Like flathood, I suspect doggie cancer is related to what they get fed. I suspect that the best food for dogs (and cats) is meat. Duh! They're carnivores! The dog food industry I suspect is like the vitamin industry, foisting untested crap on unsuspecting consumers. I feed my Jack Russell some dry dog food but mostly meat. I buy a ham or turkey when it is on sale, freeze it in week-size portions. A ham on sale may be cheaper than dog food. Also feed him chicken livers, raw hamburger, etc.
At one time I thought no sane human would have a dog, and had a list of reasons as long as my arm why no logical person would want one. My wife came home with this two month-old Jack and dropped him in my arms. All my reasons for not wanting a dog went out the window. Now, he's MY dog. The scary thing is, if I was that wrong about something like a dog, what else am I wrong about?
