IVF GOES to the Dogs
by Kate elDreDge
O n December 8th the Cor- nell University College of Veterinary Medicine announced some exciting news—the first litter of puppies con- ceived through in vitro fertilization. The full study was published the follow- ing day. The puppies were born in the spring of 2015. In vitro fertilization, frequently referred to as IVF, is when a sperm and egg are combined in a laboratory set- ting rather than live animals—test tube babies, if you will. Scientists have been doing in vitro fertilization with humans and other species for quite some time, but dogs and other canines pose some unique reproductive challenges. The biggest obstacle to overcome is that while most species release a fully mature egg at ovulation, dogs do not. Instead, dog eggs take a few extra days to finish maturing while already in the oviduct, with optimum fertility being two to four days after ovulation (four to six days after the surge in luteinizing hormone, which is also when proges- terone levels start to rise). Another obstacle was that the dog’s female reproductive tract acts to pre- pare sperm for fertilization. Dog sperm cells (and humans) have an acrosome, which is a cap-like structure on the front of the cell that contains digestive enzymes used to break through the outer covering of the egg. Once that outer covering has been pierced, the plasma membranes of the sperm and egg cells come into contact and the genetic material is able to fuse, forming a zygote. Initially, fertilization was fail- ing even though the researchers were using mature eggs and viable sperm. The researchers found that adding
“THE BIGGEST OBSTACLE TO OVERCOME is that while most species release a fully mature egg at ovulation, DOGS DO NOT. INSTEAD, DOG EGGS TAKE A FEW EXTRA DAYS...”
magnesium to the cell culture greatly assisted with sperm cells’ ability to pen- etrate the eggs. According to Dr. Alex- ander Travis, one of the Cornell faculty members who worked on the project, they were able to achieve 80 to 90 per- cent successful fertilization rates after that addition! The process does not end with fer- tilization, however. The brand-new zygotes must be transferred to a surro- gate mother and successfully implant and grow. Since bitches only come in heat about twice a year, this means that either the timing of the recipient and donor’s reproductive cycles must be
in sync or that the zygotes need to be stored until the recipient bitch is ready. Obviously the second option is far more practical. A team consisting of many of the same researchers did just that in 2013 by freezing canine embryos and then transferring them to a surrogate bitch. A puppy named Klondike became “the first puppy born from a frozen embryo in the Western Hemisphere.” So the researchers froze the embryos and waited until their surrogate bitch was ready for her historic litter. The IVF litter consisted of seven puppies from three different sire x dam crosses.
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