Under the Federal Food, Drug and Cosmetic Act (FFDCA) 201(f), a "food" is defined as articles used for food or drink for man or other animals...and articles used for components of any such articles. In part, a drug is defined in the FFDCA 201(g)(1)(B) as a substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals; and 201(g)(1)(C) an article (other than food) intended to affect the structure or function of the body of man or other animals. The word “food” in the parenthetical "other than food" has been interpreted by the courts as an article that provides taste, aroma, and/or nutritive value. Claims on animal feed labels are limited to those that can be attributed to the taste, aroma, or nutritive value of the food. Claims that indicate that a product can be used to diagnose, cure, mitigate, treat or prevent disease, or alter the structure or function of the body, in a manner or extent that exceeds its nutritive value, are not permitted on animal feed labels.
For animals, the Food and Drug Administration Center for Veterinary Medicine (CVM) regulates two classes of products: food or drugs. Depending on the intended use, an animal food supplement product is considered either a food or drug. There is no separate category for "supplements" for animals. The term "dietary supplement" is defined in the Dietary Supplement Health and Education Act (DSHEA). On April 22, 1996, CVM published a notice in the Federal Register to explain that DSHEA does not apply to animal products. CVM has objected to the use of the terminology "dietary supplement" and their respective labeling on animal products. Federal laws and regulations do not recognize a category of products for animals called dietary supplements. Depending on the stated intended use, a product is either a food or drug.
For more information on drug claims, please refer to the CVM Program Policy and Procedures Manual Guide 1240 "Regulating Animal Foods with Drug Claims". The Policy Matrix, appearing on pages 3-5 of Guide 1240.3605, provides a visual reference for explaining how CVM interprets claims on animal feed labels. Another good resource is the guidance document Structure/Function Claims Small Entity Compliance Guide.