Quality of grass silage infected with spores of Clostridium tyrobutyricum

The influence of adding clostridial spores to silage was studied in 2 successive years. Direct-cut, precision-chopped herbages were infected with spores of Clostridium tyrobutyricum in doses varying from 0 to 10⁶ g^?l fresh material (FM), and ensiled in experimental silos. The material was treated with or without 4 ml formic acid (85%) kg^?1 FM. Silo contents were studied after 4.20 (or 50) and 100 days of ensiling.
Contents of dry matter, water-soluble carbohydrate, nitrate as well as buffering capacity of FM varied between the 2 years at harvest, whereas the numbers of clostridial spores were about the same (< 10² g^?1).
Infecting the crop with clostridial spores negatively affected the quality of silage in the first year. After 50 days spore numbers in the silages had increased by 40 × 10³ to 150 × 10³ times in the infected silage, compared with 5 × 10³ in the uninfected silage. No effect was seen in the second year.
Silage with high spore counts showed no residual nitrate content. Formic acid improved silage quality from a chemical point of view but had no anti-clostridial effect. Ensilability of a crop seems to be more important than the initial count of Clostridia for a successful ensiling process.