If you’re thinking about adding a puppy to the family, in addition to deciding what type of dog is right for you, you’ll also be making lots of lifestyle choices for the long-term health and happiness of your new best furry friend. Many of the decisions you make over the next few months will affect your dog for a lifetime: the diet you choose, the vaccine protocol, socialization and training, and decisions about when to sterilize.
Sterilization is what I want to discuss today. Most people in the US are familiar with just one type of sterilization for dogs: spaying or neutering. But these are actually desexing procedures that go well beyond simply sterilizing a dog so that he or she can no longer reproduce.
Desexing removes hormone-producing organs (the ovaries or testicles) that researchers are now finding are actually quite important to overall health. Studies also indicate that the earlier a puppy is spayed or neutered, the greater the likelihood of health problems later in life. Here are examples of studies evidencing some of these potential issues.
Abnormal Bone Growth
Back in the 1990s, studies showed that dogs spayed or neutered before one year of age grew significantly taller than dogs not spayed/neutered until after puberty. And the earlier the spay/neuter procedure, the taller the dog.
A study published in 2000 in the Journal of Pediatric Endocrinology and Metabolism explains:
At puberty, estrogen promotes skeletal maturation and the gradual, progressive closure of the epiphyseal growth plate, possibly as a consequence of both estrogen-induced vascular and osteoblastic invasion and the termination of chondrogenesis.
In addition, during puberty and into the third decade, estrogen has an anabolic effect on the osteoblast and an apoptotic effect on the osteoclast, increasing bone mineral acquisition in axial and appendicular bone.
Translation: The hormone estrogen, which is no longer produced in spayed or neutered dogs, plays a crucial role in bone growth and development. The removal of estrogen-producing organs in immature dogs can cause growth plates to remain open. The dogs continue to grow and wind up with abnormal growth patterns and bone structure, which can result in irregular body proportions.
In a retrospective cohort study conducted at Cornell University’s College of Veterinary Medicine, and published over 10 years ago in the Journal of the American Veterinary Medical Association, results showed that both male and female dogs desexed at an early age were more prone to hip dysplasia.
Cranial Cruciate Ligament (CCL) Injuries
While it’s not clear at what age the dogs were desexed, a study conducted at Texas Tech University Health Sciences Center on canine cranial cruciate ligament (CCL) injuries concluded that spayed and neutered dogs had a significantly higher incidence of CCL rupture than their intact counterparts. And while large breed dogs had more CCL injuries, sterilized dogs of all breeds and sizes had increased rupture rates.
In a study of Rottweilers published in 2002, it was established that the risk for bone sarcoma was significantly influenced by the age at which the dogs were desexed. For both male and female Rotties spayed or neutered before one year of age, there was a one-in-four lifetime risk of bone cancer, and the desexed animals were significantly more likely to develop the disease than intact dogs of the same breed.
A 1998 study published in the Veterinary Journal using data from the Veterinary Medical Database for the period 1980 through 1994 concluded that the risk for bone cancer in large breed, purebred dogs increased twofold for spayed or neutered dogs.
Other Health Concerns
Early gonad removal is commonly associated with urinary incontinence in female dogs and has been linked to increased incidence of urethral sphincter incontinence in males. Spayed and neutered Golden Retrievers are more likely to develop hypothyroidism. A cohort study of shelter dogs conducted by the College of Veterinary Medicine at Texas A&M University concluded that infectious diseases were more common in dogs that were desexed at less than 24 weeks of age.
Among the reports and studies pointing to health concerns associated with early spaying and neutering, you can also find mention of increased incidence of:
- Adverse reactions to vaccines
- Noise phobias
- Fearful behavior
- Undesirable sexual behaviors
Spay And Canine Breast Cancer: Theory, Not Fact
Results of a UK study published in 2012 in the Journal of Small Animal Practice were unable to validate the theory – a theory that is widely assumed to be a fact – that early spaying protects female dogs from mammary neoplasia. The objective of the study was to evaluate the evidence that spaying, or the age at which a dog is spayed, has an effect on the risk of mammary tumors. The Royal Veterinary College researchers concluded:
Due to the limited evidence available and the risk of bias in the published results, the evidence that neutering reduces the risk of mammary neoplasia, and the evidence that age at neutering has an effect, are judged to be weak and are not a sound basis for firm recommendations.
Translation: The idea that spaying, and early spaying of a female dog before her first estrus cycle, removes or reduces her risk of breast cancer is at the present time a theory rather than a fact.
Sterilization and My Patients
Over the years, I’ve changed my view on spaying and neutering dogs, based on emerging research, and also on the health challenges faced by so many of my canine patients after I spayed or neutered them. These were primarily irreversible metabolic diseases that appeared within a few years of a dog’s surgery.
My current approach is far removed from the view I held in my early days as a vet, when I felt it was my duty and obligation to spay and neuter every dog at a young age. These days I work with each pet owner to make decisions that will provide the most health benefits for the dog.