Like pigs anywhere, they stink. But three of them are special, containing genetic modifications that may make their organs a bit more like those of human beings. Some day, the people who run this place envision growing thousands of genetically modified pigs whose lives would be sacrificed so that their hearts and kidneys could be transplanted into sick people. If it works, this technique would solve the shortage of organs for transplant, saving lives. The sheep were produced by an earlier method, not by cloning, but they are special nevertheless.
Sheep are good for producing some drugs, and so are rabbits.
But for proteins likely to be needed in large quantity, cows are likely to be the best factories. That is one of the factors that led PPL to buy out a tiny Blacksburg biotechnology company and expand onto American soil in 1993. Cattle in North America are considered free of mad cow disease. With little public attention, PPL's American scientists have achieved one milestone after another. There is no longer any doubt that human genes can be inserted into cows or that the mammary glands of the cows will use those genes as templates to make human proteins.