Comparison of the content of clostridial spores in wilted grass silage ensiled in either laboratory, pilot-scale or farm silos.

Abstract

Fifty-two laboratory silages (1.5 litres), 108 samples of pilot-scale silos (2-4 t) and 167 samples of farm silages were analysed for clostridial spore contents, proximate composition and concn of fermentation products. Numbers of clostridial spores ranged from 100 to 10 million/g. Relationships between spore counts as dependent variable and DM, butyric acid and ammonia-N contents as independent variables were established for the 3 silage types by regression analyses. Similarity existed in the relationships for pilot-scale and farm silages, showing a gradual drop of spore counts with higher DM levels. Laboratory silages showed either a pronounced clostridial fermentation with high levels of butyric acid, ammonium-N and spores or no clostridial fermentation at all. In contrast to the larger-scale silages, no clostridial fermentation was found at DM contents above 250 g/kg. In laboratory and in pilot-scale silages about 60% of the variation in spore count could be explained from either the butyric acid or ammonia content. In farm silages this figure dropped to 20-30% and it was concluded that the chemical parameters cannot be used to predict spore counts in farm silages. The differences between the larger scale silages and laboratory silages are attributed to the heterogeneity of the pilot-scale and farm silages. (Abstract retrieved from CAB Abstracts by CABI’s permission)