By spaying or neutering your pet, you’ll help control the pet homelessness crisis, which results in millions of healthy dogs and cats being euthanized in the United States each year simply because there aren’t enough homes to go around. There are also medical and behavioral benefits to spaying (female pets) and neutering (male pets) your animals.
Your female pet will live a longer, healthier life. Spaying helps prevent uterine infections and breast tumors, which are malignant or cancerous in about 50 percent of dogs and 90 percent of cats. Spaying your pet before her first heat offers the best protection from these diseases.
Neutering your male companion prevents testicular cancer and some prostate problems.
http://www.aspca.org/pet-care/genera...euter-your-pet