Infectious Diseases 2024

Updated research, supported by the US Poultry & Egg Association, has been released, quantifying on-farm antibiotic use in the US poultry industry. This report includes data from 2023, expanding upon previously published peer-reviewed studies, and now encompasses antibiotic usage from 2013 to 2023 for US broiler chickens and turkeys, and from 2016 to 2023 for US layer chickens. The data for turkeys and broiler chickens covers the years 2013 to 2023, accounting for 71% and 86% of annual US production, respectively. Meanwhile, the data for layer chickens spans from 2016 to 2023, representing 46% of annual US table egg production.

BROILERS:
Hatchery Antimicrobials: The approximate percentage of broiler chicks placed that received hatchery antimicrobials decreased from 90% in 2013 to less than 1% in 2023. Hatchery gentamicin use in broiler chicks decreased approximately 71% between 2013 and 2017 and has remained minimal through 2023.
In-Feed Antimicrobials: In-feed virginiamycin use decreased approximately 97% between 2013 and 2023. In-feed tetracycline use decreased approximately 96% between 2013 and 2017 and has not been used since 2020.
Water-Soluble Antimicrobials: Medically important water-soluble antibiotic use in broiler chickens decreased substantially 2013-2020 but has increased for some antibiotics from 2020-2023. Water-soluble penicillin use decreased 64% from 2013-2019 but has increased 60% from 2019-2023 due to increases in gangrenous (clostridial) dermatitis incidence. Water-soluble tetracycline use decreased by more than 87% since 2013. Water-soluble lincomycin use decreased 66% from 2013-2020 but has increased 11% from 2020-2023 due to increases in gangrenous (clostridial) dermatitis incidence. Water-soluble sulfonamide use decreased by 82% since 2013. There was a shift to greater use of antimicrobial drugs that are not medically-important: In-feed and water-soluble bacitracin remained a commonly-used antimicrobial drug for the prevention and treatment of necrotic enteritis.
In-feed avilamycin use increased, as it is a not medically important antimicrobial drug for the prevention of necrotic enteritis. There were substantial reductions in the use of most medically important antimicrobials in broiler production, regardless of route of administration.
TURKEYS:
Turkey companies participated voluntarily and represented a large percentage of the overall U.S. turkey production.
Hatchery Antimicrobials: The approximate percentage of turkey poults placed that received hatchery antimicrobials decreased from 97% in 2013 to 40% in 2023. Hatchery gentamicin use in turkey poults decreased almost 48% between 2013 and 2023.
In-Feed Antimicrobials: In-feed tetracycline use decreased more than 58% between 2013 and 2023. Some approved uses of in-feed antimicrobial drugs were discontinued with implementation of GFI #213. There are no remaining approved uses of virginiamycin or in-feed tylosin in turkeys, and thus use of both of these antimicrobial drugs in-feed went to zero in 2017.
Water-Soluble Antimicrobials: Medically important water-soluble antibiotic use in turkeys decreased substantially 2013-2019 and then stabilized or increased slightly 2019-2023. Increases were typically due to increased disease incidence, as seen in other countries as well, during the 2019-2023 period. Water-soluble penicillin use decreased by more than 52% since 2013. Water-soluble lincomycin use decreased 58% from 2013 to 2019 but has increased almost eightfold from 2019-2023 due to increases in clostridial dermatitis incidence and a shortage of penicillin. Water-soluble tetracycline use decreased 18% from 2013-2023 but increased approximately 14% from 2019-2023, largely due to increases in colibacillosis. Water-soluble neomycin use decreased by more than 53% since 2013. 
There were substantial reductions in the use of most medically important antimicrobials in turkey production, regardless of route of administration.
LAYER CHICKENS:
The antimicrobial use datasets represent approximately 46% of eggs produced annually based on USDA: National Agricultural Statistics Service published numbers.
Hatchery Antimicrobials: All chicks in the dataset received gentamicin in the hatchery (day 1 of age). 
In-Feed Antimicrobials: Most antimicrobial use in layers is via the feed. The only medically important antibiotic used in layer hens for treatment and control of disease in this dataset was chlortetracycline (CTC), used in part because it has a zero-day withdrawal, meaning that there is no loss of eggs during the treatment period. CTC was only administered via the feed of pullets and hens. The majority (>95%) of CTC was used in the laying hens for treatment of disease. Less than 0.2% of total hen-days were exposed to CTC. Bacitracin, a not medically important antimicrobial, was used in both pullets and layers for treatment of necrotic enteritis. Monensin and salinomycin are the only ionophores approved for use in egg production and only for the pullet phase of production. 
Water-Soluble Antimicrobials: Almost no water-soluble antimicrobials were used during this six-year period, with only two pullet flocks in the dataset being treated with lincomycin. Antimicrobial use in U.S. egg production is minimal: There are no approved water-soluble antimicrobials for use in U.S. layers that have a zero-day withdrawal.