ICSI EMBRYO TRANSFER SERVICES
IN NEW ZEALAND

ICSI in horses is now available in New Zealand at EquiBreed NZ Ltd. It involves fertilisation in the laboratory by injection of one sperm into one egg. After ICSI, the egg is then cultured in the laboratory until the time of embryo transfer or freezing.

ICSI PROCESSES INVOLVE

  1. Oocyte recovery (Ovum Pick Up, OPU, TVR)
    1. Using a transvaginal ultrasound guided technique, the egg is harvested directly from the follicle of the mare
    2. This is a standing procedure and typically takes about 45-60minutes
    3. The mare is sedated and given a rectal relaxant and in some cases an epidural
    4. There will be drug withholding periods for mares in competition
    5. The ideal sized follicles for good quality oocytes are 10-30mm
    6. Normally there is about 50-60% oocyte recovery rate (so if there are 4-10 follicles there should be 2-5 oocytes recovered)
  2. In vitro culture
    1. The oocytes are then matured in the laboratory for 36hours before fertilisation.
    2. A very small volume (<0.1ml) of sperm is processed for the procedure.
    3. Fresh, chilled or frozen sperm can be used.
    4. One sperm is selected under the microscope for the injection of each oocyte.
    5. The injected oocytes (now called zygotes) are cultured in the laboratory for up to 10 days prior to non-surgical transfer or embryo freezing.

RESULTS FROM ICSI

Under ideal conditions:

  • Oocyte recovery rate 50-60% of follicles aspirated (eg: 5 oocytes from 10 follicles)
  • Oocyte maturation rate 70-80% (eg: 4 oocytes)
  • Cleavage (cell division) rate after injection 50% (eg: 2 oocytes)
  • Blastocyst production 10-20% of oocytes recovered (eg: 1 blastocyst) per session

FACTORS THAT AFFECT ICSI RESULTS

  • Number and size of follicles available for aspiration
  • Age of the mare - younger is better
  • Heat stress – keep your mares cool
  • Seasonal factors – better results may be Autumn, Winter, Spring rather than mid-Summer
  • Stallion fertility (including batch variation)
  • Laboratory conditions
  • Nutritional factors such as omega-3 oils or L-carnitine supplements may help

ADVANTAGES OF ICSI IN HORSES

  • Walk in walk out procedure for local mares
  • Maximises use of sperm (especially frozen sperm)
  • The procedure works all year round as long as there are follicles present
  • Options to use multiple stallions
  • Can be repeated at 2-4 weekly intervals to maximise recovery rates
  • Can be easily arranged to avoid competition schedules
  • Works well on a “service fee when pregnant” basis
  • Mares can continue with training and competition during their breeding programme
  • Embryos can be frozen with 50-60% survival rates after transfer to improve recipient management and reduce costs
  • Can be used as a fertility treatment for problem mares or stallions
  • Costs per embryo will be similar to current embryo programmes
  • Efficient use of recipient mares when using frozen embryos
Embryo transfer_ICSI set up

DISADVANTAGES OF ICSI IN HORSES

  • Sedation may have withholding periods (up to 8 days) to consider in competition mares at FEI level, but training can continue uninterrupted
  • Involves rectal palpation and transvaginal techniques with risk of infection or perforation of the rectum
  • Mares are treated with antibiotics for 3 days after the procedure
  • Some mares produce more or less eggs or embryos than others
  • Some stallions will not be suitable for use in the procedure
  • It is biology and not all mare x stallion combinations are going to work
  • Environmental factors that affect fertility eg: exposure to toxins, estrogens, heat stress will still have detrimental effects on the outcome

STATUS OF ICSI IN NEW ZEALAND HORSES

We have now confirmed live foals born and more foals are due this season. These pregnancies are from both fresh and frozen ICSI embryos.

Analysis of our results since March 2022 shows that >60% of OPU sessions produce an embryo. Some of these sessions have produced multiple embryos so that on average we have 1.3 embryos per OPU session. Our results are improving all the time, but there are still some mares that fail to produce an embryo and other mares that produce multiple embryos.

Embryo transfer_OPU
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