Evaluation of the influence of sprinkling powdered slaked lime on microorganisms for the prevention of domestic animal infectious diseases.

When infectious diseases arise in domestic animals, a large amount of slaked lime is sprinkled on cattle sheds and their surroundings for disinfection and prevention. However, optimal sprinkling methods, standard and upper limit of slaked lime, and influence of slaked lime on non-target microorganisms remain unclear. In this study, we clarified detailed microbicidal effects of slaked lime via in vitro experiments and the influence of sprinkling powdered slaked lime (PSL) in field soil on microorganisms. In vitro disinfection tests assessing the appropriate amount of water and ventilation conditions were also performed in sterilized glass bottles with soil and Salmonella enterica subsp. enterica serovar Typhimurium. Under conditions with a small amount of water relative to the amount of PSL, the bactericidal effect and sustainability of powdered slaked lime (PSL) tended to be lower than those without spraying water. Moreover, the sterilization effect markedly decreased after 7 days under conditions with abundant water. These results indicate that the amount of sprayed water is very important for the bactericidal effect and persistence of PSL. A field experiment showed that the pH and exchange calcium (Ca) content of the soil sprinkled with over 1000 g m-2 PSL remained high even after a long period (≥1 year), with values of approximately 0.5-1.0 and approximately 3-11 times the level without PSL, respectively. However, sprinkling PSL did not influence viable microbial counts at any concentration.