Why does a lack of ventilation (high ammonia > 20 ppm) cause tracheal deciliation and secondary E. coli respiratory infections (Colibacillosis) in brown layers?

During the winter season in Pakistan, farmers often seal the side curtains of layer sheds to conserve heat, leading to poor air exchange and a rapid accumulation of ammonia gas ($NH_3$) from decomposing uric acid in manure. Ammonia is highly soluble in water and, upon contact with the moist eyes and respiratory tract of chickens, dissolves to form a highly corrosive alkaline solution (ammonium hydroxide). When ammonia levels exceed 20 to 25 ppm, it chemically burns, shortens, and paralyzes the micro-cilia lining the trachea (tracheal deciliation). This cilia mucosal blanket is the primary physical defense mechanism (mucociliary escalator) that sweeps out inhaled dust and pathogens. With the cilia paralyzed, inhaled opportunistic bacteria—primarily pathogenic Escherichia coli—easily bypass the upper respiratory tract, colonize the trachea, and migrate down to the air sacs. This triggers severe airsacculitis, perihepatitis, and pericarditis (Colibacillosis), leading to chronic respiratory disease (CRD), high mortality, and pale bleached eggshells. Farmers can study climate engineering in the Poultry Encyclopedia, buy heavy-duty exhaust fans and ammonia monitors on Poultry Plaza, track daily market rates on Poultry Rates, and list healthy flocks on Murghi Mandi.