Hygienic Aspects of Cattle Slurry Storage as the Most Popular and Cheapest Method of Handling Liquid Animal Excrements / Higieniczne aspekty składowania gnojowicy bydlęcej jako najpopularniejszej i najtańszej metody postępowania z płynnymi odchodami zwierzęcymi

Slurry is a very valuable natural fertilizer, but its improper use in agriculture poses a serious sanitary threat. Therefore its treatment before use for fertilization is advisable. One of such methods, which is still the most popular, is storage of liquid excrements. The aim of this study was to estimate the sanitization effectiveness of storage at 4ºC and 20ºC based on parameters describing the kinetics of changes in the population of some indicator bacteria in cattle slurry with different dry matter content. The material for the study was fresh cattle slurry. The liquid excrements used in the experiment had a dry matter content of 2, 6 and 14%. Slurry was stored at 4ºC and 20ºC. Bacilli of Salmonella Dublin, E. coli and enterococci were used as indicator bacteria. Number of microorganisms was determined based on MPN method in a 3-tube design. Basic parameters of the bacteria inactivation kinetics were calculated and statistical analysis was made using the program SAS 9.2 PL. In stored slurry a gradual elimination of all the studied microorganisms was observed. Hygienization effect of storage was smaller at 4ºC than at 20ºC and in excrements with a high dry matter content. Depending on storage temperature and dry matter proportion, the theoretical times of survival ranged from 81.85 to 220.80 days for bacilli of Salmonella Dublin, from 74.93 to 199.36 days for E. coli, and from 118.67 to 335.84 days for enterococci. The study showed explicitly that statutory time of slurry storage is insufficient to ensure its complete hygienization.