American Society of Agricultural and Biological Engineers , Paper number 012237 , 2001

Wang, L., Mankin, K.R.

Contamination of surface waters with fecal pathogens has been linked to many outbreaks of human illness worldwide. The objective of this study is to evaluate the environmental factors that influence pathogen mortality in exposed manure and their initial migration from manure to the surface water. A 13 mm thickness of manure was held at constant environmental conditions for more than 6 weeks. Concentrations of fecal coliforms (FC), E. coli, and fecal streptococci (FS) were measured on multiple occasions during this period. A factorial design of 3 temperatures (4, 27, and 41 C) and 3 manure moisture contents (79, 69, and 50% wet basis). All treatments had high bacterial concentrations, initially 7.7´103 to 7.9´105 cfu/g for FC and 7.0´104 to 8.8´106 cfu/g for FS. In most cases, those concentrations increased over the 42 to 47 day experimental period. In general, 27 C appeared to provide the best conditions for bacterial growth, whereas 41 C demonstrated the low growth or slight dieoff under otherwise-similar conditions. This study demonstrates that fecal bacteria are resilient under a wide range of natural conditions; even after cattle leave a feedlot, microbial populations are still likely to be high.