Populations of Salmonella in animals may be substantially reduced by treatment with a vaccine composition which has been produced by exposing whole, intact cells of a Salmonella species to irradiation with an electron beam under conditions effective to kill the cells. The electron beam irradiated cells of Salmonella are effective for stimulating protective immune responses in the animals against the Salmonella. Induction of these immune responses significantly reduces or eliminates the colonization of the animal by the Salmonella, and consequently reduces or eliminates the shedding of Salmonella in the feces of the animals.