Spaying is the surgical removal of the female reproductive organs - the ovaries and uterus - from dogs and cats. The male equivalent is called castration, which is the surgical removal of the testicles. Collectively, spaying and castration are often referred to as sterilisation, neutering, fixing or dressing. But why do we do it?

Humane Dog Population Management

The primary reason for neutering animals is to prevent reproduction, which is an essential component of any humane dog population management programme. Many countries around the world have free-roaming dog populations, which if left uncontrolled can have a significant negative impact on public health, local wildlife and the health and welfare of the dogs themselves.

Historically, several countries have used culling of dogs in their attempts to control free-roaming dog populations. This inhumane practice may appear to be effective in the short term, as it immediately reduces the number of dogs on the streets. However, culling only has a temporary effect on population numbers, because it does not address the production of new puppies. The adult dogs that are missed by the culls will continue to reproduce (at a faster rate than they did previously because they now have access to more space and food) and the population will grow again. Since it is easier to catch the friendlier dogs, it also tends to be the more aggressive or feral dogs which are missed, meaning that the replenishing population will typically be more aggressive overall than the original population.

Neutering has been proven to be a much more humane and effective method of controlling free-roaming dog populations. In a neutering programme, dogs are caught, surgically sterilised and then returned to their original environment. This causes the population to naturally stabilise and then gradually decline over time, simply because fewer puppies are being born each breeding season.

Other Benefits

As well as the main purpose of controlling population numbers, there are some additional benefits to neutering free-roaming dogs.

  • Catching dogs to neuter them gives the opportunity for them to be vaccinated, which leads to a healthier dog population and improves welfare. It also reduces the spread of serious diseases which are a public health risk, such as rabies.
  • The general health and welfare of female dogs improves greatly after being spayed, as pregnancy and nursing of multiple litters in her lifetime takes a huge toll on the body.
  • There is an overall increase in welfare of all the dogs in a controlled population due to there being less competition for resources such as food, water and shelter. This also reduces the incidence of dog fight injuries.
  • Because neutered dogs don’t have the urge to mate, sterilisation curbs the spread of Transmissible Venereal Tumour (TVT), a malignant cancer found in free-roaming dog populations worldwide which is sexually transmitted between dogs.


The principles and benefits of neutering as a humane population control method also applies to feral cat colonies.

Responsible Pet Ownership

It’s not just free-roaming animals that benefit from neutering, there are many advantages for pet dogs and cats and their owners, too.

  • Neutering completely eliminates the risk of unplanned pregnancies. Whilst the thought of having a litter of puppies or kittens around is very tempting for many pet owners, they are extremely hard work! It’s a huge responsibility to find them all suitable homes, and it can be very costly to get them wormed, vaccinated and microchipped before being rehomed.
  • Spayed females no longer have heat cycles, so won’t have any of the associated behaviour changes such as irritability (dogs) or extreme vocalisation (cats).
  • Neutering has many health benefits, particularly for female dogs. Pyometra is a life-threatening womb infection which affects approximately 1 in 4 entire female dogs. The most effective treatment for pyometra, and the only treatment option in most cases, is spaying. However, although the surgical procedure itself is identical to a routine spay, the risks are much greater in a pyometra spay, as the dog is systemically unwell rather than fit and healthy. Although this condition is less common in cats, they can develop pyometra too.
  • Up to 75% of entire female dogs may experience one or more false pregnancies in her lifetime. This is a condition which develops after a heat cycle in which the female feels and acts as though she were pregnant. It can be distressing for both the dog and her owner, and dogs which have repeated false pregnancies are at higher risk of developing pyometra.
  • Male dogs and cats which have been castrated are usually less likely to show territorial aggression and are less likely to get into fights. It also stops male cats from urine spraying.
  • Entire male dogs and cats will roam huge distances looking for females and are commonly injured on roads or in fights with other males in the process. Castration removes this urge to roam and means they’ll be happier to stay close to home.


It is important to note that, while neutering is the responsible thing to do for the vast majority of pets, there are a few specific circumstances where it may not be in an individual animal’s best interests to be spayed or castrated, for either behavioural or medical reasons. You should always discuss your pet’s individual requirements with your vet and follow their advice with regards to the best time to get your pet neutered.

IAPWA's Work

Neutering campaigns are a key component of IAPWA’s work in all three of our core projects in Borneo, Penang Island and Romania, which includes targeted catch-neuter-release programmes, neutering within sanctuaries and neutering of owned animals. However, this is just one part of a comprehensive programme which includes education, adoption and foster care initiatives, and legislative reform.

Since IAPWA was established in 2009, we have provided veterinary services to over 23,000 dogs and cats, and our aim is to reach a further 7,000 animals this year to meet our goal of 30,000 by the end of 2022.

Written by: Jo Mackenzie
IAPWA Romania Programme Manager