Recent research has revealed that cats spayed before their first heat cycle have a 91% lower risk of developing mammary cancer. Cats and dogs in the United states have a far greater risk of dying from mammary gland cancer than from contracting rabies (about 1500 times greater.) The morbidity and mortality of feline mammary gland cancer are so great that it takes the lives of an estimated 75,000 cats every year.

One could argue that the standard of vet care requires practitioners to advise their clients of this at the first kitten visit. The risk of pyometra is also eliminated early in life.

Spaying/neutering generally results in the following behavioral changes: reduces roaming behaviors, aggression, territorial marking in males, howling and other heat related behaviors in females, and is therefore useful in keeping cats in their homes. Over 80% of cats relinquished to shelters or abandoned are unspayed or unneutered.

Spaying eliminates the possibility of unwanted litters; Each year millions of surplus kittens are born who may – or may not – find a permanent home. Shelters are inundated with kittens, and older cats who may have found homes are often passed over for adoption.

Cat complaint calls are at or near the top of the list of complaint calls to public health and/or animal control departments. And there are millions of feral cats, the result of people abandoning cats often due to preventable behavior problems and unwanted litters.