Females should be spayed (ovaries and uterus removed) and males neutered (testicles removed) by six months of age. Spaying before maturity significantly reduces the risk of breast cancer, a common and frequently fatal disease of older female pets.
Spaying also eliminates the risk of pyometra (an infected uterus), a very serious problem in older females that requires surgery and intensive medical care. And spaying protects your female pet from having unwanted litters. Neutering males prevents testicular and prostate diseases, some hernias and certain types of aggression (which differ from protectiveness, which this surgery won't affect). Read more about neutering/spayed...