<OL> <LI> Determine if the addition of a cationic peptide to the feed formulation of weaned pigs decreases Salmonella and Campylobacter colonization of the pig's gut. <LI> Investigate the effects of using cationic peptides as feed additives in weaned pig rations on the innate immune response of weaned pigs.
Approach: At weaning (17-21 days of age), piglets will be randomly placed in pens with heat lamps for additional warmth in groups of 5 individuals. Piglets will be provided with water and an unmedicated Phase I diet ad libitum that meets the National Research Council (1994) guidelines. Body weights will be recorded on Days 0, 3, 5, and 7 post-weaning. Utilizing a completely randomized block design, pigs will be placed into 4 experimental groups. Groups 1 and 2 will each contain 5 pigs fed a control balanced unmedicated corn and soybean meal-based diet that will contain 0 or 12 ppm BT(peptide), respectively. Groups 3 and 4 will be fed diets that contain 0 or 12 ppm BT, but pigs in these groups will be challenged with ST or CI, respectively (see experimental designs below). Pigs will be fed these diets throughout the experiments. Experiments for each infection will be repeated for two repetitions. Neutrophils and monocytes will be isolated using density gradient separation as previously described (4,5,8). Functional assays will then be performed to assess the capabilities of neutrophils and monocytes isolated from pigs receiving the different treatments. Two methods of microbial killing used by neutrophils will be investigated. Specifically, neutrophil degranulation, the release of bactericidal products from granules inside the neutrophil, and the oxidative burst, the production of bactericidal reactive oxygen species (ROS), will be assayed. The phagocytosis of Salmonella by neutrophils and monocytes will also be observed using established methods. Briefly, the assays are described below. In addition, samples from leukocytes will be collected and frozen for future studies on cytokine gene expression.