Currently available Salmonella Choleraesuis live avirulent vaccines are efficacious for the prevention of disease caused by S. Choleraesuis. This research was conducted to determine if these same vaccines could prevent infection by Salmonella Typhimurium, an important human foodborne pathogen present in pigs pre-harvest. These results indicate that S. Choleraesuis avirulent vaccines do not prevent the rapid dissemination of S. Typhimurium when pigs are challenged either with a high dose (intranasal) or a low dose (natural challenge via pen contamination) of the organism. It is very likely these avirulent vaccines do decrease the levels of Salmonella in pigs at slaughter but this protection occurs when pigs are exposed to Salmonella during the finishing phase of production, not during transport and lairage. Treatment of pigs with spray-dried plasma does not prevent the rapid dissemination of S. Typhimurium.