The ten worst excuses not to alter or neuter a pet are:

Simply one litter and then we'll have Downy spayed.
(Studies show that virtually the entire pet overspill stems from the "just one litter mentality.)

My dog doesn't run loose, so he doesn't need to be fixed.
(Murphy's Law says otherwise.)

We always find homes for the kittens.
(And that means that an equal number of kittens at the pound wish be killed.)

I want the children to witness the miracle of birth.
(Rent a video.)

My dog is so cute and unique, there should be more of her.
(The shelters and pounds are full of cute and unique dogs, most with only a few days to live.)

It's not natural.
(There hasn't been thing "natural" simply about dogs since we began to develop breeds thousands of years ago.)

I simply couldn't look my dog in the eye if I had him castrated.
(Watch it, you're anthropomorphiizing.)

A female dog or cat should have at least one litter for health reasons.
(Medically, factually and ethicaly indefensible.)

Fixing my dog wish do him fat and lazy.
(Too more food and not enough exercise do a dog fat and lazy.)

Fixing my pet wish change its personality.
(The main influences on an animal's personality are the kindness and care with which it is raised.)