Age-dependent variations in aerosol-borne particulates and microbial communities in multi-tier broiler housing systems: A metagenomics environmental health risk assessment.

By investigating the temporal dynamics of airborne microbial communities associated with particulate matter in multi‑tier broiler housing, this study offers a systematic reference for understanding how environmental microbiota shift with broiler age. Fine particulate matter (PM(2.5)) and total suspended particulate (TSP) were collected from the housing environment at three growth stages: D10 (10-day-old), D24 (24-day-old), and D38 (38-day-old). The concentration and LPS content of the collected TSP and PM(2.5) samples from each stage were measured, followed by metagenomic sequencing. Results revealed that the concentrations of TSP and PM(2.5) peaked at D24 (P < 0.05), showing a trend of first increasing and then decreasing, and the change trend of mortality in the early stage was similar. Metagenomic results identified that Faecalibacterium, Pseudomonas, and Acinetobacter were the dominant genera at D24, whereas Enterococcus and Macrococcus were the dominant genera at D10 and D38, respectively. Correlation analysis further indicated that TSP was positively associated with mortality and g_Pseudomonas, while PM(2.5) was positively associated with g_Faecalibacterium. Significant enrichment was observed in metabolic pathways such as glycosyltransferase 35 and glycoside hydrolase 23, macB, LOS(CVF494), and other antibiotic resistance and virulence genes in TSP and PM(2.5) (P < 0.05). Collectively, these findings elucidate the stage‑specific dynamics of environmental microbiota in broiler housing and underscore particulate matter as a potential driver of both microbial shifts and health outcomes, thereby providing evidence to inform interventions aimed at improving environmental and flock health.