Aeration improves the hygiene of cattle slurry and the quality of grass forage and silage†

Abstract

The aeration of slurry at mesophilic temperature improves its hygiene, provided no fresh slurry is added to the tank during the 3–4 weeks of aeration. Microorganisms, such as Listeria monocytogenes, Yersinia enterocolitica and related species and coliphages, were reduced by 90–99.9%. However, the number of Clostridium was not affected. The typical odour of slurry diminished. The use of aerated slurry as fertilizer on growing grass may cause less risk of contamination either by enteric microorganisms or by butyric acid‐producing clostridia than the use of non‐aerated slurry. The hygiene level of grass was also sufficient when grown in a cold, rainy late summer and used for silage. None of the 62 samples of silage prepared from a second‐harvest grown in rainy conditions and fertilized with aerated slurry were found to have deteriorated. However, three samples out of 63 made during the same period but fertilized with non‐aerated slurry were observed to have deteriorated completely. Neither spreading method, band‐spreading or injection of the slurry into sward, had any effect on the microbiological hygiene of the samples.