What Does Research Say about the Best Time to Spay or Neuter Your Pet?

Spaying or neutering your pet is a responsible and beneficial decision that can improve their health and behavior, as well as prevent unwanted litters and pet overpopulation. However, the best age to spay or neuter your pet may vary depending on their breed, size, sex, and health condition.

According to the American Veterinary Medical Association, veterinarians should make an informed, case-by-case assessment of each individual patient, taking into account all the potential risks and benefits of spay/neuter. Some factors that may influence the decision include:

- The risk of mammary cancer, which is greatly reduced by spaying female cats and dogs before their first heat cycle.

- The risk of testicular cancer, which is eliminated by neutering male cats and dogs.

- The risk of joint disorders and some cancers, which may be increased by spaying or neutering large or giant breed dogs at an early age.

- The risk of unwanted behaviors, such as roaming, marking, spraying, and aggression, which may be reduced by spaying or neutering cats and dogs.

Generally speaking, small-breed dogs (under 45 pounds projected adult body weight) should be neutered at six months of age or spayed prior to the first heat (five to six months). Large-breed dogs (over 45 pounds projected adult body weight) should be neutered after growth stops, which usually is between 9 and 15 months of age. The decision on when to spay a large-breed female dog is based on many factors—your veterinarian can help narrow down the recommended window of 5 to 15 months depending on your dog’s disease risk and lifestyle.

For cats, the American Animal Hospital Association has endorsed the “Fix Felines by Five” initiative, which recommends sterilization of cats by five months of age. This recommendation prevents unwanted litters and greatly decreases mammary cancer risks in female cats as well as spraying/marking in male cats, but still allows kittens time to grow.

Spaying or neutering your pet is a safe and effective procedure that can be performed by your veterinarian at any age. However, it is advisable to consult with your veterinarian about the best time to spay or neuter your pet based on their individual needs and circumstances.