Pathogen Reduction and Correlation to Factors Responsible for Pathogen Reduction in Dairy Farm Operations Treating Agricultural Waste
American Society of Agricultural and Biological Engineers

Narula, r., Grimberg, S.J., Rogers, S., Mondal, S.

Approximately 350 million tons of manure is produced annually by agriculture in the U.S. Manure disposal at large concentrated animal feeding operations presents a challenge. Anaerobic digestion of livestock manure to reduce odor and produce biogas for energy generation is a profitable waste management option on farms, but out of reach of most farmers because of high capital costs. For operations reusing solids for bedding, reduction of causative agents of mastitis is a concern. Waste management practices that cause reduction of populations of zoonotic pathogens such as Salmonella spp. and Campylobacter spp. may also reduce public health risks following runoff events. Enteric bacterial reduction in agricultural waste is likely dependent upon operational parameters, moisture, temperature, pH, influent substrate composition and type of medium. Thorough analysis to establish correlations between these different parameters has not been conducted. Our hypothesis is that pathogen concentration in samples is dependent upon physical factors (moisture content and volatile solids content), farm processes and sample type. The objective of this research is to determine factors that control pathogen reduction and/or removal during current dairy manure management practices using Real-time q-PCR techniques. Results indicate that processes including anaerobic digestion and composting cause a significant reduction of pathogens. From regression models it was observed that pathogen concentrations are strongly correlated to moisture content, volatile solids content and sample type. These results will help identify processes and operational parameters that yield greater pathogen reduction, allowing better recycling of farm waste solid residuals, increasing economic benefits for dairy farms.