Global study finds tetracyclines most common in animal faeces

Antibiotic use in food-animal production is a major driver of antimicrobial resistance, yet global patterns of use and environmental release remain poorly characterised. There is an under-explored indicator: because antibiotics are typically incompletely metabolised and excreted in faeces, faecal residues directly reflect what was administered and what may reach the environment. A study published in the Journal of Hazardous Materials, with an issue date of 15 September 2026, made the first global analysis of that indicator.

The authors compiled 1,334 faecal residue records for 84 antibiotics from 88 studies across 28 countries. Coverage is highly uneven: 42% of studies were conducted in China and 28% in Europe, while several major meat-producing countries have no measurements. Tetracyclines showed the highest faecal residue levels globally, with median doxycycline, chlortetracycline and oxytetracycline concentrations of 382, 284 and 260 μg/kg dry weight respectively. Pigs generally showed the highest overall residues.

The most striking finding is comparative: despite lower reported veterinary use and stricter regulatory controls in Europe, European faecal residue levels did not differ significantly from those observed in China. Temporal analysis, on the other hand, revealed significant declines in residues of several tetracyclines and sulfonamides in China. For the authors, the results expose substantial limitations in current monitoring coverage and demonstrate the potential of faecal-residue surveillance to strengthen assessment of veterinary antibiotic use, environmental loading and associated resistance selection pressure.

The scale of use was estimated in 2023 in PLOS Global Public Health, with data from 42 countries combined with regression models and FAO livestock projections, calibrated to use-intensity reports from the World Organisation for Animal Health. Global antimicrobial use in food-producing animals was estimated at 99,502 tonnes in 2020, with a wide confidence interval (68,535 to 198,052), and projected to rise by 8.0% to 107,472 tonnes by 2030 on current trends. Use hotspots were overwhelmingly in Asia (67%), with under 1% in Africa. The authors call for national reporting to evaluate the effect of policies.

The fate of residues is addressed by a review published in 2022 in Frontiers in Microbiology on the impact of manure on the environmental pool of residues and resistance. Soils fertilised with manure-derived products harbour a higher and chronic abundance of resistant bacteria, multiple resistance genes and an enriched mobilome, sometimes also detected in crops grown on them. Different processing techniques vary in efficiency: composting seems to reduce or eliminate most residues, enteric bacteria and resistance genes more rapidly and effectively than lagoon storage, but there is little data from commercial farms. The review recommends stopping veterinary use of human reserve antibiotics and of unprescribed antimicrobials, and limiting use on farms.

Together, the three papers describe a measurable chain: tonnes administered, residues excreted and genes that persist in soil. The 2026 study's proposal is simple to state and hard to execute: turn faecal analysis into a routine surveillance tool, with geographic coverage that does not exist today, including in large producers in Latin America.