Ten million dogs and cats end up in shelters in the U.S. annually. Three to four million, mostly healthy, are euthanized. Where do these “unwanted” animals come from? The majority are from unplanned litters that occur because owners didn’t get around to having their pet neutered, or didn’t adequately understand or take responsibility for the animal’s reproductive cycle and preventing pregnancy. This has been a driving force behind the push in our country to promote neutering of all dogs and cats early enough to preclude breeding. When I was a veterinary student, long, long ago, we were taught to advise spaying females before their first estrus cycle and neutering males before full puberty. This usually meant surgery at six to nine months old.
Veterinarians, like shelter and animal welfare workers, have firsthand experience with pet overpopulation. My defining moment occurred three years out of vet school, while doing “relief” work filling in for a veterinarian in rural New Hampshire whose practice was also the local “pound.” When I arrived on the job, there was a young Golden Retriever that had been abandoned there with her eight puppies. The technician informed me they had 48 hours left, after which I was expected to euthanize them all. I spent the next two days frantically seeking alternative placements, agonizing about what I was being asked to do. When the deadline arrived, I simply told the tech I wouldn’t do it. Next morning, dog and pups were gone. The support staff had “taken care of them.”
It’s no wonder most American veterinarians are adamant about neutering. Besides providing population control, the conventional wisdom has been that neutering has health benefits, reducing risk of mammary, prostate, and testicular cancer, life-threatening uterine infections, and male behavioral issues such as urine marking and aggression. In the past few decades, veterinarians began neutering pets even earlier, at four to six months. It’s easier and faster, for both patient and surgeon. Reproductive organs are smaller, less vascular. Animals bounce back faster. Then animal shelters upped the ante even more, many neutering all their wards at eight weeks old, prior to adoption. Pediatric neutering insures newly adopted pets will not inadvertently reproduce, especially since statistics show even folks who prepay for neutering when adopting a young intact pet frequently don’t follow through with getting it done.
Then in 2013–14 came several studies from University of California, Davis, School of Veterinary Medicine looking at incidence of certain joint diseases and cancers in golden and Labrador retrievers in neutered versus unneutered individuals. The results were very confusing, but clearly showed neutering can have some negative health effects, depending on breed, gender, and age at surgery. For example, intact males and females of both breeds had a 5 percent rate of certain joint disorders. In neutered Labradors, that doubled to 10 percent. In neutered goldens, even higher. What about cancer? Incidence in intact dogs of both breeds ranged from 3 to 5 percent, except male goldens, who showed a whopping 11 percent rate. Neutering did not appear to affect this significantly in males of either breed. Neutering female Labradors increased cancer incidence only slightly, but in female goldens, neutering any time before 8 years of age increased cancer risk three- to fourfold! OMG!
But wait … With further studies it soon became clear … no … wait … well, nothing became completely clear. Factors impacting effects of neutering include breed, gender, familial genetics, age at surgery, and lifestyle, i.e., owner responsibility. Think neutered pets are fatter? Think again. Recent studies show this may be true postsurgery, but after two years it evens out, and being neutered does not increase obesity. Longevity? A study looking at 70,000 dogs representing 1,985 breeds concluded neutering increases life expectancy — 14 percent for males, 26 percent for females. Another study confirmed increased life expectancy of 18 percent for neutered males and 23 percent for females. In cats it’s even more staggering — 62 percent longer for neutered males, 39 percent for spayed females! Some (though not all) neutered animals may have increased risk of cancer, but most appear significantly less likely to die from trauma, or from infectious, vascular, and degenerative diseases.
In Europe, neutering pets is the exception rather than the rule. I asked Dr. Eva Skibild, a veterinarian from Denmark who has practiced veterinary medicine both in the U.S. and abroad, about her experiences. “I think it’s now clear that the benefits of delaying the procedures outweigh the benefits of doing it early. Especially in the males and the large-breed dogs. My only concern are the small-breed dogs,” she wrote. “I worked in England and Denmark before coming here, and I definitely saw a lot of mammary tumors in the small breeds. Every surgery day I would remove mammary masses, often full mastectomies. It was such a difference when I started working in the U.S., where I hardly ever have to remove mammary tumors … I would definitely not recommend a small-breed female to go through more than one heat cycle.
“During my years working in Great Britain and Denmark, I saw almost no incontinent females and far less ruptured ACLs. The hair coat is also often better on the intact dogs. IIn general, I think I saw less cases of other types of cancers, but there’s so many other factors involved in cancer risks that it’s hard to tell. The studies, however, suggest a relationship.
“I still recommend early neutering if there’s a population control issue. They don’t have that problem in Northern Europe, In Denmark the yards are fenced in, and it’s very rare to see a dog roaming. I recommend early castration if there’s any signs of aggression, but it’s questionable if that even has an impact.”
In conclusion, there is no simple conclusion. I am still in favor of neutering. With cats, it’s a no-brainer. Neuter all cats at 4 to 6 months old. Period. For dogs, discuss your particular animal and situation with your veterinarian. Little dogs are probably better off neutering early. Large- and giant-breed dogs may benefit from waiting to reach full size, especially if you want a dog with classic breed conformation and appearance. This can take as long as two years. But if you wait, you must confine and control your pup, and understand the reproductive cycle. This is much harder than you might think. Personally, I opted to spay our medium-size mutt at 8 months old, knowing my family would not easily cope with her going through even one heat cycle … and I’m a veterinarian! So let’s keep learning as new information comes in, continuing to work for population control, and doing what’s right for each individual dog and family.