AbstractThe influence of level of formaldehyde application at ensiling on fermentation patterns in ryegrass, red clover and maize silages was studied in three experiments using small‐scale silos. Formaldehyde was applied, together with formic acid at 2 litre t−1fresh crop, over the range 0 to 166 g formaldehyde kg−1crude protein (CP) in the crop. In ryegrass and red clover, but not in maize, low levels of formaldehyde application (<60 g kg−1CP) induced clostridial‐type fermentations, as evidenced by increases in the content of volatile fatty acids and ammonia N. The concentrations of ethanol and 2,3‐butanediol were also increased. At higher levels of application, formaldehyde was particularly effective in restricting fermentation in ryegrass and red clover silages, there being little acid production above 120 and 80 g kg−1CP, respectively. Only low levels of formaldehyde (ca20 g kg−1CP) were required to achieve this effect in maize silage. In each crop the insoluble N content of the silages increased with level of formaldehyde application. The recovery of formaldehyde in both the treated herbage and silage improved with level of application, but did not exceed 50 of that applied. As physical losses of formaldehyde would be expected to be minimal under the conditions of the experiments, it appears that chemical bonding was the main reason for the lack of recovery
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