Has your dog ‘had the snip?’. Neutering was once considered to be a key part of responsible dog ownership, blanketly applied for all animals. With a growing evidence base for both the benefits and risks of this procedure, vets and owners now need to take a little more time discussing what is right for your individual dog.
What is neutering?
Neutering is the complete or partial removal of a dog’s reproductive organs, primarily to stop the dog getting pregnant or fathering puppies. These are surgical procedures that need to be done under general anaesthetic by a qualified vet.
In females, this is called spaying. There are a variety of techniques:
- A traditional spay, or ovariohysterectomy, involves removing the ovaries and uterus through an incision in the belly. The vagina remains, tied off at the level of the cervix. This procedure is major surgery that takes a few weeks to recover from.
- A keyhole, or laparoscopic spay, involves removing only the ovaries through two or three small incisions, meaning a quicker recovery. The dog will not produce or release eggs, so cannot get pregnant even though the uterus remains.
- An ovary-sparing spay involves removing the uterus through an incision in the belly, but leaving the ovaries behind. This procedure means a dog cannot carry a pregnancy, but still produces sex hormones.
In males, neutering is called castration.
- This usually refers to the removal of both testicles through an incision just in front of the scrotum. The scrotum is left behind, and reduces in size with time. The dog no longer produces sperm or testosterone.
- Male dogs can also have a vasectomy, where a portion of the tube that carries sperm to the outside world is removed. The dog cannot impregnate a female, but still produces testosterone from the testicles that are left behind.
- It is also possible to use chemical castration in dogs, where an implant is placed under the skin to block the production of testosterone temporarily. This is usually done with the dog awake (much like a microchip) and will stop sperm and testosterone production for a period of around 6-12 months. When it wears off, the dog becomes sexually active again (entire).
What are the benefits of neutering?
Vets recommended neutering in dogs for a number of reasons:
Population Control
Neutering is an effective and ethical way to stop dog populations getting too big and stop unwanted pregnancies.
Removes risk of uterine infections
Dogs do not go through menopause, but continue cycling throughout their life. This increases the risk of a disease called pyometra, where the uterus fills up with pus. Untreated, this causes sepsis and death, and to treat it involves expensive and risky surgery. This is probably the main reason vets recommend neutering in females.
Reduced risk of reproductive cancers and other diseases
Removing ovaries, uterus or testicles removes the risk of cancer in these organs, and also reduces the risk of prostate disease, such as prostatitis and benign prostatic hypertrophy in males; and is reported to substantially decreases the risk of mammer (breast) cancer
Reduced risk of roaming and urine marking
Entire male dogs are driven to mark their territory with urine, and may try to run away from their owners if they smell a bitch in season.
Reduced risk of aggression
Testosterone increases aggression between entire males as they fight for territory and females. This aggression can be directed at humans too! Some female dogs can also be more aggressive when they are in season.
Removes hassle of seasons and phantom pregnancy
A female dog has, on average, two ‘seasons’ a year where they bleed from the vulva for up to 3 weeks. This creates a lot of mess in the home, and they need to be walked on a lead and kept away from male dogs during this time. Bitches also have ‘phantom pregnancies’, where their body believes they are pregnant even when they are not. This can cause aggressive behaviour, and even mean medication from the vets for unnecessary milk production.
Reduces risk of theft
Dog thieves will preferentially steal dogs they can breed from.
Reduced risk of inbreeding
Dogs are not so fussy about their breeding partners as humans, and will even mate with their siblings! Neutering dogs living together removes this risk of inbreeding and deformed puppies.
What are the risks of neutering?
All procedures come with risks, and neutering is no exception. Some to be aware of include:
Need for general anaesthesia and surgical recovery time
Neutering is an elective surgery i.e. one that does not have to be done, but we choose to do. Any anaesthetic involves some risk, and all surgeries require time afterwards to allow healing
Change in behaviour for some dogs
For some male dogs, the testosterone in their body is the only thing giving them any confidence in life! Neutering a nervous male dog removes this confidence and can make fear aggression worse.
We also know that timing of spaying is critical in females, and that neutering too close to a season or phantom pregnancy can ‘fix’ the dog in a more aggressive hormonal state.
Increases the risk of weight gain
The reproductive organs use a surprising amount of energy to produce hormones, eggs and sperm, and removing this need means the dog is burning fewer calories. If diets are not adjusted after neutering, dogs are more likely to gain weight.
May influence the development of urinary incontinence in females
The bladder needs oestrogen to help it work, and reduction of this can mean urinary incontinence can be seen in some females after neutering.
May increase the risk of joint disease and cancer in some breeds
Sex hormones are critical for growth, and so the skeleton and muscles are impacted by the timing of neutering. There is evidence to suggest that neutering before a dog is fully grown can increase the risk of developmental joint diseases (like hip dysplasia and cruciate disease) and some types of bone cancer. This is of particular concern in large and giant breeds. In addition, there is evidence that in some breeds, neutering can increase the risk of other tumours; and a castrated dog seems to be at higher risk of prostate cancer.
I’ve heard neutering will make my dog fat – is this true?
As discussed above, the reduction in energy demand from the reproductive organs after any kind of neutering means that if your dog is fed the same as they were before neutering after their surgery, then yes, they will put on weight. It is not uncommon in practice to see a dog a few months after neutering and find they have gained a few kilos.
However… this does not have to be the case! We are in control of what our dogs eat, and whatever diet you are choosing to use, you can always feed less of it after neutering. In practice I usually recommend a reduction of 10-20% of daily ration from the day of neutering, followed by regular weight checks in the 6 months afterwards. If your dog becomes underweight, you can always increase the amount up again, and this is far easier than having to put them on a diet once the weight is there.
One particular aspect to be aware of with weight gain is that we know some breeds are genetically more likely to put on weight. These include:
- Labrador retrievers
- Golden retrievers
- Beagles
- Pugs
- Bichon Frises
If this is your dog, take extra care after any neutering procedure!
Does age of neutering affect the risk of my dog gaining weight?
When exactly is the right time to neuter? This is something vets are continually researching, and the evidence is evolving all the time. Because of this, we have a large volume of data that can be analysed to help us find the best answer for now.
A recent paper published in the Journal of American Veterinary Medicine looked at rates of obesity in over 155,000 dogs neutered between 2013 and 2019. By looking at the five most common large breeds and the ten most common small breeds, they were able to compare rates of obesity with how old these dogs were at neutering.
Their results showed:
- Before neutering, there were already substantial differences in rates of obesity between the 15 breeds
- For small breeds, neutering before puberty were associated with similar rates of obesity than if the dog was neutered when they were fully grown, and this was similar for all 10 breeds
- For large breeds, these results varied significantly by breed. Being neutered before puberty or when significantly older increased the risk of obesity, but young adulthood showed the lowest hazard ratios for obesity.
The authors of the study concluded that the risks of neutering timing and obesity are not consistent across breeds, and the complexity of this situation means that all dogs should be considered on a case-by-case basis.
So when should I be neutering my dog?
The short answer is…ask your vet!
Do you need or want to neuter your individual dog? What are the most concerning risks to you, and do they match what your vet thinks? What breed is your dog and how will this affect your decision?
Summary
Neutering is a common place practice in the UK for control of population and disease in dogs, but as with all procedures, comes with some risks as well as benefits. A common effect of neutering (without proper diet adjustment) is obesity, but the likelihood of this is affected by your dog’s breed as much as timing of neutering. Speak to your vet to find the best way forward for your individual dog.
References
Neutering of Dogs, Cats, Rabbits and Ferrets | BSAVA
When To Neuter Your Dog | Neutering Advice & FAQs | Dogs Trust
Does neutering dogs cause cancer?
WSAVA issues new guidelines on neutering – recommends against routine neutering of all dogs
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