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Posted on Mon, Mar 18, 2013 : 6 a.m.

Non-surgical option for neutering dogs could have full FDA approval by mid-2013 & may significantly address pet overpopulation

By Lorrie Shaw


Flickr photo by powazny

As someone who is as immersed in the world of animals as I am, one topic — pet overpopulation — is something that comes up multiple times per day in conversation, especially on social media. And it's no wonder: animal rescues and humane societies are inundated with dogs and cats who need permanent homes. Although the numbers of those waiting to be adopted are not limited to young animals, the litters of puppies and kittens that are seen are certainly a stark reminder of how much work needs to be done when it comes to getting pet populations under control.

Some sad realities come to mind when I think of the problem of pet homelessness and overpopulation, like the needless suffering of many degrees and instances of euthanasia that are, in some situations, the only solution.

Educating the public about the problem is paramount: humans are the ones who have the ability to discern where the problems lie, and where the best solutions are.

First, understand that from a biological standpoint, we are in a battle with pets.

Reproductive success drives evolution, pure and simple. It's the strongest biological factor in any species. Biology has a way of taking over, jumping any hurdle that is put in its path and compensating. The pets themselves have no control over their biological drives, and therefore can't curb their behavior when it comes reproducing.

That's why spaying and neutering have been the go-to tactic to making an effort to getting pet overpopulation under control. It's safe, effective and, best of all, it's permanent.

In 1972, the American Society for the Prevention of Cruelty to Animals made a policy decision that rocked the boat: from then on, every animal adopted from their shelters had to be spayed or neutered — a real shift in forward thinking.

Now, this policy is standard when adopting from most any shelter or rescue.

But is the message of how easy and effective spay and neuter procedures are getting through to the public-at-large? That's a good question. Here we are four decades later, and we're still battling stereotypes and biology.

Some people cite the cost of the procedure as something that stands in the way of their scheduling the procedure. (It's actually pretty affordable.) Perhaps the misconceptions surrounding the idea of neutering that keep people from having it done. ('It's emasculating!')

A new frontier of pet sterilization — the non-surgical route — just might get people to rethink the issue.

Last year, I wrote about one new drug, Esterilsol, (as it's known outside of the United States), and how it was being tested for approval by the Food and Drug Administration in countries like Guatemala and the Dominican Republic.

The good news is that the drug is expected to have full approval for use by the midpoint of 2013 here in the U.S. as a non-surgical option for neutering dogs.

Known as Zeuterin in the U.S., the drug is a safer, faster and much less invasive way to sterilize male dogs age three to ten months.

It works like this: Zeuterin (a solution of zinc gluconate; zinc is a natural spermicide) is injected into each testicle — leaving it incapable of producing sperm.

No anesthesia is needed, and the procedure is much easier, compared to the traditional surgical option. For these reasons alone, zinc neutering could be a boon to shelters.

Canines who have been Zeutered have a microchip implanted or are tattooed with the letter "z".

One drawback to surgical neutering is that it involves eliminating the source of testosterone production, therefore leaving the animal no benefits of what the hormone offers — like protecting metabolic functions. With Zeuterin, testosterone is only lowered by about half.

The surgical option has been long-touted as a way to reduce mating behaviors and to calm male dogs down. Feedback given by owners and custodians of dogs who have been sterilized with Zeuterin indicate that the same behaviors have been suppressed.

For more on zinc neutering, click here to read Dr. Marty Becker's recent piece on VetStreet.

Lorrie Shaw leads the pets section for and owner of Professional Pet Sitting. Shoot her an email, contact her at 734-904-7279 or follow her adventures on Twitter.


Valerie B.

Wed, Mar 20, 2013 : 7:11 p.m.

I live in Ann Arbor and work for the Alliance for Contraception in Cats & Dogs (ACC&D). Our mission is to expedite the successful introduction of methods to non-surgically sterilize dogs and cats and to support the distribution and promotion of these products to humanely control cat and dog populations worldwide. We're delighted that Zeuterin is gaining recognition as a valuable tool to non-surgically sterilize male dogs -- thank you, Ms. Shaw! Just wanted to mention that for those interested in learning more, we recently updated our Product Profile and Position Paper on Zeuterin/Esterilsol. Please feel free to access it at

Lorrie Shaw

Fri, Mar 22, 2013 : 12:29 a.m.

Valerie, I appreciate you sharing that info. It's such a valid mission. Best, Lorrie


Tue, Mar 19, 2013 : 12:12 p.m.

side effects?? I'm sure there must be some. The dog I adopted last year (as well as the cat earlier) was neutered at 8 weeks. While I understand the reasons, I think that is too young. Esp for the dogs. I worry about his future bone health, he is an 80 lb Lab/Shepard mix.

Lorrie Shaw

Fri, Mar 22, 2013 : 12:27 a.m.

LA, Ooh, great point! Yes, as I understand it, neutering too early can certainly impact the long-term health of a pet -- especially large breed dogs as you point out. I have one client who is a giant breed. She was spayed young and her clinicians believe that because of that, her growth plates had not had a chance to fuse properly. This resulted in some problems. In the clinician's best estimation, waiting until after 12 months of age in dogs like this might be best. That said, all breeds mature at different ages and with mindfulness on the owner's part and good dialogue with their vet, determining the best age for each pet on a case-by-case basis might be a good idea. In cats, it's better to spay before 12 months, and it reduces the risk of mammary gland cancer tremendously. In looking at it from a health issue in this way, there's definitely a lot to consider when approaching this issue, isn't there? You made a valid point. I appreciate that. Best, Lorrie


Mon, Mar 18, 2013 : 5:15 p.m.

Behavior Modification: It is suggested that Zeuterin may suppress the male mating behavior and I would like to know as to how such behavior modification impacts the female population of the species. The females during estrus may actually desire the mating behavior of the male members. A few weeks ago, the science journal 'Nature' published a story about the evolution of dogs from the wolf population. Dogs moved towards places of human habitation for they have the enzyme amylase and have the ability to digest starchy foods and grains that humans consume. It is not surprising to read about obesity and diabetes among the pet population which depend upon food supplied by their human masters. If evolution is about reproductive success of a species, the pets have no chance as they become increasingly dependent upon human behavior and human choices.

Lorrie Shaw

Fri, Mar 22, 2013 : 12:18 a.m.

BhavanaJagat, Well, if it does impact the females, I see that as a good thing: there is likely to be mating and fewer litters of animals who we'll struggle to find homes for. But your point about the success of the species is intriguing. It will be interesting to see how the species holds up over time, thanks to our intervention. We have done a good job of mucking things up for them in so many ways, but we've been helpful as well in others. Many thanks for your input! I value it! Lorrie

tom swift jr.

Mon, Mar 18, 2013 : 2:50 p.m.

"injected into each testicle"....."No anesthesia is needed"..... I'm guessing that nobody got the dog's opinion on that....

Lorrie Shaw

Fri, Mar 22, 2013 : 12:14 a.m.

Tom, I was thinking the same thing, but quite honestly compared to the alternative procedure, it might be preferable if a dog was given the choice. Thanks for commenting! Lorrie