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

The aeration of slurry at mesophilic temperature improves its hygiene, prov ided no fresh slurry is added to the tank during the 3-4 weeks of aeration. Microorganisms, such as Listeria monocytogenes, Yersinia enterocolitica an d related species and coliphages, were reduced by 90 99.9%. However, the nu mber of Clostridium was not affected. The typical odour of slurry diminishe d. The use of aerated slurry as fertilizer on growing grass may cause less risk of contamination either by enteric microorganisms or by butyric acid-p roducing clostridia than the use of non-aerated slurry. The hygiene level o f grass was also sufficient when grown in a cold, rainy late summer and use d for silage. None of the 62 samples of silage prepared from a second-harve st 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 deteri orated completely. Neither spreading method, band-spreading or injection of the slurry into sward, had any effect on the microbiological hygiene of th e samples.