 As the eggs in a female canine are only fertile during the estrus phase of the estrous cycle, the eggs could only be harvested during a three-week period each year. Due to complexities with removing eggs from canine ovaries the eggs had to be extracted from the oviduct, which required constant monitoring to achieve. The nucleus of each egg was replaced with the cell from the ear of the adult dog and then electrified and fused using a chemical reaction. The embryos were then transferred to the surrogate dogs. Three of the surrogate mothers became pregnant and two successfully gave birth. Snuppy, the first to be born, survived while the other died two weeks after birth. This process of cloning Snuppy took nearly three years of intensive effort.
