From the paint on their toes and the tips of their tails, the puppies stand out as unusual. But the litter of seven will go down in history for more than the colours that tell them apart. Now five months old and doing well, the dogs are the first to be born through IVF.

The healthy delivery of the dogs by caesarean section on 10 July marks a success that has eluded scientists for 40 years since efforts began in the mid-1970s. The procedure could transform attempts to save endangered dog species, and potentially help prevent the genetic disorders that afflict so many breeds.



Born to the same beagle mother, the puppies included two produced from a different beagle mother and a cocker spaniel father, and five from two other pairings of beagles. The seven pregnancies came after 19 IVF embryos were transferred to the mother, according to a report in Plos One.



Dog days: Britain's endangered breeds Read more

“We had people lined up, each with a towel, to grab a puppy and rub them and warm them up,” said Alex Travis, a specialist in reproductive biology at Cornell University, in Ithaca, New York. “When you hear that first cry and they start wriggling a bit, it’s pure happiness. You’re ecstatic that they’re all healthy and alive and doing well.”



The team used small daubs of coloured nail varnish to tell the dogs apart. Since they were born, all but one has been adopted. Their names are Ivy, Cannon, Beaker, Buddy, Nelly, Red and Green. Travis gave a home to Red and Green, and while Red’s name honours the informal name for the Cornell sports teams, Travis says Green has yet to be renamed because his children cannot reach a consensus. Nelly will be homed after she has had her own litter of puppies.



The struggle to make IVF work in dogs is down to the curiosities of the canine reproductive system. Dogs ovulate only once or twice a year and the eggs they release are very immature. They are also unhelpfully dark, thanks to fatty molecules inside them, making them hard to work with under a microscope. The list of problems goes on.



Facebook Twitter Pinterest The seven puppies have three sets of biological parents and are said to be healthy and doing well. Photograph: Cornell University College of Veterinary Medicine/PA

Travis and his colleagues first worked out how to obtain eggs that were mature enough to fertilise. The solution turned out to be leaving the eggs in the dogs’ oviducts – the canine equivalent of human fallopian tubes – for a day longer than usual, allowing them to reach a later stage of natural development.



The next hurdle was mimicking the effect of the female reproductive tract, which prepares incoming sperm for fertilisation. Jennifer Nagashima and Skylar Sylvester, researchers in Travis’s lab, found that adding magnesium to the sperm culture did the job. With those two changes, the scientists achieved fertilisation rates of better than 80%.



The final part of the process was to freeze the embryos, so they can be stored until the surrogate mother is at the right stage in her reproductive cycle. Travis had worked out how to do this before, and in 2013 oversaw the birth of the first dog, named Klondike, from a frozen embryo.



Travis said the breakthrough could help conserve threatened and endangered species of dogs in captivity. “If you are managing a species such as the African painted dog, and a male dies, you can collect sperm. And if a female dies, you can collect ovarian follicles from the ovaries and try to mature oocytes in vitro. But then what? To be able to use these resources, you need IVF to be able to produce an embryo from the sperm and eggs,” he said.



Travis added: “Because dogs share so many genetic traits and diseases with people – over 350, which is vastly more than any other species – this technique also gives us new opportunities both to study genetic disease, and with gene editing, potentially prevent it from happening. This will have important implications for both veterinary and human medicine.”

