Scientists reported they have genetically engineered pigs to produce large amounts of a mouse protein in their milk, a step toward creating "bioreactor" farm animals that make medicines for people.

The "transgenic swine" probably would not be practical, however, as living drug factories because pigs are too hard to milk, researchers said Thursday.But the pigs indicate a modified version of the gene used in the pigs could be spliced into the genes of cows or goats to make them produce milk containing large amounts of drugs that are currently expensive or hard to produce, they said.