Abstract: The present disclosure relates to deoxyribonucleic acid (DNA) editing agents, and their use in preparing DNA-edited cells and birds. The present disclosure further relates to gene-edited or genetically modified avians and gene-edited or genetically modified avian primordial germ cells (PGCs) for producing gene-edited or genetically modified avians (birds) that can serve as surrogate hosts for donor PGCs. The present disclosure further relates to methods for producing avian strains that can produce viable embryos and offspring, in both sexes, and for their subsequent use as surrogate hosts for donor PGCs.

Abstract: The present disclosure provides exogenous polynucleotide cassettes for generating chimeric bird cells and chimeric birds. The polynucleotide cassettes can be used to produce conditionally-lethal phenotype in male bird embryos. In one embodiment, the present disclosure provides methods for destroying male chick embryos in-ovo.

Abstract: A DNA editing agent is disclosed which comprises a first nucleic acid sequence for eliciting in an inducible manner a lethal phenotype of male chick embryos in an egg of a bird and a second nucleic acid sequence for directing said nucleic acid sequence for effecting said lethal phenotype to a Z chromosome of a cell of the bird. Use of the DNA editing agent is also disclosed.