Neutering

All the information below has been taken from scientific studies and is up to date as of November 2020. Currently we neuter as general practice and because we as owners believe (and are told) it’s the right thing to do. This is here to give you the information you need to make the decision as to whether or not to neuter your dog. I then advise you chat this through with your veterinarian. 

The Boys 

Testicles usually descend by 12 weeks of age.  Testosterone will be present from birth and continues to increase through development. At around 10-11 months of age this is seen to be at its peak. Sperm can begin to be produced around 8 months of age with viability by about 11months. These ages are averages and can vary amongst breeds. Levels of testosterone can vary amongst dogs and also within the same dog between days.

During castration both testicles and their associated structures are removed, which greatly reduces testosterone production.  Testosterone has many functions, with one being to close growth plates. Secondary characteristics of testosterone can include widening and muscular development, leg cocking and marking, all the things that make a boy a boy as it were. They may do a lot of kick back after toileting and perform teeth chattering after smelling particular urine (often females). If a dog is neutered before 5 months, they will not develop these secondary characteristics.

Unlike popular thought, Testosterone does not cause aggression, it can aggravate aggression that is already there though. So it doesn’t turn on these pathways as such but it can increase the volume of the ones already turnt on! Internal rewards are much more reinforcing and powerful during adolescence which is why many of us will find this stage difficult. Adolescents find risky behaviours such as running up to other dogs, pushy greeting behaviours, intimidating, mounting, chasing, rough play and competing style behaviours reinforcing at this age, often resulting in success and thus a shot of testosterone. This makes your dog feel good, which encourages them to take the risk again. This behaviour then becomes addictive due to the internal feedback loop. I would be careful what you allow your adolescent dogs to practice during this phase, the good news here is this can all be managed and you can prevent your adolescent dog from taking part and thus becoming addicted to these behaviours. Just so you know what to look out for, these risk taking behaviours can begin around as young as 15-16 weeks, the age of onset of adolescence (yes they really are puppies for such a short time!). So having read this, you may be surprised to read that intact dogs are actually not necessarily more aggressive than neutered males. Several studies have actually shown that aggressive behaviour is more prevalent in neutered males. Studies have found that dogs that had less time exposed to hormones, had an increased risk for reactivity, fearfulness, excessive barking and aggression to unfamiliar people and dogs. A deficit of testosterone, whether before or after castration, may mean a dog is more prone to fear and anxiety. Dogs that are more on the timid end would not be good candidates for castration. As you see from the above, whether to neuter or not when looking at emotional aspects is rather difficult and should not be looked at as a blanket case for all. A puppy could be fearful and therefore should not be neutered, or a puppy was fearful but they learnt a successful strategy to win, gained a shot of testosterone and fear is no longer the motivating factor!

Having a one size fits all when it comes to castration is often less than ideal. What will be beneficial for one dog, may be a disaster for another.

Castration  Pros:
  • Eliminates risk of potential unwanted (and not needed!) litters
  • If a testicle is retained, it is currently more advantageous to neuter these males. Retained testicles have the ability to become cancerous and have been linked to behaviour problems 
  • They won’t develop secondary characteristics such as marking and leg cocking when castrated young, some of you may find this a benefit
  • Testosterone can increase risk taking behaviours through adolescence making them difficult to handle and train
  • Beneficial when treating unwanted behaviours that are more likely in males than in females. Urine marking, roaming away from home to track down bitches in heat, inappropriate sexual behaviour (note, humping has many other reasons, you will very rarely see it in a sexual context in puppies), and inter-male competitive behaviour is often reduced after castration.
  • Eliminates the risk of testicular cancer. Testicular cancer accounts for 16-27% of tumors of intact males, although this is rare and are treatable if they do occur
  • Reduced risk of prostate disease 
  • Reduced risk of Perianal Fistulas. Intact males over 7 years are more likely to be diagnosed than neutered males, most can respond well to treatment 
  • Most daycare and walking facilities will currently only except neutered males
Castration Cons:
  • They won’t develop secondary characteristics such as muscle development, they will often end up looking very girly or puppy like long term. 
  • Castration is often seen as an easy fix for many behaviours but please be aware that the more social experience an individual has had prior to castration, the more likely that behaviour will persist, even when castrated. So if your dog has had lots of practice at some behaviours, learning is likely to be a problem here.  Nature vs nurture! 
  • It will not simply calm your dog down since excitable and unruly behaviours are seldom influenced by testosterone 
  • Testosterone can affect learning and memory modulation. Cognitive ability has been shown to be linked with Testosterone. Intact males show slower cognitive impairment with age than neutered dogs. 
  • Testosterone can help with fear based behaviours 
  • The surgery itself poses a small risk. Little research exists on long term effects of post-surgery problems 
  • Increased risk of Prostatic neoplasia- uncommon but poor prognosis
  • Increased risk of transitional cell carcinomas of urethra and bladder – uncommon but poor prognosis
  • Increased risk of lymphoma – relatively common
  • Increased risk of mastocytoma (mast cell tumours)- relative common, 16-21% of all cutaneous tumours in dogs. Almost 10% of early neutered males will develop
  • Possibly increases risk of Osteosarcoma – uncommon and incidence varies between breeds
  • Increased risk of hemangiosarcoma – uncommon but poor prognosis
  • Increased risk of hypothyroidism – uncommon and  treatable 
  • Increased risk of diabetes- Neutered males twice as likely to be diagnosed but uncommon 
  • Increased risk of acute pancreatitis – uncommon 
  • Increased risk of cruciate ligament disease – common but varies amongst breeds 
  • Increased risk of musculoskeletal problems – removed hormonal influence on developmental skeleton can result in delayed growth plate closure and confirmation. This is higher in dogs neutered before 12 months, especially large breeds 
  • Increased risk of obesity – preventable but common 
  • Increased risk of hip dysplasia – incidence varies amongst breeds, increased risk when neutered at an early age
The Girls 

Most females will begin seasons around 6-13months of age, some can be later than this though. Most dogs have seasons twice a year, which last around 3-4 weeks. 

When coming into season a female will experience physiological and possibly behavioural changes.

There are 4 stages to Estrus cycle:
  • Proestrus – The stage you will begin to notice changes.  The vulva may be swollen, teats pronounced (these tend to remain this way once a female has had a season), vaginal discharge (blood), males are attracted at this stage but a female will not be receptive. The female may do more marking behaviours during this time on walks. They may be seen to be more reserved than normal or a little agitated or anxious. This lasts around 4-20 days with an average of 9. 
  • Estrus – The stage where the female will be receptive to the male and the fertile period occurs. The vulva will be enlarged and soft, and may have a yellowish discharge. This lasts around 5-13days 
  • Diestrus – the period after estrus or mating. This can last around 60-90 days, if pregnant around 60-64days. This is when false pregnancies can occur. 
  • Anestrus – the period of hormonal and sexual inactivity between diestrus and proestrus. Lasts around 2-4 months. 
Silent seasons  – This can happen when a female has gone through the cycle above but no characteristic signs have been noticed.

False pregnancies – During the Diestrus phase some dogs may experience a false pregnancy. This can occur even if the dog was not mated. Symptoms can mimic that of a true pregnancy and vary amongst individuals. Behavioural changes included nesting, mothering inappropriate objects (they may become protective of these), decreased interest in physical activity and restlessness. If your dog is acting a little odd postseason, it is best to get them checked by your vet. 

Spaying involves removal of particular parts of the females reproductive organs, depending on the surgery being undertaken. Many involve the removal of the ovaries and/or the womb depending on the veterinarian.

Spaying Pros:
  • Eliminates risk of potential pregnancies and risks to giving birth 
  • Seasons can last on average 3 weeks. Your dog will need to be managed outside during this time and will be unable to attend daycares, walking and some training facilities. This can be of inconvenience to some. 
  • Reduces the risk of false pregnancies and issues that come with these
  • Prevention of pyometra (as long as removal of the womb) – Incidence around 23-24% of intact females, fatalities around 4% of these 
  • Reduces the risk of malignant mammary tumours but can depend on age spayed. Mammary tumours are very common in entire females, 50% of these however are malignant. There is a 99.5% reduction in risk when spayed prior to their first season, 92% reduction in risk if spayed before their second season, 74% if spayed before the third cycle. Spaying dogs over 2.5 years or after three cycles does not reduce the risk of developing mammary cancer. There is no protective effect in having a litter. (Note- we can catch this early if you are vigilant (the same as human females))
  • Prevents Uterine neoplasia – very rare, most are benign and usually curative
  • Prevents ovarian neoplasia- very rare, 50% are malignant, survival rates are poor
  • Reduces risk of vaginal/vulvar neoplasia – uncommon and can be treated well 
  • May help reduce conflict between entire females living together. It has however been associated with increased risk of other forms of aggression with neutered females being twice as likely  to show aggression than intact females. Like boys, this is potentially seen more in females that have been spayed prior to 11 months of age and who have already shown some form of aggression. 
  • Can reduce the risk of behavioural problems which are seen only around the time of season
  • May help females from learning defensive behaviours around other dogs as a result of being pestered (if not managed) while in season
Spaying Cons: 
  • The surgery itself poses a small risk. Little research exists on long term effects of post-surgery problems 
  • Increased risk of Urinary incontinence- clinical controllable in 65-75% of cases but can be distressing 
  • Increased risk of urinary tract infections – treatable but distressing and can have behavioural consequences 
  • May increase some forms of fear shown, especially in females who are already showing signs of fearfulness. 
  • Increased risk of lymphoma – relatively common
  • Increased risk of mast cell tumours- relative common, 16-21% of all cutaneous tumours in dogs. The earlier the age of spay, the earlier the diagnosis
  • Possibly increases risk of Osteosarcoma – uncommon and incidence varies between breeds
  • increased risk of hemangiosarcoma – uncommon but poor prognosis
  • Increased risk of hypothyroidism – uncommon and  treatable 
  • Increased risk of diabetes- uncommon 
  • Increased risk of acute pancreatitis – uncommon 
  • Increased risk of cruciate ligament disease – common but varies amongst breeds 
  • Increased risk of musculoskeletal problems – removed hormonal influence on developmental skeleton can result in delayed growth plate closure and confirmation, more common when spayed early, especially in larger breeds
  • Increased risk of obesity – preventable but common. Reduces metabolic rate and increases satiety and therefore eating
  • Increased risk of hip dysplasia – incidence varies amongst breeds, increased risk when neutered at an early age, especially in larger breeds
Alternatives

It may be that hysterectomy and vasectomy could be the best of both worlds. This will allow for hormones and its effects to still be present, removing a huge portion of risk of neutering, but removes the risk of some of the more worrying risks of not neutering. This however is not common practice at present.  

My Take Home

WHAT IS IT FOR? What are you hoping to achieve by neutering your dog? 

Ensure you neuter your dog for the right reasons and not because its something you’ve been told is the good thing to do. Look at the pros and cons lists, what is more important to you as an owner and what will suit your lifestyle and your dog better. We need to be looking at effects to health, physiology, behaviour and future cognibility for our individual.

In general, it seems that neutering of male dogs is not beneficial for health reasons and the main reasons for neutering male dogs are behavioural ones. In general, if a male dog has a tendency to run off (and you’ve tried training!), appears generally over-excited and unable to concentrate, is engaging in unwanted sexual or risk taking behaviour, or creating tension in a multi dog household, there is a good chance that neutering may improve the situation. If however, you can manage these scenarios until after adolescence where testosterone appears to drop somewhat, this may be the best option. If a male dog has a tendency to be fearful of noises, people, or other dogs, neutering is likely to worsen this situation and should be avoided. Neutering should be considered in dogs that have retained testicles.

Unfortunately the story with females becomes a little more complicated due to the owners lifestyle, with the tip of the scales being more to do with convenience. It may be more advantageous to most to spay females in which I would advise is done after their first season. This reduces some of the risks associated with early spaying (mainly to do with size and development) while not completely eradicating the benefits of spaying.

I would suggest you think about the best options for yourself and your dog and chat this through with your veterinarian.