USE OF FRESHLY CULTURED LACTIC-ACID BACTERIA AS SILAGE INOCULANTS

The main advantage of freshly cultured inoculants over their freeze-dried counterparts may lie in their metabolic state when added to herbage. The use of freshly cultured lactic acid bacteria in comparison with conventional freeze-dried preparations as inoculants for grass silage was examined. Perennial ryegrass was ensiled in laboratory silos, either untreated or treated with formic acid, or a commercial freeze-dried strain of Lactobacillus plantarum, or a fresh culture of the same strain of L. plantarum, or fresh cultures of Pediococcus pentosaceous, or Lactococcus lactis alone or in combination with L. plantarum. All inoculants were applied at a rate of 10(6) colony-forming units g(-1) fresh matter, with the mixtures containing a 1:1 ratio of each species. Herbage treated with freshly cultured inoculants exhibited shorter lag times, in relation to the initiation of pH decline, than those associated with untreated or freeze-dried inoculant-treated herbages. Treatment of herbage with inoculants containing L. plantarum increased the initial speed of pH decline. In comparison with silages made with freeze-dried L. plantarum, in measurements made during the initial 14 d of ensilage, those inoculated with fresh cultures had significantly (P < 0.05) higher lactic acid concentrations and significantly (P < 0.05) lower pH values. Both P. pentosaceous and L. lactis initiated a rapid fermentation, but compared to L. plantarum alone, or mixtures of L. plantarum with P. pentosaceous or L. lactis, these cultures demonstrated intermediate rates of lactic acid production and pH decline. Ah mature (105 d) silages were of good quality with pH values of four or less, low ammonia-N concentrations (<100 g kg(-1) total N) and no detectable levels of clostridia or butyric acid. Results suggested that the main advantage of freshly cultured inoculants over their freeze-dried counterparts may lie in their metabolic state when added to herbage.