According to the Humane Society of the United States, several million kittens and cats are turned in to shelters every year because of overpopulation. As a responsible pet owner, the question of whether to spay or neuter your kitten should be considered very seriously. Most veterinarians agree that spaying or neutering kittens makes them better pets (friendlier and gentler), easier to live with (no mating urges), less susceptible to certain infections and tumors (for females), and less prone to fighting and serious injury (for males - less territorial).
Spaying is the surgical removal of the female cat's ovaries and uterus. It is usually done after she is 6 months old or between heats or litters of kittens, although some veterinarians will spay a kitten even younger than 6 months.
An unspayed, non-pregnant cat is frequently in heat. Spaying stops the howling, rolling, roaming, and pacing associated with mating behavior. Early spaying also eliminates pyometra, a severe uterine infection, and may reduce your cat's risk of mammary (breast) cancer.
Neutering a male cat (castration) is the surgical removal of his testicles. It is a simple procedure usually done at about age 6 months and important to do before your cat starts spraying.
Neutering is 90% effective in eliminating roaming, howling, marking of territory, and fighting associated with mating and promotes a less aggressive, more affectionate manner. A neutered cat may have a tendency to gain weight, so exercise and attention to his diet are important. It is 100% effective in eliminating unwanted pregnancies.