EARLY SALMONELLA CHALLENGE TIME AND REDUCTION IN CHICK CECAL COLONIZATION FOLLOWING TREATMENT WITH A CHARACTERIZED COMPETITIVE-EXCLUSION CULTURE

Broiler chicks were treated by oral gavage on the day of hatch with a continuous-flow competitive exclusion culture (PREEMPT). At 4 h, 1 day , or 2 days posttreatment, chicks were challenged by oral gavage with 10(2) or 10(4) Salmonella CFU to determine the effects of challenge ti me on Salmonella cecal colonization. Cecal propionic acid concentratio ns in two trials increased (P less than or equal to 0.001) within 1 da y posttreatment in chicks given PREEMPT, and the increases were indica tive of the establishment of the PREEMPT bacteria. Salmonella cecal po pulations decreased (P less than or equal to 0.001) on average 6 log(1 0) units in these two trials in chicks challenged 4 h posttreatment wi th 10(4) Salmonella CFU. In a third trial propionic acid did not incre ase significantly until 2 days after treatment, and there was no decre ase in Salmonella colonization when chicks were challenged at 4 h afte r treatment. However, there were decreases in that same trial when chi cks were challenged at 1 and 2 days after treatment. The early establi shment of PREEMPT followed by challenges with 10(2) and 10(4) Salmonel la CFU resulted in 3% and 3%, respectively, of the ceca testing Salmon ella-culture-positive, compared to 28% and 95%, respectively, culture- positive ceca in untreated chicks. The results from this study indicat ed that in most instances young broiler chicks can be protected agains t cecal colonization when challenged with 10(2) and 10(4) Salmonella C FU as early as 4 h posttreatment on the day of hatch with the PREEMPT bacteria.