The effect of some acid-based additives applied to wet grass crops under various ensiling conditions

Abstract

Some acid-based silage additives, which are less corrosive and easier to handle than Formic acid 85% (FA), were evaluated in a laboratory-scale silage experiment. These were Foraform (645 g kg–1 formic acid, 60 g kg–1 NH3), Ensimax [213 g kg–1 formic acid, 200 g kg–1 acetic acid, 190 g kg–1 of dry matter from wood pulp liquor with a high concentration of lignosulphonates (WPL)], and a modified version of Ensimax with a higher proportion of formic acid and a lower proportion of acetic acid. Each single ingredient, and all combinations of ingredients in the original Ensimax, were studied when applied in the quantities they make up in the additive. Untreated silage was used as a negative control and FA as a positive control. The additives were assessed using three different crops and by sealing the silos immediately after filling or after a 24 h delay. Both the full and half of the recommended application rates of the additives and of the single ingredients of Ensimax were studied. No significant differences were found between FA and Foraform when applied at 3 and 4 l t–1, respectively, which provided the crop with the same dose of pure formic acid. Inclusion of WPL in Ensimax did not influence silage fermentation, i.e. the effect of Ensimax could be ascribed to the effect of formic plus acetic acid alone. Compared with Ensimax, the modified version, in which 148 g kg–1 of formic acid was substituted for 150 g kg–1 of acetic acid, clearly improved fermentation in terms of increased concentration of true protein, reduced fermentation of acetic and propionic acid, and reduced ammonia value and pH. When the silos were sealed immediately, sugar concentrations in the silage correlated positively with the application rate of acids, whereas no such relationship was found when the sealing was delayed for 24 h. No consistent relationship was found between the application rate of acids and ethanol concentrations in the silage. Easy-to-handle acidic additives like Foraform and Ensimax may replace FA when applied according to their molar concentration of acids. This means that 4·0 l t–1 of Foraform and 7·3 l t–1 of Ensimax are equivalent to 3 l t–1 of FA.