The effect of dry matter content and silage additives on the fermentation of bunker-made grass silage on commercial farms in England 1984-91

A total of 14 636 samples of silage made in bunkers on commercial farms between 1984 and 1991 were analysed to investigate the effect of dry matter (DM) content and silage additives on fermentation as measured by ammonia-N concentration and pH. Increasing DM content without additive use had a major beneficial influence on fermentation. When silage DM contents were greater than 220 g/kg about 66% of the silages were well fermented. Below this with diminishing DM concentration the proportion of well fermented silages declined such that with DM below 180 g/kg only 27% were well fermented. The benefit of silage additives, albeit at poorly defined and often inadequate rates, was extremely variable. Below DM concentrations of 220 g/kg, formic acid consistently improved the proportion of well fermented silages compared with non-additive-treated silages by about 20%. Similarly use of formic acid based, inorganic acid and acid with formalin additives increased the proportion of well fermented silages by about 15%. Acid mixtures, salts, inoculants and sugars provided little or no benefit compared with non-additive-treated silages, whilst use of enzymes increased the proportion of well fermented silages by about 8%. Above DM 220 g/kg, formic acid, acid with formalin and inoculant additives improved the proportion of well fermented silages, compared with non-additive-treated silages by about 15%. Similarly, formic acid based, inorganic acids and enzymes improved the proportion of well fermented silages by about 10%. Acid mixtures, salts and sugars produced less than 5% benefit. The minimum DM necessary to produce well-fermented silage without additive use was approximately 255 g/kg. Use of formic acid containing additives and inorganic acids reduced the target to about 240 g/kg. Similarly, the target DM for inoculant, sugar and enzyme treated silages was about 250, acid mixtures 260 and salts 270 g/kg. It is concluded that on commercial farms, weather conditions during ensilage, i.e. amount of rainfall and sunshine have a considerable effect upon subsequent silage fermentation. However, when silage DM was below 220g/kg, additives containing acid with or without formalin significantly increased the proportion of well fermented silages. © 1996 Silsoe Research Institute.