Pros & Cons of Dog Neutering

Yes, actually, there really are both pros and cons to dog neutering and puppy sterilization that may surprise you. It did me. After all, we’ve heard from animal welfare advocates for years preaching the gospel of spay/neuter.  Heck, I preached this myself and for the majority of dogs and cats (ESPECIALLY cats!), “the big fix” is the best thing that ever happens to them.

There’s evidence, though, that the pros and cons of dog neutering are not so black and white. While the University of Georgia’s sample of 40,139 canine death records from the Veterinary Medical Database from 1984-2004 concluded that neutered dogs could be expected to live a year and a half longer (on average) than intact dogs, other studies point out potential increases in hip dysplasia or cancer. Oy.


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Dog Neutering & Puppy Sterilization

So what’s a responsible pet parent to do? One possible solution is a new non-surgical sterilization technique called Zeuterin from Ark Sciences, that renders the boy dogs incapable of fathering puppies but let’s them keep about 50 percent of their testosterone that makes a beneficial health difference especially in certain breeds.

Zeuterin™, an FDA-approved nonsurgical sterilization technique for male dogs from Ark Sciences, is now available in the US for all puppies three to ten months old. Termed “Zeutering,” the injectable treatment offers an alternative to the traditional surgical castration methods.

Most pet lovers recognize that neutering boy puppies they don’t plan to breed or show can be the responsible choice. Sterilization reduces a number of potential behavior problems such as roaming, marking, mounting and fighting. The University of Georgia looked at a sample of 40,139 canine death records from the Veterinary Medical Database from 1984-2004 and concluded that neutered dogs could be expected to live a year and a half longer (on average) than intact dogs. Wow.

Animal welfare organizations such as the Humane Society of the United States provide statistics that show over 80 percent of owned dogs in the United States are sterilized. Hurray! but what about the other 20 percent? And what about in other countries?

Veterinarian sterilization operation on dog

Veterinarian sterilization operation on dog

Objections to Dog Sterilization?

Is there any good reason to NOT neuter your puppy? Surgical castration permanently removes 100 percent of the dog’s testosterone, and that can cause consequences some new studies indicate may pose problems, depending on the timing and the breed.

People with puppies they hope to develop into performance dogs—hunting, herding or other athletic-intensive activities—may be reluctant to castrate their male dogs. The sexual hormones generated by the male dog’s testis give him that “male” look, and impact bone, joint and musculature development important for performance. Also, some cancers–like prostate cancer–once thought to be preventable through neutering may in fact increase in incidence. Studies indicate that large breed dogs that are neutered are at increased risk for bone and spleen cancers.

Another study of 759 Golden Retrievers at University of California/Davis showed a doubling in the incidence of hip dysplasia in male dogs neutered before their first birthday. This early neutering also showed an increase in the occurrence of cranial cruciate ligament tear and lymphosarcoma in males and of cranial cruciate ligament tear in females. Older age sterilization was associated with the later development of mast cell tumors and hemangiosarcoma in females. Different breeds may have different results, but this information may be helpful in choosing when to time neutering your puppy.

But...PUPPIES are so CUTE! (sorry, not a good reason..)

But…PUPPIES are so CUTE! (sorry, not a good reason..)

Myths About Dog Neutering

Other objections are less founded in actual science and are more myths or opinions that are hard to change. There continues to be a perception that “fixed” boy dogs lose their ability to do protection work, get fat and lazy, and are less “macho.” None of these is accurate. Metabolism is affected by both maturity and removal of sex hormones, which means food intake must be adjusted as the puppy matures or he will, indeed, pack on too much “table muscle.”

Finally, in some areas around the world (including the southern states in the US), the stray or feral population can account for a significant number of unwanted dog pregnancies. Surgical sterilization of stray and feral population is both labor and cost-prohibitive. Currently, many veterinarians say they perform pet dog and cat sterilizations at a loss, simply as a service to owners, yet the economic climate makes even these opportunities out of financial range for many people.

Zeuterin appears to answer many of these challenges. It neuters your puppy with less pain, no anesthesia (usually only sedation is necessary), he recovers more quickly, and it costs less than surgical techniques. Because it requires less time, that’s a cost savings to the veterinarian, too.

Ark Sciences that owns the drug and procedure says its initial offer to nonprofits in the United States was 1/5th the average cost of surgical castration. That makes Zeuterin a good candidate for shelters and those dealing with stray and feral populations. Savings to the pet owner may potentially reduce the cost of sterilization by 30-50 percent compared to surgical castration.

What Is Zeuterin?

Zeuterin is an injectable spermicide composed of Zinc Gluconate (a trace element), neutralized with L-Arginene (an amino acid), two natural and essential substances for the dog’s body. It’s actually been around since 2003 when it was called Neutersol, but the company and product went away after about three years. According to Ark Sciences, the parent company owning Neutersol created too much inventory which expired before it could be used, and the company had to shut down. In addition, not enough attention was paid to teaching proper administration of the product, which increased the potential for adverse reactions and gave Neutersol a bad name.

Ark Sciences bought the rights to the product in 2007, and renamed it. The company has since conducted clinical trials starting in 1999 on 270 dogs. They have followed 40 of these dogs for over two years, and collected information on many of the study cases for over five years. Since 1999, the company has not received any reports of long-term side effects.

In addition, Ark Sciences has embarked on a veterinary education and training program targeted primarily to shelter medicine practices. Veterinarians or vet techs (under supervision of a licensed veterinarian) must be trained and certified to qualify to perform the procedure. Only those trained by Ark Sciences may administer Zeuterin, and by doing this, errors and adverse reactions are uncommon. That protects your puppy to ensure the best possible outcome.

Esterilsol™ is Ark Sciences’ product for international markets and is registered in four countries, and pending approval in several others around the world. It is approved for all dogs over three months of age in Mexico.

How Does Zeuterin Work?

Zeuterin is injected in the testicles. Ouch! Wait—nope, your pup or older dog isn’t likely to notice at all. There are no pain sensors inside the testes, only pressure sensors. So when properly administered by your trained veterinarian, little to no sensation will be experienced by your sedated dog.
When injected into the testicles, the compound diffuses throughout the testis, and the Zinc acts as a spermicide and destroys all stages of sperm maturation. The tubules that were filled with sperm are emptied, and collapse.

In response, blood flow increases to the testicles to heal, and this causes inflammation resulting in scar tissue (fibrosis) within days. These block the “feeder” conduits permanently, and causes irreversible sterility. The Zinc Gluconate and Arginine are ultimately absorbed and metabolized by the dog’s body.

Sperm stops being manufactured within three days, but sperm may reside in the organ for up to 30 days. Because sperm maturation lasts 60 days, the company recommends keeping your Zinc-neutered adult dog away from a female for at least that period. Over time the interior structures of the testicles including the prostate all atrophy, and shrink in size.

Unlike castration that removes 100 percent of testosterone from the body, “Zeutering” removes only about 50 percent. Leydig cells that are responsible for the endocrine function of the testis are not affected and in test dogs, overall testosterone levels were reduced by 41-52 percent. The testis continues to produce the hormones at a level that recent research shows are protective and beneficial.

Are There Side Effects?

There’s a low incidence of severe side effects in surgical castrations, with discomfort and swelling, licking and occasional infection noted. Similar adverse reactions may occur with Zeuterin, and most do not require medical care.

Minor local reactions include testicular swelling, which is a normal reaction to the inflammation from the injection. Pain may be demonstrated by the dog not wanting to sit, or sitting with hind legs open, or licking/biting the area. More rarely, systemic reactions include vomiting, loss of appetite, lethargy and diarrhea.

Most reactions in the clinical trial group of 270 dogs were seen with the first week after the injection treatment, and more than 93 percent didn’t show any painful signs. When discomfort was noted, it usually happened within the first two days and then went away.

Long-term observations have shown no increase in risk for testicular cancer in dogs neutered with Zeuterin. But to date, no studies have been performed to see if there might be a decreased risk of testicular cancer.

What Else Should I Know About Zeuterin?

If your puppy has undescended testicles, surgical castration is still the best option. Not all dogs are the best candidates and your veterinarian will know if he has a history of allergic reactions to any of the components in the drug, for example.

Zeutering may or may not eliminate the behaviors associated with mating, although anecdotal reports from owners of dogs indicate the effects are similar to those expected from surgical castration. Of course, surgical castration doesn’t guarantee to totally suppress mounting, roaming, marking or aggression, either.

Puppies and dogs sterilized with Zeuterin will still appear to be intact. For dogs and pet parents getting the “hairy eyeball” at dog parks and gatherings, you may want to invest in a bandana or other way to show off your pet’s special Zeutered status.

Because he’ll still look intact, it’s recommended that you document the dog’s sterilized status on his microchip and/or a tattoo (a “Z” near the scrotum) be placed. That way if the worst happens and your dog becomes lost, he won’t be castrated at a later date if found by a rescue organization.
How to Find A Zeutering Option

Ark Sciences continues to conduct training sessions at spay/neuter shelters, animal centers and private practices. Ask your veterinarian about becoming certified. She can contact the folks at to learn more.

It’s important to learn all the facts, and figure out the best options for your individual puppy. Different breeds and lifestyles may impact your decision. So do your research, consult with your veterinarian, and ask questions. Your puppy is counting on you!

What do you think? Go ahead and comment–let ‘er rip! *s*

UPDATE: Ark Sciences discontinued distribution of Zeuterin in 2016. Currently, there are no nonsurgical procedures available that are widely recommended for pets in the United States.

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Pros & Cons of Dog Neutering — 31 Comments

  1. Because we have male/female litter mates, we had both pups operated on at about 6 months. We also live in a rural area where a lot of dog owners don’t contain their dogs. I wanted to reduce the appeal of breaching the fence. I’ve gotten flack from people who think we should have bred both dogs as they are quite beautiful. (not with each other) There are lots of beautiful BCs out there. We don’t need to contribute to the population.

    • Bravo for making the decision right for you and your dogs. *s* Yes, there are lots of gorgeous BCs and honestly, it takes soooo much energy, time and $$ to raise a litter right. Much more fun to spend all that time and attention (and treat money!) on the pair you have!

  2. Thanks for the info. I’ll start reading on it sometime but we have all the rescues now we have room for at the moment. Interesting that some cancers are lessened and some may be worsened depending on which way you go.

    Any surgery always has risks so I wrongly guessed that might be the downside. I haven’t read about this one before, but if it is truly new I would be cautious about a new surgery until, say, 7 years or so — whatever the length of time that Public Citizen tends to recommend on pills as in the first few years of anything the downsides of that come out? (The people who have warned about many drugs years before they were taken off the market are who inspires that thought. I’ve been hearing something recently about one of the non-surgical female human sterilizations too — several years out — having problems.)

    Our vet outlined for me the things he does that made his surgeries cost more than the free spay and neuter and that included the tests for things — defects, diseases — that might kill a pet in surgery.

    We had to have our little rescue girl fixed as had we not there’d have been yowling cats everywhere — inside & out — when she went into heat since some neighborhood cats, though somewhat owned, are not fixed.

    • You’re right to be cautious. This injection has been around for many years and thus far, there haven’t been any more adverse reactions than are found in traditional male dog castration. *shrug*

  3. One of the things that concerns me with this product is the fact that there are unethical individuals that may try to make money (offer their dog for breeding/showing)when the dog is actually sterile. It’s impossible to visually distinguish from an unaltered male.

    • I hadn’t thought of that. But would the dog with only 50% testosterone levels be all that interested? There are always unethical people–and Neuticals could present the same problem, I suppose. *s*

  4. I am a firm believer in spay/neuter. Unless I were to become a licensed breeder I have no business bringing animals into the world where I can’t guarantee that they will be going to a loving home. But we encountered something strange when we got our blonde boy Mac fixed. When we brought him home from the vet he would sit in the hall and growl at anyone who walked past. I had not encountered this issue with the other four kitties we had fixed. I was finally forced to put him into a room by himself for fear that he would scratch or bite our then 15 yr old daughter. It wasn’t until I went to feed him over 12 hours post surgery that he seemed to snap out of it. And I do mean snap, it was a visible shudder, like he was throwing off something unwanted. His eyes went back to normal (they were really dilated) and his body posture changed. He seemed to remember what he had done because he kept rubbing up against me and purring, as if to say he was sorry for the way he acted. I think he had a negative reaction to the anesthesia.

    • I’ve not been able to access my blog all day. Sorry for the delays I’m using my phone. Hopefully will figure out a solution soon.

      Sue that does seem like an anesthesia “something” and glad it went away!

  5. I am a fan of knowledge, and knowing that certain breeds might do better if they delay neutering is good to have, unfortunately the information out there is way too broad based. Some large breed dogs show some benefit to waiting, some males vs females, etc.. but that information isn’t making it along with the delayed neuter recommendations. I am now starting to see that recommendation make it out to cats too, with absolutely NO scientific reasoning behind it other than it helps the hips and knees of some large breed dogs.

    Too many animals lose their homes due to their hormone driven behavior.

  6. That’s so interesting! We were advised to wait until Henry was seven months old before having him neutered (to avoid ‘little dog’ syndrome). He still cops an attitude in certain situations (with certain dogs). Perhaps this would have been a better option for him. Regardless, with so many pets in the shelter system, spay/neuter/adopt will always be our choice. We will research the ‘method’ further if we’re ever in that situation again.

  7. This sounds like a very interesting alternative for dog owners. I think the important thing is that pets get sterilized until the overpopulation problems can be corrected. Personally, I’m not tied to spay/neuter if there is a safe, effective alternative.

    • This is specific to male doggies at the moment, of course. And cats are NOT dogs–so the same issues raised in dogs likely are different in a different species.

  8. I’ve also written about spay/neuter issues, and was surprised to receive quite a bit of flak from it. While there are other options available, a very small (think 1%) of vets actually offer the services in North America. One I learned about was an ovary-sparing spay. Again, not many people know about it, and there are precautions you need to take when your dog goes into heat – not something the average pet parent wants to deal with. A chemical castration, to me, sounds like something that is tangible for the average pet parent, and I’m looking forward to learning more about it.

    • It’s interesting that in other countries, where spay/neuter is NOT the “automatic” procedure for pets as it is here, there don’t seem to be the same “con” issues of having intact animals–at least not to the same degree. Clearly, sterilization has benefits but I don’t think it’s the absolute black-and-white solution we’ve promoted for so long.

  9. To get completely to the bottom line, how could removing functional parts of a body be a good thing? It might be on a global scale, but for the individual, not so much.

  10. This is a very interesting topic. Dr. Karen Becker has written quite a bit on it too, especially in regard to the health benefits of not spaying female dogs.

  11. After finally having a female dog in the home this time around I can say it’s a little bit harder to sympathize with the male dogs in this department. After Laika’s spay I felt terrible for her – nothing went wrong but just seeing her in such discomfort was tough to watch. I’d never heard of Zeuterin before – that’s pretty interesting (and promising) stuff. I know if owners are really upset about a dog losing his stuff they can get Neuticles – testicle implants.

    • Jen, that’s one reason that if I had a non-performance boy dog I’d be inclined to go with an early sterilization. It’s so much less problem when recovering. Same with the girl puppies and especially the older girls. It’s major abdominal surgery, after all!

  12. I’m all for anything that prevents unwanted litters, which translates into too many animals in shelters, which invariably leads to euthanasia of shelter pets. I’ve heard a lot about non surgical sterilization. It might be a great option for those guys who refuse to neuter their dogs. You know, the brainiacs who say things like “I wouldn’t want someone to do that to me, so why should I do that to my dog!?” DUH!! Excellent post!

    • Hi Cathy. Me, too! I want more options, preferably low cost/less invasive. I know they’re working on some things for ferals, and just wish the application was already further along for our pets, too.

  13. I really like this! I think if I had a male dog I would get this done for him. I think making him wear a bandana all the time proclaiming his zeuterness would be a pain after a while though

  14. Pingback: Spay Neuter Pets: Learn About Feline Fix By Five Months & Complete Kitten Care

  15. We had our dog Zeutered several years ago and I felt it was a mistake. He was in a LOT of pain for several days after the procedure. He now has prostate issues which the vet believes he would have been less likely to have if he had been surgically neutered.

    • Hi Nancy, Thanks so much for the comment. I had not heard of that consequence (prostate issues) with Zeutering, which are more typically issues of intact dogs. I wonder if others have also had this issue? So sorry your dog had such pain issues, too.

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