The Use of Drugs in Food Animal Species

Christie Balcomb, BVSc, DACVIM
YourVet Maui
1476 S. Kihei Rd, Kihei, HI 96753
(808) 879-5777

The use of medications in food-producing animals can have some challenges, as current demographics seem to be shifting for more people to have livestock as pets and other food-producing animals that are treated more as companion animals than in the past. Livestock are being kept as pets in more urban settings and will likely be seen by veterinarians that treat solely companion animals. Some owners are more willing to pursue medical and surgical treatment for these animals such as backyard chickens or pet goats. However, the Federal Drug Administration (FDA) designates “food animals” as any species that are raised and used for food production or consumption by humans. The species considered to be Major food animal species include: Cattle, Swine, Chickens and Turkeys. Minor species include sheep, goats, camelids, aquaculture species and honeybees, and rabbits. There are several important regulatory distinctions made between Major and Minor food animal species.

“Food-producing animals” are animal species or classes that are used to create a food or food by-product that does not require slaughter, such as milk (also used to make cheese and butter), eggs and honey.1

It is important to note that the FDA does not recognize the owner’s intended purpose of the animal, such as companion miniature pigs versus commercial pig breeds, and all fall under the classification as a Major food animal species. So, even if the animal is considered by the owner as a pet, rather than a production animal, the government regulations and restrictions still apply. Unfortunately, veterinarians cannot always guarantee the outcome and disposition of an animal for the rest of its life.

Extralabel drug use (ELDU) is allowed under the American Medicinal Drug Use Clarification Act (AMDUCA) of 1994, as long as certain requirements are met, including the existence of a valid Veterinary Client Patient Relationship (VCPR). 2-4

Extralabel use is defined as the use or intended use of a drug that is not in accordance with the approved labeling in regards to:

  1. Species
  2. Indication
  3. Dose rate
  4. Dose frequency
  5. Route of administration

For ELDU in Food Animal Species, the following requirements must be met:

  1. There is no approved animal drug labeled for use for that species, indication, dose rate and concentration. [An approved human drug must not be used in extralabel fashion if an approved animal drug exists that can be used in an extralabel fashion]
  2. There must be a diagnosis based on evaluation of the condition suspected
  3. Establish an appropriately extended withdrawal time prior to sale or consumption of milk, eggs, meat or edible products
  4. Maintain records to identify the treated individual
  5. Take precautions to ensure that the established extended withdrawal times are met to prevent any violative residues are found in products to enter the food chain

As clinicians, we are often faced with challenges, as many of the species that we treat are not listed on the label of many veterinary medications, and thus we need to use drugs in an extralabel fashion.  As such, we are also very dependent on scientific data and utilizing the Food Animal Residue Avoidance Database (FARAD) is an essential tool to ensure that we are following the appropriate requirements of ELDU as defined by AMDUCA.

FARAD is a USDA-funded university-based consortium that is overseen and operated by faculty and staff within the Colleges of Veterinary Medicine at the University of California-Davis, the University of Florida, Kansas State University, North Carolina State University and Virginia-Maryland College of Veterinary Medicine. FARAD is a great resource for veterinary practitioners to provide guidance and advice to avoid violative residues in animal products intended for human consumption. The program provides a hotline for requests, as well as online submission of withdrawal times, and a wealth of information on the use of medications in both major and minor use species.  It is highly recommended for any extralabel drug use in a food animal or food-producing animal species to submit a request for appropriate withdrawals to avoid violative residues. For example, the labeled dose rate of procaine penicillin is considered now to be subtherapeutic, and thus it is common for clinicians to use much higher dose rates or frequency of administration, and thus the withdrawal times can extremely prolonged compared to what is listed on the label.5 Current updates on prohibited and restricted drugs used in food animals can be found on their website:

The purpose behind many of the major and minor designations and regulations is to protect public health and food safety. Drugs and drug classes that have been prohibited for use in these species have been found to cause potential disease or harm to humans through exposure, or do not have an acceptable analytical method established. Other restricted drugs include classes of antimicrobials that are considered important for human health, and extralabel use of these medications may put the public at risk if antimicrobial resistance develops. In the next few years, it is likely that these regulations will grow to include other antimicrobial classes, or restrict their use further in an attempt to slow the tide of antimicrobial resistance in bacteria.

Violations of these regulations could end up with a consequence of drug residues in food products, which may have health implications for the humans consuming these products. Any products sold to the product could be considered a liability issue due to sale of an adulterated product into the human food chain.6 For those food animals considered as pets, administration of a prohibited antimicrobial may result in transmission of bacteria with resistance to that microbial to the rest of the flock or to the owners, themselves. Other options of antimicrobials with similar spectrum of activity may be available to use in ELDU, rather than these prohibited drugs.

In conclusion, as veterinarians that may practice on both companion and production animals, it can be challenging to adhere to FDA regulations for certain medications, such as the prohibition of any ELDU of fluoroquinolone antibiotics in any food animal species. It can also be uncomfortable to mention the term “food animal” species to a client who has a sanctuary for farm animals that will not be entering the food chain, and some clients may be offended. However, as part of the ELDU requirements, keeping records with some acknowledgement of withdrawal times for food products must be written. It may be more palatable to clients if there is a written statement about the FDA requirements based on species, but understanding that this animal is considered a pet. Finally, FARAD can be an extremely useful resource in case of determining withdrawal periods in case of historical administration, or pre-emptive research to provide the best estimate based on scientific literature. The FARAD digest publications have useful summaries of ELDU in backyard poultry, small ruminants and other species.6-10 FARAD is not a regulatory or governing body, but a program to help support veterinarians maintain public health and food safety.

FARAD Contact Info
Hotline: 1-888-873-2723

Please also feel free to contact Extension Veterinarian Jenee Odani to discuss any issues: or (808) 956-3847.

Drug or drug class Special considerations
Antiviral drugs – adamantane and neuraminidase inhibitors Prohibited ELDU in all poultry
Cephalosporins Except for cephapirin, any ELDU in MAJOR species (cattle, swine, chickens, turkeys) is prohibited. ELDU in MINOR use species is permitted.
Chloramphenicol Any use is prohibited in food animals
Clenbuterol Any use is prohibited in food animals
Diethylsilbesterol (DES) Any use is prohibited in food animals
Fluoroquinolones ELDU is prohibited in all food animal species (MAJOR and MINOR)
Gentian Violet Any use is prohibited in food animals
Glycopeptides Any use is prohibited in food animals (e.g. vancomycin)
Indexed drugs 11 Some use permitted in MINOR species
Medicated feeds Any ELDU prohibited – Veterinary Feed Directive 2017
Nitrofurans Any use is prohibited in food animals (e.g. topical use of nitrofurazone)
Nitroimidazoles Any use is prohibited in food animals (e.g. metronidazole)
Phenylbutazone Prohibited in dairy cattle >20 months
Sulfonamides * Use in milking sheep and goats is discouraged; Prohibited in dairy cattle >20 months, except for approved labeled use
Table adapted from FARAD, updated 7/16/2018



  1. FARAD. Available at Accessed on 9/30/2018.
  2. US FDA. Animal Medicinal Drug Use and Clarification Act (AMDUCA) 1994. Available at: Accessed on 9/30/2018
  3. Extralabel drug use in animals. 21 CFR 530.
  4. AVMA. VCPR. Available at: Accessed 9/30/2018.
  5. DeDonder KD, Gehring R, Baynes RE et al. Effects of new sampling protocols on procaine penicillin G withdrawal intervals for cattle. JAVMA 2013, 243:10, 1408-1412.
  6. Marmulak T, Tell LA, Gehring R et al. Egg residue considerations during treatment of backyard poultry. JAVMA 2015, 247:12, 1388-1395
  7. Webb A, Baynes RE, Craigmill AL et al. Drugs approved for small ruminants. JAVMA 2004, 2224:4; 520-523
  8. Baynes RE, Payne M, Martin-Jimenez T et al. Extralabel use of ivermectin and moxidectin in food animals. JAVMA 2000, 217:5, 668-671
  9. Riveiere JE, Tell LA, Baynes RE et al. Guide to FARAD resources: historical and future perspectives. JAVMA 2017, 250: 10, 1131-1139
  10. Davis JL, Smith GW, Baynes RE et al. Update on drugs prohibited from extralabel use in food animals. JAVMA 2009, 235:5, 528-534
  11. US FDA. Index of legally marketed unapproved new animal drugs for minor species. Accessed 9/30/2018.