Similar experiments are also taking place in animals. Genetically altered cows and goats can produce milk containing human proteins that can then be separated from the milk and used for therapeutics. But proponents of "biopharming," as the plants-to-drugs experiments are commonly called, note that it is faster and less expensive to plant additional acres of modified tobacco than to produce an additional herd of cows. In addition, drugs made from mammalian cells and animal milk might carry viruses that could affect humans, while plant viruses pose no known risk to people.

Biopharming, in which genes for pharmacologically active agents are inserted and grown in crops such as potatoes, is another rapidly expanding area.