>"These factors are slowing the interest in transgenic animals as a production alternative (...) as protein purification is generally easier from serum-protein free cell cuture media than from milk" (...) "the benefic of trangenics is in cost-of-goods, the ability to scale up by breeding animals instead of building bioreactors (...)<
This is a comment that applies almost specifically to monoclonal antibodies. For any other protein, milk has the starting advantage.