Strain Rederivation

  • Introduction

TAF offers rederivations of a particular strain of mice or rats into A-rated facilities on campus.   Whether an investigator needs to recover a strain which previously had been cryopreserved, needs to rederive a strain from embryos shipped from a source outside the university, or a strain within the university that carries unwanted pathogens, we will work with the investigator to generate and/or collect embryos for transfer into pathogen-free pseudopregnant recipients.  

The basic steps in a rederivation project are:

  1. generation of embryos by mating superovulated females to males
  2. collection of embryos from females
  3. transfer of embryos into pseudopregnant females

  • Getting Started

Prior to rederivation, the investigator will need to meet with TAF staff to determine the specific needs of the investigator, develop a strategy and schedule for rederivation, and discuss fees. Please contact Kathy Krentz ( or (608) 890-3785 to schedule an initial meeting.

  • Embryo Generation, Collection and Transfers


  1. Meet with Kathy Krentz to discuss rederivation strategy
  2. Amend animal protocol to include IP injections of hormones
  3. complete a billing request form

If a previously cryopreserved strain is being recovered from liquid nitrogen, straws are thawed and embryos transferred into pseudopregnant ICR (for mice) and SD (for rats) recipients.

For projects involving the transfer of a strain from another university, the investigator will generate embryos and ship these embryos to TAF via overnight delivery.  The TAF staff will work with the investigator to provide the necessary guidance so that the investigator can superovulate, mate, collect embryos and prepare the embryos for delivery to the TAF laboratory.

For projects involving the rederivation of pathogen-carrying strains from within the university, we will provide investigators with protocols, hormones and training (if necessary) so that they can superovulate and dissect reproductive tracts from the animals, thereby allowing us to avoid contact with donor animals.  We will collect the embryos from the reproductive tracts and transfer them into pseudopregant ICR (for mice) and SD (for rats) recipients.  The number of transfers completed depends on the number of good quality embryos collected.

In all situations, pups will be born about three weeks later and weaned three weeks after that. Recipient moms will be screened for pathogen status by serological testing. The pups will be transferred to the investigator as soon as serology results indicate the recipient mom is pathogen-free and the animal transfer form has been completed by the investigator and an LAR veterinarian from the relevant school.

When rederiving strains, investigators are charged based on the number of embryo transfers performed.