The objective of this study was to determine the effect of the acidification of pelleted feed on the carriage and seropositivity against Salmonella in finisher pigs of a commercial herd. Three different diets were assayed: 0.8% formic acid (group 1); 0.4% lactic acid plus 0.4% formic acid (group 2) and a feedstuff without additives (group 3). one thousand pigs were included in each treatment that was administered from 19 to 26 weeks of age