Animal board invited review: Germplasm technologies for use with poultry.

Over the last century, several reproductive biotechnologies beyond the artificial incubation of eggs were developed to improve poultry breeding stocks and conserve their genetic diversity. These include artificial insemination (AI), semen storage, diploid primordial germ cell (PGC) methodologies, and gonad tissue storage and transplantation. Currently, AI is widely used for selection purposes in the poultry industry, in the breeding of turkeys and guinea fowl, and to solve fertility problems in duck interspecies crosses for the production of mule ducklings. The decline in some wild game species has also raised interest in reproductive technologies as a means of increasing the production of fertile eggs, and ultimately the number of birds that can be raised. AI requires viable sperm to be preserved in vitro for either short (fresh) or longer periods (chilling or freezing). Since spermatozoa are the most easily accessed sex cells, they are the cell type most commonly preserved by genetic resource banks. However, the cryopreservation of sperm only preserves half of the genome, and it cannot preserve the W chromosome. For avian species, the problem of preserving oocytes and zygotes may be solved via the cryopreservation and transplantation of PGCs and gonad tissue. The present review describes all these procedures and discusses how combining these different technologies allows poultry populations to be conserved and even rapidly reconstituted.