Surgical sterilization of your pet can dramatically improve its quality of life and prevent some frustrations for you. For males, sterilization is called castration or to "neuter." For a female, sterilization is called ovariohysterectomy or to "spay." Spayed females and neutered males cannot reproduce.
When to spay or neuter your pet? We recommend that you spay or neuter your cats at around 6-months-of-age. By that time their organs are reaching maturity, but they will typically not have started the negative behaviors such as wandering in search of females and inappropriate urination. Cats will start breeding between 6-9 months of age if they are not spayed or neutered. Female dogs may be spayed at 6-months, or may be allowed to have one heat. There is some evidence that letting them to have one heat allows the urinary tract to mature and helps reduce the chance of urinary incontinence later in life. If you plan to spay your bitch, only allow one heat cycle, though, as allowing her to have more heats increases her chance of developing breast cancer later in life. For male dogs, as long as it is manageable in your family, we recommend waiting until they are over one year to neuter. Neutering male dogs at a young age increases their chance of developing orthopedic problems like ruptured cruciate ligaments later in life. However, neutering as a young age also decreases their chances of developing prostate and testicular cancer, so it is best to consult with your veterinarian regarding what is best for your dog and your family.
Breast cancer is common in female dogs that are either not spayed or were spayed after 2 years of age. In dogs, the size of malignant mammary tumors is important. The smaller the mass is at the time of surgery (3–5cm or smaller) the less likely it will recur, or metastasize (spread) elsewhere. Dogs can live several years after complete removal of some malignant mammary tumors. So once a mass is found, having surgery to remove it earlier is better. Small mammary tumors often feel like a BB under the skin beneath the belly. We recommend spaying at the time of mammary tumor removal because recent studies have shown a beneficial effect in dogs with mammary tumors.