SPAYING AND NEUTERING
Spay/Neuter Decisions Should Be Based on Your Pet?s Health and Quality of Life
If your dog is not yet spayed or neutered, here are some general recommendations for timing of the procedure:
- Your dog should be old enough to be a balanced individual both physically and mentally. For the majority of dogs, this balance isn't achieved until a dog has reached at least one year of age. Although some breeds reach maturity faster than others, many giant breed dogs are still developing at two years of age.
- Other considerations include your dog's diet, level of exercise, behavioral habits, previous physical or emotional trauma, existing health concerns, and overall lifestyle. If your pet is emotionally balanced (has no behavior problems) consider investigating a vasectomy or tubal ligation instead.
- I encourage you to learn all you can about surgical sterilization options and the risks and benefits associated with each procedure.
Don?t Neuter Your Dog YET ? Read This Life-Saving Information First!
Dr. Becker's Comments:
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.
The same amount of evidence has not been compiled for early spay/neuter of cats, but it's not clear how well the subject is being studied for kitties. Funding for research into feline health issues falls well below dollars allocated for their canine counterparts.
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. Twelve breeds had greater than average risk of developing a cardiac tumor, whereas 17 had lower risk."
In a study of Rottweilers published 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 Rotties 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.
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 in the Journal of Pediatric Endocrinology and Metabolism may explain 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, 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.
It appears the removal of estrogen-producing organs in immature dogs, 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.
According to Chris Zink, DVM:
"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.
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:
- Noise phobias
- Fearful behavior
- Undesirable sexual behaviors
For Responsible Pet Owners, Decisions About When to Spay or Neuter Should be Part of a Holistic Approach to Your Pet's Health and Quality of Life
If you own an intact pet, I can offer a general guideline for timing a spay/neuter procedure.
Your dog should be old enough to be a balanced individual both physically and mentally. This balance isn't achieved until a dog has reached at least one year of age. Although some breeds reach maturity faster than others, many giant breed dogs are still developing at two years of age.
Other considerations include your dog's diet, level of exercise, behavioral habits, previous physical or emotional trauma, existing health concerns, and overall lifestyle.
If you own an intact animal and need to make a spay/neuter decision, I encourage you to first learn all you can about surgical sterilization options and the risks and benefits associated with the procedures.
Talk with reputable breeders and other experienced dog owners, and consult a holistic vet to understand what steps you can take to ensure the overall health and longevity of your pet.
Study Looked at the Impact of Spay/Neuter on One Breed, Both Genders, and Five Different Diseases
The UC Davis study looked at the health records of 759 Golden Retrievers. Goldens were chosen because they are one of the most popular breeds in the U.S. and Europe, are often used as service dogs, and are also susceptible to various cancers and joint disorders.
The intent of the study was to investigate the effects of neutering on the risks of several diseases in a single breed of dog, distinguishing between males and females, and between dogs that had been neutered or spayed early (before one year), late (after one year), or not at all.
The dogs ranged in age from 1 to 8 years and had been seen at UC Davis? William R. Pritchard Veterinary Medical Teaching Hospital for one or more of the following problems: hip dysplasia (HD), cranial cruciate ligament (CCL) tear, lymphosarcoma (LSA), hemangiosarcoma (HSA), and mast cell tumor (MCT).
The researchers focused on joint disorders and cancers because neutering or spaying removes the testes or ovaries and disrupts production of hormones that play important roles in body processes like bone growth plate closure.
Findings Reveal Significantly Higher Disease Rates in Spayed/Neutered Dogs
The study revealed that for all five diseases, the rates were significantly higher in both males and females that were neutered or spayed (before or after one year of age) compared with intact dogs.
Of special concern is that results showed a 100 percent increase in the rate of hip dysplasia in male Goldens neutered before 12 months of age. Ten percent were diagnosed with the condition, which was double the rate of occurrence in intact males. Past studies have reported a 17 percent increase among all neutered dogs compared to all intact dogs.
- There were no cases of CCL tears in intact male or female Goldens. In early neutered males there was a 5 percent occurrence, and in early spayed females, an 8 percent occurrence.
- Almost 10 percent of early-neutered males were diagnosed with lymphosarcoma, which was 3 times more than intact males.
- Hemangiosarcoma in late-spayed females was 8 percent -- 4 times more than intact and early-spayed females.
- No intact females had mast cell tumors, but 6 percent of late-spayed females did.
The UC Davis findings are in line with the results of earlier studies, however, it's the first study to identify a connection between late spaying and mast cell tumors and hemangiosarcoma in female dogs.
What These Results Mean for Dog Owners
The study authors consider their findings clinically relevant as follows:
"Specifically for Golden Retrievers, neutering males well beyond puberty should avoid the problems of increased rates of occurrence of HD, CCL, and LSA and should not bring on any major increase in the rates of HSA and MCT (at least before nine years of age). However, the possibility that age-related cognitive decline could be accelerated by neutering should be noted2.
For females, the timing of neutering is more problematical because early neutering significantly increases the incidence rate of CCL from near zero to almost 8 percent, and late neutering increases the rates of HSA to 4 times that of the 1.6 percent rate for intact females and to 5.7 percent for MCT, which was not diagnosed in intact females."
According to lead study investigator Benjamin Hart, professor emeritus at the UC Davis School of Veterinary Medicine, The study results indicate that dog owners and service-dog trainers should carefully consider when to have their male or female dogs neutered.
Hart goes on to say it's important to keep in mind that different breeds have different vulnerabilities to various diseases, and the effects of spay/neuter and when it is done very likely vary from breed to breed. The Golden Retriever findings can?t be generalized to other breeds, or dogs in general. However, in other breeds with a propensity for joint disorders and types of cancer different than those prevalent in Goldens, spaying and neutering may increase the risk for those breed-specific disease tendencies.
More breed-specific studies are needed for a full understanding of the disease conditions affected by spaying and neutering.