Semen cryopreservation for ex situ management of genetic diversity in chicken: creation of the French avian cryobank.

The need for semen preservation in domestic birds is a result of the reduction in genetic variability of domestic bird livestock and of the increasing risk of line extinction for health and safety reasons. Cryopreservation of embryos and primordial germ cells (PGC) is not routinely feasible in birds. The project therefore involved semen frozen in optimal safety and traceable conditions. Whole blood samples were also frozen to provide samples of analyses of genomes and health status. The feasibility of using ex situ conservation, i.e., collecting biological material to be stored outside the usual production area of the species (ex situ genetic stock), to preserve and manage rare breeds was tested with 4 subfertile populations: 3 rare experimental lines used for research into energy metabolism (R+), growth (Y33), and immunity (B4/B4), reared under known health status and the oldest endangered patrimonial French breed, the Gauloise dorée with an unknown health status. A general infrastructure was set up for the health screening and remediation of diseases, collection and storage of frozen cells and 2 sites were created for the storage of frozen samples. The screening and remediation of diseases of the Gauloise dorée, which was contaminated with various Salmonella and Mycoplasma strains, was achieved by successive treatment of parents, incubated eggs and young chicks with Baytril followed by Tiamulin. For each line, 474 to 994 semen straws have been frozen, thawed, and the semen evaluated. Insemination of frozen-thawed semen into females of the same genetic origin or of an egg-type commercial breed produced chicks in every case. For the most subfertile lines, insemination with egg-type females significantly increased the reproductive success. In conclusion, we report on the benefits of a semen and blood cryobanking complex for the management of endangered lines and strains of domestic birds. Current stocks made possible the restoration of more than 96% of the initial genome. This project also provided technical solutions to resolve some of the health problems frequently encountered for gene preservation in poultry.