Animals who have been sterilized get fat and lazy. Sterilizing an animal does decrease his or her metabolic rate. After spaying or neutering an adult animal, feed a diet appropriate to his or her life cycle. Males don't need to be neutered because they aren't the ones having the litters. One un-neutered male can impregnate hundreds of female animals in the time it takes one litter of kittens or puppies to be born.
Studies show that the majority of dog bites are made by intact, untrained male dogs.
Females need to have one litter before being spayed. There is no medical support for this. Every responsible home found means one less home available to the many shelter animals hoping for adoption. Each day animal shelters are forced to kill thousands of dogs and cats for lack of responsible homes. Spay and neuter surgical procedures are done under general anesthesia.