Inoculation of experimental silages with different Clostridium spores

Since 1989, we have tested the effect of different factors on clostridial development in grass-based silages. In most of these experiments we added a special strain of Clostridium tyrobutyricum. Over the years, we became increasingly concerned about how representative this strain is for Swedish farmyard silage. Fresh forage was wilted in the field to approx. 300 (low DM) and 400 g/kgDM (high DM) before being chopped in a stationary forage cutter. Forage from each DM level was homogenised and 11 portions of 3 kg forage were weighed into 125-litre plastic bags. 10 different spore cocktails (#1-10) were applied to the bags with spray bottles, adding approx. 1000 cfu spores/gFM. The 11th portion was left untreated and served as a control. After mixing, triplicate laboratory silos were filled from each bag. Silos were stored at room temperature (19-22°C) for 103 to 126 days before they were opened, sampled and analysed for DM, pH, ammonia-N, butyric acid and counts of viable Clostridium spores/gFM. Inoculation of grass-based forage with our previously used Cl. tyrobutyricum strain (cocktail #1) resulted in silages with high clostridial activity compared with the other spore cocktails. This confirms that this particular strain is a suitable challenge organism for experiments focusing on the inhibition of clostridial activity in silages