Abstract: Transgenes for producing recombinant polypeptides transgenic bovine species. A transgene for producing recombinant polypeptides in the milk of transgenic bovine species comprises at least one expression regulation sequence, a secretory DNA sequence encoding a secretory signal sequence which is functional in mammary secretory cells of the bovine species and a recombinant DNA sequence encoding the recombinant polypeptide. Also included are methods for producing transgenic bovine species. The method includes introducing the above transgene into an embryonal target cell of a bovine species, transplanting the transgenic embryonic target cell formed thereby into a recipient bovine parent and identifying at least one female offspring which is capable of producing the recombinant polypeptide in its milk.