The Effect of Intrabronchial or Subcutaneous Immunization on the Respiratory Tract of Calves

The objective of this investigation was to compare the pulmonary immunological responsiveness of two groups of calves that had been immunized by either subcutaneous or bronchoalveolar instillation of sheep red blood cells (SRBC). Immunological competence was determined by studying various parameters of nonspecific and humoral immunity. These included the determination of differential and total white blood cells counts, albumin and total protein concentrations in lavage samples, antigen-specific level s of IgM, lgG, and lgA and total immunoglobulins in serum and lavage fluids; in addition, antigen-specific antibody-forming cells were enumerated. Bovine respiratory disease (BRD) is not a single disease entity, instead, it is a complex network of sequential interactions between infectious agents and environmental stress. BRD affects the entire beef industry and is especially detrimental to the feedlot enterprise. Preliminary data suggest that 40-80% of all cattle disease involves the respiratory tract. Economic losses result from deaths, weight loss, expensive treatments for disease, inefficient feed conversion, and delayed marketing. During the last three decades studies were designed to investigate the effectiveness of various vaccination methods to prevent BRO. However, these studies failed to directly examine basic pulmonary immunoreactivity. BRD has had a major economic impact on the cattle industry. As early as the mid 1950\u27s total losses within the cattle industry due to BRD were estimated at approximately 25 million dollars. In 1972 the loss due only to mortality increased to approximately 76 million dollars. Past research has concentrated on investigating the causative agents and factors contributing to the overt development of BRD but have not addressed either basic or specific respiratory immunological reactivity. Some studies involved vaccination of cattle with killed bacterins of Pasteurella haemolytica. The vaccinations failed due to enhancement of fibrous pneumonia after challenge exposure. These studies point to the need of a thorough knowledge of bovine pulmonary immunoreactivity before an effective vaccination protocol can be developed