Ammonia produced by decomposing manure in poultry facilities causes chronic respiratory irritation in laying hens and broiler chickens, contributing to significant welfare costs that are often invisible to consumers and regulators.
Chronic ammonia exposure represents one of the most prevalent and underappreciated welfare problems in commercial poultry production. The respiratory and ocular irritation caused by ammonia creates constant low-level discomfort across millions of birds simultaneously. Hens clearly experience ammonia as aversive — they will work to avoid it in preference tests — but confined hens have no ability to escape their environment. The welfare cost is invisible from outside the building and rarely features in consumer communications about chicken welfare, yet it affects virtually all commercially housed poultry at levels that cause measurable physiological harm.