Help, dogs eating dirt and much more.

I want to ask when my dogs are out side, they eat everything, from dirt, bugs, worms, caterpillars ect.. Our Heinz who is 8 years old never did this until we got his sister Ressi Cup 2 years old. I have looked it up and all I find is that they might be lacking something in there diet. We have change dog foods several times and no change. Does any body else's dog's do this? They actually have mud caked in there teeth when they come in. How do I get to to stop?


All I can add is that I have to pull half dead lizards out of Bree's mouth periodically. It disgusts me, personally, but he's a hunter after all. He hasn't gone for the dirt yet, but I never say never! Hope you get some good advice on this one.:confused: