Neutering is a surgical process that removes the reproductive organs of an animal, either completely or to a large extent. Spaying is also neutering, but this term is used specifically in the context of females and female reproductive organs. Animals are often spayed or neutered for reasons beyond birth control — to lessen behavior issues, suppress aggression, and increase work capacity in work animals, like oxen or mules.
Dogs or other animals are neutered mainly by surgically removing the sexual organs (testes). This results in reduced levels of testosterone, the primary hormone responsible for regulating male sexuality. Besides being incapable of reproduction, the animal shows increased submissiveness and obedience, less aggression and a higher capacity to work.
Spaying is when the sexual organs of female animals are surgically removed. Spaying dogs often results in more attachment towards the owner, but may also mean more aggression in general. Spaying reduces the risk of ovarian cancer, but there is a slim chance of urinary incontinence.
When is the Best Time?
The video below gives detailed information on when and why animals should be spayed or neutered, and the advantages and risks that come with it.