A total number of twenty calves aged (4-6 months) weighing (80-120 kg) was used for this study. Calves were divided into 4 equal groups. The first group (clinically healthy) was kept as normal control group, the second group (pneumonic calves) was kept as infected non treated group, the third group (pneumonic calves) was treated with Tilmicosin (10 mg/kg B.wt. S/C single injection), the fourth group (pneumonic calves) was treated with Tulathromycin (2.5 mg/kg B.wt. S/C single injection). All calves were clinically observed for 7 days with collection of nasal swabs at zero day and standard bacteriological techniques were used for isolation and identification of Pasteurella multocida. Specific identification of
purified suspected ten isolates biochemically identified as P. multocida strains, only four were confirmed as P. multocida by polymerase chain reaction (PCR), of which two strains harbored the virulence gene tbpA and pfhA. Two blood samples were collected from each calf of all groups at 2nd day and 7th day post treatment. Infected non treated group showed
significant increase in alanine transaminase (ALT) and aspartate transaminase (AST) activities, C- reactive protein (CRP) concentration and Malondialdehyde (MDA) and significant decrease in reduced glutathione (GSH) along the whole experimental period. Tilmicosin administration evoked significant increase in MDA and significant decrease in GSH. Tulathromycin-treated group showed significant increase in ALT and AST activities and significant decrease in GSH. Recovery rate of calves suffered from pneumonia caused by P.multocida was determined as 100% in Tulathromycin-treated group and 80% in Tilmicosintreated group.