Neutrophils are one of the main effector cells of innate immunity and were shown to kill bacteria by phagocytosis more than 100 years ago. Neutrophils are also capable of antimicrobial activity by producing extracellular structures named neutrophil extracellular traps (NETs). This thesis is an investigation of porcine neutrophils and their ability to produce NETs, as well as the antimicrobial ability of secretions from activated porcine neutrophils in combating a variety of common porcine pathogens. Porcine neutrophils were found to produce NET-like structures, and secretions from activated neutrophils were found to possess variable bactericidal activity against common pathogens of swine. Antimicrobial proteins dependent on elastase activity were shown to be partially responsible for the bactericidal activities of activated neutrophils. Several antimicrobial proteins and peptides were identified via proteomic techniques. This work allows for better understanding of innate immunity in swine, and identification of potential targets for addressing porcine health. / Ontario Ministry of Agriculture Food & Rural Affairs, Ontario Pork, Natural Sciences and Engineering Research Council of Canada