Influence of management and air quality conditions on development of respiratory and gastroenteric disease, and antibiotics phenotypic resistance in domestic canaries ( <i>Serinus canaria domesticus</i> )

Air quality plays a crucial role in maintaining the health of birds housed in indoor facilities. This study evaluated the impact of environmental and air quality parameters on the health of domestic canaries (<i>Serinus canaria domesticus</i>) in 102 Italian flocks, classified according to disease prevalence: healthy (H) and diseased (D), with D further divided into respiratory (RD) and gastrointestinal (GID) disorders. Environmental indicators included particulate matter (PM), carbon dioxide (CO₂), formaldehyde (HCHO), total volatile organic compounds (TVOC), temperature (T°), relative humidity (RH) and bird stocking density (<i>n</i>/m³). These variables were analysed alongside clinical status, the presence of canary circovirus (CaCV) and polyomavirus (CaPyV), microbiological findings, and antimicrobial resistance patterns. Significantly higher PM and CO₂ concentrations were detected in RD flocks, supporting the role of poor air quality in respiratory disease onset. CaCV and CaPyV circulation were detected in 30.4% and 6.9% of flocks, respectively. Flocks positive for CaCV showed significantly higher CO₂ levels and bird stocking density, suggesting a link between inadequate environmental management and viral persistence. Microbiological analysis revealed widespread antimicrobial resistance: 60.8% of Gram-negative and 54.4% of Gram-positive isolates were multidrug resistant (MDR). Moreover, correlations between environmental parameters and resistance profiles were identified, though highly variable by microbial type and health status. Overall, these results emphasize that maintaining optimal air quality and environmental conditions is essential for preventing disease and limiting antimicrobial phenotypic resistance in canary breeding facilities.