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Pathogen re-colonization of in-house composted and noncomposted broiler litter

J.P. Brooks, M.R. McLaughlin, A. Adeli, D.M. Miles
Journal of applied poultry research 2015 v.24 no.2 pp. 157-167
Campylobacter, Listeria, ammonia, animal pathogenic bacteria, bacterial colonization, beneficial microorganisms, composting, cost effectiveness, growers, industry, microbial competition, poultry, poultry manure, ribosomal RNA, zoonoses
In-house litter composting has been reintroduced to the industry and shown to reduce bacteria by as much as 2 orders of magnitude. Other industries have demonstrated that pathogens can recolonize a waste-residual when microbial competition has been reduced or inhibited following composting. Poultry growers, in the process of shifting to in-house composting for pathogen control, should be aware of this potential problem. A laboratory microcosm study investigated pathogenic bacteria recolonization into composted and noncomposted broiler litter over a simulated broiler grow-out cycle. Objectives were to: 1) determine colonization potential for zoonotic and poultry bacterial pathogens, 2) identify beneficial bacteria which reduce pathogen recolonization, and 3) identify the effects of ammonia on pathogen recolonization. Composted broiler litter allowedListeria andCampylobacter to colonize within the first 2 wk of the grow-out period while noncomposted litter resisted colonization. Colonization was nearly identical by the end of the grow-out period, and showed that bacterial pathogens had essentially been overtaken by commensal or normal bacteria. 16S rRNA libraries demonstrated reductions in Proteobacteria associated with composted litter (48 vs. 16%), which may indicate that this phylum occupies a niche which zoonotic pathogens prefer to occupy. Ammonia generation neither inhibited nor promoted bacterial colonization, as levels were high for both litter treatments. This study neither suggests nor condemns the continued use of this cost-effective, litter-treatment process; findings suggest that while the beneficial microbial population was initially reduced, it quickly recovered and pathogen colonization was neither enhanced nor inhibited because of this. This study demonstrates that the recently adopted in-house composting process may continue to be used, provided poultry health gains continue to be seen.