What is the right timing for spaying and neutering of pets?

Bulldog puppy headshot

For most pet owners in the United States, spaying and neutering dogs and cats is an important way to benefit animals, their households and society.

Black and brown cat headshotWhy should you spay or neuter pets?

For female pets, spaying provides important health benefits, while castrating male pets can help reduce their anxiety and aggression. For pet owners, it’s helpful to eliminate the dilemma of unwanted litters. Society benefits from decreased pet overpopulation and the public-health problems that arise with feral animals; society further benefits as we limit the number of animal-control, shelter and euthanasia programs needed for unwanted, neglected, stray and feral pets.

In fact, spaying and neutering has so many advantages that veterinarians at Colorado State University consider sterilization surgery a cornerstone of preventive care for pets.

At what age should pets be spayed or neutered?

Recently, veterinarians have discussed the age at which pets should be spayed and neutered. Many interesting studies – especially so-called “lifetime studies” that follow pets through their lives – seek to answer this question. So far, there’s no definitive answer; timing for spay and neuter surgeries should take into account research-based information and the needs of an individual pet and its owner.

The most recent research has shown that spaying and neutering pets as puppies and kittens can affect their growth. Early spaying and neutering increases the length of time that the bones grow, which results in a taller pet. The concern is that increased growth may affect how joints align. Therefore, spaying and neutering early may not be in a pet’s best interest, especially if the animal is prone to breed-related orthopedic problems.

Unfortunately, we don’t yet know the age at which this growth effect ceases. So many orthopedic surgeons recommend waiting until skeletal maturity to spay and neuter pets, especially those predisposed to orthopedic disease, such as large dog breeds.

That seems easy enough: Let’s wait until skeletal maturity to spay and neuter our pets, right? Well, it’s not that simple.

An important health benefit of spaying female pets is reduction in the incidence of mammary cancer. If we spay a female dog before her first estrus, or “heat,” we essentially eliminate her chances of developing mammary cancer. This benefit holds true for any female dog spayed before the age of 2, yet incidence of mammary cancer increases with each estrus period.

As we wait for a dog to reach skeletal maturity, she may go through her first estrus cycle. Then her risk for mammary cancer rises, and she must be kept away from intact male dogs so she isn’t accidentally bred. Waiting to spay also means the hassle of cleaning up after a dog in heat.

Spaying and neutering mature pets can pose increased risk of surgical complications. And in older males, the hormone testosterone may lead to unwanted behaviors.

Bulldog puppy headshotWhat to ask your veterinarian?

When making the decision about the timing of spay and neuter procedures, it is best to consult your veterinarian and to discuss your circumstances and your individual pet. Here are some topics to cover with your vet during the decision-making process:

  • What are the risks of orthopedic disease and other health problems for your pet, and how might these be influenced by the timing of spay or neuter?
  • Are you willing and able to manage the hassles that come with a cycling female pet or an intact male? This includes, for females in heat, limiting interaction with other animals in order to avoid unwanted litters.
  • Is your pet fully vaccinated? We prefer to wait at least two weeks after the pet’s last vaccine.
  • Can the operation be performed laparoscopically? Minimally invasive sterilization is an option at some veterinary practices, and at the CSU Veterinary Teaching Hospital.

Talking through the pros and cons of timing for spay and neuter will help you arrive at a decision that’s best for you and your pet.

Dr. Heather Weir is a veterinarian with the Community Practice service at Colorado State University’s James L. Voss Veterinary Teaching Hospital. Community Practice provides general care, wellness services, and treatment of minor injuries and illnesses for pets. This Pet Health column is the fourth in a series, called Cornerstones of Preventive Care. Earlier columns addressed pet vaccinations, health insurance and exercise. Find them here.