Since the mid-20th century, pet overpopulation concerns have given rise to a message prevalent in public service announcements, veterinary education and rescue/shelter philosophies. That message is “Spay and neuter, the earlier the better.” However, in recent years, a controversy surrounding health risks of spaying and neutering at an early age has been increasing. New studies show uneven bone growth (certain bones growing longer than their counterparts), infectious diseases, adverse reaction to vaccines, cancer, and other problems being documented at statistically significant rates, even when adjusting for genetic, lifestyle and other factors.
Like most body systems, the endocrine system – which produces hormones – affects more than just the reproductive system. Sex hormones, by communicating with a number of other growth-related hormones, stimulate the closure of growth plates at puberty. And they do a lot more, too.
EARLIER, MORE FREQUENT CANCER IN EARLY SPAY/NEUTER DOGS
A Veterinary Medical Database search of the years 1982 to 1995 revealed that in dogs with tumors of the heart, the relative risk for spayed females was over four times that of intact females.
In addition to cardiac tumors, this and other studies have found that early spay/neuter practices contribute to a higher incidence of bone cancer, prostate cancer, and other types of cancer.
KNEE AND HIP PROBLEMS IN EARLY SPAY/NEUTER DOGS
A study of 1444 Golden Retrievers performed in 1998 and 1999 found that animals spayed and neutered at less then a year of age were significantly taller than those spayed or neutered at more then a year. Because of the absence of sex hormones that signal a slowdown in growth rates after puberty, early spayed/neutered dogs have longer limbs, lighter bone structure, narrower chests and narrower skulls.
A study by Dr. Kathy Linn and Dr. Felix Duerr showed that females spayed prior to seven month of age have a significantly greater tibial plateau angle. This is because the tibial growth plate stays open longer then it is supposed to and the tibia continues to grow longer relative to the femur in “fixed” animals as opposed to those animals who are intact. It is widely known and accepted that animals with a greater tibial plateau angle are at a much higher risk for ACL rupture.
Rob Foley, of South Bellmore Veterinary Group, examined ten years of patient data from his practice. “A summary of the data shows that while 2.1% of our spayed and neutered patients had to undergo knee surgery for an ACL rupture, only 0.3% of the intact animals had to have the surgery,” he says. This represents a seven fold increase for animals that have been spayed and neutered before the age of 6 months.
Other orthopedic abnormalities like osteoarthritis and hip dysplasia have also been correlated with early spay and neuter. In addition, spayed and neutered animals tend to gain weight, are more likely to develop obesity, and have decreased lean muscle mass. Obesity itself is a major risk factor for orthopedic abnormalities and injury.
WHY DO WE SPAY/NEUTER SO EARLY?
More and more veterinarians are recommending waiting until 18-24 months before spaying, or until the dog reaches full maturity (which can vary from breed to breed and individual to individual).
For most of us, spaying and neutering early is just something everyone knows. We hear it so often, from so many sources, that it becomes tradition to spay/neuter early. But few of us examine the reasons or evidence given. It is commonly believed that neutering male dogs early can prevent prostate cancer. But a recent study conducted by the University of Michigan found that it has no affect on the rate of prostate cancer incidence. It is also believed, but not proven, that “fixing” a dog will solve behavioral problems. However, new research shows that this is unproven.
Many of the early spay/neuter messages aimed at the public come from activist groups. However, remember that their objective is ONLY to prevent litters while there are dogs needing homes. The thinking is that the only way to be sure to prevent a dog from reproducing is to spay/neuter before it can. This message serves their agenda, but I don’t see any discussion on their blogs, message boards or public service campaigns about the health hazards of pediatric spaying and neutering.
Many spay/rescue organizations spay and neuter as early as six weeks. However, they may be hampered by state laws that require shelter dogs to be spayed or neutered prior to being adopted. When someone adopts a puppy from a shelter, it’s not realistic to leave the pup at the shelter until it’s finished growing. One shelter solves the early spay/neuter problem with a higher adoption fee for intact puppies, a contractual obligation to spay/neuter and a portion of the adoption fee refunded with proof of spay/neuter when the puppy is older. And they do follow up.
Why do so many vets recommend early spay/neuter? Partly because of social messaging from spay/neuter activists, and partly because of two studies done in the ’60s and ’70s that concluded that spay/neuter solves behavioral problems. Those studies gained momentum and have been quoted so often that they’ve become part of the zeitgeist without anyone ever actually examining the data. The studies were not scientifically rigorous, because there were no control groups (groups of dogs that were intact to compare to the groups of dogs who were spayed/neutered). And the behavioral findings were not evaluated by canine behaviorists.
SHOULD I WAIT?
The recent research suggests it’s best and healthiest for your dog to wait until he or she achieves maturity before you spay or neuter. Does this mean you should? It depends on how much you’re willing to take on in order to give your dog the implied health benefits of waiting. You can’t leave your dog in the back yard while no one is home. You can’t let your male dog off leash unless you’re in an enclosed area (or get distracted by conversation when you are). You have to be ready to intervene if he begins to exhibit sexual behavior with a female.
I’ve seen intact males at our dog park plenty of times, and they’ve all been relaxed, playful, well-mannered dogs. This attests to their training and supervision. It can be done, until it’s time to neuter.
For a female dog, waiting means providing the extra care needed if she goes through her first heat cycle before you spay. She’ll go into her first heat cycle at 6-12 months old (although if she’s not around intact males, she may not go into heat for two years or more). Once she’s had her first heat cycle, she’ll go into heat about every six months. Outdoor pens and back-yard fences don’t keep male dogs out when a female is in heat, so you’ll have to keep her primarily indoors, except for walks. Here’s a good article on how to care for a dog in heat.
Waiting is extra work, there’s no doubt. But it is possible. You have already taken on the responsibility for the health and safety of your dog. You already buy food, take your dog to the vet, provide fresh water, exercise him or her … these are thing you go out of your way to do for the health of your dog. If you’re not breeding your dog to keep exceptional genes and traits in the gene pool to improve the breed, it is best to spay. But choose for yourself the best age and time to do it. Remember, your dog relies on you — no one else — to make decisions that are best for him or her.
Thanks to AngryVet.com, CanineSports.com, HealthyPets.com, National Institutes of Health, Laura J. Sanborn