Antibiotic Resistance in Poultry: A Look Back and the Path Forward

Antibiotics have played an important role in poultry production, helping birds stay healthy and grow efficiently. Over time, however, concerns about antibiotic resistance have led to changes in how these tools are used.

Today, poultry producers face a new landscape that’s shaped by stricter regulations, changing consumer expectations and the need for effective alternatives. As the industry adapts, there’s a stronger focus on understanding the science of resistance and finding new ways to support bird health through nutrition, management and gut health technologies.

This blog takes a closer look at where antibiotic use in poultry began, why it’s changing and how producers can move forward with confidence.

Where Antibiotics Started in Poultry Production

The use of antibiotics in poultry began in 1946 with an unexpected discovery. Researchers found that leghorn chicks fed a byproduct of vitamin B12 fermentation grew significantly faster than expected. The growth was not due to the vitamin itself, but rather to trace levels of antibiotics present in the residue.(1)

This discovery sparked widespread use of antibiotics as growth promoters. By 1951, the FDA had approved several antibiotics for use in poultry species. That same year, researchers also reported the first known instance of antibiotic resistance in food animals.(2) Although concerns about resistance were limited at the time, they began to grow steadily over the following decades.

Regulatory Changes Aim to Slow Resistance

Today, antibiotic resistance is a major concern for both animal and human health. In 2019, nearly 5 million human deaths globally were associated with antimicrobial-resistant infections.(10)

Public health agencies began raising concerns about antibiotic resistance in the late

1960s. Over time, research has shown that the use of medically important antibiotics in livestock, including poultry, can contribute to the development of antibiotic-resistant bacteria. These are antibiotics that are also used to treat infections in humans.

When bacteria in animals are exposed to antibiotics, some may survive due to genetic mutations or resistance traits. These resistant bacteria can multiply and spread, and in some cases, they can be transferred to humans through food, direct animal contact or the environment. Once in the human population, these resistant bacteria may cause infections that are more difficult to treat because the antibiotics that usually work against those bacteria are no longer effective.

To address this concern, the FDA introduced a series of policies to promote responsible antibiotic use in livestock. In 2017, the agency began requiring veterinary prescriptions for antibiotics considered important to human medicine that had previously been available over the counter. These rules applied to antimicrobial drugs used in poultry feed and water.

In 2023, the FDA expanded these requirements to include all medically important antimicrobials, regardless of how they were accessed.(3) You can view the complete list of medically important antimicrobials on the FDA’s website.

These regulations aim to support antibiotic stewardship by reducing unnecessary antibiotic exposure and ensuring that critical medications remain effective for treating infections in both animals and people. Requiring veterinary oversight helps ensure that antibiotics are used only when medically appropriate and not as a routine practice.

Consumers Push for Antibiotic-Free Labels

While regulatory oversight has increased, consumer attitudes have also played a role in changing poultry practices. Over the last decade, shoppers have shown more interest in how their food is raised, including the use of antibiotics in livestock. This has led to the rise of production systems labeled "Antibiotic-Free" or (ABF) which is now widely recognized in the market. (4,5)

Although these systems align with consumer expectations, they also require poultry producers to rely more heavily on tools that support bird health through management, nutrition and environment. This has increased interest in the role of the gut microbiome and how it can be supported naturally.

The Role Antibiotics Played in Poultry

In poultry production, antibiotics have traditionally been used in two ways. Therapeutic antibiotics are administered when birds are sick and need treatment. Subtherapeutic antibiotics are used in small, consistent amounts in feed or water to prevent disease and improve growth and feed efficiency.(4)

Research has shown that subtherapeutic use could improve growth by 4-8% and increase feed utilization by 2-5%.(6) Scientists have proposed several reasons for these improvements. These include reduced bacterial interference with nutrients, better intestinal absorption of nutrients, reduced toxin production and fewer subclinical infections that may otherwise go unnoticed.(6)

Common Approaches That Support Gut Health

Today, poultry producers have a variety of tools that are both natural and synthetic to support bird health and performance. These approaches often focus on improving digestion and strengthening the intestinal environment. Some commonly used ingredients and technologies include:

Probiotics
Prebiotics
Essential oils
Organic acids such as formic, butyric and propionic acid
Phytogenics and phytonutrients
Enzymes that improve nutrient breakdown and absorption (7,8)

When used as part of a well-managed nutrition program, these components can help support a balanced gut and efficient digestion, which are essential to bird performance.

Going Beyond Antimicrobial Action

Antimicrobial activity is only one piece of the gut health puzzle. Many ingredients both synthetic and natural lack the ability to distinguish between beneficial and harmful bacteria. When beneficial microbes are reduced, the intestinal environment becomes more vulnerable to imbalance and disease.

One well-documented mechanism in poultry is competitive exclusion, where healthy populations of beneficial bacteria prevent harmful ones from becoming established. When the gut is well-colonized by beneficial microbes, it becomes more difficult for pathogens like Salmonella and E. coli to grow and cause disease.(10)

Understanding Ralco’s Technologies

Ralco supports poultry producers with technologies designed to promote digestive health and microbial balance.

Microfused® Essential Oil technology is a delivery method that protects and stabilizes essential oils, helping them remain active through digestion. Essential oils, such as those derived from oregano have been studied for their effects on gut microbes and antioxidant activity.(9) The Microfused process ensures consistent dispersion and bioavailability, allowing essential oils to make contact in the gut where they are needed most.

Actifibe® Prebiotic technology is an exclusive prebiotic fiber that selectively nourishes beneficial bacteria, including Lactobacillus and Bifidobacteria and promoting competitive exclusion. Unlike traditional prebiotic fibers, Actifibe is designed to avoid feeding harmful microbes and preserve beneficial bacteria, promoting a more favorable microbial environment in the gut.(11)

These technologies are intended to support gut integrity, digestion and overall bird health.

Can Essential Oils Be Used with Antibiotics?

Lastly, essential oils have been shown in some studies to work alongside antibiotics, potentially enhancing their effects and helping address bacterial populations that are more difficult to manage.(12,13) This area of research continues to grow, and it offers promising insights into how natural compounds and traditional treatments may work together in certain applications.

The ability to use multiple tools in a responsible, science-based way helps poultry producers take a more comprehensive approach to managing flock health and performance.

References

Moore, P. R. et al. (1946). Use of sulfasuxidine, streptothricin, and streptomycin in nutritional studies with the chick. CABI Digital Library. https://www.cabidigitallibrary.org/doi/full/10.5555/19461404251
Singer, R. S. et al. (2019). Antibiotic Resistance in Agricultural Animals: A Review. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC6872647
Pennsylvania State University Extension. (2023). Understanding Poultry Medication Regulations. https://extension.psu.edu/understanding-poultry-medication-regulations
Mississippi State University Extension. Antibiotic Resistance, Alternatives and the U.S. Poultry Industry. https://extension.msstate.edu/publications/antibiotic-resistance-alternatives-and-the-us-poultry-industry
U.S. Poultry & Egg Association. (2024). Antibiotic Stewardship Report. https://www.uspoultry.org/poultry-antibiotic-use-report/docs/USPOULTRY-AntibioticStewardshipReport-2024.pdf
Dibner, J. J. & Richards, J. D. (2005). Antibiotic growth promoters in agriculture: history and mode of action. Journal of Applied Microbiology. https://www.ars.usda.gov/alternativestoantibiotics/PDF/publications/12JJDibner.pdf
Gadde, U. et al. (2017). Alternatives to antibiotics for maximizing growth performance and feed efficiency in poultry. ScienceDirect. https://www.sciencedirect.com/science/article/pii/S0032579122000013
Luise, D. et al. (2021). Antimicrobial alternatives in poultry: efficacy and modes of action. MDPI Antibiotics. https://www.mdpi.com/2079-6382/10/8/1010
Park, Y. et al. (2022). Phytochemicals and their mechanisms in animal nutrition. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC9102588/
CDC. (2023). What is Antimicrobial Resistance? https://www.cdc.gov/antimicrobial-resistance/about/index.html
Merchant & Gould IP Counsel, Ralco, & Southwest Minnesota State University. (n.d.). Internal research collaboration.
School of Health Sciences, Department of Chinese Medicine, International Medical University, No. 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000 Kuala Lumpur, Malaysia https://www.sciencedirect.com/science/article/abs/pii/S0944711313000858
Langeveld WT, Veldhuizen EJ, Burt SA. Synergy between essential oil components and antibiotics: a review. Crit Rev Microbiol. 2014 Feb;40(1):76-94. doi: 10.3109/1040841X.2013.763219. Epub 2013 Feb 28. PMID: 23445470.
https://pubmed.ncbi.nlm.nih.gov/23445470/