Transgenic animals are one of the most potent and dynamic research tools in almost every biological science ranging from basic
biological studies to the generation of livestock with high economic
value. The use of genetically engineered farm animals as bioreactors
to produce therapeutic proteins may be a promising and economical
approach. Since the term ‘‘transgenic’’ was first introduced in 1981
[1], the mammary gland of mammals has been considered to be a
primary candidate organ for a bioreactor because of its capacity for
opulent milk production, and some pharmaceutical proteins were
produced in the milk of several species of transgenic farm animals
(reviewed in [2]).