Dr. Alexander Travis, who runs the lab at the Baker Institute for Animal Health at Cornell University's College of Veterinary Medicine in Ithaca, New York said they took a puppy and rubbed it with a little towel and when it started to squiggle and cry, they knew they had success.
The lab kept track of the puppies by painting their nails with different color polish.
In vitro fertilization, the process of fertilizing an egg with sperm outside the body, is widely used to assist human reproduction these days. The first human birth from IVF took place in 1978.
But IVF efforts with dogs repeatedly failed until now, according to Dr. Pierre Comizzoli, a reproductive physiologist for the Smithsonian Conservation Biology Institute in Front Royal, Virginia, which works with Cornell.
"The biology of the dog is really, really different than humans," Comizzoli said. Dog pregnancies last only two months and females go into heat just once or twice a year, releasing immature eggs instead of mature eggs needed for IVF.