The donor mare's oocytes are obtained through the aspiration of ovarian follicles. The technique used is oocyte pick-up (OPU). To perform this technique, the donor mare is regularly monitored by ultrasound to identify the presence of multiple follicles in her ovaries, ranging from 5 to 25 mm in diameter. When a minimum of 10 follicles are present in both ovaries, the mare is ready for OPU.

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This technique is performed by specialized veterinary personnel. It is a procedure that takes between 45 and 60 minutes, depending on the number of follicles present in each donor's ovaries. The procedure is conducted with the mare standing, under the influence of tranquilizers and analgesics. The specialist will aspirate the follicles one by one, performing numerous scrapings and rinses to ensure the retrieval of the oocytes. The follicular fluid is collected in a container, then filtered, and the presence of oocytes is searched for.

 

Once collected, the oocytes are prepared for transport to the laboratory.

In the laboratory, the oocytes undergo a maturation and selection process prior to fertilization by ICSI.