Heterofermentative lactic acid bacteria (LABhe) can help to increase aerobic stability of silages. As high dry matter silages are especially prone to aerobic deterioration, the question was whether an in vitro test could help to select for LABhe with tolerance to these conditions, that is, to high osmolality. A medium proven for homofermentative lactic acid bacteria (LABho) with high sugar concentration was applied in vitro while validating the results in high DM grass silages in situ. The pH was measured at 0, 24, 36 and 48 h or after 5 d as indicator for the bacterial fermentation activity and compared. As a result, LABhe showed to be far less susceptible to high DM and osmolality respectively, compared to LABho. It was concluded that the in vitro test allows for qualitative assessment of the osmotolerance of LABhe, but not for quantitative ranking between LABhe strains.
Martens et al. (Mon,) studied this question.