Project Objectives

• Establish non‑surgical embryo transfer (NSET) as an alternative to surgical embryo transfer for mice and rats.
• Compare pregnancy outcomes, pup numbers, and chimerism between NSET and surgical methods.
• Optimise procedural steps using commercial NSET devices and assess reproducibility and ease of use.
• Train staff and assess required learning time for reliable NSET performance.
• Share protocols and findings with Swiss transgenic facilities (ETH Zurich, University of Geneva).
• Integrate NSET into routine workflows and future animal licence applications.

How This Advances 3Rs Implementation

• Provides validated evidence supporting non‑surgical embryo transfer (NSET) as a replacement for surgical procedures.
• Reduces procedure‑related suffering by removing incisions and post‑operative recovery.
• Supports reduction by improving success rates and lowering procedural repetition.
• Enables implementation across laboratories through training and protocol sharing.
• Integrates a refined method into licensing and operating procedures for ongoing use.
• Improves reproducibility by minimising the variability introduced by surgical skill.

Background

The generation of transgenic rodent models traditionally relies on surgical embryo transfer, an invasive procedure requiring anaesthesia and incisions through the body wall and uterus. While effective, the method causes post‑operative pain and carries risks of infection and other complications. Non‑surgical embryo transfer (NSET) offers a refinement by delivering embryos into the uterus using a soft catheter inserted through the vagina under brief anaesthesia. This avoids surgical intervention and substantially reduces the burden on animals. Despite clear welfare benefits, the method has seen limited adoption in Switzerland due to training gaps and uncertainty about efficiency compared with surgery.

This project established and validated NSET within a transgenic facility, generating direct comparisons with conventional surgery and building practical expertise. The team refined procedural steps, assessed success rates, and shared the method with additional Swiss institutions to support wider, evidence‑based implementation of this less invasive technique.