Mixing cheap dog food with the good stuff

Ok, I figure my family has been cutting corners to get by and we have reduced our food budget by cooking a turkey on Sunday and then having various leftovers from it throughout the week. Turkey casserole, hot turkey sandwiches, turkey soup.... So, when I saw a huge, inexpensive bag of dog food at Menards, I bought it and we mixed it with the good Iams stuff. Our two chocolate labs haven't complained, and I figure it has saved us $40 a month.