Pathogen reduction in minimally managed composting of bovine manure

Spread of manure pathogens is of considerable concern due to use of manure for land application. In this study, the effects of four static pile treatment options for bovine manure on die-off of a generic Escherichia coli, E. coli O157:H7 surrogate, Salmonella Senftenberg, Salm. Typhimurium, and Listeria monocytogenes were evaluated. Bovine manure spiked with these bacteria were placed in cassettes at the top, middle, and bottom sections of four static pile treatments that reflect minimal changes in pile construction with and without straw. Temperatures were monitored continuously during the 28day self-heating period. E. coli and salmonellae were reduced from 8 to 9log₁₀ CFUg^-1 to undetectable levels (<1.77log₁₀MPNg^-1) at 25-30cm depths within 7days in all pile sections except for the manure-only pile in which 3-4 logs of reduction were obtained. No L. monocytogenes initially present at 6.62log₁₀CFUg^-1 were recovered from straw-amended piles after 14days, in contrast with manure-only treatment in which this pathogen was recovered even at 28days. Decline of target bacterial populations corresponded to exposure to temperatures above 45°C for more than 3days and amendments of manure with straw to increase thermophilic zones. Use of straw to increase aeration, self-heating capacity, and heat retention in manure piles provides producers a minimal management option for composting that enhances pathogen die-off and thereby reduces risk of environmental spread when manure is applied to land.