and vaccinated as required.
    • They should be from a known source which is compatible with the donors’ health status.
    • Free from mastitis, lameness and any other illnesses.
  • Capable of cycling naturally at the time of implanting. They should be mature ewes with a sound breeding history or have had at least one lambing. It is preferable that they have a reliable history of achieving pregnancies as a recipient in previous years.
  • Have been on the farm for at least 3 months before the ET day.
  • Be fit but not fat and on a rising plane of nutrition three weeks prior to ET.
  • Of a breed that shows good mothering and milking qualities- after all they will be looking after very valuable offspring.
  • Of adequate size in order to lamb easily.
  • Of good temperament and accustomed to handling.
  • Fertile – please check the ewes are not already pregnant and that they have not been sold for being barren or having poor udders/ teats.
  • Use teaser rams to heat detect recipients.
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