The following four articles are being presented to you in an effort to be proactive in the management of your new puppy. It is my overall opinion that Golden Retrievers regardless of sex should not be altered prior to maturity and that it is time to look to changes in management of our pets in many aspects of care; Including altering, vaccinating, feeding, weight and exerecise management.That all dogs are allowed to obtain full growth, prior to sterilization, using simple specific factors to determine full growth see gender recommendations below. It is additionally my recommendation that your dog be kept lean during all stages of life, paying particular attention to the juvenile period of the first 6 months. And finely that you be proactive in the vaccination of your dog and vaccinate appropriately for your geographic area, your individual life style and your dogs individual case.
Update: November 28th 2007
The above said, and that I do believe it's time to look to making changes in how we manage our pets and that I do support and suggest dogs do not be altered until maturity -- I do as well feel the responsibility to post an article which is a rebuttal to the philosophy I subscribe to and directed to Dr. Zink's article that encompasses in my opinion very valid reasons *not to alter young*. See Article 5.
Gender Recommendations - Age to Alter
- Females: After the completion of one full estrus cycle and verification by x-ray that growth plates are closed.
- Males: After 18 months of age and verification by x-ray that growth plates are closed.
Article 1:
Faera Rhonda Hovan
Hovan Slow Grow Plan 2005
The goal of this Plan is to produce a slow rate of growth for puppies between the ages of birth and 4 months. The purpose of the slowed growth rate is to permit the healthiest possible development of bones and joints. Rapid growth and overweight has been linked to a greater incidence and severity of orthopedic disease such as hip and elbow dysplasia (Kealy et al, 2000), and panosteitis. Faster growing pups are also more likely to sustain soft tissue injuries during play or exercise. Additionally, there is compelling evidence that heavier pups may be at increased risk for developing cancer later in life, and may have a significantly decreased life span as compared to trim puppies (Kealy et al, 2002).
A slowed rate of growth will cause pups to be shorter and less physically developed than faster growing pups of the same age. However, adult height and body development will not be permanently altered, and these pups will eventually reach their full genetic potentials. They do this by growing more slowly, but for a longer period of time, than faster growing pups. That is, their growth curves will be more gradual and even, avoiding the steep, unnatural acceleration that is produced by overfeeding.
The rate of growth can be influenced by the type and amount of food that the puppy eats. Culturally, most of us have been conditioned to believe that nutrient and calorie dense “Puppy” foods are beneficial to a pup. But in fact these can be harmful, for they are often in opposition to how Nature intended young canines to eat and grow. Thousands of years of evolution have designed dogs with an optimal growth rate that is slow and steady, and an ideal body composition that is lean and muscular. (Wild fox kits and wolf pups are not roly-poly sedentary youngsters!) The common misconception that a plump pup is healthy and robust turns Nature upside down!
Show prospect pups are particularly at risk for over-nutrition, because their owners are often in a hurry for them to develop the bone, head, coat, and stature of mature, competitive dogs. And it is true that overfed pups will be ahead of their properly trim counterparts in those attributes – temporarily. While these differences completely disappear with maturity, the potential damage to the health of rapidly growing puppies will remain. (And those who believe that plump, fast maturing puppies are more competitive in Puppy Class, might want to examine the success of Faera puppies raised on this Slow Grow Plan – which includes numerous major wins and CH’s finished from Puppy Class, including from 6-9 month Class.)
In order to effectively maintain a normal and healthy growth rate, the pup must be quite thin and fit. Since most people are accustomed to seeing pups that are soft and growing too rapidly, these trim pups may appear extreme to many people, including many veterinarians. And in fact, the perception of “thin” varies from one person to another. Therefore, this Plan includes specific weight and exercise guidelines which have proven successful through many generations of Golden Retrievers. While following these guidelines will not completely eliminate all chance of developing disease, it will allow a pup to become the healthiest adult that his genetic potential permits.
It is important to follow these guidelines closely, because any excess food is first used for growth. That is, even if he is getting too much food, the pup will not get fat -- he will simply grow faster. By the time a pup actually looks or feels fat, he is already at an extreme, and growing far too rapidly. A weekly weigh-in will help ensure that minor deviations from the charts are corrected promptly. To increase Buyer compliance, Breeders may wish to require monthly weights to be recorded on the veterinarian’s chart as a condition of a sales contract or guarantee.
2
Target Weights: Birth to 10 weeks
Age Weight Age Weight Birth Approx. 1 lb. 5 wks. 6 lbs.
1 wk. 2 lbs. 6 wks. 7 lbs.
2 wks. 3 lbs. 7 wks. 8 lbs.
3 wks. 4 lbs. 8 wks. 9.5 lbs.
4 wks. 5 lbs. 10 wks. 12 lbs.
Monitor weights regularly from birth to 5 weeks, rotating pups as necessary to approximate a gain of 1 lb. per week. Do not be alarmed if the gain is slightly less, particularly in large litters. Try to maintain equal size between all pups, within about 4 ounces. (This is extremely important to accuracy when making comparisons between pups within a litter for the purposes of selecting show prospects.) If gain begins to exceed 1 lb. per week, take mother away for several hours periodically; after 2 weeks old, she can even be away overnight if necessary.
Wean at approximately 5 weeks, directly onto a good quality adult food (i.e., Iams Mini Chunks or comparable) or a puppy food formulated specifically for large breeds (i.e., Eukanuba Large Breed Puppy Food or comparable). Do not choose a high performance grade. Feed two to three times per day, either dry or adding nothing but water. The amount will vary with activity level, so it is impossible to recommend a precise amount; although it will probably be approximately 1/2 cup per day, per pup in the beginning. (Not per meal!) This will gradually increase to about 3/4’s cup per day, per pup by 8 weeks. Very frequently, it is necessary to feed several pups separately, since there are usually some that will tend to get more than their share (or less) from a common feeding bowl. Please note that it is always more important to feed to correctly manage each individual pup's weight gain, rather than to try to schedule a certain specific amount of food.
Continue to feed as above, but cut back to two meals a day at eight weeks. As before, the correct amount of food may vary due to differences among puppies. DO NOT add any vitamin or mineral supplements, such as vitamin C or calcium.
Target Weights: 12, 16 & 20 weeks
Age Weight
12 wks. 15-16 lbs.
16 wks. 22-23 lbs.
20 wks. 28-30 lbs.
Notice that the charted Target Weights jump several weeks at a time. Between 8 and 12 weeks, the recommended weight gain totals about 6 lbs. This divides to approximately 1-1/2 lbs. per week. Don't let the pup gain it all the first week! The total weight gain in the next eight weeks from 12 to 20 weeks is 14 lbs., or about 1-3/4's lbs. per week.
Of course, there may be minor variations from these charts without upsetting the Plan. But remember that sometimes just a few pounds can represent a large percentage. For example, at the 12 week target weight of 15 lbs., a three pound increase would actually be 20%. So while 3 lbs. may not sound like a lot, 20% would certainly be significant enough to accelerate the growth rate.
Over 20 Weeks
Once the pup has reached the final check point of 20 weeks old, his growth rate will have been slowed for the most critical period of his development. It is now time to begin encouraging a mildly increased growth rate. And of course, this is done by increasing the amount and density of food. Four months old is also an excellent time to do an OFA preliminary hip x-ray, because pups raised on the Slow Grow Plan have a very high likelihood of rating the same at this age as they will at their two year old final x-ray (Corley et al, 1997)
3
At this point, gradually switch to a premium adult food (i.e., Eukanuba Large Breed Premium Performance or comparable) and increase the amount. Pups should to begin to look a bit fuller, but never fat. One good indicator of soft muscle tone or too much weigh gain is a side to side "roll" over the loin when the pup gaits. Of course, it will take some time for these pups to catch up completely. They may even appear slightly undersize as they reach the 6-9 month Puppy Class; but should be within lower limits shortly thereafter, usually by approximately 7-8 months old. And their growth will continue until they reach their normal genetic potential.
Exercise Recommendations
Exercise is a vital component of the Slow Grow Plan. An active puppy can eat more food, and thus will be more assured of getting enough nutrients. Furthermore, his muscle-to-fat ratio will be more favorable, reinforcing the desired goal of a slowed rate of growth. And the stronger muscles will properly support the skeletal system, which combined with greater coordination, will help protect him from injury.
Free-walking is a suitable exercise for dogs of any age, because it permits them to chose their own pace and level of exertion. Of course, this must be done in a safe environment. While this may not possible on a regular basis for most people, perhaps it can be a special weekend treat. Alternatively, flexileads are workable.
Begin with approximately 1/2 mile walks with the 8 week old pup, 4-5 days per week. Add about 1/2 mile every other week. If you fall behind schedule, do not jump ahead to make up for lost weeks. Instead, resume where you left off. If there has been an extended layoff, begin back several weeks and build up again, as below. An exercise level of 3 miles per day will result in a fit, healthy puppy. Of course, as with any exercise, be very cautious in hot weather; cold is rarely a problem.
8 wks. old = 1/2 mile, 4-5 times weekly 14 wks. = 2 miles, 4-5 times weekly
10 wks. = 1 mile, 4-5 times weekly 16 wks. = 2-1/2 miles, 4-5 times weekly
12 wks. = 1-1/2 miles, 4-5 times weekly 18 wks. = 3 miles, 4-5 times weekly
Do not jog, bike, or otherwise roadwork a young Golden under 4 months of age. Prior to beginning these types of more stressful exercises, it is advisable obtain a preliminary OFA hip evaluation. Only puppies with a preliminary rating of “Good” or above should be considered candidates for this more serious athletic training. Always build speed and distance very gradually.
This information is provided for the benefit of all Golden Retrievers, and may be copied only in its entirety (must include Faera Goldens contact information) to be shared with others on an individual basis. However, any large scale distribution (Internet or hard copy) or publication is prohibited without the specific written permission of the author.
References
Kealy RD, Lawler DF, Ballam JM, Lust G, Biery DN, Smith GK, Mantz SL. Evaluation of the effect of limited food consumption on radiographic evidence of osteoarthritis in dogs. J Am Vet Med Assoc. 2000 Dec 1;217(11):1678-80.
Kealy RD, Lawler DF, Ballam JM, Mantz SL, Biery DN, Greeley EH, Lust G, Segre M, Smith GK, Stowe HD. Effects of diet restriction on life span and age-related changes in dogs J Am Vet Med Assoc. 2002 May 1;220(9):1315-20.
Corley EA, Keller GC, Lattimer JC, et al. Reliability of early radiographic evaluations for canine hip dysplasia obtained from the standard ventrodorsal radiographic projection. J Am Vet Med Assoc 1997; Vol 211, No. 9; 1142-1146
PO Box 1110 • Bath, OH • 44210
Phone: 330-668-0044 • Cell: 330-338-4236
Article 2:
The Long-Term Health Effects of Spay / Neuter in Dogs Laura J. Sanborn March 27, 2007
INTRODUCTION
Dog owners in America are frequently advised to spay/neuter their dogs for health reasons. A number of health benefits are cited, and dog owners are told that “responsible owners spay/neuter their pets”. Yet evidence is rarely cited to support the alleged health benefits.
When discussing the health impacts of spay/neuter, the adverse health effects are often not mentioned. At times, some adverse effects are mentioned, but the most severe effects usually are not.
This article is an attempt to summarize the long-term health effects associated with spay/neuter in dogs, both positive and negative, that can be found in the veterinary medical literature. This article will not discuss the impact of spay/neuter on population control, or the impact of spay/neuter on behavior.
Nearly all of the health effects summarized in this article are findings from retrospective epidemiological studies of dogs, which examine potential associations by looking backwards in time. A few are from prospective research studies, which examine potential associations by looking forward in time.
SUMMARY
An objective reading of the veterinary medical literature reveals a complex situation with respect to the longterm health impacts of spay/neuter in dogs. The evidence shows that spay/neuter correlates with bothpositive AND adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
On balance, it appears that no compelling case can be made for neutering most male dogs, especially immature male dogs, in order to prevent future health problems. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
On the positive side, neutering male dogs
• eliminates the small risk (probably <1%) of dying from testicular cancer
• reduces the risk of non-cancerous prostate disorders
• reduces the risk of perianal fistulas
• may possibly reduce the risk of diabetes (data inconclusive)
On the negative side, neutering male dogs
• if done before maturity, increases the risk of osteosarcoma (bone cancer) by a factor of 3.8; this is a common cancer in medium/large and larger breeds with a poor prognosis.
• increases the risk of cardiac hemangiosarcoma by a factor of 1.6; this is a common cancer and
major cause of death in some breeds
• triples the risk of hypothyroidism
• increases the risk of geriatric cognitive impairment
• triples the risk of obesity, a common health problem in dogs with it the many associated health
problems associated with obesity
• quadruples the small risk (<0.6%) of prostate cancer
• doubles the small risk (<1%) of urinary tract cancers
• increases the risk of orthopedic disorders
• increases the risk of adverse reactions to vaccinations
For female dogs, the situation is more complex. The number of health benefits associated with spaying may exceed the associated health problems in some (not all) cases. On balance, whether spaying improves the odds of overall good health or degrades them probably depends on the age of the female dog and the relative risk of various diseases in the different breeds.
On the positive side, spaying female dogs
• if done before 2.5 years of age, greatly reduces the risk of mammary tumors, the most common malignant tumors in female dogs
• nearly eliminates the risk of pyometra, which otherwise would affect about 23% of intact female dogs; pyometra kills about 1% of intact female dogs
• reduces the risk of perianal fistulas
• removes the very small risk ( 0.5%) from uterine, cervical, and ovarian tumors
On the negative side, spaying female dogs
• if done before maturity, increases the risk of osteosarcoma by a factor of 3.1; this is a common cancer in larger breeds with a poor prognosis
• increases the risk of splenic hemangiosarcoma by a factor of 2.2 and cardiac hemangiosarcoma by a factor of >5; this is a common cancer and major cause of death in some breeds
• triples the risk of hypothyroidism
• increases the risk of obesity by a factor of 1.6-2, a common health problem in dogs with many
associated health problems
• causes urinary “spay incontinence” in 4-20% of female dogs
• increases the risk of persistent or recurring urinary tract infections by a factor of 3-4
• increases the risk of recessed vulva, vaginal dermatitis, and vaginitis, especially for female dogs spayed before puberty
• doubles the small risk (<1%) of urinary tract tumors
• increases the risk of orthopedic disorders
• increases the risk of adverse reactions to vaccinations
One thing is clear – much of the spay/neuter information that is available to the public is unbalanced and contains claims that are exaggerated or unsupported by evidence. Rather than helping to educate pet owners, much of this has contributed to common misunderstandings about the long-term health impacts of spay/neuter in dogs.
The traditional spay/neuter age of six months as well as the modern practice of pediatric spay/neuter appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or (perhaps in the case of many male dogs) foregoing it altogether unless medically necessary.
The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Across-the-board recommendations for all pet dogs do not appear to be supportable from findings in the veterinary medical literature.
FINDINGS FROM STUDIES
This section summarizes the diseases or conditions that have been studied with respect to spay/neuter in dogs.
Complications from Spay/Neuter Surgery
All surgery incurs some risk of complications, including adverse reactions to anesthesia, hemorrhage, inflammation, infection, etc. Complications include only immediate and near term impacts that are clearly linked to the surgery, not to longer term impacts that can only be assessed by research studies.
At one veterinary teaching hospital where complications were tracked, the rates of intraoperative, postoperative and total complications were 6.3%, 14.1% and 20.6%, respectively as a result of spaying female dogs 1. Other studies found a rate of total complications from spaying of 17.7%2 and 23%3.
A study of Canadian veterinary private practitioners found complication rates of 22% and 19% for spaying female dogs and neutering male dogs, respectively4.
Serious complications such as infections, abscesses, rupture of the surgical wound, and chewed out sutures were reported at a 1- 4% frequency, with spay and castration surgeries accounting for 90% and 10% of these complications, respectively.4
The death rate due to complications from spay/neuter is low, at around 0.1%5.
Prostate Cancer
Much of the spay/neuter information available to the public asserts that neutering will reduce or eliminate the risk that male dogs develop prostate cancer. This would not be an unreasonable assumption, given that prostate cancer in humans is linked to testosterone. But the evidence in dogs does not support this claim.
In fact, the strongest evidence suggests just the opposite.
There have been several conflicting epidemiological studies over the years that found either an increased risk or a decreased risk of prostate cancer in neutered dogs. These studies did not utilize control populations, rendering these results at best difficult to interpret. This may partially explain the conflicting results.
More recently, two retrospective studies were conducted that did utilize control populations. One of these studies involved a dog population in Europe6 and the other involved a dog population in America7. Both studies found that neutered male dogs have a four times higher risk of prostate cancer than intact dogs.
Based on their results, the researchers suggest a cause and effect relationship: “this suggests that castration does not initiate the development of prostatic carcinoma in the dog, but does favor tumorprogression”6 and also “Our study found that most canine prostate cancers are of ductal/urothelial origin….The relatively low incidence of prostate cancer in intact dogs may suggest that testicular hormones are in fact protective against ductal/urothelial prostatic carcinoma, or may have indirect effects on cancer development by changing the environment in the prostate.”7
This needs to be put in perspective. Unlike the situation in humans, prostate cancer is uncommon in dogs. Given an incidence of prostate cancer in dogs of less than 0.6% from necropsy studies8, it is difficult to see that the risk of prostate cancer should factor heavily into most neutering decisions. There is evidence for an increased risk of prostate cancer in at least one breed (Bouviers)6, though very little data so far to guide us in regards to other breeds.
Testicular Cancer
Since the testicles are removed with neutering, castration removes any risk of testicular cancer (assuming the castration is done before cancer develops). This needs to be compared to the risk of testicular cancer in intact dogs.
Testicular tumors are not uncommon in older intact dogs, with a reported incidence of 7%9. However, the prognosis for treating testicular tumors is very good owing to a low rate of metastasis, so testicular cancer is an uncommon cause of death in intact dogs. For example, in a Purdue University breed health survey of Golden Retrievers 10, deaths due to testicular cancer were sufficiently infrequent that they did not appear on list of significant causes of "Years of Potential Life Lost for Veterinary Confirmed Cause of Death” even though 40% of GR males were intact. Furthermore, the GRs who were treated for testicular tumors had a 90.9% cure rate. This agrees well with other work that found 6-14% rates of metastasis for testicular tumors in dogs11.
The high cure rate of testicular tumors combined with their frequency suggests that fewer than 1% of intact male dogs will die of testicular cancer.
In summary, though it may be the most common reason why many advocate neutering young male dogs, the risk from life threatening testicular cancer is sufficiently low that neutering most male dogs to prevent it is difficult to justify.
An exception might be bilateral or unilateral cryptorchids, as testicles that are retained in the abdomen are 13.6 times more likely to develop tumors than descended testicles12 and it is also more difficult to detect retained tumors by routine physical examination.
Osteosarcoma (Bone Cancer)
A multi-breed case-control study of the risk factors for osteosarcoma found that spay/neutered dogs (males or females) had twice the risk of developing osteosarcoma as did intact dogs13.
This risk was further studied in Rottweilers, a breed with a relatively high risk of osteosarcoma. This retrospective cohort study broke the risk down by age at spay/neuter, and found that the elevated risk of osteosarcoma is associated with spay/neuter of young dogs14. Rottweilers spayed/neutered before one year of age were 3.8 (males) or 3.1 (females) times more likely to develop osteosarcoma than intact dogs.
Indeed, the combination of breed risk and early spay/neuter meant that Rottweilers spayed/neutered before one year of age had a 28.4% (males) and 25.1% (females) risk of developing osteosarcoma. These results are consistent with the earlier multi-breed study13 but have an advantage of assessing risk as a function of age at neuter.
The researchers suggest a cause-and-effect relationship, as sex hormones are known to influence the maintenance of skeletal structure and mass, and also because their findings showed an inverse relationship between time of exposure to sex hormones and risk of osteosarcoma.14
The risk of osteosarcoma increases with increasing breed size and especially height13. It is a common cause of death in medium/large, large, and giant breeds. Osteosarcoma is the third most common cause of death in Golden Retrievers 10 and is even more common in larger breeds 13.
Given the poor prognosis of osteosarcoma and its frequency in many breeds, spay/neuter of immature dogs in the medium/large, large, and giant breeds is apparently associated with a significant and elevated risk of death due to osteosarcoma.
Mammary Cancer (Breast Cancer)
Mammary tumors are by far the most common tumors in intact female dogs, constituting some 53% of all malignant tumors in female dogs in a study of dogs in Norway15 where spaying is much less common than in the USA.
50-60% of mammary tumors are malignant, for which there is a significant risk of metastasis16. Mammary tumors in dogs have been found to have estrogen receptors17, and the published research18 shows that the relative risk (odds ratio) that females will develop mammary cancer compared to the risk in intact females is
dependent on how many estrus cycles she experiences:
# of estrus cycles before spay Odds Ratio
None 0.005 1 0.08 2 or more 0.2 Intact 1.00
The same data when categorized differently showed that the relative risk (odds ratio) that females will develop mammary cancer compared to the risk in intact females is indicated that:
Age at Spaying Odds Ratio
29 months 0.06 30 months 0.40 (not statistically significant at the P<0.05 level) Intact 1.00
Please note that these are RELATIVE risks. This study has been referenced elsewhere many times but theresults have often been misrepresented as absolute risks. A similar reduction in breast cancer risk was found for women under the age of 40 who lost their estrogen production due to “artificial menopause”19 and breast cancer in humans is known to be estrogen activated.
Mammary cancer was found to be the 10th most common cause of years of lost life in Golden Retrievers, even though 86% of female GRs were spayed, at a median age of 3.4 yrs10. Considering that the female subset accounts for almost all mammary cancer cases, it probably would rank at about the 5th most common cause of years of lost life in female GRs. It would rank higher still if more female GRs had been kept intact up to 30 months of age.
Boxers, cocker spaniels, English springer spaniels, and dachshunds are breeds at high risk of mammary tumors15. A population of mostly intact female Boxers was found to have a 40% chance of developing mammary cancer between the ages of 6-12 years of age15. Purebred dogs are at higher risk than mixed breed dogs, and purebred dogs with high inbreeding coefficients are at higher risk than those with low inbreeding coefficients.20
In summary, spaying female dogs significantly reduces the risk of mammary cancer (a common cancer), and the fewer estrus cycles experienced at least up to 30 months of age, the lower the risk will be.
Reproductive Tract Cancer (Uterine, Cervical, and Ovarian Cancers)
Uterine/cervical tumors are rare in dogs, constituting just 0.3% of tumors in dogs21. Spaying will remove the risk of ovarian tumors, but the risk is only 0.5%22. While spaying will remove the risk of reproductive tract tumors, it is unlikely that surgery can be justified to prevent the risks of uterine, cervical, and ovarian cancers as the risks are so low. Urinary Tract Cancer (Bladder and Urethra Cancers) An age-matched retrospective study found that spay/neuter dogs were two times more likely to develop lower urinary tract tumors (bladder or urethra) compared to intact dogs23. These tumors are nearly always malignant, but are infrequent, accounting for less than 1% of canine tumors. So this risk is unlikely to weigh heavily on spay/neuter decisions.
Airedales, Beagles, and Scottish Terriers are at elevated risk for urinary tract cancer while German Shepherds have a lower than average risk23.
Hemangiosarcoma
Hemangiosarcoma is a common cancer in dogs. It is a major cause of death in some breeds, such as Salukis, French Bulldogs, Irish Water Spaniels, Flat Coated Retrievers, Golden Retrievers, Boxers, Afghan Hounds, English Setter, Scottish Terrier, Boston Terrier, Bulldogs, and German Shepherd Dogs24.
In an aged-matched case controlled study, spayed females were found to have a 2.2 times higher risk of splenic hemangiosarcoma compared to intact females24.
A retrospective study of cardiac hemangiosarcoma risk factors found a >5 times greater risk in spayed female dogs compared to intact female dogs and a 1.6 times higher risk in neutered male dogs compared to intact male dogs.25 The authors suggest a protective effect of sex hormones against hemangiosarcoma, especially in females.
In breeds where hermangiosarcoma is an important cause of death, the increased risk associated withspay/neuter is likely one that should factor into decisions on whether or when to sterilize a dog.
Hypothyroidism
Spay/neuter in dogs was found to be correlated with a three fold increased risk of hypothyroidism compared to intact dogs.
The researchers suggest a cause-and-effect relationship26. They wrote: “More important [than the mild direct impact on thyroid function] in the association between [spaying and] neutering and hypothyroidism may be the effect of sex hormones on the immune system. Castration increases the severity of autoimmune thyroiditis in mice” which may explain the link between spay/neuter and hypothyroidism in dogs. Hypothyroidism in dogs causes obesity, lethargy, hair loss, and reproductive abnormalities.27
Obesity
Owing to changes in metabolism, spay/neuter dogs are more likely to be overweight or obese than intact dogs. One study found a two fold increased risk of obesity in spayed females compared to intact females28.
Another study found that spay/neuter dogs were 1.6 (females) or 3.0 (males) times more likely to be obese than intact dogs, and 1.2 (females) or 1.5 (males) times more likely to be overweight than intact dogs29.
A survey study of veterinary practices in the UK found that 21% of dogs were obese.28 Being obese and/or overweight is associated with a host of health problems in dogs. Overweight dogs are more likely to be diagnosed with hyperadrenocorticism, ruptured cruciate ligament, hypothyroidism, lower urinary tract disease, and oral disease30. Obese dogs are more likely to be diagnosed with hypothyroidism, diabetes mellitus, pancreatitis, ruptured cruciate ligament, and neoplasia (tumors)30.
Diabetes
Some data indicate that neutering doubles the risk of diabetes in male dogs, but other data showed no significant change in diabetes risk with neutering31. In the same studies, no association was found between spaying and the risk of diabetes.
Adverse Vaccine Reactions
A retrospective cohort study of adverse vaccine reactions in dogs was conducted, which included allergic reactions, hives, anaphylaxis, cardiac arrest, cardiovascular shock, and sudden death. Adverse reactions were 30% more likely in spayed females than intact females, and 27% more likely in neutered males than intact males32.
The investigators discuss possible cause-and-effect mechanisms for this finding, including the roles that sex hormones play in body’s ability to mount an immune response to vaccination.32
Toy breeds and smaller breeds are at elevated risk of adverse vaccine reactions, as are Boxers, English Bulldogs, Lhasa Apsos, Weimaraners, American Eskimo Dogs, Golden Retrievers, Basset Hounds, Welsh Corgis, Siberian Huskies, Great Danes, Labrador Retrievers, Doberman Pinchers, American Pit Bull Terriers, and Akitas.32 Mixed breed dogs were found to be at lower risk, and the authors suggest genetic hetereogeneity (hybrid vigor) as the cause.
Urogenital Disorders
Urinary incontinence is common in spayed female dogs, which can occur soon after spay surgery or after a delay of up to several years. The incidence rate in various studies is 4-20% 33,34,35 for spayed females compared to only 0.3% in intact females36. Urinary incontinence is so strongly linked to spaying that it is commonly called “spay incontinence” and is caused by urethral sphincter incompetence37, though the biological mechanism is unknown. Most (but not all) cases of urinary incontinence respond to medical treatment, and in many cases this treatment needs to be continued for the duration of the dog’s life.38 Retrospective study found that persistent or recurring urinary tract (bladder) infections (UTIs) were 3-4 times more likely in spayed females dogs than in intact females39. Another retrospective study found that female dogs spayed before 5 ½ months of age were 2.76 times more likely to develop UTIs compared tothose spayed after 5 ½ months of age.40
Depending on the age of surgery, spaying causes abnormal development of the external genitalia. Spayed females were found to have an increased risk of recessed vulva, vaginal dermatitis, vaginitis, and UTIs.41 The risk is higher still for female dogs spayed before puberty.41
Pyometra (Infection of the Uterus)
Pet insurance data in Sweden (where spaying is very uncommon) found that 23% of all female dogs developed pyometra before 10 years of age42. Bernese Mountain dogs, Rottweilers, rough-haired Collies, Cavalier King Charles Spaniels and Golden Retrievers were found to be high risk breeds42. Female dogs that have not whelped puppies are at elevated risk for pyometra43. Rarely, spayed female dogs can develop “stump pyometra” related to incomplete removal of the uterus. Pyometra can usually be treated surgically or medically, but 4% of pyometra cases led to death42. Combined with the incidence of pyometra, this suggests that about 1% of intact female dogs will die from pyometra.
Perianal Fistulas
Male dogs are twice as likely to develop perianal fistulas as females, and spay/neutered dogs have a decreased risk compared to intact dogs44. German Shepherd Dogs and Irish Setters are more likely to develop perianal fistulas than are other breeds.44
Non-cancerous Disorders of the Prostate Gland
The incidence of benign prostatic hypertrophy (BPH, enlarged prostate) increases with age in intact male dogs, and occurs in more than 80% of intact male dogs older than the age of 5 years45. Most cases of BPH cause no problems, but in some cases the dog will have difficulty defecating or urinating.
Neutering will prevent BPH. If neutering is done after the prostate has become enlarged, the enlarged prostate will shrink relatively quickly.
BPH is linked to other problems of the prostate gland, including infections, abscesses, and cysts, which can sometimes have serious consequences.
Orthopedic Disorders
In a study of beagles, surgical removal of the ovaries (as happens in spaying) caused an increase in the rate of remodeling of the ilium (pelvic bone)46, suggesting an increased risk of hip dysplasia with spaying.
Spaying was also found to cause a net loss of bone mass in the spine 47. Spay/neuter of immature dogs delays the closure of the growth plates in bones that are still growing, causing those bones to end up significantly longer than in intact dogs or those spay/neutered after maturity48. Since the growth plates in various bones close at different times, spay/neuter that is done after some growth plates have closed but before other growth plates have closed can result in a dog with unnatural proportions, possibly impacting performance and long term durability of the joints.
Spay/neuter is associated with a two fold increased risk of cranial cruciate ligament rupture49. Perhaps this is associated with the increased risk of obesity28 or to changes in body proportions in dogs spay/neutered before the growth plates in the bones have closed48.
Spay/neuter before 5 ½ months of age is associated with a 70% increased aged-adjusted risk of hipdysplasia compared to dogs spayed/neutered after 5 ½ months of age40. The researchers suggest “it is possible that the increase in bone length that results from early-age gonadectomy results in changes in joint conformation, which could lead to a diagnosis of hip dysplasia”.
In a breed health survey study of Airedales, spay/neuter dogs were significantly more likely to suffer hip dysplasia as well as “any musculoskeletal disorder”, compared to intact dogs50, however possible confounding factors were not controlled for, such as the possibility that some dogs might have been spayed/neutered because they had hip dysplasia or other musculoskeletal disorders. Compared to intact dogs, another study found that dogs neutered six months prior to a diagnosis of hip dysplasia were 1.5 times as likely to develop clinical hip dysplasia.51
Geriatric Cognitive Impairment
Neutered male dogs and spayed female dogs are at increased risk of geriatric cognitive impairment compared to intact male dogs52. There weren’t enough intact geriatric females available for the study to determine their risk. Geriatric cognitive impairment includes disorientation in the house or outdoors, changes in social interactions with human family members, loss of house training, and changes in the sleep-wake cycle52.
The investigators state “This finding is in line with current research on the neuro-protective roles of testosterone and estrogen at the cellular level and the role of estrogen in preventing Alzheimer’s disease in human females. One would predict that estrogens would have a similar protective role in the sexually intact female dogs; unfortunately too few sexually intact female dogs were available for inclusion in the present study to test the hypothesis”52
CONCLUSIONS
An objective reading of the veterinary medical literature reveals a complex situation with respect to the longterm health impacts of spay/neuter in dogs. The evidence shows that spay/neuter correlates with both positive AND adverse health effects in dogs. It also suggests how much we really do not yet understand about this subject.
On balance, it appears that no compelling case can be made for neutering most male dogs to prevent futurehealth problems, especially immature male dogs. The number of health problems associated with neutering may exceed the associated health benefits in most cases.
For female dogs, the situation is more complex. The number of health benefits associated with spaying mayexceed the associated health problems in many (not all) cases. On balance, whether spaying improves the odds of overall good health or degrades them probably depends on the age of the dog and the relative risk of various diseases in the different breeds.
The traditional spay/neuter age of six months as well as the modern practice of pediatric spay/neuter appear to predispose dogs to health risks that could otherwise be avoided by waiting until the dog is physically mature, or (perhaps in the case of many male dogs) foregoing it altogether unless medically necessary.
The balance of long-term health risks and benefits of spay/neuter will vary from one dog to the next. Across-the-board recommendations for all dogs do not appear to be supportable from findings in the veterinary medical literature.
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25 Ware WA, Hopper, DL. Cardiac Tumors inDogs: 1982-1995. J Vet Intern Med 1999;13:95–103.
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29 McGreevy PD, Thomson PC, Pride C, Fawcett A, Grassi T, Jones B. Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Vet Rec. 2005 May 28;156(22):695-702.
30 Lund EM, Armstrong PJ, Kirk, CA, Klausner, JS. Prevalence and Risk Factors for Obesity in Adult Dogs from Private US Veterinary Practices. Intern J Appl Res Vet Med • Vol. 4, No. 2, 2006.
31 Marmor M, Willeberg P, Glickman LT, Priester WA, Cypess RH, Hurvitz AI. Epizootiologic patterns of diabetes mellitus in dogs Am J Vet Res. 1982 Mar;43(3):465-70. ..
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33 Thrusfield MV, Holt PE, Muirhead RH. Acquired urinary incontinence in bitches: its incidence and relationship to neutering practices.. J Small Anim Pract. 1998. Dec;39(12):559-66.
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40 Spain CV, Scarlett JM, Houpt KA. Long-term risks and benefits of early-age gonadectomy in dogs. JAVMA 2004;224:380-387.
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51 van Hagen MA, Ducro BJ, van den Broek J, Knol BW. Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of boxers. Am J Vet Res. 2005 Feb;66(2):307-12.
52 Hart BL. Effect of gonadectomy on subsequent development of age-related cognitive impairment in dogs. J Am Vet Med Assoc. 2001 Jul 1;219(1):51-6.
Article 3:
Early Spay-Neuter Considerations for the Canine Athlete © 2005 Chris Zink DVM, PhD
To neuter or not to neuter...
There are a number of studies that suggest that those of us with canine athletes should be carefully considering our current recommendations to spay or neuter all dogs at 6 months of age or earlier. A study by Salmeri et al in 1991 (Salmeri et al JAVMA 1991;198:1193-1203) found that bitches spayed at 7 weeks were significantly taller than those spayed at 7 months, and that those spayed at at 7 months had significantly delayed closure of the growth plates than those not spayed (or presumably spayed after the growth plates had closed). The sex hormones close the growth plates, so the bones of dogs or bitches neutered or spayed before puberty continue to grow. This growth frequently results in a dog that does not have the same body proportions as he/she was genetically meant to. For example, if the femur is 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 becomes heavier (because it is longer), causing increased stresses on the cranial cruciate ligament. This is confirmed by a recent study showing that spayed and neutered dogs have a higher incidence of CCL rupture (Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM. Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res. 2004 Dec;(429):301-5).
In addition, a study in 2004 in JAVMA (Spain et al. JAVMA 2004;224:380-387) showed that dogs spayed or neutered before 5 1/2 months had a significantly higher incidence of hip dysplasia than dogs spayed or neutered after 5 1/2 months of age. If I were a breeder, I would be very concerned about this, because it would mean that I might be making incorrect breeding decisions if I were considering the hip status of pups I sold that were spayed or neutered early. Interestingly, this same author also identified an increased incidence of sexual behaviors in males and females that were neutered early.
A number of studies, including the one by Spain referenced above, have shown that there is an increase in the incidence of female urinary incontinence in dogs spayed early. This problem is an inconvenience, and not usually life-threatening, but nonetheless one that requires the dog to be medicated for life.
Yes, there is the concern that there is an increased risk of mammary cancer if a dog has a heat cycle. But it is my observation that fewer canine athletes develop mammary cancer as compared to the number that damage their cranial cruciate ligaments. In addition, only about 50 % of mammary tumors are malignant, and those that are malignant don't metastasize very often, particularly in these days when there is early identification and removal of lumps found on our dogs.
In addition, when considering cancer, there is another study of 3218 dogs that showed that dogs that were neutered before a year of age had a significantly increased chance of developing bone cancer (Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters D, Cancer Epidemiol Biomarkers Prev. 2002 Nov;11(11):1434-40), a cancer that is much more life-threatening than mammary cancer, and which affects both genders.
Finally, in another study, unneutered males were significantly less likely than neutered males to suffer cognitive impairment when they were older (Hart BL. J Am Vet Med Assoc. 2001 Jul 1;219(1):51-6). Females were not evaluated in that study.
For these reasons, I have significant concerns with spaying or neutering dogs before puberty, particularly for the canine athlete. And frankly, if something is more healthy for the canine athlete, would we not also want that for pet dogs as well? I think it is important, therefore, that we assess each situation individually. If a pet dog is going to live with an intelligent, well-informed family that understands the problem of pet overpopulation and can be trusted to keep their dogs under their control at all times and to not breed them, I do not recommend spaying or neutering before 14 months of age.
Article 4:
2006 AAHA Canine Vaccination Guidelines for the General Veterinary Practice
Simplified version by Gina Hetiz.
See AAHA for complete report: http://www.aahanet.org/About_aaha/vaccine_guidelines06.pdf
Core Vaccines: My Notes are marked with an (* ) I am not a Veterinarian nor do I play one on TV, but I am a breeder and I do try to keep myself up to date on issues related to health and welfare of our pets. Please do run all of this by your chosen Veterinarian as well as please be proactive in your pets health care.
Canine Parvovirus
(CV-2) (MLV)
AAHA Initial Puppy Vaccine: Administer at 6 to 8 weeks of age, then every 3 - 4 weeks until 12 - 14 weeks of age.
AAHA Revaccination (booster) Recommendation: After a booster at 1 year (unless manufacturer label recommendations otherwise) revaccination once every 3 years or more is considered protective.
AAHA Comments and Recommendations: Core: Although annual boosters are recommended by some vaccine manufacturers, studies have shown protection against challenge (DOI) up to 7 years postvaccination with MLV vaccines. Products with CPV-2, regardless of genotype ( i.e.: CPV-2, 2a, or 2b) all provide excellent protection against field isolates.
Canine Distemper Virus
(CDV) (MLV)
AAHA Initial Puppy Vaccine: Administer at 6 - 8 weeks of age, then every 3 - 4 weeks until 12 - 14 weeks of age.
AAHA Revaccination (booster) Recommendation: After a booster at 1 year (unless manufacturer label recommendations otherwise) revaccination once every 3 years or more is considered protective.
AAHA Comments and Recommendations: Core: Although annual boosters are recommended by some vaccine manufactures, adult dogs challenged 7 years (Rockborn Strain) and 5 years (Ondertepoort Strain) following MLV vaccination were protected (DOI)
* Distemper vaccine: I choose not to use multi-agent vaccines on puppies under 10 to 11 weeks of age because of the possible side affects to the immune system. There has been a study done that suggests that mixing the Parvovirus and Distemper vaccines prior to 10 weeks of age can lead to immune mediated disease. And vaccine protocols call for 3 to 4 week intervals because the immune system needs at least 21 days to assimilate and recover from a vaccine challenge. So please do not vaccinate your puppy with a multi - agent vaccine prior to 11 weeks as I have vaccinated your puppy with the Parvovirus (CVP) at 8 weeks.
Canine Adenovirus 2
(CAV-2) (MLV parenteral)
AAHA Initial Puppy Vaccine: Administer at 6 to 8 weeks of age, then every 3 - 4 weeks until 12 - 14 weeks of age.
AAHA Revaccination (booster) Recommendation: After a booster at 1 year (unless manufacturer label recommendations otherwise) revaccination once every 3 years or more is considered protective.
AAHA Comments and Recommendations: Core: Demonstrated cross-protection against canine hepatitis caused by CAV-1 as well as CAV-2, one of the agents known to be associated with the infectious tracheobronchitis. Adult dogs challenged y 7ears following the CAV-2 MLV vaccination were found to be protected (DOI) against the more virulent CAV-1.
Rabies 3 - year (killed)
AAHA Initial Puppy Vaccine: Administer one dose as early as 3 months of age.
AAHA Revaccination (booster) Recommendation: The second rabies vaccination is recommended 1 year following administration of the initial dose, regardless of the animal's age at the time the first dose was administered, Booster vaccines should be administered every 3 years. State, provincial, and or local laws apply.
AAHA Comments and Recommendations: Core: State, provincial, and local statutes govern the frequency of distraction for products labeled as "3 year rabies vaccines." The 1-year rabies vaccine is sometimes admistered as the initial dose followed 1 year later by distraction of the 3-year rabies vaccine. State, provincial, and local statutes may dictate otherwise. Route of distraction may not be optional: see product literature for details.
*The above noted vaccines are the ONLY vaccines (Core) you should need to vaccinate your dog for. After the puppy series, one year from the final puppy booster revaccinate. From there at the most, revaccinate every 3 years or check for updated current vaccination guidelines. Please be pro-active in your dog's vaccine procedures. Please do not rely on your Veterinarian for sloe information regarding vaccines. Though equally important do ask and listen to what your Veterinarian has to say about particular geographic concerns and anecdotal information they may have about particular diseases and risk factors for your dog and lifestyle. For example in WA and OR there have been verified reported cases of Leptospira, and while the vaccine is a non core vaccine some individuals may need to be vaccinated if they are in a high risk environment. These are the AAHA Guidelines, with my note to follow.
Leptpspira interrogans (combined with serovars canicila and icterohaemorrhagiae) (killed bacterian) (Also available with serovars Grippotyphosa and Pomona)
Initial Puppy Vaccination: Administer one dose at 12 weeks and one dose at 14-16 weeks. For optimal response do not administer to dogs younger than 12 weeks.
Revaccination (Booster) Recommendations: Annually (manufacturer). Annual boosters are not routinely recommended for all dogs. Vaccinations should be restricted to use in areas where a reasonable risk of exposure has been established. Veterinarians are advised of anecdotal reports of acute anaphylaxis in toy breeds following admistration of leptospiroisis vaccines. Routine vaccination of toy breeds should only be considered in dogs known to have a high exposure risk. Dogs determined to be at exceptionally high risk should be vaccinated at 12 and 16 weeks of age and then at intervals of 6 - 9 months until the risk has been reduced.
AAHA Comments and Recommendations: Noncore: Disease prevalence is likely to vary fro each serovars. Vaccine recommendations are therefore difficult to make due to the lack of information on prevalence of specific serovars infections in dogs in various geographic regions. Anecdotal reports from Veterinarians and breeders suggest that incidence of postvaccination reactions (acute anaphylaxis) in puppies (<12weeks of age) and small breed. Therefore, routine use of the vaccine should be delayed until dogs are 12 weeks of age. Minimum DOI based on challenge studies has been shown to be approximately 1 year for Serovars L. canicila and L. icterohaemorrhagiae; however, efficacy to the products can be as low (<75%) DOI for serovars Grippotyphosa and Pomona are assumed to be up to 1 year.
*Ask your Veterinarian how he/she feels about your particular area and the activities you plan to do with your dog. For example dogs who are going to be in remote areas where there is standing water (ponds, lakes, steams with stagnant pools) and wildlife is abundant such as beavers, raccoons, and other such type animals you may want to consider vaccination. In that case however you really should consider vaccinating for Lepto totally separate from any other vaccines and at least 3 weeks following any other vaccines, this is to not over challenge the immune system.Personally I have just begun to vaccinate with the new 4 way lepto vaccine and only with my dogs I will be taking to high risk areas and I will not vaccinate for Lepto until about 8 months, because I want the immune system to not be challenged by too much too soon.
In conclusion: Vaccines play a major role in many aspects of our dogs lives and while we should vaccinate we also need to be informed and we must maintain proactivity.
Article 5:
Rebuttal to "Early Spay-Neuter Considerations for the Canine Athlete"
Lisa M. Howe, DVM, PhD, Dipl. ACVS
Associate Professor, Small Animal Surgery Co-Chief
Surgical Sciences Section Dept. of Veterinary Small Animal Clinical Sciences
College of Veterinary Medicine and Biomedical Sciences
Texas A&M University College Station, TX, 77843
I have written a rebuttal to Dr. Zink's article entitled "Early Spay-Neuter Considerations for the Canine Athlete" in which Dr. Zink attempts to make an argument for revisiting the "standard protocol in which all dogs that are not intended for breeding are spayed and neutered at or before 6 months of age." In his discussion, Dr. Zink quotes manuscripts incorrectly in some instances, doesn't present all of the data from given studies (ie, misrepresenting the findings of the studies) in other instances, and doesn't include the interpretation of the data by the study's authors (leading to erroneous interpretations of some data by Dr. Zink) in yet other instances. While I typically don't write rebuttals to others' writings, or opinions (after all, we are all entitled to our opinions), the multiple errors and misrepresentations of the scientific literature quoted in this dissertation compelled me to "set the record straight" with regard to the literature being incorrectly cited by Dr. Zink. While I respectfully disagree with Dr. Zink's opinion on the appropriate age at which to spay and castrate dogs not intended for breeding, my primary purpose for this rebuttal is to present the literature that Dr. Zink cites in a more accurate, and more complete, fashion so that the veterinarian reader may reach their own conclusions regarding the most appropriate time to spay or castrate the nonbreeding animal, based upon accurate representation of the scientific literature.
Orthopedic Considerations
Dr. Zink points out correctly that in Salmeri's 15-month study (examining the effects of prepubertal gonadectomy on skeletal growth, weight gain, food intake, body fat, and secondary sex characteristics in 32 mixed-breed dogs neutered at seven weeks or seven months or left intact) that bitches spayed at 7 weeks grew significantly taller than those spayed at 7 months, and that those spayed at 7 months has significantly delayed closure of the growth plates (but didn't grow significantly taller) than those not spayed (Salmeri, 1991). However, the concerns expressed by Dr. Zinc regarding changes in stifle joint angles are not supported by any existing literature, and don't make sense as an argument against "early age "gonadectomy (ie, gonadectomy performed well before 6 months of age). Since the animal that is gonadectomized early will not have likely had closure of any of the hind limb long bone physes, it stands to reason that closure of all of the physes will be delayed resulting in longer, but proportional, bone growth as related to the stifle joint. In fact, Salmeri's study did not identify any changes in the proportional nature of bone growth of the forelimb (she was studying growth and maturation of the radius and ulna). It seems that Dr. Zink may be arguing against performing gonadectomy during the time period between 7 or 8 months of age and final closure of all the growth plates, which isn't relevant to a discussion of "early age" gonadectomy. Dr. Zink's speculation regarding joint angles cannot be applied to, and isn't discussed in, the article cited regarding increased incidence of cranial cruciate ligament rupture in gonadectomized dogs. There is no information in the article (Cooley, 2002) as to the timing of gonadectomy in the study population, so there is no way of knowing if animals were spayed/castrated after adulthood, at the "traditional age", or at an "early age", and it is, therefore, not appropriate for Dr. Zinc to be applying his theory to that article. In fact, in the article, bone lengths and joint angles are never mentioned, and the authors speculate their findings may be attributable to: "alterations in sex hormones may affect the size, shape, or material properties of the ACL."
Regarding hip dysplasia, long-term studies have examined the incidence of hip dysplasia in dogs and the association with age at gonadectomy, and Dr. Zink quotes one of them. The study of 1842 dogs found that early age gonadectomy was associated with a significant increased incidence of hip dysplasia (Spain, 2004). Puppies that underwent gonadectomy before 5.5 months of age had a 6.7% incidence of hip dysplasia, while those that underwent gonadectomy at the more traditional age had an incidence of 4.7%. However, Dr. Zink fails to note the additional finding of that study which included finding that those dogs that were gonadectomized at the traditional age were three times more likely to be euthanized for the condition as compared to the early age group, leading the authors to suggest that early age gonadectomy may be associated with a less severe form of hip dysplasia.
Cancer Considerations
Dr. Zink states: "There is a slightly increased risk of mammary cancer if a female dog has one heat cycle." Others would tend to believe, based on the scientific literature, that there is more than a "slightly increased" risk. In fact, the literature states that the risk of developing mammary tumors in dogs spayed prior to the first estrus is 0.5%, 8% after the first estrus, and after the second estrus the risk will increase to 26% (Schneider, 1969). The sparing effect of OHE is lost after females have cycled more than twice or are older than 2.5-4 years of age. Hence, this is one of the reasons veterinarians recommend spaying before the first heat cycle. Mammary neoplasms are the most common tumors of the female dog (MacEwen, 1996). Additionally, the rate of malignancy of mammary tumors in dogs is typically considered to be closer to 50% (rather than the 30% stated by Dr. Zink) and clearly a significant problem in the intact female dog (Brodey, 1983; Gilbertson, 1983). Dr. Zink then goes on to state his own personal belief that canine athletes have more problems with cranial cruciate ligament injury than with mammary neoplasia. Clearly, there is no information in the literature to support such a statement, or comparison. This is comparing apples and oranges, and not appropriate. As with human athletes, it is probably appropriate to believe that the canine athlete will suffer athletic injuries (ie, torn cruciate ligaments, etc.), but to compare disease entities, and make statements about the prevalence of these entities (based upon personal biases) is not valid.
Related to the incidence of cardiac tumors, the study by Ware, et al., has been misquoted when Dr. Zink stated that: "A retrospective study of cardiac tumors in dogs showed that there was a 5 times greater risk of hemangiosarcoma, one of the three most common cancers in dogs, in spayed bitches than intact bitches and a 2.4 times greater risk of hemangiosarcoma in neutered dogs as compared to intact males." The study, in fact, stated that "the relative risk of a tumor in intact males was 2.44 times the risk in intact females" (Ware, 1999). That study did show that the relative risk for hemangiosarcoma in spayed females was >5 times that for intact females, but "that castrated males had only a slightly greater risk (1.6 times) of developing a heart tumor than did intact males." The exact cause for the increased risk in spayed females, as compared to intact females was not identified. It is important to recognize that cardiac tumors are not common compared to other tumor types (including mammary neoplasia in the intact bitch) and the overall incidence of cardiac tumors in that study was 0.19%.
Osteosarcoma has been demonstrated in some studies to occur more frequently in gonadectomized dogs, however, one of the studies cited by Dr. Zink has been mischaracterized. Dr. Zink describes Cooley's study as "a study of 3218 dogs" in which dogs neutered before a year of age were found to have a significantly increased chance of developing bone cancer." In reality, however, Cooley's study is a study of 683Rottweiler breed dogs (Cooley, 2002). Rottweilers were selected for the study, as stated by the authors of the study, because their risk of bone sarcoma is very high compared with other breeds. The study found that bone sarcoma was diagnosed in 12.6% of the dogs, and that male and female dogs that underwent gonadectomy before 1 year of age (can't be defined as "early age" gonadectomy) were significantly more likely to develop bone sarcoma than dogs that were sexually intact. The second study quoted by Zink did indeed find a twofold higher risk of osteosarcoma among neutered dogs as compared to intact dogs (Ru, 1998). This study involved 3062 purebred dogs with osteosarcoma as compared to 3959 purebred dogs without osteosarcoma. However, in that study, no information was reported regarding when surgical neutering took place, so it is inappropriate to apply this article to arguments pertaining to "early age" gonadectomy.
Regarding the relation of castration and neoplasia, it is well documented that prostatic neoplasia occurs in both intact and neutered male dogs, and that castration does not protect against the development of prostatic carcinoma (Obradovich, 1987; Krawieic, 1992; Bell, 1991; Barsanti, 2003). However, it is also well documented in the scientific literature that castration (including early castration) does help prevent other prostatic diseases seen in intact male dogs including benign prostatic hyperplasia, cystic hyperplasia, squamous metaplasia, paraprostatic cysts, prostatitis, and prostatic abscessation (Berry, 1986; Black, 1998; Cohen, 1995; White, 1987; Barsanti, 2003; Cowan, 1991; White, 1995; Hardie, 1984; Mullen, 1990).
Behavioral Considerations
Dr. Zink begins the discussion of behavioral considerations by incorrectly stating that "The study that identified a higher incidence of cranial cruciate ligament rupture in spayed or neutered dogs also identified an increased incidence of sexual behaviors in males and females that were neutered early (Slauterbeck, 2004). In fact, Slauterbeck's paper never mentions anything about sexual behaviors. The next paper cited is Spain's paper which did demonstrate an increased incidence of noise phobias and undesirable sexual behaviors in the dogs undergoing early age gonadectomy (Spain, 2004). Dr. Zink fails to point out other behaviors that were decreased in dogs gonadectomized before 5.5 months, including escaping behavior, separation anxiety, and urinating in the house when frightened. The study also found that three behaviors were significantly associated with age at gonadectomy for males but not females, and included aggression towards family members, barking or growling at visitors, and excessive barking that bothered a household member. These three behaviors were significantly associated with one another, and were seen more frequently in males gonadectomized before 5.5 months of age. When looking at all the behaviors taken together, authors found that overall, the relinquishment rate was lowest among dogs gonadectomized before 5.5 months (7.5%), whereas those gonadectomized > 5.5 months of age had a higher relinquishment rate (10.4%). Howe's study of 269 dogs also showed that "early age" gonadectomy was not associated with higher return rate or increased rate of placement in another home after adoption, compared with traditional age gonadectomy (Howe, 2001). In that study, there was no difference in the incidence of overall or specific behavioral problems between age groups. Regarding the recent report of the American Kennel Club Canine Health Foundation, Dr. Zink stated that the study "reported significantly more behavioral problems in spayed and neutered bitches and dogs". However, upon reading the reference cited by Dr. Zink, there is no such finding reported in the paper (http://www.akcchf.org/pdfs/whitepapers/Biennial_National_Parent_Club_Canine_Health_Conference.pdf, 2005). The report does, however, note 2 behaviors seen more frequently in neutered animals and the paper states that "male dogs had more aggression behavior problems and that females were more fearful. These differences were even more extreme when looking at only neutered animals, even after excluding animals neutered for behavior problems." The reference states that dogs were 1 year of age when studied, but doesn't report when dogs underwent gonadectomy (ie, at an "early age" or at the "traditional age").
Dr. Zink goes on to state that another study "showed that unneutered males were significantly less likely than neutered males to suffer cognitive impairment when they were older" (Hart, 2001). However, that study did not show that intact males were less likely than neutered males to suffer cognitive disorders when they were older. In fact, results of the paper demonstrated that "there were no significant differences among groups (gender status) in regard to percentages of dogs that progressed from not having any impairments to having impairments in 1 category or to having impairments in > 2 categories". Hence, the study showed that neutered male dogs were not any more likely to suffer cognitive disorders than intact dogs. However, what the study did show in dogs that were already affected, was that the "percentage of dogs that progressed from being mildly impaired (ie, impairments in 1 behavioral category) at the time of the first interview to being severely impaired (ie, impairments in > 2 categories) at the time of the second interview was significantly higher for neutered than sexually intact male dogs." However, it is important to note that the animals in this study were spayed at a mean age of 2.8 years (SD, 0.1) and the mean age for castration of the male dogs was 4.8 years (SD, 1.2), making the paper irrelevant to a discussion of "early age" gonadectomy.
Other Health Considerations
Dr. Zink mentions other health considerations that should be considered when deciding whether the canine athlete should undergo gonadectomy at, or before, 6 months of age. Dr. Zink states: "A number of studies have shown that there is an increase in the incidence of female urinary incontinence in dogs spayed early", and gives one reference for this (Stocklin-Gautschi, 2001). Indeed, there have been several studies that have demonstrated an increased incidence of urinary incontinence in dogs spayed early, as well as a study that demonstrated a much higher incidence of urinary incontinence (20.1%) in bitches spayed after the first estrus, as compared to those spayed before the first estrus (Arnold, 1992). In fact, in the reference (Stocklin-Gautschi, 2001) that Dr. Zink quotes, the authors go on to interpret the findings of their study in relation to similarly performed studies, and then state in the discussion: "A comparison of the present results with those of Arnold, et al. (1992) indicates that the risk of urinary incontinence is lower in early spayed bitches than in bitches spayed after the first oestrus, but that the clinical signs of the affected animals are significantly more pronounced." The authors continue and state: "However, assuming that most incontinent bitches respond well to medication, this factor is of minor importance. This relative disadvantage of early spaying is negligible when compared with the benefits, such as lower incidence of urinary incontinence and the protection against mammary tumours." On the other hand, the recent study of 1842 dogs by Spain, et al., demonstrated that there was an increased incidence of urinary incontince in female dogs, with the risk being greatest in females gonadectomized before 3 months of age, compared with those gonadectomized at, or after, 3 months of age (Spain, 2004). Based upon their findings, Spain concludes: "Because urinary incontinence was greater among puppies gonadectomized before 3 months of age and incontinence can be a lifelong condition requiring ongoing treatment, it is reasonable to conclude that female dogs should not be gonadectomized until at least 3 to 4 months of age." The authors continue: "This may be particularly prudent for a shelter that does not have an excess of puppies and is focused on reducing medical and behavioral conditions that could lead to relinquishment of adolescent and adult dogs. Conversely, for shelters with excess puppies, the advantages of gonadectomy of all dogs before adoption may outweigh the risk of urinary incontinence."
Dr. Zink also points out that neutering of male dogs has been associated with an increased likelihood of urethral sphincter incontinence (Aaron, 1996) and seems to imply that early neutering plays a role in this. However, when one examines Aaron's paper, it becomes obvious that the dogs that developed urethral sphincter incompetency following castration were adult dogs when castrated, with the median age of onset of urinary incontinence being 6 years (range 6 months to 10.5 years), and the median period between castration and the onset of incontinence being 10 days (range "immediately" to 18 months). Clearly, this paper should not be quoted as an argument against early neutering (or late neutering, for that matter) in male dogs. Urethral sphincter incompetency is quite uncommon in male dogs, and is likely multifactorial in nature, considering male dogs don't tend to respond well to hormonal replacement (Aaron, 1996). When one considers the incidence of prostatic hyperplasia, cysts, and abscesses in older male dogs (much higher than urethral sphincter incompentency), and the potential life threatening nature of some of these problems, the role for castration in preventative health care for male dogs becomes obvious.
Hypothyroidism is cited as another health reason to avoid early gonadectomy. Dr. Zink is correct that both the cited references (http://www.grca.org/healthsurvey.pdf and Panciera, 1994) do demonstrate that hypothyroidism occurs more commonly in gonadectomized dogs (including the Golden Retriever breed) than in intact dogs. While there is an association, the overall incidence of hypothyroidism is 0.2% in canines (Panciera, 1994 - although it may be higher in certain breeds such as the Golden Retriever and Doberman Pinscher). It would not be prudent to discourage spaying/castrating of dogs (early or not) to prevent a disease with such a low incidence that has a good response to treatment in most dogs (Panciera, 1994), when other diseases have much higher incidences (mammary neoplasia, pyometra, prostatic hyperplasia, etc.) and may not have as favorable an outcome.
Infectious diseases are cited as another reason to avoid early gonadectomy. While Dr. Zink does correctly state the findings of the cited reference which were that infectious diseases were more common in dogs spayed/castrated at 24 weeks of age or less as compared to those undergoing gonadectomy at more than 24 weeks (Howe, 2001), Dr. Zink fails to point out the conclusions of the author related to this issue. Howe notes in that article that: "Parvoviral enteritis was the most commonly reported infectious disease and was reported exclusively in dogs that underwent prepubertal gonadectomy. Parvovirus enteritis is common from puppies from shelter environments, but uncommon in older dogs. The potential influence of anesthesia and surgery on the incidence of parvoviral enteritis in puppies that underwent gonadectomy could not be determined in our study, because comparisons with puppies that did not undergo gonadectomy were not performed." Spain's study of 1842 dogs also found that dogs gonadectomized before 5.5 months had a significantly greater incidence of parvoviral enteritis (as compared to those gonadectomized later), but went on to say: "In that study (Howe, 2001), as with ours, however, the increased rate of parvovirus infection probably represented increased susceptibility of dogs < 6 months of age during the periadoption period and not long-term immune suppression or long-term susceptibility as a result of early-age gonadectomy" (Spain, 2004).
Interestingly, Dr. Zink did not address one of the major health concerns of the unspayed bitch which is pyometra, a potentially life threatening condition. Pyometra occurs at a very high rate in unspayed bitches, and the incidence has been reported to approach 66% in bitches over 9 years of age (Johnston, 2001). Unlike the United States, in Scandinavian countries, female dogs are at risk of developing pyometra since elective neutering of healthy bitches is seldom performed, resulting in only 7% of bitches being spayed (Egenvall, 1999). A recent study in Sweden was conducted to assess the incidence of pyometra in bitches using data obtained from a Swedish pet insurance company, and it was found that overall, almost 25% of the insured dog population had developed pyometra by 10 years of age. In the three breeds at highest risk of developing the disease (rough-haired Collie, Rottweiler, Bernese Mountain Dog), approximately 50% of the bitches had experienced pyometra before reaching 10 years of age (Hagman, 2004). Pyometra can be a life threatening, and expensive to treat, condition that occurs with much greater frequency than rupture of the cranial cruciate ligament or cardiac tumors, and can easily be prevented by ovariohysterectomy.
In summary, while I respectfully disagree with Dr. Zink as to the most appropriate time at which to gonadectomize the animal that is not used for breeding purposes, it is important for any veterinarian to base their decisions upon a well versed understanding of the scientific literature. As new studies are performed, and our knowledge base grows as to the effects, both good and bad, of sterilization of pet animals (including "early age" gonadectomy), current recommendations may (or may not) be changed. With regard to the canine athlete, I would encourage those who feel that they are seeing certain problems more frequently in animals that have undergone early age gonadectomy (as compared to traditional age gonadectomy) to collect, and analyze, data and contribute the information to the scientific literature. Until such studies are performed, anecdotal information remains just that - anecdotal, unverified, and unsuitable for making broad sweeping recommendations regarding the appropriateness of spaying and castrating (at any age) animals that are not used for breeding purposes (or for making recommendations regarding tubal ligation/vasectomy which clearly don't have the same health benefits as gonadectomy).
References:
Aaron A, Eggleton K, Power C, Holt PE. Urethral sphincter mechanism incompetence in male dogs: a retrospective analysis of 54 cases. Vet Rec. 139:542-6, 1996
Arnold S, Arnold P, Hubler M, et al. Urinary incontinence in spayed bitches: prevalence and breed predisposition. Eur J Companion Anim Pract 2:65-68, 1992
Barsanti J. Diseases of the prostate gland. In: Morgan, ed. Handbook of Small Animal Practice, 4th edition. p. 577
Bell FW, Klausner JS, Hayden DW, et al. Clinical and pathologic features of prostatic adenocarcinoma in secually intact and castrated dogs: 31 cases (1970-1987). J Am Vet Med Assoc 199:1623-1630, 1991
Berry SJ, Coffey DS, Strandberg JD, et al. Effect of age, castration and testosterone replacement on the development and restoration of canine benign hyperplasia. Prostate 9:295, 1986
Berry SJ, Strandberg JD, Saunders WJ, et al. Development of canine benign prostatic hyperplasia with age. Prostate 9:363, 1986
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