Comparison of Bacterial Community Structure in PM2.5 within Broiler Houses under Different Rearing Systems in China

Animal welfare with Chinese characteristics: Chinese poultry producers' perceptions of, and attitudes towards, animal welfare

China's poultry industry faces challenges in adopting and sustaining cage-free systems for poultry production. Effective interventions are crucial to support producers transitioning from cages to alternative systems or maintaining cage-free systems to improve animal welfare. However, little is known about how Chinese poultry producers perceive animal welfare in relation to cage-free systems and the importance of animal welfare in poultry production. Through a qualitative interview study with 30 Chinese farm owners, managers and senior managers from large-scale egg and broiler farms using cages and non-cage systems (collectively referred to as "producers"), this paper explores Chinese poultry producers' attitudes and perceptions regarding animal welfare and welfare in different poultry housing systems. Template analysis was used to analyse the data from semi-structured interviews, which generated themes related to the participants' awareness and understanding of the concept of animal welfare, the factors that impacted their choices of different housing systems, and the perceived priorities in poultry production. The responses revealed that the participating producers had a strong awareness and knowledge of animal welfare. However, the participants' understanding of the term is heterogeneous: generally, egg producers emphasised natural behaviours, whereas broiler producers prioritised health and productivity. Nevertheless, profitability, leadership, and organisational policies primarily influenced housing system choices rather than animal welfare values. Economic motives drove egg producers towards cage-free systems, prompted by consumers' and companies' demand for cage-free eggs committed to transitioning away from cages by 2025. In conclusion, tailored interventions for different poultry sectors within China are necessary. While animal welfare values matter, economic incentives seem more promising for steering the shift towards and maintaining cage-free poultry production.

Spatial distribution of airborne bacterial communities in caged poultry houses

Microbial aerosols in intensive broiler houses whose species and concentrations are closely related to human health are ubiquitous. Based on 16S rRNA gene sequencing, the aim of this study was to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. Significant spatial variations in airborne bacterial concentrations were observed inside the poultry farmhouse. The results indicated that bacteria in the air samples could be grouped into a total of 1,674 OTUs. Alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (p < 0.01). The Sankey diagram illustrated species dynamic changes in Proteobacteria, Firmicutes, and Actinobacteria among the different locations. From the aspect of LEfSe (LDA Effect Size) analysis, we discovered that the abundance of Planctomycetes was significantly higher in the entry than in the rear and middle. This study shows the spatial distribution of the entire bacterial community in intensive broiler houses, which offers a new perspective for studying airborne total bacteria in those environments.Implications: The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. The results observed that bacterial aerosol concentrations in the examined broilers house varied greatly at different positions, and a significantly higher exposure to bacterial aerosol was observed at the middle than at the other positions (p < 0.05). The alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (P<0.01). Sankey diagram illustrated species dynamic changes of Proteobacteria, Firmicutes and Actinobacteria among the different locations. The microbial communities in genus level in the samples of entry and rear were closer, while the species diversity of middle and rear samples in chicken house was highly similar (P>0.05). Altogether, results revealed that the effects of spatial factors on the diversity and abundance of bacteria in the air of closed-cage broiler houses, which poses a potential threat to the health of animals and workers in those environments.

Bacterial Community Characteristics Shaped by Artificial Environmental PM2.5 Control in Intensive Broiler Houses

Multilayer cage-houses for broiler rearing have been widely used in intensive Chinese farming in the last decade. This study investigated the characteristics and influencing factors of bacterial communities in the PM2.5 of broiler cage-houses. The PM2.5 samples and environmental variables were collected inside and outside of three parallel broiler houses at the early, middle, and late rearing stages; broiler manure was also gathered simultaneously. The bacterial 16S rRNA sequencing results indicated that indoor bacterial communities were different from the outdoor atmosphere and manure. Furthermore, the variations in airborne bacterial composition and structure were highly influenced by the environmental control variables at different growth stages. The db-RDA results showed that temperature and wind speed, which were artificially modified according to managing the needs for broiler growth, were the main factors affecting the diversity of dominant taxa. Indoor airborne and manurial samples shared numerous common genera, which contained high abundances of manure-origin bacteria. Additionally, the airborne bacterial community tended to stabilize in the middle and late stages, but the population of potentially pathogenic bacteria grew gradually. Overall, this study enhances the understanding of airborne bacteria variations and highlighted the potential role of environmental control measures in intensive farming.

Airborne bacterial communities in the poultry farm and their relevance with environmental factors and antibiotic resistance genes

The accelerating occurrence and environmental dissemination of bacteria, gas pollutants and antibiotic resistance genes (ARGs) in aerosols of poultry farms have become emerging environmental issues due to their potential threat to animals, workers, and the communities located near such farms. Here, aerosol samples were gathered from inside and outside of the chicken house in winter with a transportable high-flow bioaerosol sampler. Then, 16S rRNA gene amplicon sequencing was used to categorize the bacteria in air samples, and the abundance of 12 ARG subtypes was researched via the real-time quantitative polymerase chain reaction (qPCR). Results indicated that the bacterial richness and diversity and total absolute abundance of ARGs were similar in the bioaerosols from indoor and downwind site of the poultry farm. The zoonotic pathogens, Staphylococcus and Corynebacterium, were detected both inside and outside of the chicken house, and the four most abundant target genes were bla_TEM, tetQ, ermB and sul1 in aerosols. Moreover, the correlation between the bacterial communities and environmental factors, such as NH₃ and H₂S concentrations, wind speed, temperature and relative humidity, was analyzed. The result revealed that the indoor bacteria community was positively associated with temperature and concentrations of air pollutants (NH₃ and H₂S), and could spread from confinement buildings to the ambient atmosphere through wind. In addition, the network analysis result showed that the airborne bacteria might significantly contribute in shaping the ARGs' profiles in bioaerosol from inside and outside of the poultry house. Overall, our results revealed the airborne bacterial communities and their associated influencing factors in the micro-environment (inside of the chicken house and nearby the boundary of the farm), and brought a new perspective for studying the gas pollutants and bioaerosol from poultry farms in winter.

Effects of biochar and organic-inorganic fertilizer on pomelo orchard soil properties, enzymes activities, and microbial community structure

Fertilizer management can influence soil microbes, soil properties, enzymatic activities, abundance and community structure. However, information on the effects of biochar in combination with organic-inorganic fertilizer after 3 years under pomelo orchard on soil bacterial abundance, soil properties and enzyme activities are not clear. Therefore, we conducted a field experiment with seven treatments, i.e., (1) Ck (control), (2) T1 (2 kg biochar plant^–1), (3) T2 (4 kg biochar plant^–1), (4) T3 (2 kg organic-inorganic mixed fertilizer plant^–1), (5) T4 (4 kg biochar + 1.7 kg organic-inorganic mixed fertilizer plant^–1), (6) T5 (4 kg biochar + 1.4 kg organic-inorganic mixed fertilizer plant^–1), and (7) T6 (4 kg biochar + 1.1 kg organic-inorganic mixed fertilizer plant^–1). The soil microbial communities were characterized using high-throughput sequencing of 16S and internal transcribed spacer (ITS) ribosomal RNA gene amplicons. The results showed that biochar combined with organic-organic fertilizer significantly improved soil properties (pH, alkali hydrolysable nitrogen, available phosphorus, available potassium, and available magnesium) and soil enzymatic activities [urease, dehydrogenase (DHO), invertase and nitrate reductase (NR) activities]. Furthermore, soil bacterial relative abundance was higher in biochar and organic-inorganic treatments as compared to control plots and the most abundant phyla were Acidobacteria (40%), Proteobacteria (21%), Chloroflexi (17%), Planctomycetes (8%), Bacteroidetes (4%), Verrucomicrobia (2%), and Gemmatimonadetes (1%) among others. Among the treatments, Acidothermus, Acidibacter, Candidatus Solibacter and F473 bacterial genera were highest in combined biochar and organic-inorganic treatments. The lowest bacterial abundance and bacterial compositions were recorded in control plots. The correlation analysis showed that soil attributes, including soil enzymes, were positively correlated with Chloroflexi, Planctomycetes, verrucomicrobia, GAL15 and WPS-2 bacterial abundance. This study demonstrated that biochar with organic-inorganic fertilizer improves soil nutrients, enzymatic activities and bacterial abundance.