Growth of Clostridium tyrobutyricum during fermentation and aerobic deterioration of grass silage

Grass experimentally infected with Clostridium tyrobutyricum, Hansenula anomala and Candida lambica was inoculated with lactic acid bacteria or formic acid, ensiled at 20°C, 28°C and 37°C and stored for 100 days. Chemical and microbial compositions were determined after 4, 11, 40 and 100 days of storage. According to the chemical and microbial criteria, all the silages were of good quality. The silage were exposed to air for 14 days after 40 and 100 days of anaerobic storage, which stimulated clostridial growth. High concentrations of spores of Clostridium tyrobutyricum and a high content of butyric acid were found in deteriorated parts of the silages, both on the surface and at 7‐cm depth. Increased levels of ATP were registered in deteriorated parts. The deteriorated parts had high concentrations of the bacteria Bacillus polymyxa, B licheniformis and B sphaericus and of the mould Monascus ruber while yeast counts were low. High levels of the initially added Hansenula anomala and Candida lambica were only observed in formic acid treated silages after the air exposure.