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 102 or 10 4 Salmonella CFU to determine the effects of challenge time on Salmonella cecal colonization. Cecal propionic acid concentrations in two trials increased (P ≤ 0.001) within 1 day posttreatment in chicks given PREEMPT, and the increases were indicative of the establishment of the PREEMPT bacteria. Salmonella cecal populations decreased (P ≤ 0.001) on average 6 log 10 units in these two trials in chicks challenged 4 h posttreatment with 104 Salmonella CFU. In a third trial propionic acid did not increase significantly until 2 days after treatment, and there was no decrease in Salmonella colonization when chicks were challenged at 4 h after treatment. However, there were decreases in that same trial when chicks were challenged at 1 and 2 days after treatment. The early establishment of PREEMPT followed by challenges with 102 and 104 Salmonella CFU resulted in 3% and 3%, respectively, of the ceca testing Salmonella-culture-positive, compared to 28% and 95%, respectively, culture-positive ceca in untreated chicks. The results from this study indicated that in most instances young broiler chicks can be protected against cecal colonization when challenged with 102 and 10 4 Salmonella CFU as early as 4 h posttreatment on the day of hatch with the PREEMPT bacteria.