The following statement is a MYTH:
By products are low quality ingredients.
A by product is a secondary product produced in addition to the main product. AAFCO (the Association of American Feed Control Officials) defines meat by products as "the non-rendered, clean parts, other than meat, derived from slaughtered mammals. It includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low temperature fatty tissue, stomachs, and intestines freed of their contents.
It does not include hair, horns, teeth, and hoofs." These products may be considered delicacies by certain cultures (especially Tripe and chicken feet). These products provide excellent sources of iron, vitamins A, B12, E, K, riboflavin, biotin, and folic acid. A dog or cat that ate only skeletal muscle would develop a nutritional deficiency.