Traditionally, veterinary schools have taught only one technique to sterilize pets, which is what we know as spaying or neutering.

The procedure involves the complete removal of the ovaries and uterus in female dogs, and the testes in males. For females, early spaying (spaying at a young age) was thought to eliminate the risk of pyometra (a disease of the uterus), and reduce the incidence of mammary tumors. Results of a study published in 2012 in the Journal of Small Animal Practice were unable to validate the theory that early spaying protects female dogs from mammary neoplasia. This leaves the elimination of the risk of pyometra as the sole health benefit of early spays.

Given the mounting evidence that intact animals may have fewer long-term health problems than sterilised pets, the last remaining issue surrounding this topic appears to be ethical, as in: responsible sterilisation to reduce the millions of unwanted litters of puppies and kittens feeding the pet overpopulation crisis.

There’s actually a big difference between desexing an animal (which is removing all gonadal tissue), and sterilization, which depending on the technique, may preserve sex hormone-secreting tissues. Many pet parents are beginning to rethink what type of surgical sterilisation technique is best for their pet, but most veterinarians are unable to offer anything other than spaying or neutering because those are the only procedures we learned to perform at vet school.

I stumbled upon a demo video online by Dr. Kutzler, on how to perform an ovary-sparing spay procedure. This procedure involves removal of the uterus while leaving the ovaries in place. It renders the dog sterile, but still able to produce important hormones. I contacted Dr. Kutzler and asked if she if she would consider talking with us about this topic, and she graciously agreed.

Dr. Kutzler’s educational background, training and experience in the field qualify her as an expert in reproductive physiology.

Dr. Kutzler explained that she first became interested in the subject during her undergraduate training at Washington State University, where she took a required course in reproduction. Intrigued? See Dr. Kutzler’s video on YouTube...

I asked her at what point along her professional path she began connecting the dots between the endocrine imbalance that results from spay / neuter, and increased disease potential.

Dr. Kutzler answered that she doesn’t remember hearing anything about the side effects of spay / neuter in veterinary school. But once she was in private practice, she began treating cases of urinary incontinence after ovariohysterectomies (traditional spays). She asked the owners of the practice and her colleagues how common this was, and why it wasn’t better documented as a problem following spay procedures. But at that time, there was still debate as to whether urinary incontinence was a result of trauma to pelvic nerves due to removal of the uterus, or whether it was the result of removing the ovaries and the hormones they produce.

The only treatment for the condition at that time was hormone supplementation (estrogens). The drug most commonly used was diethylstilbestrol (DES). Phenylpropanolamine (PPA) wasn’t available, and the only alternative was phenylephrine, but it carried more side effects than PPA, including hypertension, anxiety and behavioral changes. So DES was the drug of choice.

Dr. Kutzler explained that as many of us are aware, dog bone marrow is exquisitely sensitive to the effects of estrogens. DES had to be used very carefully to prevent a decline in bone marrow production.

So it was early in her career that Dr. Kutzler started to question the need to remove the ovaries as part of sterilisation of female dogs. But she really began connecting the dots in 2009 when Dr. David Waters published one of several papers looking at the effects of gonadal hormones and longevity in Rottweilers.

Dr. Kutzler explains that she looked at data from countries outside the U.S. that don’t routinely remove the ovaries of female dogs. Those countries have conducted 10 years or more of studies of pet health as a basis for the importance of maintaining the ovaries.

In Scandinavian countries – Sweden, Norway, Denmark and Finland – routine surgical sterilisation of pets is prohibited. It is actually illegal unless medically necessary. The responsibility for controlling an animal’s reproduction falls to the owner.

There are also more non-surgical alternatives for sterilising pets available in Europe than there are in the United States. Of course, this is primarily due to pet owner demand in countries where surgical sterilisation for purposes of contraception is illegal. But regardless, being a responsible pet parent is a very important part of the equation.

As Dr. Kutzler explains, it is too easy for pet parents to say, “I’m not going to worry about my pet’s reproductive health. I’m just going to remove the reproductive tract, and then I don’t have to worry about it.”

In addition to the convenience factor, spaying and neutering procedures have traditionally been viewed not only as harmless, but actually beneficial to an animal’s health. So it’s no wonder they’ve been so popular for so long with both pet parents and veterinarians.

But Dr. Kutzler makes the point that most female dogs only cycle once or twice a year, and some females may only cycle once or twice every two years. So the period when owners need to be responsible for their pet’s reproductive health in order to prevent unwanted litters is a short amount of time over the entire lifespan of a dog.

And, of course, if the entire lifespan of the dog is decreased to three or four years because of the early onset of bone cancer or hemangiosarcoma, it really comes down to making the best decision for the pet’s health and longevity.