The object of this dissertation was to investigate the respiratoryproblems affecting calves with special reference to bacterial etiologicalagents, and to discuss the best methods of treatment and control ofinfected at 3 weeks old with Cl. Perfringens type ”A”. The thirdexperiment (Infected and treated chicks) comprised 20 chickenssubdivided into 2 groups, the 8th and 9th group were received normal