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Evaluation of a Competitive Exclusion Culture and Megan Vac 1 on Salmonella Typhimurium Colonization in Neonatal Broiler Chickens

J. L. McReynolds^*,1, R. W. Moore, A. P. McElroy, B. M. Hargis and D. J. Caldwell^||

^* USDA, Agricultural Research Service, Southern Plains Agricultural Research Center, College Station, TX 77845; USDA, Agricultural Research Service, Russell Research Center, Athens, GA 30605; Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg 24061; Department of Poultry Science, University of Arkansas, Fayetteville 72701; and ^|| Departments of Poultry Science and Veterinary Pathobiology, Texas A&M University, College Station 77843

Correspondence: ¹ Corresponding author: mcreynolds{at}ffsru.tamu.edu

The present study was designed to evaluate the effect of individual or simultaneous application of 2 products, a competitive exclusion culture (CEC) or Megan Vac 1 (MV), for bioefficacy in reducing Salmonella Typhimurium (ST) cecal colonization in broiler chicks following experimental challenge. In experiment 1, CEC and MV were applied to day-of-hatch broiler chicks, and chicks were experimentally challenged with ST approximately 48 h later. In control chicks, ST was recovered at a level of 3.84 log₁₀ cfu/g following direct plating of cecal contents, and 12 of 19 (63.15%) cultured individual ceca were positive following selective enrichment. In chicks receiving CEC by spray application on day of hatch, a numerical reduction in ST recovered from cecal contents (2.63 log₁₀ cfu/g) and a significant reduction (P < 0.05) in recovery of ST from cultured ceca following selective enrichment (4 of 18, or 22.2%) was observed when compared with controls. Significant reductions in ST cecal colonization in chicks treated with MV alone were not observed in experiment 1. In experiment 2, chicks received day-of-hatch spray application of CEC alone, MV alone, or CEC and MV as a combined application immediately prior to or within 24 h of chick placement. When chicks were experimentally challenged with ST 48 h posthatch, significant reductions (P < 0.05) in cecal colonization by ST were observed with each experimental group when compared with nontreated controls. These data suggest that both commercially available products, alone or in combination, are efficacious in reducing cecal colonization in broiler chicks challenged with ST.

Key Words: Salmonella • chicken • competitive exclusion • vaccine