OPU (Ovum pick-up) & ICSI

Ovum pick-up (OPU)/intracytoplasmic sperm injection (ICSI) is a form of in-vitro fertilization (IVF), now used widely in horses. It is the process by which oocytes (egg) are harvested from the mare, transported to and matured in a lab and fertilized by injection of a single sperm into each oocyte, to produce an embryos which can then be transferred into a recipient mares.


Mare fertility issues

  • OPU/ICSI bypasses the need for normal in-vivo embryo production and so is a valuable tool in mares with certain fertility issues

Stallion issues

  • Limited sperm availability- since a single sperm only is required for ICSI, the technique is useful for stallions with limited semen reserves. In addition, the same straw can be used for multiple ICSI sessions, optimizing efficient use of valuable semen
  • Subfertility- OPU/ICSI can be successfully performed in stallions with certain fertility problems where their pregnancy rates with conventional breeding mare be poor

Competition mares

  • OPU/ICSI Can be scheduled to suit the mare’s training schedule, and can be performed outside the breeding season
  • No hormonal treatment or repeated scanning required


  • OPU/ICSU can be performed outside the breeding season
  • Embryos are generally frozen and then thawed and transferred to a recipient when convenient, thereby removing the need to synchronize a recipient mare
  • Oocytes can also be harvested around the time of death of a mare


OPU is performed with the mare sedated in the stocks. The ovary is visualized using a transvaginal ultrasound probe. A long needle is passed through a guide in the ultrasound handle, through the wall of the vagina, and into the follicle. The follicle is then flushed and scraped several times and the oocyte is aspirated out of the follicle. 

The oocytes are then processed and shipped overnight to an ICSI laboratory, where they will be matured, and fertilized by ICSI. Developing embryos are cultured usually over 6-8 days. The embryo can then be transferred fresh to a recipient mare or more commonly, frozen.


  1. The mare should undergo health testing for Equine Infectious Anaemia (EIA) and Contagious Equine Metritis (CEM) prior to admission to our clinic for the procedure
  2. In order to maximize success rates, the mare should have at least 15 small follicles at the time of the procedure

Please do not hesitate to contact B&W Stud and Reproduction Services if you have further questions regarding this service.

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