DO NOT NEUTER YOUR SCOTTIE BEFORE 12 MONTHS OF AGE
A veterinary oncologist and founder of the pet hospice program Pawspice in the US, Dr. Villalobos concedes, "It is earth shattering to consider that some of the cancers we have been battling may have been enhanced by early neutering instead of the reverse."
It's unfortunately true that a growing body of research is pointing to early sterilization as the common denominator for development of several debilitating and life-threatening canine diseases.
On one hand, we certainly want to know what's causing our precious canine companions to develop disease. On the other hand, it's troubling to learn a procedure we've historically viewed as life-saving and of value to the pet community as a whole, has likely played a role in harming the health of some of the very animals we set out to protect.
Hormones are really important to bone strength and development. Hormones are chemicals made by glands that travel throughout the body and have many effects on growth, maturation, energy, weight, and bone strength. Sex hormones (estrogen made in the ovary of females and testosterone made by the testes in males) control ability to reproduce. They also are a major reason that bone strength increases in the early teenage years. When teenagers have low estrogen or testosterone levels, the bone becomes weaker.
Abnormal Bone Growth and Development
Studies done in the 1990's concluded dogs spayed or neutered under one year of age grew significantly taller than non-sterilized dogs or those not spayed/neutered until after puberty. And the earlier the spay/neuter procedure, the taller the dog.
Research published in 2000 explains why dogs sterilized before puberty are inclined to grow abnormally:
At puberty, estrogen promotes skeletal maturation and the gradual, progressive closure of the epiphyseal growth plate.
It appears neutering (removing estrogen-producing organs, female and male), can cause growth plates to remain open. These animals continue to grow and wind up with abnormal growth patterns and bone structure. This results in irregular body proportions.
"For example, if the femur has achieved its genetically determined normal length at 8 months when a dog gets spayed or neutered, but the tibia, which normally stops growing at 12 to 14 months of age continues to grow, then an abnormal angle may develop at the stifle. In addition, with the extra growth, the lower leg below the stifle likely becomes heavier (because it is longer), and may cause increased stresses on the cranial cruciate ligament."
Higher Rate of ACL Ruptures
A study conducted at Texas Tech University Health Sciences Center on canine anterior cruciate ligament (ACL) injuries concluded that spayed and neutered dogs had a significantly higher incidence of ACL rupture than their intact counterparts. And while large breed dogs had more ACL injuries, sterilized dogs of all breeds and sizes had increased rupture rates.
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.
For the most common type of cardiac tumor, hemangiosarcoma (HAS), spayed females had a greater than five times risk vs. their intact counterparts. Neutered male dogs had a slightly higher risk than intact males.
The study concluded that, "… neutering appeared to increase the risk of cardiac tumor in both sexes. Intact females were least likely to develop a cardiac tumor, whereas spayed females were most likely to develop a tumor.
In another published study in 2002, it was established the risk for bone sarcoma was significantly influenced by the age at which the dogs were sterilized.
For both male and female spayed or neutered before one year of age, there was a one in four lifetime risk for bone cancer, and the sterilized animals were significantly more likely to develop the disease than intact dogs of the same breed.
In another study using the Veterinary Medical Database for the period 1980 through 1994, it was concluded the risk for bone cancer in large breed, purebred dogs increased twofold for those dogs that were also sterilized.
It's commonly believed that neutering a male dog will prevent prostatic carcinoma (PC) – cancer of the prostate gland.
But worthy of note is that according to one study conducted at the College of Veterinary Medicine at Michigan State University, "…castration at any age showed no sparing effect on the risk of development of PC in the dog."
This was a small study of just 43 animals, however. And researchers conceded the development of prostate cancer in dogs may not be exclusively related to the hormones produced by the testicles. Preliminary work indicates non-testicular androgens exert a significant influence on the canine prostate.
In a retrospective cohort study conducted at Cornell University's College of Veterinary Medicine, and published in the Journal of the American Veterinary Medical Association, results showed that both male and female dogs sterilized at an early age were more prone to hip dysplasia.
Other Early-Age Spay/Neuter 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 sterilized at less than 24 weeks of age.
The AKC's Canine Health Foundation issued a report pointing to a higher incidence of adverse reactions to vaccines in sterilized dogs.
Among the reports and studies pointing to health concerns associated with early spaying and neutering, you can also find mention of increased incidence of behavioral problems including:
Undesirable sexual behaviors
Risks versus Benefits of Early Sterilization
Every important decision in life comes with pros and cons.
As responsible animal guardians, we owe it to our pets to make the best health choices we can for them.
As responsible members of society, we owe it to our communities to proactively protect our intact pets from unplanned breeding at all costs.
Clearly, there are health benefits to be derived from waiting until after puberty to spay or neuter your dog.
There are also risks associated with owning an intact, maturing pet.
How seriously you take your responsibility as a pet owner is the biggest determining factor in how risky it is to leave your dog intact until he or she matures. If you are responsible enough to absolutely guarantee your unsterilized pet will not have the opportunity to mate, I would encourage you to wait until your pet is past puberty to spay or neuter.
If you are unable to absolutely guarantee you can prevent your dog from mating and adding to the shameful, tragic problem of pet overpopulation, then I strongly encourage you to get your animal sterilized as soon as it's safe to do so.
Your Scottie should be old enough to be a balanced individual both physically and mentally. This balance isn't achieved until they have reached at least 10 to 12 months of age.