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These are the first puppies born through in vitro fertilization

Mike Carroll/College of Veterinary Medicine at Cornell University

The puppies pictured above are an adorable and historic bunch. They're the first litter of pups to be conceived through in vitro fertilization. Cornell researchers transferred 19 fertilized embryos into one female dog, which then gave birth to a raucous romp of seven canines. Two of the puppies have a beagle mother and a cocker spaniel father, while the other five are from two pairs of beagle parents.

To make the pups, the researchers collected eggs from within the mothers' oviducts — the passageways between the ovaries and the uterus. (In humans, the oviducts are called fallopian tubes.) Female dogs differ slightly from other mammals, in that their ovaries don't release mature eggs right away; the eggs must reside in the oviducts for a few days to grow and develop more fully. The researchers gave the eggs two days of maturation time before harvesting them.

The technique could be helpful for wildlife conservation programs

In a cell culture, the eggs were combined with the sperm from the father dogs. The sperm were first incubated in magnesium and other chemicals that are found inside the female's oviducts, to simulate what the environment is normally like for fertilization to take place. Once the sperm fertilized the eggs, the resulting embryos were frozen and then inserted into the oviducts of the host dog.

The researchers say that this reproductive success could be helpful for wildlife conservation programs, such as boosting the numbers of endangered canid species that are struggling to breed in the wild. It can also be used to preserve rare dog breeds or weed out heritable diseases among canines.

Although this is the first time that dogs have been born through in vitro fertilization, other animals have been conceived through the technique before. The Audubon Center for Research of Endangered Species, for example, successfully conceived a black-footed wildcat in vitro. The kitten was then transferred into the womb of a domestic cat, which later gave birth.