Pneumonic pasteurellosis (PP) is defined as one of the pivotal infectious diseases caused by Pasteurella multocida and Mannheimia haemolytica. This study aimed to determine the levels of Bcl-2-associated protein X (Bax), B-cell lymphoma 2 (Bcl-2), caspase-3, autophagy related-5 (Atg5), beclin-1 and receptor interacting protein-3 (RIP3) in lung tissues with naturally infected PP caused by P. multocida and M. haemolytica, and to reveal their effects on the pathogenesis of P. multocida and M. haemolytica pneumonia. The material of the study consisted of 150 fibrinous pneumonia/pleuropneumonia and 10 healthy lung tissue samples. Relevant samples were examined by histopathological, immunohistochemical and real-time PCR methods. Immunohistochemically, 23 (15.3%) were positive for P. multocida, and 17 (11.3%) were positive for M. haemolytica. Subsequently, the processes of apoptosis, autophagy and necroptosis for P. multocida and M. haemolytica were evaluated by real-time PCR. P. multocida pneumonia increased Bax, Caspase-3, Atg5, Beclin-1, and RIP3 gene expressions (4.2, 3.8, 2.9, 2.1, 2.8-fold, respectively), whereas Bcl-2 gene expression was decreased (0.22-fold). While Bax, Caspase-3, Atg5, Beclin-1, and RIP3 gene expressions were increased in M. haemolytica pneumonia (2.3, 1.9, 1.7, 1.2, 4.2-fold, respectively), it was observed that Bcl-2 gene expression was reduced (0.52-fold). The results obtained in the study revealed the importance of necroptosis, apoptosis and autophagy processes in the pathogenesis of PP caused by P. multocida and M. haemolytica and contributed to the literature. In addition, we found that the processes of apoptosis and autophagy play a more active role in PP caused by P. multocida, and the process of necroptosis plays a more active role in PP caused by M. haemolytica.