The risk of mammary cancer is reduced if a dog is spayed before its first heat. Also, spayed pets cannot develop pyometra, a serious uterine infection. Finally, difficult pregnancy and delivery in older or ill pets is prevented. Your pet will not gain weight if you provide a balanced diet and encourage regular exercise. Your dog does not need to have a litter to mature.
Neutering is the primary method of sterilizing male dogs and cats.
Neutering an immature dog inhibits development of mating and roaming behavior. Because these instincts are diminished, the neutered dog is usually more compatible with people and easier to train. Neutering an immature cat usually prevents development of mating behavior and the obnoxious habit of spraying urine to mark territory around the house and yard. An unneutered male dog or cat cannot control its mating instincts. Given freedom to wander, such an animal may become hurt or lost and is almost certain to be responsible for unwanted litters.