Ensiling of manured crops—effects on fermentation

The quality of silage from crops fertilized with cattle manure and an inorganic fertilizer was compared in experiments from 1985 to 1989. Manure was spread either as farmyard manure (FYM, 25t ha⁻¹) or as slurry (20-50t ha⁻¹). Crops were direct cut (approximately 200 g DM kg⁻¹) or wilted (approximately 300 g DM kg⁻¹), precision chopped and ensiled in experimental silos. Silage was treated with 4 kg 85% fonnic acid t⁻¹ fresh matter (FM), an inoculant or no additives. The use of manure, particularly FYM, resulted in more Bacillus spores on crops at harvest compared with fertilized crops. Clostridium spores increased as a result of manuring in 1989 only on FYM-treated crops. Differences in the chemical composition of crops were usually small between fertilizer treatments. The quality of silage from slurry-dressed crops, compared with that of silage from fertilized crops, varied between years. The FYM resulted in reduced silage quality, i.e. high pH values (> 4·5), high ammonia N (> 150 g kg⁻¹ total N) and butyric acid (> 6·3 g kg⁻¹ water) concentrations, and high numbers of Bacillus (10⁵ g⁻¹ FM) and Clostridium spores (10⁵ g⁻¹ FM). The concentration of lactic acid was low (≤ 12 g kg⁻¹ water). Wilting and additives generally improved silage quality and reduced the differences between treatments. However, the efficiency of the inoculant on farmyard manured crops was limited.     

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.