Longitudinal patterns of antimicrobial use across production stages in semi-intensive broiler systems in Uganda

Antimicrobial use (AMU) in poultry production contributes to selection pressure for antimicrobial resistance, yet quantitative evidence describing antimicrobial exposure under routine production conditions remains limited in many low- and middle-income countries. We conducted a longitudinal study of 32 broiler flocks from 19 semi-intensive farms in Wakiso district, Uganda, to quantify AMU patterns across production stages and identify opportunities for targeted stewardship. AMU was quantified as milligrams of active antimicrobial ingredient (AAI) per kilogram of estimated flock biomass (mg/kg), with milligrams per population correction unit (mg/PCU) and DDD_vet based treatment incidence (TI_DDDvet) per 100 bird days used as complementary metrics. AMU was recorded in 28/32 flocks (87.5%). Fourteen AAIs from seven antimicrobial classes were identified among 35 commercial antimicrobial products. Tetracyclines accounted for 43.8% of total quantified AAI mass. Fourteen of the 35 products (40%) contained multiple AAIs, and combination products accounted for 40.4% of total AAI mass. Biomass-normalised AMU varied across production stages (p < 0.001) and was highest during brooding, which also had the highest TI_DDDvet. Median cumulative flock-level AMU was 74.3 mg/kg. The highest-use quartile of flocks accounted for 53.7% of total quantified AAI mass. Biomass-normalised AMU was not associated with reported clinical signs or deaths, suggesting that AMU patterns were not explained by reported disease occurrence alone. These findings identify early production stages, frequent use of combination products and antimicrobials of particular importance to human medicine, and high-use flocks as priorities for targeted stewardship, alongside strengthened preventive flock health management.