One of the hottest topics in veterinary medicine currently revolves around the optimal time to neuter or spay a dog or cat. As a holistic veterinarian who looks at the individual circumstances and health factors when making a medical decision, this decision is no different for an animal guardian. In shelter medicine, where there are SO many unwanted and neglected pets, and where there is a severe overpopulation problem, neutering at younger ages (i.e. 6 months) is probably satisfactory. However, in recent years, there has been increasing evidence that, for the individual pet, waiting to at least sexual maturity to spay or neuter a pet may be the most health-conscious decision.
Emerging evidence and research has shown that certain types of cancers, especially bone tumors and tumors of the blood vessels known as hemangiosarcomas in large breed dogs, are more commonly seen in pets that were spayed and/or neutered too young. The incidence of prostate cancer is actually higher in the neutered male dog, which is something most veterinarians and guardians are not aware of. Some sports veterinarians are attributing spay and neuter practices to the now-epidemic levels of ruptured anterior cruciate ligament (ACL) issues of the stifle or knee joint.
It is believed that waiting until sexual maturity when the growth plates of the bones are closed is probably best for long-term bone and joint health in the later years. Hormonal diseases like hypothyroidism and Cushing’s disease have a higher incidence in neutered/spayed dogs. Even certain types of behavioral problems, including certain types of aggression, are actually increased in certain spayed/neutered pets.
It is for these reasons that I personally recommend in most cases that pets be sexually mature at 1-2 years of age, before spaying or neutering. Of course, this recommendation is based on trusting that the individual guardian will not let intact pets wander unattended, and risk contributing to the pet overpopulation problem.