My dogs both eat the red clay around here. I am assuming based on a quick google search that the soil here has very high iron content. They were both digging into the ground and eating the dirt at agility tonight and my trainer suggested that it might be a sign that they were missing something in their diets? Would you change up their diet? I can't remember if they've always eaten the dirt but I know they have for a long time on different foods. I have pictures from a year or two ago where Mia's eaten dirt and it's all over her face. Right now they are on a mixed diet with the base kibble being Acana Regionals (rotating flavors), Stella and Chewy's raw, Ziwipeak dehydrated (training meals), and very occasionally canned food.