Sumio Kumai

Effect of NaCl‐tolerant lactic acid bacteria and NaCl on the fermentation characteristics and aerobic stability of silage

NaCl‐tolerant lactic acid bacteria (LAB) strains LC‐10 (Lactobacillus casei) and LP‐15 (Lact. plantarum) and NaCl were used as additives to sorghun (Sorghum bicolor). Numbers of LAB were significantly (P < 0·05) higher in all the additive‐treated silages than in the control silage at an early stage of ensiling. During the fermentation process, addition of NaCl or LAB effectively inhibited the growth of aerobic bacteria and clostridia, but not yeasts. All the additive‐treated silages had significantly (P < 0·05) lower pH, ammonia nitrogen content, dry matter loss and gas production but significantly (P < 0·05) higher lactic acid content and residual water soluble carbohydrates compared with the control silage. The improvement in silage quality was in the order : LAB > NaCl > control. Yeast counts were high in all additive‐based silages and they increased during the exposure of the silages to air. As a result, these silages suffered aerobic deterioration, whereas the control silage was stable. The results confirmed that the NaCl or LAB improved fermentation quality but did not prevent aerobic deterioration of the silage.

Characteristics of lactic acid bacteria isolated from forage crops and their effects on silage fermentation

Enterococcus faecalis CA 6, E faecium CA 10, E casseliflavus CA 13, Weissella paramesenteroides CA 14, Leuconostoc pseudomesenteroides CA 17, Pediococcus pentosaceus CA 21, P acidilactici CA 25 and Lactobacilus plantarum CA 28 isolated from forage crops were characterised and their effects on silage fermentation were studied. Strains CA 6, CA 10 and CA 13 grew only at relatively high pH (above 5.0), while strains CA 21, CA 25 and CA 28 were able to grow at pH values below 4.0. Strain CA 25 grew at 50°C, but the others did not grow at above 45 °C. These strains were used as inoculants for perennial ryegrass silage ensiled at 25 or 45 °C. At 25 °C all strains significantly (P < 0.01) reduced the pH value and butyric acid content and greatly increased the lactic acid content compared with the control, particularly strains CA 21, CA 25 and CA 28. At 45°C strain CA 25 markedly improved the fermentation quality of silage, but the others did not. These silages had a lower lactic acid content and a higher proportion of L(+)- to total lactic acid than equivalent silages kept at 25 °C. The results confirmed that at 25 °C P pentosaceus CA 21, P acidilactici CA 25 and L plantarum CA 28 were the most effective, whereas at 45 °C only Pacidilactici CA 25 had a beneficial effect on silage fermentation quality.