What makes the brands on this list worth avoiding is simply that they fail to provide many -if any- of those nutrients your dog needs to stay healthy, instead using a variety of low-quality ingredients and various types of filler. At best, all these ingredients do is fill up your pup with empty calories devoid of any nutritional value. At worst, they could actually make them sick. Here are the main ingredients used in cheap, low-quality dog food that make them a poor choice for your pooch. Meat By-products and 4-D Meats......