Reduction of caecal Listeria monocytogenes in Leghorn chicks following treatment with a competitive exclusion culture (PREEMPT™)

Day‐of‐hatch Leghorn chicks were treated by oral gavage with PREEMPT™, a continuous‐flow competitive exclusion culture containing broiler caecal bacteria, followed by an oral challenge with Listeria monocytogenes, to determine the effects of PREEMPT™ on L. monocytogenes caecal colonization. Increased (P < 0·001) concentrations of caecal propionic acid in control chicks compared with PREEMPT™‐treated chicks at 3 days of age were indicative of the establishment of the PREEMPT™ bacteria. Caeca from control chicks at 7 days after the oral challenge with L. monocytogenes contained mean 3·4 ± 1·4 log cfu g−1 of caecal content, while caeca from PREEMPT™‐treated chicks contained no detectable Listeria. Enrichment for L. monocytogenes resulted in 100 % of caeca from control chicks testing culture‐positive for L. monocytogenes, while none of the caeca from PREEMPT™‐treated chicks were culture‐positive. The results indicated that prophylactic treatment of newly hatched chicks with PREEMPT™ significantly reduced caecal colonization by L. monocytogenes.