Huage Liu

Fungal bioaerosols play a critical ecological and health role in intensive poultry production systems. However, their dynamic characteristics and community succession patterns in confined cage environments during winter remain poorly understood. This study investigated a typical confined broiler house in Hebei Province, China, during winter. A combined approach of Andersen six-stage sampling, colony counting, and Internal Transcribed Spacer (ITS) high-throughput sequencing was employed to comprehensively analyze the concentration, particle size distribution, diversity, and community composition of fungal bioaerosols across three key growth stages: 7 days (brooding phase), 21 days (growing phase), and 35 days (finishing phase). The results revealed a significant increasing trend in fungal aerosol concentration as the rearing cycle progressed, increasing from 1125 ± 125 CFU/m³ at day 7 to 3872 ± 565 CFU/m³ at day 35 (p < 0.001), reaching high-risk exposure levels in the later stages. Small-sized fungal bioaerosols (p < 0.001), demonstrating a clear community succession from early-stage yeast-dominated forms (e.g., Diutina, Blumeria) to mid- and late-stage assemblages dominated by filamentous fungi (e.g., Aspergillus, Cladosporium, Alternaria). Notably, several zoonotic pathogenic genera were detected throughout all rearing stages, highlighting the potential risks of airborne fungi to animal health, occupational exposure, and environmental safety under winter ventilation restrictions. This study characterizes a stage-dependent pattern of increasing airborne fungal concentrations accompanied by shifts in particle size distribution and community composition under winter confined conditions. The findings provide a crucial scientific basis for optimizing winter ventilation and environmental management strategies, improving environmental control technologies, establishing airborne biosafety standards, and developing targeted fungal monitoring and prevention technologies.

Bioaerosols are a major source of airborne microbial contamination in intensive poultry production systems. Their concentration and community structure can profoundly influence animal health, public health, and the overall safety of the farming environment. However, the dynamic characteristics of bacterial aerosols in enclosed poultry houses during winter remain insufficiently studied. Using Taihang chickens as a model, this study investigated three key production stages—brooding (15 days), growing (60 days), and laying (150 days)—under winter cage-rearing conditions. A six-stage Andersen sampler was employed alongside culture-dependent enumeration and 16S rRNA high-throughput sequencing to analyze variations in bacterial aerosol concentration, particle size distribution, and community succession patterns. The results revealed a significant increase in the concentration of culturable airborne bacteria with bird age, rising from 8.98 × 10³ colony-forming unit (CFU)/m³ to 2.89 × 10⁴ CFU/m³ (p < 0.001). The particle size distribution progressively shifted from larger, settleable particles (≥4.7 μm) toward smaller, respirable particles (p < 0.05), while beta diversity exhibited stage-specific clustering, reflecting clear differences in community assembly. The composition of dominant bacterial genera transitioned from potentially pathogenic taxa such as Acinetobacter and Corynebacterium during the brooding stage to a greater abundance of beneficial genera, including Bacteroides, Lactobacillus, and Ruminococcus, in later stages. This shift suggests a potential ecological link between aerosolized bacterial communities and host development, possibly related to the aerosolization of gut microbiota. Notably, several zoonotic bacterial species were detected in the poultry house air, indicating potential public health and occupational exposure risks under winter confinement conditions. This study is the first to elucidate the ecological succession patterns of airborne bacterial aerosols in Taihang chicken houses across different growth stages during winter. The findings provide a scientific basis for optimizing winter ventilation strategies, implementing stage-specific environmental controls, and reducing pathogen transmission and occupational hazards.

Fungal aerosols are critical yet understudied bioaerosol components in enclosed poultry environments, particularly during winter when ventilation is restricted. This study investigated stage-specific variations in fungal aerosol concentration, size distribution, and community composition in Taihang chicken houses across three growth stages (15, 60, and 150 days). Culturable fungal concentrations significantly increased from 3.16 × 10³ CFU/m³ to 1.24 × 10⁴ CFU/m³ with bird age (p < 0.001, ANOVA). Respirable particles (Aspergillus, Cladosporium, Cryptococcus, and Fusarium, were detected across all stages. These findings demonstrate that wintertime enclosed ventilation, while thermally beneficial, promotes the accumulation of respirable fungal aerosols and elevates occupational and environmental health risks. From a One Health perspective, stage-specific mitigation strategies—such as ventilation optimization, reduction in organic dust sources, and routine monitoring of respirable fungal fractions—are essential for reducing exposure risks in cold-season poultry production.

Airborne bacterial aerosols are a significant yet understudied component of intensive poultry farming, particularly in cold climates. This study characterized the concentration, size distribution, and community composition of airborne bacteria in closed-cage broiler houses during winter in Hebei Province, China. Air sampling was conducted at three growth stages (7, 21, and 35 days) and analyzed using culture-based methods and 16S rRNA sequencing. Culturable bacterial concentrations increased significantly with broiler age, from 1.1 × 10³ to 1.6 × 10⁴ CFU/m³. The particle size distribution shifted from a predominance of large particles (≥4.7 µm) at day 7 to a dominance of small, inhalable particles (Stenotrophomonas, Lactobacillus, and Ruminococcus. Notably, potential zoonotic pathogens (Shigella and Acinetobacter) were detected in later stages. This study provides critical insights into winter bioaerosol dynamics, highlighting implications for animal welfare, occupational health, and public health.

Antibiotic residues in poultry pose health and resistance risks, necessitating breed-specific WDTs. In this study, the residue elimination patterns of seven antibiotics in Taihang chicken tissues under free-range conditions were studied and the appropriate WDT was formulated. A total of 240 healthy Taihang chickens aged 100 days were randomly divided into 8 groups, each comprising 30 chickens. Chickens in groups 1 to 7 were administered oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin, respectively. Regarding the administration method, we adopted the highest dose and maximum course of treatment recommended by the Veterinary Pharmacopoeia of the People’s Republic of China. Group 8 served as the control group. Muscle, sebum, liver, and kidney samples were collected at 4 h, 1 d, 2 d, 3 d, 5 d, 7 d, 10 d, 13 d, and 16 d after drug withdrawal. Our results demonstrated that the drug residues after drug withdrawal gradually decreased with the increase in drug withdrawal days, and the elimination rate in the early stage of drug withdrawal was significantly faster than that in the later stage. At 4 h after drug withdrawal, the drug residues in various tissues reached their highest values. In most cases, the drug concentrations in the kidney and liver were higher than those in the muscles and sebum; however, some drugs also exhibited concentration peaks in the sebum. On the first day of drug withdrawal, the amount of residues in various tissues decreased rapidly. In general, the elimination rate of various drugs in the muscles, liver, and kidneys is faster but slower in the sebum. Based on the WDT calculation software WT1.4, the recommended WDTs for oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin chickens are 4 d, 5 d, 11 d, 8 d, 13 d, 13 d, and 7 d, respectively. These findings support food safety and industry development.

The objective of this study was to examine the residue elimination patterns of seven antibiotics in the eggs of Taihang chickens under free-range conditions and develop suitable withdrawal times (WDTs). A total of 240 healthy Taihang chickens, aged 180 days, were randomly divided into eight groups of 30 birds each. The first seven groups were administered oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin, respectively, in accordance with the maximum dosages and longest durations of treatment recommended by the Veterinary Pharmacopoeia of the People’s Republic of China. Group 8 served as the control group, and the test period continued until no drug residue could be detected. The results demonstrate that the residues of oxytetracycline, chlortetracycline, tylosin, tylvalosin, and tiamulin throughout the test period were below the maximum residue limits (MRLs) outlined in GB 31650-2019, “National food safety standard-Maximum residue limits for veterinary drugs in foods”. The egg yolk was identified as the target tissue for estimating the withdrawal time periods (WDTs) of these seven drugs. It was thus concluded that the recommended withdrawal time for tiamulin should be 0 days. However, the WDTs of oxytetracycline, chlortetracycline, tylosin, tylvalosin, were 2.8, 0.3, 2.4, and 7.4, respectively, when the upper limit of the 95% confidence interval was found to be lower than the MRLs. It was thus determined that the recommended WDTs for oxytetracycline, chlortetracycline, tylosin, and tylvalosin should be 3, 1, 3, and 8 days, respectively. In contrast, erythromycin and lincomycin exhibited concentrations below the permitted MRLs on days 7 and 8, respectively. However, the upper limits of the 95% confidence intervals for erythromycin and lincomycin were found to be below the MRLs when the WDTs were 11 and 8.9, respectively. This suggests that the recommended WDTs for these two antibiotics should be 11 days and 9 days.

The continued evolution of H3 subtype avian influenza virus (AIV)—which crosses the interspecific barrier to infect humans—and the potential risk of genetic recombination with other subtypes pose serious threats to the poultry industry and human health. Therefore, rapid and accurate detection of H3 virus is highly important for preventing its spread. In this study, a method based on real-time reverse transcription recombinase-aided isothermal amplification (RT–RAA) was successfully developed for the rapid detection of H3 AIV. Specific primers and probes were designed to target the hemagglutinin (HA) gene of H3 AIV, ensuring highly specific detection of H3 AIV without cross-reactivity with other important avian respiratory viruses. The results showed that the detection limit of the RT–RAA fluorescence reading method was 224 copies/response within the 95% confidence interval, while the detection limit of the RT–RAA visualization method was 1527 copies/response within the same confidence interval. In addition, 68 clinical samples were examined and the results were compared with those of real-time quantitative PCR (RT–qPCR). The results showed that the real-time fluorescence RT–RAA and RT–qPCR results were completely consistent, and the kappa value reached 1, indicating excellent correlation. For visual detection, the sensitivity was 91.43%, the specificity was 100%, and the kappa value was 0.91, which also indicated good correlation. In addition, the amplified products of RT–RAA can be visualized with a portable blue light instrument, which enables rapid detection of H3 AIV even in resource-constrained environments. The H3 AIV RT-RAA rapid detection method established in this study can meet the requirements of basic laboratories and provide a valuable reference for the early diagnosis of H3 AIV.