In the United States of America, livestock feed is regulated by U.S. Food and Drug Administration. The office of Animal Food and Feed is part of the FDA Animal and Veterinary department.
U.S. Food and Drug Administration, Animal and Veterinary , Animal Food and Feed Link
FDA Animal Food and Feed Ingredients and Additives Link
FDA 101: Animal Feed Link PDF
FDA Safe Animal Feed Video Link
FDA partners with the Association of American Feed Control Officials to develop Animal Feed Regulatory Program Standards Link PDF
AAFCO (Association of American Feed Control Officials) Link
AAFCO Publication Link