Influence of temperature on Salmonella survival in hog manure slurry and seasonal temperature profiles in farm manure storage reservoirs

AimsAssess the influence of temperature on Salmonella survival in stored hog manure slurry from different production phases and characterize the seasonal temperature exposure experienced by manure during on-farm storage.Methods and resultsThe survival of Salmonella was determined in sow, feeder and nursery barn manures stored at 4, 25 or 37 °C following inoculation with a four serovar bacterial cocktail containing Salmonella serovar Typhimurium, Salmonella Agona, Salmonella Hadar and Salmonella Oranienburg. Temperature fluctuations in manure slurry were monitored in an aboveground and earthen reservoir at different depths for ≤ 16 months at two farms. Salmonella numbers in manure declined during storage; however, survival was > 300 days when manure was stored at 4 °C and survival was slightly better in nursery barn manure. At higher temperature survival was significantly (p < 0.05) shorter in all types of manure. The decimal reduction time (DRT) of Salmonella in slurry stored at 37, 25 and 4 °C ranged from 0.9 to 1.4 days, 8 to 19 days, and 22 to 60 days, respectively. Manure temperatures in reservoirs during fall–winter–spring ranged from 0.5 to 8 °C in the aboveground tank, and from 1.5 to 11 °C in the earthen reservoir. During the summer manure temperatures ranged from 14 to 19 °C with an average of 16 and 17 °C in the aboveground and earthen reservoirs, respectively.ConclusionsWhile Salmonella did not grow in hog manure, storage reservoir temperatures observed would facilitate Salmonella survival over winter enabling contamination of fields at spring application.Significance and impact of studySince untreated liquid hog manure may contain Salmonella, manure should be held for 60 days without commingling with fresh manure in reservoirs before application to fields with actively growing crops to minimize risk of plant and soil contamination by Salmonella.