Experimental studies on effect of ammonia, dust and Escherichia coli on respiratory tract of broiler chicks

An investigation was undertaken to study clinical symptoms, gross and pathomorphological changes in the respiratory tract of broiler chicks exposed to the ammonia, dust and E. coli at different intervals. The common symptoms in various treatment groups included head shaking, eye rubbing, keratoconjunctivitis, lacrimation, huddling, decreased feed consumption and body weight gain with poor feed efficiency. Other additional clinical symptoms included decreased respiratory rate. The mean viable count of E.coli were found to be increased significantly (P< 0.05) in various groups at several time points as compared with that in controls. The post mortem changes noticed in the trachea included congestion, haemorrhages, increased goblet cell hyperplasia leading to excess mucus secretion, matting of cilia, segmental deciliation and leucocyte infiltration. The histopathological changes in the lungs comprised congestion, haemorrhages, perivascular and interstitial odema and the secondary bronchi revealed goblet cell hyperplasia, matting of cilia and deciliation. The severity of pathomorphological changes in the trachea and lungs was increased with the progression of time.