Airborne dust and bioaerosols in Canadian conventional and alternative houses for laying hens.

Awareness about laying hen welfare has led to the phase-out of conventional battery cages in favor of the adoption of alternative housing systems for egg production in many countries. However, the greater freedom of movement for animals and the presence of manure and litter (sawdust, straw, feathers, etc.) on the floor in some alternative housing systems may be suitable conditions for dusts, bacteria, and fungi to be aerosolized, raising concerns about indoor air quality and respiratory health of workers. The present project aimed at assessing and comparing indoor air quality and bioaerosols in conventional and alternative houses for laying hens. Six were conventional houses (with battery cages), six were enriched colonies, and six were aviary (multi-level cage-free houses) visited in Eastern Canada from 2020-2022. Higher airborne concentrations of particulate matter (PM) from all size fractions (PM1, PM2.5, PM4, PM10, and total dust), culturable bacteria, total endotoxins, and Clostridium perfringens were found in aviaries compared to houses for laying hens in conventional and enriched colonies. Total endotoxin and Clostridium perfringens concentrations were higher in enriched colonies than in conventional laying-hen housing systems. Campylobacter coli, Campylobacter jejuni, and Salmonella sp. were detected in few hen houses. This study highlights possible markers for indoor air quality evaluation inside laying hen houses. These airborne contaminants could be targeted by mitigation strategies to improve indoor air quality in alternative housing systems for laying hens.