Preheat oven to 300F. In a large bowl, combine flours, corn meal, cracked wheat, milk, and salt. Combine yeast and water; add to dry ingredients along with stock. Beat egg and milk. Add to other ingredients. Turn mixture onto a floured surface, and knead three minutes. Dough will be very stiff. Roll out to a one-quarter inch thickness. Cut dough with cookie cutters. Bake on ungreased cookie sheets for 45 minutes. Turn off heat and dry crackers in oven overnight. Store in an airtight container labeled dog crackers.
