EPIPHYTIC LACTIC-ACID BACTERIA (LAB) IN GRASS-LEGUME MIXTURES

The results of the study demonstrate that pure grass, harvested in the same location and at the same time as a luceme crop, tends to contain higher epipytic numbers of lactic acid bacteria (LAB) than luceme. This might be accountable for by either the composition of exudates or by structural differences of the plant surfaces as well as stomata density between both crops. When mixtures of grass and lucerne are investigated a smaller number of LAB can be recovered from the composite sample than from each of the individual components. As far as the microbial status of mixtures and their suitability for ensiling is concerned, the determination of the epiphytic LAB from each crop separately seems to reflect the situation numerically more accurate. However, the early stage of ensiling with its sudden collaps of tissue structures and the release of cell contents, creates conditions comparable to the disintegration of the forage sample after preparation for the microbiological analysis in the stomacher lab blender. The same applies to an even larger extent to the harvesting process with a chopper or other methods such as the mat making technique. Consequently, in spite of the obvious underestimation of the true LAB population, there is no other significant alternative, than to use the composite sample for the enumeration of LAB, especially as this approach probably also reflects in the best possible way the metabolic activity of the LAB to be expected during the silage fermentation of such forage mixtures. A verification of these results by using other grass legume mixtures but just lucerne will be necessary.