Experimental design

In the first phase of this study we collected data on the physical characteristics of six 5 to 8 ton stacks of poultry litter. Piles 1, 2 and 3 were extensively monitored for physical characteristics, while Piles 4, 5, and 6 were less extensively monitored for physical characteristics and primarily devoted to bacterial studies. Temperature was measured using 2 methods. A six foot temperature probe was used to obtain repeated measures at fixed points in the pile, 2 foot from the ground level (height) and at 1, 2, 3, 4 and 5 feet into the pile (depth). A Diagram of a typical poultry litter pile showing how height, depth and section were defined is included in Appendix 2. Secondly, data-logger temperature probes set to record temperature at 10 minute intervals for up to 28 days were placed at predetermined sites within the pile. Water activity (Aw) and moisture content (% dry matter, DM) were measured from grab samples at a 1 foot depth at 3 locations. These three parameters, temperature, water activity and moisture content, are likely to be the primary determinants governing the process of composting and thermal sterilization of pathogens. Three trials were conducted in winter and three in summer (cool and wet versus hot and dry) to assess seasonal effects on the temperature profiles. In the second phase of our study we quantified the log reduction of Salmonellae, E. coli and Campylobacter spp., in poultry litter, placed in mesh bags at predetermined depths within the litter piles. All bags began with an equal number of bacteria. A set of samples from were removed at various time points and cultured onto selective media. MacConkey's agar was used for E. coli, xylose lactose deoxycholate (XLD) for Salmonella and CampyFDA for Campylobacter. Temperature, Aw, DM, pH and water activity were also recorded when each sample was removed from the pile.