At LOBUND, investigators derived and maintained many species , including germ-free guinea pigs, chickens, monkeys, cats, dogs, rabbits, mice, flies, and fish.1 The first germ-free rats were derived at LOBUND by cesarean section and were hand raised in isolators by

round-the-clock feeding using hand-drawn glass pipettes as feeding tubes. Cesarean section and hand raising are still used to produce germ-free piglets, puppies, kittens, ferrets, calves, and other larger animals, but most laboratories that use germ-free animals today primarily use mice and breed them in the germ-free environment. Because mice and rats can live their entire lives germ-free, rederivation is necessary only when new strains are to be introduced, and most laboratories now use embryo transfer to produce new germ-free mouse strains, obviating much of the manual labor necessary to raise neonates inside the germ-free isolator.