Thursday, February 28, 2013

Spay or Neutering Your Mastiff or Other Giant Breed Dog

I wanted to do a quick edit to this specific blog because I think is it a very important topic.  I wanted to add a link to an article recently published by The Dog Place; Rethinking Spay and Neuter.

A lot of new pet owners are under the assumption that they should have their new puppy spayed or neutered by the age of six months.  This timeframe has been preached by vets, animal shelters, rescue organizations and numerous other sources for ages.  The funny thing is that there is no real proof that this is the magic age to alter your pet. 

It is EXTREMELY important that you do not alter your Mastiff until at least 18 months of age, and preferably after 2 years of age.  The growth plates in a giant breed dog are regulated by hormones.  If you chose to remove those hormones by spaying or neutering your Mastiff  prior to completion of growth you are asking for numerous joint, bone and growth issues down the line.

The first thing that will happen is you will get a Mastiff that is as tall as a Great Dane and not much wider.  The hormones that tell the growth plates to stop growing upward are removed when the animal is altered, so the bones just keep going up and up. 
There is a very good article published by the National Animal Interest Alliance titled Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs. (Laura J. Sanborn M.S. May 14, 2007) Here is a summary of the article:

An objective reading of the veterinary medical literature reveals a complex situation with respect to the long- term health risks and benefits associated with 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, 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 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); 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
•triples the risk of hypothyroidism
•increases the risk of progressive geriatric cognitive impairment
•triples the risk of obesity, a common health problem in dogs with many associated health problems
•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 1 year of age, significantly increases the risk of osteosarcoma (bone cancer); 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 it has contributed to common misunderstandings about the health risks and benefits associated 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. Breed, age, and gender are variables that must be taken into consideration in conjunction with non-medical factors for each individual dog. Across-the-board recommendations for all pet dogs do not appear to be supportable from findings in the veterinary medical literature.”

A few other statistics I pulled from the article in regards to early spay or neuter and the correlation of Osteocarcenoma are as follows:
“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 dogs.”

“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.”

“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.”
Some other important health aspects related to early spay/neuter are the increased risk of obesity, spay incontinence in female dogs, increased risk of vaccine reactions and other orthopedic issues.

I recommend that any pet and specifically giant breeds such as Mastiffs are NOT to be altered before they are 18 months of age for these reasons.  When it comes to the lifelong health of your pet these highly increased risks are just not worth taking.


  1. Great article. From a behavioral standpoint, altering the animal prior to full hormonal development prevents the dog from fully becoming what it was genetically programmed to be.

    Many vets say this isn't true and there is no science to back up what I propose. My response is that there is no science to refute it as well.

    A heavy dose of common sense can solve the riddle though. If sex hormones play a part in development and maturation in an animal, and you remove the parts that involve the sex hormones, it would seem that there would be a different outcome than if you did not.

    There are always 3 sides to a story, and the giant campaign to spay and neuter ASAP to prevent health risks to the animal is merely one of those sides.

    Thanks for the info!!

    1. There might not be any scientific evidence to support your claim, but there is quite a lot of it that supports the increased statistical probability of various medical issues when a dog is spay/neutered young.

  2. I had no idea about the hormone growth and wonder if this is the reason for the shorter lifespan of mastiffs I've known - they were altered early. Our dogs were altered at 6 months; our puppy was altered before he came to us (he was probably 3 months old). We have smaller dogs (compared to a Mastiff). I've noticed stories coming out promoting alternatives to the standard surgery procedure. I'm curious to know what more we'll learn.

  3. Like KD said, it makes perfect sense that sex hormones play a part in development! We waited till 1 year to have our Am. Pit Bull neutered, and when we got our mastiff (cane corso), we planned on doing the same. Our mastiff's 11 months old now, and I'm glad I came across this article in time! I think we'll wait until at least 18 months, but GOOD LORD how much bigger is he gonna get?! LOL He's already 155 lbs... the "big boy" of the litter! :D

  4. Thank you for putting out information on negatives and positives of spayed/neutering. We have had four English Mastiffs, 2 males and 2 females. We spayed our females ( first was at 18 months and the second one was done at 4 years) both became obese even with their continued daily exercise routine and the female spayed at 18 months ended up with a cruciate ligament tear, she also had Addison's disease (diagnosed at about 2 1/2 years of age), she ended up passing away at 6 years old. We still have our other three mastiffs, including her brother, he is our oldest, he just turned 8 years old and is in excellent physical shape and health, both that I contribute to him being intact. Our youngest is our 3 year old intact male, who also has elbow displaysia for which he has had two surgeries. Being a large breed dog we had already decided to wait until he was three (just had birthday Dec 2013) to determine if he would need to be neutered. It is not our preferred choice, but he is more aggressive and "nosey" around our spayed female, his behavior is becoming a constant daily battle. Not to mention she fights back, which has resulted in several trips to the vet for stitches. Really hoping for an alternative option, he is about 160 lbs and has a very good lean physique, I am very worried about him putting on weight if he's neutered, I don't believe his right elbow could take it. The female is a rescue that had a very rough life before coming to us and we know she likely wouldn't be able to go on to live with anyone else and its hard to fault her for her aggression toward our 3 year old since he is always the instigator.

  5. We have two female mastiff/ st. Bernard 1 yr. olds. This is our first experience with female dogs and having just gone through the first messy heat, I have been calling local docs talking to them regarding spaying. I think of it as a VERY SERIOUS MOVE in this large a breed and would not want anyone but a surgeon with a good reputation, but we are still nervous about them "going under a knife" Your article has been very helpful. Should we determine to try to get through the heat cycles and leave them in tact, do they ever stop the bleeding as they age? Is it better, if we are going to spay them, to do them younger -say at 2 rather than wait till they are 5 or 6?? It is a huge step and we would like to think it through. Both girls have excellent dispositions one of the two is exceptionally beautiful and we think she would throw beautiful puppies, but honestly we have not gone down that road and would not want puppies unless we could be pretty certain good homes would be available for such large breeds. Any suggestions out there???

    1. I would definitely spay them both, but probably wait another year. Make sure before you take them in your vet understands what anesthesia's are not safe for use on Mastiffs. (

      In regards to breeding, PLEASE do not breed your already mixed breed dog. We as reputable breeders do everything we can to preserve the integrity of these breeds, including genetic health testing, matching pedigrees, etc. Unless you do complete health testing on your females (no matter what breed) and the male you use you are not doing the ethical and reputable thing. Plus I'm doubtful you would find a respectable owner of a male that would allow you to breed to a mix. I know your dogs are your loves and pets and please keep them at just that. It isn't worth condemning a litter of puppies to a life of hip dysplasia or them end up in the wrong hands and end up in a breeding mill. Plus there are a lot of risks to losing your female in a pregnancy or with birthing complications. Thousands of people think it's okay to breed their pets, purebred or not and that's why craigslist ends up being the fighting bait dog grocery store and why shelters put to sleep so many wonderful animals. Just please consider all these things before you decided to breed your beloved pet.

    2. No the bleeding does not get better. My first Mastiff I did not spay and it was difficult to stay ahead of the blood every time, twice a year. I have my third Mastiff now she is just seven months old. I had her spayed at six months for two reasons. first the blood and second last year my second Mastiff had a litter. 13 puppies in all. It was an oopsy pregnancy. Fortuantely for me I have a lot of friends that wanted a mastiff/german shepherd puppy. I was very careful and made sure I walked her to the six foot fenced in yard on a leash to make sure she did not get away. the GSD male dug under the fence to get to her. And for those of you who do not know this Mastiffs are not known as great moms. Many females won't even feed. I was lucky she did feed hers but with 13 of them she did not have enough milk. It was alot of sleepless nights for me. I am a single working girl. I had to go to work and hope for the best. God shines on children and fools. Lucky me. So I figure spay is the right way to go for me. I also can not stand the thought of one of the pups being put down or intentionally hurt by someone that promised to love them.

    3. Hi I have a mixed St/ Great Dane I was going to have her fixed at 2 but found out she had a bad heart. Vet said she would not survive surgery. So I have to keep her intact. I put a kennel in my garage which is attached to the house. When she is in heat I keep her in the kennel on the days she is bleeding. I make sure we have a lot of time outside. I also keep the door open that connects to the house so she can still hear us. I have to do this only twice a year, it may be a little inconvenience but her health is worth it.

  6. Thank you for all the information. We adopted two siblings (Sam and Violet) who are 3 1/2 months old. Until reading your article we had plans on having both altered at 7 months but now we will wait till they are 18 months to 2 years. We have no intention on breeding, as stated they are brother and sister so we really do not want them to have any puppies. Do you know if they make a "birth control" for female dogs so this won't happen? Thank you for any support you can give and for all your hard earned advise.

    1. Birth control for dogs boils down to keeping them seperate and being adamant about it during your females heat cycle. There is a 'morning after' treatment for dogs, but it makes them VERY sick and can be very very hard on them. Just make sure when she is in heat to utilize crates and DO NOT LEAVE them alone together. It takes 2 seconds for a tie and that can end up in a pregnancy. Good luck, many many people have intact dogs of opposite sexes in the same household, so it can be done right. If you are lucky your female won't start coming into season until she's older, but they can start as early as 6 or 7 months or start as late as 18 months.