1. The document describes using transgenic livestock animals as bioreactors for producing pharmaceutical proteins in their milk. 2. Specifically, it details an experiment where researchers created transgenic sheep that produced the human protein alpha-1-antitrypsin (AAT) in their milk by fusing the AAT gene to the regulatory sequences of the ovine beta-lactoglobulin gene. 3. The transgenic sheep were able to stably pass the transgene to offspring and produced over 1g of fully active, glycosylated human AAT per liter of milk.