Guide to Fresh Embryo Transfer in Cows

Overview This guide outlines the procedure for fresh embryo transfer (ET) in cattle, typically used in donor-recipient programs where embryos are collected and transferred the same day. It covers preparation, recipient selection, embryo handling, and transfer technique to achieve high pregnancy rates.

Required Equipment (WTA Tech)
- ET Gun (Universal or 0.25 mL / 0.5 mL specific) WTA
- ET Sheaths (Soft-tip, non-traumatic) WTA
- Sanitary Chemise (Disposable cover) WTA
- OB Sleeves (Gloves) WTA Waterproof Nylon Apron WTA
- Lubricant (Non-spermicidal)
- Embryo Handling Dish WTA
Option 1: Petri Dish 60 mm (standard for field work)
Option 2: Five-Well Dish (for multiple washes or sorting)
- Micropipette or Embryo Pipette
- Dissecting Microscope
- TSV Embryo & Oocyte Transporter: WTA
- Clean Forceps or Embryo Handling Tools
- Paper Towels
- Recipient Cow Identification Records 

Step-by-Step Procedure

1. Recipient Cow Preparation
- Restrain the recipient in a chute with side access.
- Confirm recipient ID and verify synchronization stage (Day 7 post-estrus ideal).
- Check for functional corpus luteum (CL) via palpation or ultrasound.
- Clean the vulva and perineal area with clean water and dry.
- Wear OB sleeve and apply lubricant to rectal arm. Wear apron to protect clothing. 

2. Embryo Handling
- Under the dissecting microscope, locate and evaluate embryo quality.
- Place embryo in Petri Dish 60 mm or Five-Well Dish pre-warmed with holding medium. 
- Select Grade 1 or 2 embryos for transfer.
- Use a sterile micropipette to load the embryo into the ET gun.
- Attach ET sheath and cover with a sanitary chemise.
- Keep the loaded gun and embryo at approximately 37 °C until transfer (use TSV transporter if moving between locations). 

3. Transfer Technique
- Insert gloved rectal arm to stabilize cervix.
- Guide ET gun into the vulva and advance to the anterior vagina.
- Remove sanitary chemise.
- Pass through cervical rings into the uterine body.
- Advance the tip into the uterine horn on the side of the corpus luteum.
- Slowly depress the plunger over 5 seconds to deposit the embryo.
- Hold position briefly, then withdraw smoothly.
- Record all details (recipient ID, embryo ID, transfer side, date). 

4. Post-Transfer Care
- Allow the cow to rest and monitor in a low-stress environment.
- Mark for identification and pregnancy checks.
- Schedule pregnancy diagnosis at 28–35 days post-transfer. 

Best Practices
- Timing: Day 7 after standing heat is optimal. 
- Embryo Handling: Always use sterile, embryo-safe tools.
- Avoid sudden temperature fluctuations.
- Cow Health: Avoid recipients with uterine infections or poor body condition.
- Environment: Work in shade or protected indoor space.
- Record Keeping: Track donor, recipient, transfer technician, and embryo quality. 

Conclusion Fresh embryo transfer allows for high viability and flexibility in in-herd reproduction programs. With sterile techniques and proper synchronization, conception rates often exceed 60%.

Additional Notes and Best Practices Synchronization Protocols To ensure recipients are at Day 7 post-estrus, consider these widely used synchronization programs:

Ovsynch Protocol
Day 0: GnRH injection
Day 7: PGF₂α injection
Day 9: Second GnRH injection
Transfer 7 days after confirmed ovulation

Prostaglandin-Based Protocols
-Two PGF₂α injections 11–14 days apart 
-Estrus expected 2–5 days after the second injection
- Transfer 7 days after standing heat CIDR-Based

Protocols (Controlled Internal Drug Release)
- Insert CIDR for 7 days PGF₂α given upon removal
- Estrus occurs within ~48–72 hours
- Transfer 7 days post-estrus
Note: Synchronization choice depends on herd management, technician experience, and donor-recipient scheduling. 

Recipient Selection Criteria Ideal recipients should meet the following conditions:
- Age: 2–7 years old 
- Body Condition Score (BCS): 2.75–3.5 on a 5-point scale
- Reproductive History: No history of metritis, dystocia, or retained placenta in the last calving
- Cyclicity: At least one confirmed natural estrus cycle before synchronization Health: No lameness, mastitis, or systemic illness
- Functional Corpus Luteum: Confirmed via palpation or ultrasound Stress Management

Recommendations

Reducing stress around handling and transfer significantly improves conception rates:
- Move cows calmly and quietly — avoid shouting or abrupt gestures 
- Minimize the presence of dogs or unfamiliar people
- Use well-designed chutes and pens to avoid slipping or injury
- Schedule transfers during cooler parts of the day (morning)
- Allow recipients to rest undisturbed for at least 30–60 minutes after transfer 

Managing Transfer Failure

If pregnancy is not achieved:
Review Records
Was synchronization timing correct? Were embryos properly handled (thawing temperature, timing)? Were recipients healthy and cycling?

Resynchronize Recipients
Repeat synchronization protocol after verifying reproductive status Consider a different synchronization protocol if conception rates are consistently low

Evaluate Additional Factors
Heat stress at transfer Technician technique (depth of deposition, side of CL) Embryo quality or source

Plan Next Steps
Reschedule embryo transfer If repeated failures occur, investigate herd nutrition, disease status, and handling practices.