{"data":{"id":"us/21-cfr-558.4","jurisdiction":"us","citation":"21 CFR 558.4","heading":"Requirement of a medicated feed mill license.","body":"(a) A feed manufacturing facility must possess a medicated feed mill license in order to manufacture a Type B or Type C medicated feed from a Category II, Type A medicated article.\n(b) The manufacture of the following types of feed are exempt from the required license, unless otherwise specified:\n(1) Type B or Type C medicated feed using Category I, Type A medicated articles or Category I, Type B or Type C medicated feeds; and\n(2) Type B or Type C medicated feed using Category II, Type B or Type C medicated feeds.\n(c) The use of Type B and Type C medicated feeds shall also conform to the conditions of use provided for in subpart B of this part.\n(d) This paragraph identifies each drug by category, the maximum level of drug in Type B medicated feeds, and the assay limits for the drug in Type A medicated articles and Type B and Type C medicated feeds, as follows:\nCategory I\nDrug Assay limits percent 1 Type A Type B maximum (200x) Assay limits percent 1 Type B/C 2\nAmprolium with Ethopabate 94-114 22.75 g/lb (5.0%) 80-120.\nAvilamycin 90-110 7.3 g/lb (1.6%) 80-110.\nBacitracin methylenedisalicylate 85-115 25.0 g/lb (5.5%) 70-130.\nBacitracin zinc 84-115 5.0 g/lb (1.1%) 70-130.\nBambermycins 90-110 800 g/ton (0.09%) 80-120/70-130.\nChlortetracycline 85-115 40.0 g/lb (8.8%) 80-115/70-130.\nCoumaphos 95-115 6.0 g/lb (1.3%) 80-120.\nDecoquinate 90-105 2.72 g/lb (0.6%) 80-120.\nDichlorvos 100-115 33.0 g/lb (7.3%) 90-120/80-130.\nDiclazuril 90-110 182 g/t (0.02%) 85-115/70-120.\nEfrotomycin 94-113 1.45 g/lb (0.32%) 80-120.\nIodinated casein 85-115 20.0 g/lb (4.4%) 75-125.\nLaidlomycin propionate potassium 90-110 1 g/lb (0.22%) 90-115/85-115.\nLasalocid 95-115 40.0 g/lb (8.8%) Type B (cattle and sheep): 80-120; Type C (all): 75-125.\nLincomycin 90-115 20.0 g/lb (4.4%) 80-130.\nLubabegron 87-107 908 g/ton 85-115/80-120.\nMelengestrol acetate 90-110 10.0 g/ton (0.0011%) 70-120.\nMonensin 85-115 40.0 g/lb (8.8%) Chickens, turkeys, and quail: 75-125; Cattle: 5-10 g/ton 80-120; Cattle: 10-30 g/ton 85-115; Goats: 20 g/ton 85-115; Liq. feed: 80-120.\nNarasin 90-110 9.0 g/lb (1.98%) 85-115/75-125.\nNicarbazin (granular) 90-110 9.0 g/lb (1.98%) 85-115/75-125.\nNarasin 90-110 9.0 g/lb (1.98%) 85-115/75-125.\nNystatin 85-125 5.0 g/lb (1.1%) 75-125.\nOxytetracycline 90-120 20.0 g/lb (4.4%) 75-125/65-135.\nPoloxalene 90-110 54.48 g/lb (12.0%) Liq. feed: 85-115.\nRactopamine 85-105 2.46 g/lb (0.54%) 80-110/75-125.\nSalinomycin 90-110 6.0 g/lb (1.3%) 80-120.\nSemduramicin (as semduramicin sodium) 90-110 2.27 g/lb (0.50%) 80-110\nSemduramicin (as semduramicin sodium biomass) 90-110 2.27 g/lb (0.50%) 80-120\nTylosin 80-120 10.0 g/lb (2.2%) 75-125.\nTylvalosin 90-110 3.86 g/lb 85-115.\nVirginiamycin 85-115 10.0 g/lb (2.2%) 70-130.\nZoalene 92-104 11.35 g/lb (2.5%) 85-115.\n1 Percent of labeled amount.\n2 Values given represent ranges for either Type B or Type C medicated feeds. For those drugs that have two range limits, the first set is for a Type B medicated feed and the second set is for a Type C medicated feed. These values (ranges) have been assigned in order to provide for the possibility of dilution of a Type B medicated feed with lower assay limits to make Type C medicated feed.\nCategory II\nDrug Assay limits percent 1 Type A Type B maximum (100x) Assay limits percent 1 Type B/C 2\nAmprolium 94-114 11.35 g/lb (2.5%) 80-120.\nApramycin 88-112 7.5 g/lb (1.65%) 80-120.\nCarbadox 90-110 2.5 g/lb (0.55%) 75-125.\nClopidol 94-106 11.4 g/lb (2.5%) 90-115/80-120.\nErythromycin 85-115 4.625 g/lb (1.02%) 75-125.\nFamphur 100-110 5.5 g/lb (1.21%) 90-115/80-120.\nFenbendazole 93-113 8.87 g/lb (1.96%) 75-125.\nFlorfenicol 90-110 9.1 g/lb (2.0%) Swine feed: 85-115 Catfish feed: 80-110. Salmonid feed: 80-110.\nHalofuginone hydrobromide 90-115 272.0 g/ton (.03%) 75-125.\nHygromycin B 90-110 1,200 g/ton (0.13%) 75-125.\nIvermectin 95-105 1,180 g/ton (0.13%) 80-110.\nMaduramicin ammonium 90-110 545 g/ton (.06%) 80-120.\nMorantel tartrate 90-110 66.0 g/lb (14.52%) 85-115.\nNeomycin 80-120 20 g/lb (4.4%) 70-125.\nOxytetracycline 80-120 20 g/lb (4.4%) 65-135.\nNeomycin sulfate 80-120 100 g/lb (22.0%) 70-125.\nNicarbazin (granular) 90-110 5.675 g/lb (1.25%) 85-115/75-125.\nNicarbazin (powder) 96-104 9.08 g/lb (2.00%) 85-115/80-120.\nNovobiocin 85-115 17.5 g/lb (3.85%) 80-120.\nPyrantel tartrate 90-110 36 g/lb (7.9%) 75-125.\nRobenidine 95-115 1.5 g/lb (0.33%) 80-120.\nSulfadimethoxine 90-110 Poultry: 5.675 g/lb Fish: 85.1 g/lb 80-115/75-125.\nOrmetoprim 90-110 Poultry: 3.405 g/lb Fish: 17.0 g/lb 80-115.\nSulfamerazine 85-115 18.6 g/lb (4.0%) 85-115.\nSulfamethazine 85-115 10.0 g/lb (2.2%) 80-120.\nChlortetracycline 85-115 10.0 g/lb (2.2%) 85-125/70-130.\nSulfamethazine 85-115 10.0 g/lb (2.2%) 80-120.\nTylosin 80-120 10.0 g/lb (2.2%) 75-125.\nSulfaquinoxaline 98-106 11.2 g/lb (2.5%) 85-115.\nTiamulin hydrogen fumarate 90-115 10 g/lb 90-115/70-130.\nTilmicosin 90-110 37.9 g/lb (8.35%) Swine Type B/C feed: 85-115. Cattle Type B feed: 85-115. Cattle Type C feed: 80-110.\nZilpaterol 90-110 680 g/t (0.075%) 80-110/75-115.\n1 Percent of labeled amount.\n2 Values given represent ranges for either Type B or Type C medicated feeds. For those drugs that have two range limit, the first set is for a Type B medicated feed and the second set is for a Type C medicated feed. These values (ranges) have been assigned in order to provide for the possibility of dilution of a Type B medicated feed with lower assay limits to make a Type C medicated feed.\n(e) When drugs from both categories are in combination, the Category II requirements will apply to the combination drug product.","path":["Title 21—Food and Drugs","CHAPTER I—FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES","SUBCHAPTER E—ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS","PART 558—NEW ANIMAL DRUGS FOR USE IN ANIMAL FEEDS","Subpart A—General Provisions"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-21.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:47Z","sha256":"edbfd82a59d940852282f153ea22bd05073c3e2f83ef259640dfe4fe8ddd3b01","source_id":"us-cfr","stale":true,"prev":"us/21-cfr-558.3","next":"us/21-cfr-558.5"},"notice":"GroundRules: Original legal text. Not legal advice."}