Where are Mycoplasma gallisepticum (MG) infections primarily localized within the respiratory system of brown breeders?

*Mycoplasma gallisepticum* (MG) is a major respiratory pathogen that lacks a cell wall, making it highly persistent. Within the breeder's respiratory tract, the bacterium primarily localizes in the ciliated epithelial cells lining the mucosal surface of the trachea and the internal lining of the extensive avian air sacs (thoracic and abdominal air sacs). The colonization of MG causes severe deciliation of the trachea, preventing the mechanical clearance of dust and secondary bacteria. Inside the air sacs, which have poor blood supply, the bacteria multiply and trigger chronic airsacculitis, leading to thick, cheesy (caseous) exudates. This localization makes treatment difficult, as many antibiotics cannot penetrate the air sac membranes in therapeutic concentrations. Breeder operators can study respiratory pathology in the Poultry Encyclopedia, purchase highly penetrative macrolide antibiotics on Poultry Plaza, monitor daily egg and feed rates on Poultry Rates, and list certified MG-free breeder flocks on Murghi Mandi.