Antibiotic use in chicken production has long been a subject of scientific, regulatory, and public opinion debate. While antibiotics have historically played a significant role in maintaining flock health and improving production efficiency, concerns about antibiotic bacterial resistance and antibiotic effects on human health have prompted major shifts in poultry industry practices. Consumers today are inundated with marketing phrases like “Antibiotic Free”, “No Antibiotics Ever”, “No Use of Antibiotics for Growth Promotion”, and “No Antibiotics Important to Human Medicine”. What do all these phrases mean? Do they all mean the same thing? Do they all mean something different?
This UGA Poultry Tip is designed to help you understand the use of antibiotics in modern chicken production and what all these phrases mean when you see them in the grocery store.
Historical Background
The use of antibiotics in U.S. chicken farming dates back to the early 1950s, when the Food and Drug Administration (FDA) approved their use in poultry feed. Early research showed that chickens fed vitamin B12 derived from antibiotic fermentation byproducts grew significantly faster – up to 50% more – than those fed vitamin B12 from other sources. This discovery led to widespread adoption of antibiotics, not only for disease prevention, but for growth promotion as well.
Why Antibiotics Are Used in Poultry
Antibiotics in chicken production have traditionally served 2 purposes since the 1950s:
- Disease Treatment – Just as in human medicine, antibiotics are used to treat bacterial infections in chickens. Veterinarians prescribe these medications when birds become ill, ensuring positive animal welfare and preventing the spread of disease within flocks. This type of antibiotic use is known as “Therapeutic”- that is the use of antibiotics in a chicken flock once an illness is identified.
- Disease Prevention – In large-scale poultry operations, disease can spread rapidly. Historically, low-dose, wide-spectrum antibiotics are used prophylactically to prevent outbreaks before any illness is detected, especially in crowded or stressful environments. The impacts of this type of antibiotic treatment are not only reduced disease outbreaks, but also enhance growth rates and feed efficiency in chicken flocks. This type of antibiotic use is known as “Subtherapeutic”- that is the use of antibiotics in a chicken flock before any illness is identified.
Public Health Concerns
While some classes of antibiotics, such as tetracyclines, penicillins, and macrolides, are used in both human and veterinary medicine, the specific formulations, dosages, and brand names often differ. Furthermore, some antibiotics are exclusively used in either humans or animals. This “overlap” in classes of antibiotics used in human and animal medicine has led to one of the primary concerns surrounding the subtherapeutic use of antibiotics in chicken production – the potential accelerated development of antibiotic-resistant bacteria.
When antibiotics are used extensively, bacteria can evolve resistance, potentially rendering important human medicines less effective. Resistant bacteria can spread through contaminated meat products, environmental pathways (such as soil, water and farm runoff), and direct contact with animals. As awareness of these risks has grown, consumers have increasingly demanded “Antibiotic‑Free” or “No Antibiotics Ever” chicken products. However, labeling inconsistencies and limited oversight can make such claims difficult to verify.
There are 2 important notes to highlight here:
- Some research has shown that the over-prescription of Antibiotics by physicians in human medicine likely is as much or more a contributor to the development of antibiotic-resistant bacteria than agricultural animal production.
- One unfounded concerns consumers have about antibiotic use in chicken production is the possible ingestion of residual antibiotics contained in the chicken products they consume. With the exception of a few long-lasting human medicine antibiotics that require IV administration in a hospital setting, most antibiotics have a 24-hour or less “half-life”. This means they remain effective as an antibiotic for only a few days at the most. That’s why medical doctors’ instructions to you when prescribing antibiotics is always “take ALL of this antibiotic, even if you start feeling better”. Any antibiotic utilized in poultry production include a specific time to end antibiotic administration to ensure each chicken’s system is free of any antibiotic at time of processing.
What Do All These Label Mean?
- “NO Antibiotics Ever (NAE)” – When a package of chicken uses this phrase it means the chicken was never given ANY antibiotics at any point in their lives – not in the egg, not as chicks, and not as grown birds. This includes both therapeutic and subtherapeutic antibiotics. The chickens are instead raised with alternative health practices, such as probiotics, herbal supplements, or enhanced hygiene programs. Regardless of these alternative interventions, the withholding of antibiotic treatments may increase early mortality. While reducing unnecessary antibiotic use is beneficial, the absence of antibiotics in NAE chicken production does not automatically guarantee superior animal welfare or food safety. In fact, sick animals in “NO Antibiotics Ever” systems may suffer from bacterial infections if treatment is withheld to maintain label claims.
- “No Use of Antibiotics for Growth Promotion” – When a package of chicken uses this phrase it means the chicken was never given any subtherapeutic antibiotics, BUT therapeutic antibiotics might have been administered to the chicken if a bacterial infection was diagnosed during production.
- “No Antibiotics Important to Human Medicine” – When a package of chicken uses this phrase it means the chicken might have been administered antibiotics labeled for “Animal-Use Only”.
- “Raised Without Antibiotics” – When a package of chicken uses this phrase it means the chicken was never given ANY antibiotics once hatched from its egg. It is up to the consumer to investigate if pre-hatch antibiotics were utilized in the poultry hatchery. Some companies that used this phrase in the past have shifted to “NAE” to clarify their stance on antibiotic use in their chicken production.
- “Antibiotic Free” – When a package of chicken uses this phrase it becomes the consumers responsibility to investigate exactly what the poultry company that produced the product means by “Antibiotic-Free”. Are they saying they are “NAE”? Are they saying they utilized Antibiotics during production, but verify that the chicken was “Antibiotic-Free” at the point of processing?
Antibiotic use in chicken production is a complex issue involving animal welfare, food safety, public health, and consumer expectations. While antibiotics have historically contributed to efficient chicken production, concerns about historical antibiotic use in growth promotion and potential antibiotic-resistance have driven changes in U.S. poultry industry practices. As the industry stands now, consumer awareness, education, and further investigation is often needed if the consumer what to be assured of the role antibiotics play in the production of the chicken product they purchase.
References
Centers for Disease Control and Prevention. (2023). Antibiotic use in food-producing animals. https://www.cdc.gov/antibiotic-use/food (cdc.gov)
Food and Drug Administration. (2017). Summary report on antimicrobials sold or distributed for use in food‑producing animals. U.S. Department of Health and Human Services. https://www.fda.gov/animal-veterinary (fda.gov)
Food and Drug Administration. (2021). Veterinary feed directive. https://www.fda.gov/animal-veterinary/development-approval-process/veterinary-feed-directive-vfd (fda.gov)
National Chicken Council. (2024). Antibiotics in chicken production. https://www.nationalchickencouncil.org
U.S. Poultry & Egg Association. (2024). Antibiotic stewardship in U.S. poultry production: 2013–2024 report. https://www.uspoultry.org
World Health Organization. (2017). Stop using antibiotics in healthy animals to prevent the spread of antibiotic resistance. https://www.who.int/news-room
World Organization for Animal Health. (2022). Responsible and prudent use of antimicrobials in animals. https://www.woah.org