Cryo-storing research lines of chicken to eliminate breeding and save genetic resources

Lead Research Organisation: University of Edinburgh
Department Name: The Roslin Institute


Avian reproduction differs considerably from mammalian reproduction and therefore, mammalian reproductive technologies are not transferable to birds. Discovering a way to freeze avian reproductive cells and subsequently bring back a flock will help the preservation of endangered breeds of poultry, increase food security from disease outbreaks and reduce animal usage in research.

Research chickens are currently bred in large numbers across the world in order to maintain a genetically diverse population and prevent problems with inbreeding. In other research species, reproductive materials are frozen to secure future availability while reducing the numbers of animals used in research and maintaining the genetics of the species. Additionally, when there is a high demand for particular research animals and many generations are created, care is required to ensure that the genetics of the animal don't become different from generation to generation by random chance, which is a common problem when maintaining research animals.

Our project will validate a new technology to freeze chicken reproductive cells and later bring back a genetically diverse research flock from the frozen material. We use 'host' eggs from our sterile chicken line and transfer the frozen reproductive stem cells from a different chicken breed into these eggs. The adult bird will look like the sterile line externally, but will lay eggs of the transferred chicken breed. As mentioned previously, the adult birds will only have their reproductive cells changed to the transferred cell's genetics, and therefore will be largely unaffected. We will also look to introducing genetically modified donor chicken cells into the sterile lines host eggs to refine the overall life experience of all our breeding stock.

In this project, we will optimise how to freeze the reproductive cells using three research chicken breeds currently kept at the Roslin Institute. We will next show that a single surrogate host parent can lay eggs that come from many donor parents. This result will show that we will be able to bring back a genetically diverse chicken flock. Finally, we will show that we can bring back a pure flock of chicken from frozen material and will verify the fertility and health of the flock. With this information, we will be able to confidently biobank research flocks of poultry.

Technical Summary

Our ability to cryopreserve avian species is extremely limited leading to research flocks of chicken to be raised indefinitely as permanent breeding flocks. A validated protocol for the cryopreservation for research chicken will drastically reduce or eliminate the numbers of chicken kept in research institutes, greatly reducing maintenance costs and provide increased biosecurity against pathogen outbreaks, such as avian influenza, which could result in the destruction of these genetic resources and in the end endanger sustainable food production.
The overall goal of this project is to demonstrate the reestablishment of a research chicken flock from frozen material; something to date that has not been demonstrated for a poultry species. In this project, we make use our newly developed sterile surrogate host chicken which permits 100% transmission of donor genetic material. We have also recently developed a protocol to directly freeze embryonic germ cell material eliminating the need to culture reproductive tissue before cryopreservation. We will first optimise cryopreservation procedures for three research chicken lines currently maintained at the Roslin Institute. We will next directly measure the genotype transmission rates from single sterile surrogate host chicken carrying multiple donor genotypes. This result will define our efficiencies and bird numbers needed for re-establishing a chicken flock. Finally, we will demonstrate the reconstitution of a research line of chickens followed by monitoring the fertility and health of the re-established flock. With this information, we will be able to confidently biobank and reconstitute research poultry breeds.


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