Castration is the medical term for neutering an animal. This procedure consists of surgical removal of the testicles. Such surgery is performed to eliminate sexual activities and render the pet sterile. Neutering usually (but no always) reduces a pet’s tendency to roam and fight. The general level of aggression may also be reduced. However, neutering is not a replacement for obedience training by the owner. In older pets, neutering may be necessary due to diseases of the testicle or prostate gland.