Watch what you eat The old lady put 6 cans of dog food on the supermarket conveyer belt, and began digging in her purse for her coupon. The cashier was the friendly sort, and struck up a conversation. ""So, what kind of dog do you have?"" ""Well,"" the old lady answered in a hushed tone, ""I don't really have a dog. With the price of meat these days, I've figured out that I can make some good, cheap casseroles using dog food. My husband doesn't seem to know the difference, so I'm saving a lot of…