Combined effect of antibiotic and competitive exclusion treatment on Salmonella Enteritidis fecal shedding in molted laying hens

Salmonella Enteritidis is an important pathogen for the layer industry, pri marily because of its ability to infect hens and ultimately contaminate egg contents. Studies have shown that stress situations, such as hock recyclin g (induced molting), can increase Salmonella Enteritidis problems in the fl ock. The present study examined the effect of antibiotic treatment and comp etitive exclusion (CE) on Salmonella Enteritidis shedding in the period fol lowing molt and 14-day feed withdrawal. In two separate trials, 48 birds af ter molt and feed withdrawal were divided into one group that was treated f or 10 days with enrofloxacin in water followed by administration of CE cult ure and a group that was left untreated. Salmonella Enteritidis shedding wa s significantly reduced in the antibiotic-CE group. The Salmonella Enteriti dis shedding rate was 33 and 25% in untreated birds versus 4 and 0% in the enrofloxacin-CE group on the two test days. These results indicate that tre atment of Salmonella Enteritidis-positive laying hens after molting with en rofloxacin and CE culture can substantially reduce Salmonella Enteritidis p roblems due to molting and would be a possible alternative to diverting egg s for pasteurization or slaughtering the infected flock. Possible developme nt of bacterial resistance in conjunction with antibiotic use is also discu ssed.