Microbiological Quality of Effluents from Anaerobic Swine Manure Lagoons in Mississippi.

Confined swine feeding operations in Mississippi and most of the southeastern USA routinely flush manure from pits beneath confinement barns into open anaerobic storage lagoons.  Lagoon effluent is reused for pit flushing and eventually land applied as fertilizer for grass hay.  The fertilizer quality of effluents in Mississippi has been documented, but relatively little was known of the microbiological quality, therefore, the present study was done to assess the microbiological quality.  Effluent samples were collected from September 2007 through May 2008 from >30 commercial and private farms in eight counties of eastern central Mississippi, including sow farms (breeding, gestation, farrowing), nurseries (21 days old to 18 kg feeders), and finisher farms (feeders grown to 113 kg).  At least 10 lagoons were sampled for each farm type.  Six samples of about 200 ml each were collected and analyzed from each lagoon; three from the lagoon edge proximal to the barns and influent flow, at points about one-quarter, one-half, and three-quarters of the length, respectively, along that side of the lagoon, and three from respective locations on the distal edge.  Samples were drawn by vacuum from 10-12 cm below the surface through sterile tubing into sterile polypropylene bottles.  Bottles were mounted on a PVC float that was deployed 4-5 m from the bank with an extendable pole.  Floats were decontaminated after use and a clean float used in each lagoon.  Samples were held on ice for transport to the lab and microbiological tests begun within 2-4 hours after collection.  Conventional cultural methods were combined with quantitative MPN (most probable number) PCR assays to identify and enumerate bacteria, including total and thermal tolerant coliforms, Escherichia coli, enterococci, clostridia, and selected enteric pathogens (Campylobacter, Listeria and Salmonella).  Microbiological quality varied seasonally and by farm type.