Bacteria, yeast and mammalian cell cultures have been used over the past decades for the production of commercially important biological molecules. However, the use of these production systems to obtain complex proteins involves high cost procedures and technically demanding processes. During the last few years, the pharmaceutical industry has focused on the production of recombinant proteins with potential therapeutic applications, in the mammary gland of transgenic animals. The reason for this is that replacing conventional bioreactors with transgenic livestock offers immense economic benefits. Here we report the high yield production of recombinant human growth hormone (hGH) in the milk of cloned transgenic cows, and the successful obtaining of a bovine rodeo which is transgenic for the production of different proteins of high pharmaceutical and economical interest, such as human insulin and bovine growth hormone (bGH).