The effect of aerosolized bacterial lysate on experimentally inducedpneumonia in calves.

Abstract

Bovine respiratory disease (BRD) often occurs during specific periods of increased susceptibility when stress, viral infection, or reduced air quality are thought to suppress respiratory defences. The innate immune system is rapidly responsive and broadly protective and could be a target for preventing BRD during these periods of increased susceptibility. This study tested the hypothesis that stimulation of pulmonary innate immune responses by aerosol delivery of a lysate of killedandbacteria would protect calves againstpneumonia. Ten clean-catch colostrum-deprived Holstein calves were randomly assigned to receive either aerosolized bacterial lysate or saline 24 hours beforechallenge. Effects of this treatment on clinical, hematologic, microbiologic, and pathologic outcomes were assessed. Compared to controls, lysate-treated calves had lower serum haptoglobin and blood leukocyte and neutrophil concentrations followingchallenge. There were no differences in temperature, heart and respiratory rates, clinical scores, ultrasound lesions, or number ofin the nasal cavity or lung. Thus, treatment with bacterial lysate prior tochallenge appeared to ameliorate early measures of inflammation but did not provide sufficient protection to substantially alter the course of disease.