Air quality in Canadian poultry barns: a first look

Of the 174 ammonia samples they took, 87—nearly half—exceeded the recognized limit of 25 parts per million (ppm). The average concentration was 32.5 ppm, with peaks hitting 114 ppm. Total and respirable dust levels also varied widely across sites, while CO₂ was consistently below the critical threshold of 5,000 ppm.

Concentrations rose sharply in the fall and winter compared with summer, with little difference between the two colder seasons. This pattern reflects an economic trade-off rather than negligence on the part of producers, Gaucher said.

 “In the fall, farmers tend to close ventilation vents because the weather is more humid, which increases ammonia released from the bedding; they must therefore strike a balance between heating costs and air exchange,” she said.

Gaucher believes that documenting these seasonal variations for the first time in Canada will provide producers and barn management advisors with valuable information.

In the two-story barns studied, there were no notable differences between the floors. Contaminants were relatively evenly distributed throughout the entire housing area.

For the study, 27 workers, with a median age of 45 and an average of 35 hours per week spent inside the barns, completed a respiratory health questionnaire. A majority reported occasional symptoms such as stuffy nose or mild cough, even though 96 per cent said they wore respiratory protection. No one reported chronic bronchitis or emphysema among their pre-existing conditions.

“Protective equipment is most effective when worn at all times during exposure to ammonia and other particles,” Gaucher stressed. During the field visits—conducted exclusively in Quebec—the researchers observed that the equipment was not always worn constantly. She cautioned that this finding may not apply across Canada, as no on-site observations were made in other provinces.

Veterinary examination of the birds found no eye or respiratory conditions, despite the ammonia exposure. “Breeding chickens are vaccinated adults, so they are less vulnerable to respiratory conditions than chicks would be in the same environment,” Gaucher explained. 

Approximately 30 per cent of the birds had footpad lesions, mostly mild. The researchers concluded that the environmental stress to which the breeders were subject was moderate, especially considering that they were much older than the broiler chickens typically studied. In the vast majority of facilities visited, the behaviour of the birds indicated that they were comfortable.

Targeted tweaks, not an overhaul

Gaucher does not believe these results call current farming practices into question, but they do offer a first quantitative benchmark to guide targeted adjustments. “We now have data that show what could be done,” she said. “Before, we didn’t know.” 

The study, conducted with support from Canadian Hatching Egg Producers, was designed to gather evidence for better management, not to raise alarms.

One possible adjustment would be to better coordinate ventilation, humidity control and litter management across seasons, particularly in the colder months when the trade-off with heating is an issue. In the meantime, consistently wearing personal protective equipment remains the most immediate recommendation to reduce respiratory risks for workers.

The research team plans further research on strategies tailored to the Canadian context, with longitudinal monitoring of the effects of environmental improvements on workers and birds.