LAUSR

ABSTRACT The experiment was performed to determine the effect of 20% dietary DL-Methionine (Met) in excess of modern breeder requirement level compared to Tilmicosin (Pulmotil AC®) on the humoral immune response and histopathological parameters of male broilers challenged with Mycoplasma gallisepticum (MG). Birds of Treatments 1–4 remained unchallenged while those of Treatments 5–8 were challenged with MG at 10 days of age. Diets with excess Met were formulated for birds of Treatments 3, 4, 7 and 8. Broilers of Treatments 2, 3, 6 and 7 were administered Pulmotil AC® in drinking water. The 20% excess dietary Met significantly reduced tracheal deciliation, preserved the integrity of tracheal mucosal layer and significantly decreased goblet cell degeneration in MG-challenged birds. Furthermore, MG-challenged broilers administered 20% excess Met manifested higher ELISA titers against MG and a significantly higher antibody response to p33 (MG-cytadhesin putative gene) and p66 (MG-hemagglutinin protein A (pMGA)) in comparison to the other treatments. The 20% excess Met thereby maintained the health of the respiratory system and embodied an increased protection against MG-putative gene and a greater humoral response to MG challenge in broilers.