Dogs and cats can be spayed or neutered at around 6 months. This is thought by many vets to be the perfect time for the procedure because they are mature enough for the surgery but often haven't started inappropriate behaviors such as marking. Even if a dog is several years old, unless a medical condition prohibits them from undergoing a surgical procedure, they can still be fixed. Many people have a hard time having their animals fixed. Killing these animals is far more cruel than preventing them from having babies.
Statistics show that animals that have been fixed are likely to live longer, healthier lives.
Many forms of Cancer and other diseases are less likely in animals that have been fixed. Well, hopefully we can help. You should always consult a veterinarian on matters concerning your animal's health. Please provide the following information, being as specific as possible about your question. We'll do our best to get back to you within a couple days.