What was once a very stock recommendation to all my puppy and kitty owners has evolved as new research findings have emerged of late.
And, in fairness, as I’ve dug more into the seriousness of the outcome of neutering, I had to leave the comfort of “one size fits all.”
Damn inconvenient, grumble mumble… why can’t biology be more like auto mechanics?
My newer recommendation goes something like this now:
If you can prevent unplanned pregnancies, (and if you have a female and don’t mind living through heat cycles) you may want to keep your animal intact and not neuter.

Emphasis on “if” on the pregnancy question — I’m not wanting unplanned pups or kitties any more than those on the front lines in shelters and rescue groups who see way too many of them.
Oops is not an option.
It’s interesting to note, however, “Everybody Must Get Neutered!” is a uniquely American notion. Probably born in the last 20 years, would be my guess.
Europeans don’t buy this idea.
A Swedish study of 461 dogs revealed 99% were intact, not neutered.
A Hungarian study showed 57% intact dogs, and a British survey found 46% intact dogs.
Hmmm. Do they know something we don’t?
What Happens When We Neuter?
I like to call it “instant menopause.” You know how rough life can be in peri-menopausal or menopausal times, either from your own experience or from your mom’s or wife’s?
Imagine that all being condensed into the flip of a switch.
I know in my mom’s life, a hysterectomy was the beginning of a very significant downward spiral in her health when she was in her 50s.
Sex hormone production is mostly in the testes or ovaries, though a smaller amount is produced elsewhere, for example in the adrenal glands.
When spaying or castration (collectively called neutering) takes place, we shut off the major source of the sex hormones testosterone, estrogen, and progesterone.
While neutering prevents pregnancy, you have to evaluate the risks against the benefits to decide where the balance point is for you and your animals.
Clear Benefits
The good that comes from neutering is:
- Birth control
- Cessation of heat or estrus cycles
- Absence of behavior that goes with the sexually intact animal
Birth control is the main reason neutering is pushed. Once the male loses his testicles to the surgeon’s knife or the female her ovaries and uterus, neither can create offspring from that point forward.
Estrus cycles are those periods of time when the female is in heat, surging with sex hormones, and both attractive to and receptive to the male.
Heats come typically every six months in dogs, seasonally in cats (usually spring and fall), throughout the year in cattle, and seasonally in early spring in the horse.
This all goes away when a female is spayed.
Behavior accompanying heat cycles can be both annoying and downright dangerous. Annoying is the female cat who comes mmrOOWWWwwwing at all hours, keeping you up at night with her chorus of lust.
Worse yet is the tom cat’s constant urge to leave his scent everywhere with a spritz of urine on doorways, furniture, or your shoes! Intact female cats will also “soil” your house with urine while going through their heats.
I was recently visiting my network chiropractor’s farm while her intact Dachsund was just going out of heat and her intact male Airedale was beside himself with desire, but locked up behind impenetrable fencing.
Poor Lionheart! He didn’t even recognize me when I came up to rub him and say hello. It was like I wasn’t there, and I was told he’d missed eating for several days, he was so taken with the lusty hormones he was smelling from Frieda!
The dangerous side of behavior in this instance comes from running out into traffic in “hot pursuit” of a female or, like Lionheart, running through a barbed wire fence, lacerating his penis, and bleeding for days!
Ouch.
There’s data out there on animals hit by cars: far more are intact than neutered.
And yep, it’s usually the guys.
Another danger is male aggression, though this is largely a cat issue, and in my experience much less likely in intact male dogs.
Tom cats are prone to getting into serious fights when they are intact, and this can make for wounds, abscesses, and disease transmission, if they are wounded by a cat carrying FeLV, for example.
All of this behavior, the heat cycles, and the possibility of pregnancy are gone once you neuter. (I cannot personally imagine living with unneutered cats, unless you relish the scent of cat urine!)
Downsides and Risks
What’s become of greater interest to me of late are several studies showing the ill effects of surgical gonadectomy, or instant hormone-pause.
A study done in UC Davis and published in February 2013 revealed some startling health consequences of neutered animals, both male and female.
The research tracked 759 Golden Retrievers, and looked at early neuter (less than one year of age) vs later neuter (12 months or older) vs intact dogs and five common diseases:
- Hip dysplasia (HD), the arthritis of the hip joint common to dogs
- Cranial cruciate ligament (CCL) damage, the “football injury” of dogs’ knees
- Hemangiosarcoma (HSA), a type of cancer that can be fatal
- Lymphosarcoma (LSA), immune system cancer, usually fatal
- Mast cell tumors (MCT), yet another cancer that can kill dogs
To summarize the researchers’ findings:
- Neutered animals fared significantly worse in all five diseases.
- Early neuter of males doubled the rate of hip dysplasia compared to intact males.
- None of the intact animals had cruciate ligament disease. Zero. It only appeared in the neutered animals.
- Early neutered males had three times more LSA than the intact males, while late neutered males had no LSA.
- The percentage of HSA was four times higher in late neutered females than in either intact or early neutered females.
- MCT was absent in intact females but present in neutered females. In males, neutering status made no difference.
So, in dogs of both sexes, neutering had significant ill effects in this large study, though it wasn’t uniform across the board.
The clearest loser: early neutering, which has always made holistic veterinarians cringe.
But, in fairness to how facts aren’t always clear cut (damn them!), you noticed how early neutered female Goldens had less HSA?
Still not a good reason for early neutering, as you’ll see below.
Here’s an earlier study (2004)1 on cranial cruciate ligament injury that also showed an increased prevalence in the neutered dogs, male or female.



