This invention provides vectors and methods for the stable introduction of exogenous nucleic acid sequences into the genome of avians in order to express the exogenous sequences to alter the phenotype of the avians or to produce desired proteins. In particular, transgenic avians are produced which express exogenous sequences in their oviducts and which deposit exogenous proteins into their eggs. Avian eggs that contain exogenous proteins are encompassed by this invention. The instant invention further provides novel forms of interferon and erythropoietin which are efficiently expressed in the oviduct of transgenic avians and deposited into avian eggs.