Transvaginal oocyte aspiration (OPU) followed by washing is the foundation of the equine in vivo protocol
Unlike classical embryo flushing — where the mare must be bred and carry the embryo — oocyte aspiration collects gametes directly from the ovary of a live mare. The first and critically important laboratory step after aspiration is washing: separating oocytes from follicular fluid in a specialized medium while maintaining their viability.
Oocytes can be collected from outstanding broodmares without the burden of carrying offspring. This is especially important in breeding programs where the donor continues to compete or has limited availability.
Aspiration is scheduled in a convenient window outside the competition season or between events. The procedure takes about 30–40 minutes under sedation, after which the mare can return to normal activity.
When conventional reproduction fails — chronic endometritis, age-related changes, reproductive tract injuries — direct oocyte collection from the ovary opens a path to continue the breeding line.
Aspiration is performed when follicles of suitable size are present, without strict dependence on a single ovulation day. Repeat procedures are possible at 2–3 week intervals during the season.
Oocytes and embryos can be vitrified and stored in liquid nitrogen for transfer at a convenient time. This removes the need for tight synchronization between donor and recipient mares.
After aspiration, oocytes are sensitive to medium composition, temperature and handling time. Proper washing in TSM-Asp preserves cell morphology and sets the success of the entire subsequent protocol — rinsing, freezing and thawing.
That is why every step after aspiration requires a specialized medium. Below is how the ZOOEMBRIO protocol is structured and which solutions we offer at each stage.
The ZOOEMBRIO product line covers the full cycle: washing, rinsing, vitrification and thawing. For each stage — a detailed process description and the recommended medium.
Diagram of oocyte aspiration from the mare ovary and washing in TSM-Asp medium
An oocyte is the female gamete that matures inside a follicle in the mare's ovary. In the in vivo protocol, oocytes are collected by transvaginal aspiration: an ultrasound probe and aspiration needle are introduced transrectally, follicles are punctured and follicular fluid with cells is collected. Washing is the separation of oocytes from this fluid and cellular debris in a specialized medium to keep cells viable.
TSM-Asp is supplied in 1000 and 3000 ml infusion bags — convenient for washing large volumes of follicular fluid without frequent transfers.
Diagram of oocyte rinsing in Wash medium droplets
After washing, traces of follicular fluid, granulosa cells and other components remain on the oocyte surface. Rinsing is a series of brief transfers through fresh medium portions to remove these residues and prepare the oocyte for vitrification or further culture.
Wash is available in 50 and 100 ml vials — a practical format for laboratory work with pipettes and droplets on a warming stage.
Diagram of oocyte vitrification with ViT1 and ViT2 kits
Vitrification is ultra-rapid freezing in which the cell enters a glass-like state without ice crystal formation. This allows equine oocytes and embryos to be stored long-term in liquid nitrogen (−196 °C) with high survival after thawing.
The ViT1 + ViT2 kit is a two-step system: first medium for equilibration, second for final vitrification.
Diagram of oocyte thawing in a water bath with WaM1 and WaM2 media
Thawing is the reverse of vitrification. The frozen oocyte is removed from liquid nitrogen, rapidly warmed and stepwise recovered from cryoprotectants into working medium. The goal is to restore cell viability for culture, fertilization or transfer.
The WaM1 + WaM2 kit provides a smooth transition of the cell from vitrified state to working medium without osmotic shock.
All manipulations must follow temperature control and standard laboratory practices. Media require appropriate equilibration before use.
