[Cryo]Preserving Bitch Fertility

by Martine Huslig, MS

With many issues in life, boys have the good life!!!  Nowhere is this more apparent than in the area of reproduction.  Boys have a happy tryst and then with a little cooperation from Mother Nature, they are fathers.  Girls on the other hand have a long road ahead including pregnancy, whelping and motherhood.  Some may call this "rewarding" but there is a LOT of work and discomfort involved.   Preserving fertility is no different than the other areas of reproduction.  A male dog has a quick date with a plastic baggie and presuming he has acceptable sperm quality, his fertility is preserved for literally decades into the future.  There are MANY documented litters conceived from sperm frozen OVER 20 years previously.  Sadly, for those with beloved bitches, no such options currently exist.

In a world were human pregnancies are conceived hundreds if not thousands of times a day via In Vitro Fertilization (IVF) and other Assisted Reproduction Technologies (ART), the first human pregnancy conceived via cryopreserved (frozen) oocytes (eggs) was just in 2004 (and undoubtedly involved a  number of hormone injections and a great deal of discomfort for the women involved.)  Extending female fertility beyond a female's own body is complicated by the fact that oocytes (eggs) are inherently unstable in most mammals (other than the egg laying mammals-monotremes.)  The biological process of creating eggs is inherently different than the process of creating sperm and the cellular structures of eggs are extremely delicate.  They do not respond well to being frozen.  Sperm are designed by nature to go forth and multiply and they respond well to various preservation techniques.  Eggs were designed to sit and wait for the sperm to arrive and are extremely fragile.  The egg is actually only partially mature when it is produced and does not complete maturation until fertilized by the sperm.  Complicating matters further for the female dog are 2 primary issues.  One, canine Assisted Reproductive Technologies (ART) are far less developed than for other species due to a long history of funding deficits due to a world wide belief that there is a "canine over-population problem" (and also most likely due to a lack of "commercial" interest.)  Two, canine reproduction and eggs/sperm behave differently than those of other species; therefore, the reproductive studies done and the techniques that have been well developed in other species are not readily adapted to dogs. 

The future is not entirely bleak for canine reproductive science and the possibility of preserving female canine fertility into the future.  First, although eggs that have been ovulated do not respond well to freezing, intact ovaries and parts of ovaries do well with cryopreservation and thawing.  Researchers have been able to mature ova from these frozen ovaries.  According to Dr. Robert Hutchison, one of the foremost authorities on canine reproduction in the country, and a number of "canine fertility" websites, canine ovaries can and are being cryopreserved on a regular basis with the same accounting as is currently used for canine sperm.  There is no promise at this time that the AKC will recognize breedings from banked ovarian tissue however AKC has recently approved on a one time basis the registration of a future Portuguese water dog litter that will result from eggs harvested from a now spayed bitch using a surrogate dam of same breed.  [Board Minutes from the February 2006 AKC Board Meeting.]    A similar request was approved in 1999 but no litter ever resulted.  Limits are placed on this breeding like the puppies must be DNA tested and all puppies must be the offspring of the genetic dam and NOT the surrogate dam but, given this precedent and the precedent set by the use of frozen canine sperm, there is cause to be hopeful about AKC recognition should the science to do such breeding become more readily available.  The second reason to be hopeful about the possibility for preserving bitch fertility is there are a number of endangered wild dogs.  Research in domesticated dogs can to some degree be applied to wild canid therefore research into understanding canine reproduction and developing Canine ART is being funded and proceeding.  Third, ovaries can and have been successfully transplanted. A report of a successful canine pregnancy after ovarian transplantation dates back to the late 1800's and human ovaries have been successfully transplanted and resulted in natural fertility.  This would appear to potentially offer an alternative for transferring bitch fertility to the technically complicated, cumbersome and expensive IVF and embryo transfer.

According to Dr. Hutchison, there is an especially interesting fact about the female dog as opposed to most other species.  That is that female dogs do not go through menopause.  According to Dr. Hutchison, the female dog's ability to breed indefinitely is apparently limited by her physical and uterine health but ---her ovaries remain ready to continue breeding and producing eggs.  Therefore, an important bitch can be bred as she would typically be bred, then she can be spayed and her ovaries saved for future reproductive possibilities.  Additionally, ovarian cryopreservation offers hope for those females who may fall suddenly ill.  If the veterinarian becomes aware that the bitch will not survive or that her health will not be adequate to carry a pregnancy, then her ovaries can at least be saved with hopes for the future.  If surgery is performed immediately; the viability of ovaries can also most likely be saved on bitches that have died (just as semen can also be extracted from deceased males if this is done early enough after death.)  The possibilities for these reproductive techniques also provide hope for a bitch where there is concern about a genetic disease.  Canine genetic research is moving forward at a rapid pace and in the future we will understand canine genetics and disorders that are possibly genetic much better than we do today.  With ovarian cryopreservation, there is at least the possibility of access to a bitch in the future that the breeder may not be willing to use today.   Sadly-there is no guarantee at this time that any of these technologies will ever become available nor that puppies will ever result from this stored ovarian tissue or from stored eggs.  However, there is hope and for many with bitches that are valuable to them and their breeding program, that may otherwise have no chance to reproduce, hope may just be enough.

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