Story highlights Seven puppies were born from 19 embryos

For decades researchers have tried and failed to implant embryos in dogs

The breakthrough could lead to cures for diseases in dogs and humans

(CNN) Researchers in the U.S. have created the world's first litter of puppies through in vitro fertilization (IVF), a breakthrough they say could help eradicate diseases in dogs -- and in humans.

Seven puppies were born in July from 19 embryos implanted into a host female dog, according to scientists from Cornell University and the Smithsonian Institution.

"Since the mid-1970s, people have been trying to do [IVF] in a dog and have been unsuccessful," co-author Alex Travis, associate professor of reproductive biology at the Baker Institute for Animal Health in Cornell's College of Veterinary Medicine said in a statement.

Past attempts have failed because dogs have different reproductive systems to most mammals.

The dogs were a mix of pure beagles, and beagle and cocker spaniel.

The researchers found that if canine eggs were left just one extra day in the oviduct they had a much better chance of being fertilized. And when magnesium was added to the cell culture, it helped mimic conditions inside the female canine reproductive tract, which unlike many other animals helps to prepare the egg for sperm.

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