Guide to Ovum Pick-Up (OPU) in Cows

Overview

This procedure describes the OPU technique in cattle, used to recover oocytes from live donors for embryo production through in vitro fertilization (IVF). It includes preparation, equipment, aspiration technique, and handling of cumulus–oocyte complexes (COCs) to ensure high recovery rates and viability.

Required Equipment (WTA Tech)

• Ultrasound scanner with 5–7.5 MHz transvaginal transducer
• OPU Handle - WTA 
• OPU Probe Covers  – WTA
• OPU Needles 18G or 20G  – WTA
• Aspiration Pump – WTA
• Aspiration Tubing/Line 1.2m – WTA
• Collection Filters: 75 µm – WTA
• Oocyte strainer (Mini IVF Filter): 100 µm – WTA
• Tube Warmer – WTA
• Pocket Tube Heater 50 mL (portable, hanging) – WTA
• Heated Warming Stage – WTA
• Aspiration Medium 
• OB Sleeves (long gloves) – WTA
• Non-spermicidal Lubricant
• Waterproof Apron – WTA
• Dissecting Microscope (for COC search)
• 60 mm Petri Dish or Five-Well Dish – WTA
• Laboratory Pipettes with sterile tips
• Oocyte & Embryo Transporter TSV – WTA
• Paper Towels
• Animal Identification Records

Step-by-Step Procedure

1. Donor Preparation
• Restrain the donor cow in a chute with good access.
• Confirm animal ID and record reproductive history.
• Perform perineal hygiene: wash with clean water and dry with paper towels.
• Apply epidural anesthesia (lidocaine) under veterinarian supervision to reduce straining.
• Ensure equipment, media, and tubing are pre-warmed to 37–38 °C.

2. Ultrasound-Guided Ovarian Aspiration
• Insert lubricated OPU probe with sterile cover into the vagina.
• Use rectal hand to position and stabilize the ovary against the probe.
• Visualize follicles (>2–3 mm) on the ultrasound monitor.
• Introduce OPU needle (18G or 20G) through the probe’s needle guide.
• Apply vacuum (90–120 mmHg, 18–25 mL/min flow) and puncture each follicle.
• Aspirate follicular fluid and COCs into collection tubing and filter (75 µm or 100 µm).
• Wash each follicle gently if protocol indicates.
• Repeat until all visible follicles are aspirated from both ovaries.

3. Oocyte Collection and Handling
• Collect aspirated fluid into filter and rinse with warmed medium.
• Transfer contents into Petri Dish or Five-Well Dish with handling medium.
• Under microscope, locate and assess COCs.
• Wash COCs and transfer viable ones into maturation medium (IVM).
• Maintain constant temperature (37 °C) throughout handling.
• Load oocytes into labeled transport tubes if laboratory processing is off-site, using TSV Oocyte Transporter – WTA.

4. Post-Procedure Care
• Monitor donor for signs of bleeding, discomfort, or stress.
• Return cow to a low-stress environment with access to water and feed.
• Schedule repeat OPU session in 7–14 days depending on ovarian recovery.

Best Practices

• Temperature Control: Keep all media and instruments between 37–38 °C.
• Vacuum Calibration: Always measure vacuum at the needle tip, not just at the pump.
• Sterility: Use sterile covers, needles, tubing, and media to avoid contamination.
• Donor Selection: Healthy cows with functional ovaries, good body condition (BCS 2.75–3.5), and no reproductive pathology.
• Record Keeping: Log donor ID, date, follicle count, number of COCs collected, viable COCs, and technician.

Expected Results

• COCs per session: 5–25 (variable by donor and management).
• Viability: 50–80% of COCs suitable for IVM.
• Blastocyst rate after IVF: 25–45% of viable oocytes.
Note: Actual results depend on donor genetics, follicular status, semen used, and laboratory expertise.

Troubleshooting

• Low oocyte recovery: Check vacuum level, tubing connections, and follicle targeting.
• COCs without cumulus: Vacuum too high or repeated passes damaging cells.
• Blood contamination: Minimize trauma; use gentle aspiration.
• Poor blastocyst rates: Review lab conditions (media, temperature, pH, semen preparation).

Conclusion

OPU in cattle is a repeatable and efficient way to harvest oocytes for IVF programs, enabling genetic multiplication from elite donors. With proper preparation, sterile technique, and precise equipment calibration, OPU can yield high-quality oocytes that translate into transferable embryos. Regular monitoring of KPIs (COCs per session, viability, blastocyst rates) is key to continuous improvement.